U.S. patent application number 11/953396 was filed with the patent office on 2008-06-19 for disposable absorbent articles with zones comprising elastomeric components.
Invention is credited to Fred Naval Desai, Donald Carroll Roe.
Application Number | 20080147036 11/953396 |
Document ID | / |
Family ID | 34963558 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080147036 |
Kind Code |
A1 |
Roe; Donald Carroll ; et
al. |
June 19, 2008 |
Disposable Absorbent Articles With Zones Comprising Elastomeric
Components
Abstract
Absorbent articles having a liquid permeable topsheet, a liquid
impermeable backsheet, and an absorbent core disposed between said
topsheet and said backsheet are disclosed. The absorbent articles
include a thermoplastic elastomer joined to or disposed in a
stretch zone on at least one component or region of the absorbent
article to impart an elastic resistance that provides sizing or
shaping capabilities to the article. The absorbent article can be
in the form of diapers, pull-on diapers, training pants, sanitary
napkins, wipes, bibs, incontinence briefs or inserts.
Inventors: |
Roe; Donald Carroll; (West
Chester Township, OH) ; Desai; Fred Naval;
(Fairfield, OH) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY;INTELLECTUAL PROPERTY DIVISION - WEST BLDG.
WINTON HILL BUSINESS CENTER - BOX 412, 6250 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Family ID: |
34963558 |
Appl. No.: |
11/953396 |
Filed: |
December 10, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11077779 |
Mar 11, 2005 |
|
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11953396 |
|
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60557288 |
Mar 29, 2004 |
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Current U.S.
Class: |
604/385.25 |
Current CPC
Class: |
A61F 13/4902 20130101;
A61F 13/565 20130101; A61F 13/49015 20130101; A61F 13/15203
20130101; A61F 2013/49028 20130101; A61F 2013/49026 20130101; A61F
13/5633 20130101; A61F 13/496 20130101; Y10T 442/162 20150401; A61F
13/5622 20130101; A61F 13/49012 20130101 |
Class at
Publication: |
604/385.25 |
International
Class: |
A61F 13/56 20060101
A61F013/56 |
Claims
1. A disposable wearable absorbent article comprising: a side
panel, which includes: a fastener; a first array of substantially
parallel stretch zones, each oriented at substantially the same
particular negative angle with respect to a lateral centerline of
the article, each with a laterally inboard end and a laterally
outboard end, wherein the laterally outboard end of each stretch
zone of the first array is disposed proximate to the fastener; and
a second array of substantially parallel stretch zones, each
oriented at substantially the same particular positive angle with
respect to the lateral centerline of the article, each with a
laterally inboard end and a laterally outboard end, wherein the
laterally outboard end of each stretch zone of the second array is
disposed proximate to the fastener; and a crotch region, which
includes a third array of substantially linear and substantially
parallel stretch zones, each oriented substantially perpendicular
to the lateral centerline of the article, each with a
longitudinally outboard end; wherein the longitudinally outboard
end of at least one of the stretch zones of the third array is
aligned with the laterally inboard end of at least one of the
stretch zones of the second array; and wherein each stretch zone
includes a thermoplastic elastomeric composition disposed on a
substrate.
2. The disposable wearable absorbent article of claim 1, wherein
all of the longitudinally outboard ends of the third array are
aligned with all of the laterally inboard ends of the second
array.
3. The disposable wearable absorbent article of claim 1, including
a transitional stretch zone disposed proximate to the
longitudinally outboard ends of the third array and the laterally
inboard ends of the second array.
4. The disposable wearable absorbent article of claim 3, wherein
the transitional stretch zone is disposed between the
longitudinally outboard ends of the third array and the laterally
inboard ends of the second array.
5. The disposable wearable absorbent article of claim 3, wherein
the transitional stretch zone is extensible.
6. The disposable wearable absorbent article of claim 3, wherein
the transitional stretch zone is oriented at a particular positive
angle between about plus 45 degrees and plus 90 degrees with
respect to a lateral centerline of the article.
7. The disposable wearable absorbent article of claim 3, wherein
the transitional stretch zone is oriented at a particular positive
angle between about plus 45 degrees and plus 60 degrees with
respect to a lateral centerline of the article.
8. The disposable wearable absorbent article of claim 1, wherein
the longitudinally outboard end of the at least one of the stretch
zones of the third array is disposed proximate to the laterally
inboard end of the at least one of the stretch zones of the second
array.
9. The disposable wearable absorbent article of claim 8, wherein
all of the longitudinally outboard ends of the stretch zones of the
third array are disposed proximate to all of the laterally inboard
ends of the stretch zones of the second array.
10. The disposable wearable absorbent article of claim 1, wherein
the longitudinally outboard end of the at least one of the stretch
zones of the third array is connected with the laterally inboard
end of the at least one of the stretch zones of the second
array.
11. The disposable wearable absorbent article of claim 8, wherein
each of the longitudinally outboard ends of the stretch zones of
the third array is connected with a corresponding laterally inboard
end of a stretch zone of the second array.
12. The disposable wearable absorbent article of claim 1, wherein
the stretch zones of the first array and the stretch zones of the
third array are configured together to provide a substantially
continuous pathway of elastic resistance.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/077,779, filed Mar. 11, 2005, which claims the benefit of
U.S. Provisional Application No. 60/557,288, filed Mar. 29, 2004,
the substances of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention generally relates to disposable
absorbent articles such as diapers, pull-on diapers, training
pants, sanitary napkins, wipes, bibs, incontinence briefs or
inserts and the like. More specifically, the invention is directed
to such absorbent articles that have one or more regions comprising
an elastomeric component. Such components are used in the absorbent
articles of the invention to provide the desired article shape
and/or to impart the desired stress and strain properties for
improved fit and comfort of the article on the wearer and/or for
increased convenience of the user.
BACKGROUND OF THE INVENTION
[0003] Disposable absorbent products, such as diapers, training
pants, incontinence articles typically include stretchable
materials, such as elastic strands, in the waist region and the
cuff regions to provide a snug fit and a good seal of the article.
Pant-type absorbent articles further include stretchable materials
in the side portions for easy application and removal of the
article and for sustained fit of the article. Stretchable materials
have also been used in the ear portions of disposable diapers for
adjustable fit of the article. However, it would be desirable to
have materials with improved properties that better define
directionality and intensity of the tensile forces provided by the
contractive portions of the absorbent article. In this way, such
desirable absorbent articles would have the ability to shape or
size to the wearer for better fit and comfort, yet have the ability
to maintain the required tension when on a wearer to achieve
sustained fit and prevent sagging and/or drooping of the article.
Absorbent articles of this kind would result in better fit in
various areas of the absorbent article, e.g., the crotch or waist
region of a diaper with resulting improvements in comfort. In the
case of a diaper, better fit and comfort can also impart better
functional performance such as reduced leakage since the diaper
would better conform to the shape of a wearer. Such features have
heretofore not been available for absorbent articles.
[0004] There are various approaches to providing desirable
stretchable properties in targeted areas of absorbent articles.
Stretchable materials may be strands, films or nonwoven fibrous
webs made of elastomeric materials. Typically, such materials are
stretchable in at least one, and possibly multiple, directions.
However, because the films or webs are made entirely of elastomeric
materials, they are relatively expensive, and they tend to have
more drag on skin surface, resulting in discomfort to the wearer of
the article. Sometimes, the stretchable strands or films are
laminated to one or more layers of nonwoven webs. Since typical
nonwoven webs typically are made of thermoplastic fibers, they have
very limited stretchability and, the resulting laminates provide
considerable resistance to stretch. It is necessary to reduce this
resistance substantially in order to make functional stretch
laminates. However, such materials do not have sufficient ability
to shape, size or conform to the particularities of the wearer's
anatomy upon application.
[0005] Other approaches to make stretchable materials are also
known, such as stretch-bonded laminates and neck-bonded laminates.
Stretch bonded laminates are made by stretching an elastic strand
in the machine direction (MD), laminating it to a nonwoven
substrate while it is in the stretched state, and releasing the
applied tension so that the nonwoven gathers and takes on a
puckered shape. Neck-bonded laminates are made by first stretching
the nonwoven substrate in the machine direction such that it necks
(i.e., reduces its CD dimension) then bonding CD oriented elastic
strands to the substrate while the substrate is still in the
stretched, necked state. This laminate will be stretchable in the
CD, at least up to the original width of the nonwoven before it was
necked. Combinations of stretch bonding and neck bonding have also
been known to deliver stretch in both MD and CD directions. In
these approaches, at least one of the components is in a tensioned
(i.e., stretched) state when the components of the laminates are
joined together. Again, these materials cannot be effectively used
in absorbent articles to impart the desired sizing or shaping
features desired by users and wearers of absorbent articles.
[0006] Zero strain stretch laminates are also known. The zero
strain stretch laminates are made by bonding an elastomer to a
nonwoven while both are in an unstrained state. The laminates are
then incrementally stretched to impart the stretch properties. The
incrementally stretched laminates are stretchable only to the
extent afforded by the non-recovered (i.e., residual) extensibility
of the laminate. For example, U.S. Pat. No. 5,156,793 discloses a
method for incrementally stretching an elastomer-nonwoven laminate,
in a non-uniform manner, to impart elasticity to the resulting
laminate. These stretch laminates behave similar to the materials
described previously in that they do not have sufficient ability to
size or shape to the wearer.
[0007] However, in all the approaches above, the materials or
laminates are made separately and then incorporated into the
absorbent article. For example, the stretch laminates described
herein may be cut into the appropriate size and shape, then
attached to the desired location in the product in a process
sometimes referred as the "cut-and-slip" process. Because of the
different stretch properties required for different elements of the
product, it is necessary to make a variety of laminates having
different stretchability and cut the laminates to different sizes
and shapes. Several cut-and-slip units may be needed to handle the
different stretchability of the stretch laminates and to attach
them to different locations of the product. As the number of
cut-and-slip units and/or steps multiplies, the process quickly
becomes cumbersome, complicated and expensive. These processes are
suitable for modern day absorbent article manufacture and are
desirable. However, it would also be desirable to have absorbent
articles having the desired sizing and/or shaping properties, but
which can be disposed in or on the absorbent article without the
need for such complicated and expensive "cut-and-slip"
processes.
[0008] One alternative to cut and slip processes used by the art is
to print an elastomeric composition onto a substrate. Exemplary
disclosures include U.S. Pat. No. 6,531,027 which discusses
adhering components of an absorbent article using an adhesive
printing process, PCT Application No. 03/039420 which discusses
printing first and second elastomeric compositions onto a substrate
where the compositions differ in at least one of the following
properties: elasticity, melt viscosity, composition, shape,
pattern, add-on level, and PCT Application No. WO 03/053308, which
discusses printing an elastic adhesive onto an extendable substrate
to provide a tensioning force during garment wear.
[0009] Based on the foregoing, it would be desirable to have
absorbent articles with stretchable material having elastic
properties such that it can be extended as desired but still
retains the desired degree of elasticity to facilitate sustained
fit on the wearer. It would also be desirable to have such a
material that can be disposed easily on any specific area of the
absorbent article, or component thereof in any desired amount.
Additionally, it would be desirable to have such a material or
composite having elastic properties that can be easily placed in
discrete, spaced apart areas of the absorbent article or a
component thereof via known deposition techniques such as printing
(including gravure, offset, letterpress and screen techniques),
extrusion coating, roll coating and the like.
SUMMARY OF THE INVENTION
[0010] The aforementioned needs in the art are met by the present
invention which provides an absorbent article with a material that
has elastic properties disposed in a predetermined pattern defining
a stretch zone that provides desired elastic directionality and
intensity to specific regions of the absorbent article. Such
directionality and intensity is controlled by controlling the
amount, placement and orientation of a thermoplastic elastomer that
is disposed only on certain zones or regions of the absorbent
article or a component thereof.
[0011] In accordance with one aspect of the invention, an absorbent
article is provided that comprises a liquid permeable topsheet, a
liquid impermeable backsheet, and an absorbent core disposed
between the topsheet and the backsheet. The article may also
include additional features such as one or more ears or side
panels, leg cuffs, and fastener components, elastic belts. In other
aspects of the invention, the material used in the absorbent
article is provided with one or more stretch zones where the
stretch zones may comprise at least a portion of one or more of the
features. In another embodiment of the invention a plurality of the
stretch zones are assembled into an array thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a plan view of a diaper in accordance with the
invention;
[0013] FIG. 2 is a perspective view showing a diaper chassis having
a plurality of regions with one or more stretch zones or arrays
according to the invention disposed thereon;
[0014] FIG. 3 is a perspective view of a pull-on diaper in
accordance with the invention;
[0015] FIG. 4 is a plan view of the pull-on diaper of FIG. 2;
[0016] FIGS. 5A and 5B are cross-sectional views of the pull-on
diaper shown in FIGS. 3 and 4;
[0017] FIGS. 6A-I show a diaper embodiment of the present invention
in which the diaper ears have stretch zones in various designs;
[0018] FIGS. 7A and 7B show yet another embodiment of a diaper in
accordance with invention wherein stretch zones are provided to the
ears and along the absorbent assembly for imparting the desired
elastic properties to the diaper;
[0019] FIGS. 8A-8D illustrate a diaper in which stretch zones are
disposed in a variety of locations to provide several alternative
designs for improved wearer comfort and fit;
[0020] FIG. 9 is a plan view of a diaper in accordance with the
invention in which stretch zones are provided in the diaper ears
and the front waist portion;
[0021] FIG. 10 is a plan view of a diaper in accordance with the
invention in which the stretch zones are provided in the rear waist
portion such that there is at least partial longitudinal alignment
with the diaper ears;
[0022] FIG. 11 is a plan view of a diaper having stretch zones in
the front crotch portion in accordance with the invention;
[0023] FIG. 12 is another plan view of a diaper in which stretch
zones are disposed along the lateral portions of the diaper in
order to provide the desired elastic properties in the leg
openings; and
[0024] FIG. 13 is a perspective view of a diaper where a stretch
zone is used to provide elasticity to a topsheet.
[0025] FIG. 14 is an exemplary stress-strain curve showing
"Available Strain".
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0026] The term "disposable" is used herein to describe absorbent
articles that generally are not intended 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).
[0027] As used herein, the term "disposed" is used to mean that an
element(s) is formed (joined and positioned) in a particular place
or position as a unitary structure with other elements or as a
separate element joined to another element.
[0028] As used herein, the term "joined" encompasses configurations
whereby an element is directly secured to another element by
affixing the element directly to the other element, and
configurations whereby an element is indirectly secured to another
element by affixing the element to intermediate member(s) which in
turn are affixed to the other element.
[0029] A "unitary" absorbent article refers to absorbent articles
which are formed of separate parts united together to form a
coordinated entity so that they do not require separate
manipulative parts like a separate holder and liner.
[0030] As used herein, the term "diaper" refers to an absorbent
article generally worn by infants and incontinent persons about the
lower torso.
[0031] By "stretch", it is meant that the material has the ability
to extend beyond its original length in at least one dimension when
subjected to a tensile force (i.e., tension) applied in the
direction of that dimension. "Stretch" may be unidirectional,
bi-directional, or multi-directional. The specific "stretch"
properties of a material may vary along any of the stretch vectors.
As used herein, stretch includes both plastic and elastic
deformation.
[0032] The term "elastic" or "elastomeric" as used herein refers to
any material that upon application of a biasing force, can stretch
to an elongated length of at least about 125 percent of its
relaxed, original length, without rupture or breakage, and upon
release of the applied force, recovers at least about 40% of its
elongation, preferably recovers at least 60% of its original
length, most preferably recovers about 80% of its original
length.
[0033] The term "inelastic" refers herein to any material that does
not fall within the definition of "elastic" above.
[0034] As used herein, the term elastic resistance describes an
elastic force that tends to resist an applied tensile force causing
a material provided therewith to tend to contract to an intentioned
configuration in response to a stretching force. Elastic resistance
is conveniently measured using the method described in the TEST
METHODS section below.
[0035] "Longitudinal" is a direction running parallel to the
maximum linear dimension of the article and includes directions
within .+-.45.degree. of the longitudinal direction. The "lateral"
or "transverse" direction is orthogonal to the longitudinal
direction. The "Z-direction" is orthogonal to both the longitudinal
and transverse directions. The "x-y plane" refers to the plane
congruent with the longitudinal and transverse directions.
[0036] As used herein, the term "impermeable" generally refers to
articles and/or elements that are substantially not penetrated by
aqueous fluid through the entire Z-directional thickness thereof
under a pressure of 1.0 kPa or less. Preferably, the impermeable
article or element is not penetrated by aqueous fluid under
pressures of 3.4 kPa or less. More preferably, the impermeable
article or element is not penetrated by fluid under pressures of
6.8 kPa or less. An article or element that is not impermeable is
permeable.
[0037] The term "substrate" as used herein refers to any material,
including a film, an apertured film, a nonwoven web, a woven web, a
foam or a combination thereof, or a cellulosic material including
wood pulp, derivatized or modified cellulosic materials, and the
like, having a single layer or multiple layers. The term "fibrous
substrate" as used herein refers to a material comprised of a
multiplicity of fibers that could be either a natural or synthetic
material or any combination thereof, including, for example,
nonwoven materials, woven materials, knitted materials, and any
combinations thereof.
[0038] The term "nonwoven" as used herein refers to a fabric made
from continuous filaments and/or discontinuous fibers. Nonwoven
fabrics include those made by carding staple fibers, airlaying or
wet laying staple fibers and via extrusion processes such as
spunbonding and melt blowing. The nonwoven fabric can comprise one
or more nonwoven layers, wherein each layer can include continuous
filaments or discontinuous fibers. Nonwovens can also comprise
bi-component fibers, which can have shell/core, side-by-side, or
other known fiber structures.
[0039] By "stretch zone", it is meant a portion of a region of an
absorbent article having elastic stretch properties. A stretch zone
may extend throughout an entire region or feature of the article,
extend across multiple regions or features, or comprise merely a
portion of, one or more regions or features of the article. A
region or feature may also comprise an array of individual stretch
zones.
[0040] The term "Line of Force" describes the pathway through a web
material or structure comprising such web material that is
substantially parallel to its surface, that connects two points,
zones, or features in the material, and that carries most of the
tension when tension is imposed between those two points, zones, or
features. The term also applies to pluralities of pathways of close
enough proximity, properties, and direction that they effectively
behave as a single pathway. The shape, width, and stress/strain
behavior of the pathway can be controlled by modifying the
stress/strain properties of the material in the desired location
and direction of the pathway to produce a higher effective modulus
in the pathway compared to areas adjacent to the pathway. The
proportion of the tension carried by the pathway depends on the
difference in effective modulus between the pathway and the
adjacent material. It should be understood that a line of force may
be defined by any of the stretch element geometries disclosed
herein.
PREFERRED EMBODIMENTS
[0041] In accordance with one aspect of the invention, an absorbent
article is provided that comprises a liquid permeable topsheet, a
liquid impermeable backsheet, and an absorbent core disposed
between the topsheet and the backsheet. The article may also
include one or more features such as, but not limited to, ears or
side panels, leg cuffs, fastener components, and/or a belt. The
absorbent article according to present invention is also provided
with one or more stretch zones. In most cases such stretch zones
will comprise at least a portion of the aforementioned features. In
other aspects of the invention, the stretch zones comprise a
substrate having an elastomeric composition disposed thereon. The
elastomeric composition provides an elastic resistance to the
stretch zone upon elongation of at least a portion of the stretch
zone. In preferred embodiments of the present invention, the
elastomeric composition is disposed on the substrate in a
predetermined geometric pattern (i.e., shape and orientation) so as
to provide such elastic resistance in a manner that enhances the
performance of the feature. The pattern preferably allows the
stretch zone to more efficiently carry anchoring loads and tensile
forces induced by application of the article to the wearer and/or
accommodate movement of the wearer, and/or the weight of the
article or waste contents of the article than a typical
non-patterned design.
[0042] Suitably, an absorbent article according to the present
invention must comprise at least one stretch zone wherein the
stretch zone comprises an elastomeric composition that is disposed
on a substrate so as to at least partially penetrate the substrate.
The area of a stretch zone comprises at least the portion of the
substrate that is covered by the elastomeric composition.
Typically, such stretch zones have the following properties: (1) an
elastic resistance (i.e., the load at 25% strain) of at least about
0.05 N/cm, preferably from 0.05 N/cm to about 50 N/cm, more
preferably from about 0.05 N/cm to about 40 N/cm, and most
preferably from 0.25 N/cm to about 30 N/cm; (2) a percent set of
less than about 15%, preferably less than about 12% and more
preferably less than about 10%; and (3) a stress relaxation value
of less than about 40%, preferably less than about 30%, and more
preferably less than about 25%. Methods for measuring these
properties are given in the TEST METHODS section below.
[0043] In some embodiments an absorbent article may comprise
stretch zones that are associated so as to provide an array
thereof. Such an array may be disposed on only one region or
feature of the absorbent article or may extend across two or more
regions or features. The array can comprise intersecting or
non-intersecting stretch zones. Also, the stretch zones in the
array can either be parallel to one another or form a non-zero
angle with respect to each other. When the stretch zones in an
array are non-intersecting, individual stretch zones are cut off
and their properties may be measured. However, when the stretch
zones intersect within an array, it is not possible to separate
individual stretch zones. In such cases, the array should be
sampled and evaluated as described in the TEST METHODS section
below.
[0044] Suitable elastomeric compositions comprise thermoplastic
elastomers selected from the group consisting of styrenic block
copolymers, metallocene-catalyzed polyolefins, polyesters,
polyurethanes, polyether amides, and combinations thereof. Suitable
styrenic block copolymers may be diblock, triblock, tetrablock, or
other multi-block copolymers having at least one styrenic block.
Exemplary styrenic block copolymers include
styrene-butadiene-styrene, styrene-isoprene-styrene,
styrene-ethylene/butylenes-styrene,
styrene-ethylene/propylene-styrene, and the like. Commercially
available styrenic block copolymers include KRATON.RTM. from the
Shell Chemical Company of Houston, Tex.; SEPTON.RTM. from Kuraray
America, Inc. of New York, N.Y.; and VECTOR.RTM. from Dexco
Chemical Company of Houston, Tex. Commercially available
metallocene-catalyzed polyolefins include EXXPOL.RTM. and
EXACT.RTM. from Exxon Chemical Company of Baytown, Tex.;
AFFINITY.RTM. and ENGAGE.RTM. from Dow Chemical Company of Midland,
Mich. Commercially available polyurethanes include ESTANE.RTM. from
Noveon, Inc., Cleveland, Ohio. Commercial available polyether
amides include PEBAX.RTM. from Atofina Chemicals of Philadelphia,
Pa. Commercially available polyesters include HYTREL.RTM. from E.
I. DuPont de Nemours Co., of Wilmington, Del.
[0045] The elastomeric composition may further comprise processing
aids and/or processing oils to adjust the melt viscosity of the
compositions to the desired range. They include the conventional
processing oils, such as mineral oil, as well as other
petroleum-derived oils and waxes, such as paraffinic oil,
naphthenic oil, petrolatum, microcrystalline wax, paraffin or
isoparaffin wax. Synthetic waxes, such as Fischer-Tropsch wax;
natural waxes, such as spermaceti, carnauba, ozokerite, beeswax,
candelilla, paraffin, ceresin, esparto, ouricuri, rezowax, and
other known mined and mineral waxes, are also suitable for use
herein. Olefinic or diene oligomers and low molecular weight
polymers may also be used herein. The oligomers may be
polypropylenes, polybutylenes, hydrogenated isoprenes, hydrogenated
butadienes, or the like having a weight average molecular weight
between about 350 and about 8000.
[0046] In an important aspect of the present invention, the
elastomeric composition is substantially tackifier free. Tackifiers
are well known in the adhesive arts as a component that is added to
an adhesive composition so as to increase the adhesive properties
(e.g., peel force) thereof. This provides important benefits
because, in addition to increasing tack of an adhesive material, a
tackifier acts as a plasticizer for any polymers in the composition
with a resulting reduction in tensile properties due to the
presence of the tackifier. Preferred embodiments of the elastomeric
composition have a very low peel force with a standard substrate
(304 stainless steel a #2B finish from M.sup.c Master Carr of
Cleveland, Ohio) using the method described in copending U.S. Pat.
Application Ser. No. 60/557,272, entitled "Letterpress Application
of Elastomeric Compositions", filed in the names of Desai, et al.
on Mar. 29, 2004 (P&G Case No. 9592P). Suitable elastomeric
compositions have a peel force of less than about 3 N/cm, more
preferably, less than about 2 N/cm, even more preferably, less than
about 1 N/cm, and most preferably, less than about 0.8 N/cm when
evaluated using the method described in the aforementioned
application.
[0047] In one embodiment, a phase change solvent can be
incorporated into the elastomeric composition to lower its melt
viscosity, rendering the composition processable at a temperature
of 175.degree. C. or lower, without substantially compromising the
elastic and mechanical properties of the composition. Detailed
disclosure of the phase change solvents can be found in U.S. patent
application Ser. No. 10/429,432. Alternatively, the elastomeric
composition may also comprise low molecular weight elastomers
and/or elastomeric precursors of the above thermoplastic
elastomers, and optionally crosslinkers, or combinations thereof.
The weight average molecular weight of the low molecular weight
elastomers or elastomeric precursors is between about 45,000 and
about 150,000.
[0048] Suitable elastomeric compositions for use herein are elastic
without further treatment and they do not include any volatile
solvents whose boiling point is below 150.degree. C.
[0049] In certain embodiments the elastomeric composition may
include precursor components that are activated by a post treatment
step after the elastomeric composition has been deposited onto the
substrate, so as to improve or enhance its elasticity and other
properties including strength, modulus, and the like. For example,
the thermoplastic elastomers described in copending U.S. patent
application Ser. No. 10/610,605, filed in the name of Ashraf, et
al. on Jul. 1, 2003 that comprise an elastomeric block copolymer
having least one hard block and at least one soft block, a macro
photoinitiator, a processing oil, and optionally, a thermoplastic
polymer and/or a crosslinking agent contain such precursor
components. Typically, post-treatments include drying,
crosslinking, curing or polymerizing via chemical, thermal,
radiation means (e.g., ultraviolet radiation or electron beam
radiation), and combinations thereof.
[0050] In certain preferred embodiments, a stretch zone or an array
of stretch zones may comprise more than one elastomeric
composition. In such embodiments the first composition will have at
least one of: a greater elastic resistance than any of the other
elastomeric composition disposed onto the stretch zone or array of
stretch zones, a reduced set when compared to any of the other of
the elastomeric compositions disposed onto the stretch zone or
array of stretch zones and a reduced stress relaxation.
Alternatively, certain portions of an array of stretch zones may
comprise a first elastomeric composition and other portions may
comprise one or more different compositions.
[0051] The substrate provides a continuous medium for deposition of
the elastomeric composition and contributes at least a portion of
the ultimate strength of a stretch zone. A continuous medium is
important, for example for embodiments where the embodiment
comprises an array having spaced apart stretch zones. In certain
embodiments (e.g., as provided by a fibrous substrate), the
substrate can further provide a soft, cloth-like feel to the skin
for better wearer comfort. Suitable substrate materials include but
are not limited to: films, apertured films, foams, knitted fabric,
woven fibrous webs or nonwoven fibrous webs as are known in the
art. In some embodiments, the substrates are extensible nonwoven
webs made of polyolefin fibers or filaments, such as polyethylene,
or polypropylene. The substrate material may be elastic or
inelastic, extensible or inextensible, stretchable or
non-stretchable. Preferred substrates have a 3-dimensional
morphology (i.e., via spacing between fibers, projections, holes,
etc.) that facilitates the penetration of the thermoplastic
elastomer into the substrate as described below.
[0052] Suitable elastomeric compositions are preferably applied to
the substrate in a fluid or fluid-like state capable of effecting
at least partial penetration into the substrate Such partial
penetration must be sufficient so as to provide attachment between
the resulting elastomeric composition and the substrate such that
the composite remains intact through subsequent process steps,
shipment and the article wear cycle. Preferably, the elastomeric
composition penetrates only enough to provide the desired integrity
during subsequent processing and use of the article. For example,
if the substrate is a fibrous substrate, it is believed that
elastomeric composition penetration to a depth of about one or two
fiber diameters is sufficient to provide such integrity. Means to
accomplish sufficient penetration of the substrate of the
thermoplastic elastomer upon deposition onto the substrate
includes, among other mechanisms, absorption of the elastomer into
the substrate matrix, penetration through all or a portion of the
thickness of the substrate, engulfing or entrapment of
3-dimensional protrusions from the substrate (i.e., entanglement
between the substrate and the composition), penetration of holes in
the substrate, wetting of a 3-dimensional surface of the substrate,
and the like.
[0053] To facilitate such partial penetration, the elastomeric
composition suitably has a melt viscosity from about 1 to about
1000 Pas at 175.degree. C., 5% strain and a shear rate of 1 s.sup.1
according to the method disclosed in published U.S. Pat.
Application No. 2003/0091807A1. Preferably, the melt viscosity is
between about 5 and about 500 Pas, and more preferably from about
10 to about 400 Pas. Such elastomeric compositions are suitable for
use in application processes that operate at a lower viscosity
and/or lower temperature than are typical melt extrusion and/or
fiber spinning processes.
[0054] The elastomeric composition may be applied to a stretch zone
to achieve a total add-on level of from about 5 to about 200
g/m.sup.2, preferably from about 20 to about 150 g/m.sup.2, and
more preferably from about 50 to about 100 g/m.sup.2.
[0055] An array of stretch zones may have open areas not covered by
the elastomeric composition ranging from about 5% to about 90% of
the total surface area of the region, preferably from about 10% to
about 60%, and more preferably from about 20% to about 40%. As will
be recognized, the required open area depends on the specifics or
the region or feature where the array is disposed. The selective
deposition of elastomeric compositions preferably uses less of the
materials than would otherwise be required by the conventional
lamination technology using films or sheets. The fibrous substrate
in combination with the selective deposition of the elastomeric
composition can provide the resulting composite with lower basis
weight and higher breathability than a laminate containing a
fibrous web layer and a film or sheet layer.
[0056] As will be recognized, the stretch zones described herein
may also be used in combination with stretch features described in
the art (Such stretch features include, but are not limited to an
elasticized waist, an elasticized belt, an ear, a side panel, a leg
cuff, or a fastener component. See below for a discussion of such
features in the section--Diaper Component Description Applicable to
All Embodiments of Present Invention). As will be recognized,
combining the stretch zones of the present invention with stretch
features from the art may provide benefits that neither approach
could provide by itself. For example, an elastomeric film could be
used to provide a first level of elastic resistance to a stretch
feature formed using an elastomeric, breathable three dimensional
composite material as described in U.S. Pat. No. 6,303,208 and
portions of the stretch feature could further comprise stretch
zones of the present invention to enhance the elastic resistance in
predefined positions on the stretch feature. Similar structures can
also be made by replacing the elastomeric film with one or more
elastomeric strands or fibers and providing stretch zones according
to the present invention thereto.
[0057] Referring to FIG. 1, an absorbent article in the form of an
open-style or taped diaper 10 is depicted. It should be understood
that while FIGS. 1-3 depict a diaper, the present invention also
contemplates other wearable absorbent articles, such as catamenial
and adult incontinence products, that encircle or enclose at least
a portion of a wearer's anatomy or which are otherwise secured to a
wearer. The diaper 10 has a longitudinal centerline 12 and a
lateral centerline 14 as a frame of reference for this discussion.
The diaper 10 may have a pair of opposed end edges 16 and 18, a
pair of opposed side edges 20 and 22, a rear waist region 24, a
front waist region 26, a crotch region 28 disposed intermediate the
front and rear waist regions 26 and 24, respectively, and a pair of
leg regions 30 and 32. The exact size of these various regions vary
according to the size of the diaper 10, but generally speaking, the
crotch region 28, front waist region 26 and rear waist region 24
represent equal one-third portions along the longitudinal
centerline 12. The leg regions 30 and 32 generally represent the
one-quarter areas across the width of the diaper 10 in the crotch
region 28, and the crotch region 28 itself, represents the
remaining center two-quarters or one-half the width of diaper
10.
[0058] The diaper 10 also may comprise one or more ears or side
panels 34, 36, 38 and 40 disposed generally laterally outboard of
the side edges 20, 22 in the front waist region 26 and/or rear
waist region 24. In closable diaper 10 at least one fastener
element 42 is disposed on one or more of side panels 34 and 36 and
is adapted to be secured to at least a portion of the
longitudinally opposing front side panels 38 and 40, or a portion
of the outer surface of the front waist region 26 or a component
thereof. An accompanying fastener element 44 is shown in a folded
back configuration to expose the mechanical fasteners 46, which
shown as hooks for a hook-and-loop fastening systems commercially
available from 3M or Velcro Industries. The fastener element 44 may
be capable of engaging loop material embodied in a landing zone 27
located on the outer surface of the diaper 10.
[0059] Any one or more of regions 24, 26, 28, 30, 32, 34, 36, 38,
40, 42 or 44 may comprise a stretch zone or array of stretch zones
as may be required to provide the desired elasticity in accordance
with the present invention. In this way, the diaper 10 may
preferably be configured to adapt to the specific wearer's anatomy
upon application and to maintain coordination with the wearer's
anatomy during wear (i.e., the fit should remain the same with
minimal sagging, achieving sustained fit). Any region of the diaper
10 may include a stretch zone or array of stretch zones. The front
waist region 26 and/or the rear waist region 24 and/or side panel
regions 34, 36, 38 and/or 40 preferably include at least one
stretch zone of thermoplastic elastomer in order to accommodate a
wider range of wearer waist dimensions (i.e., provide a wider fit
range) and/or to provide sufficient tension around the waist
circumference of the wearer. This provides sufficient normal force
to the wearer's skin so as to anchor the diaper 10 with respect to
the wearer's anatomy, thereby providing sustained fit.
[0060] Each stretch zone may have continuous or discontinuous
properties in any direction wherein the varying properties include
chemical composition, elasticity, extensibility, maximum
elongation, other stress/strain properties, vectors or angles,
basis weight, geometry, dimensions, 3-dimensional morphology,
visual distinctiveness, and the like. A stretch zone may have
continuous properties (e.g., because the elastomeric composition,
substrate material, treatment, etc.) has relatively homogeneous
properties. Alternatively, stretch zones may have discontinuous
properties due to provision of non-homogeneous properties thereto.
An array may comprise stretch zones having the same or different
properties. Suitable stretch zone arrays include a plurality of
straight or curved lines or bands, rectilinear shapes, curvilinear
shapes, other regular or irregular geometric shapes, and
combinations thereof which will be described in more detail
hereinafter. Two stretch zones may be longitudinally separated or
adjacent, laterally separated or adjacent, or the stretch zones may
be at least partially overlapping in such arrays. Within an array,
the individual stretch zones may vary in property, geometry,
relative orientation, spacing, or elasticity or extensibility. In
certain embodiments, at least a portion of at least one stretch
zone may be visually distinct. Stretch zones may be combined with
other elastic, extensible, or inextensible materials, such as
films, webs, strands, and the like to form laminates.
[0061] An exemplary diaper chassis comprising arrays of stretch
zones is diaper chassis 250 as is shown in FIG. 2. The diaper
chassis 250 may include a liquid impermeable backsheet and an outer
cover made of a nonwoven material. Other chassis components may be
included but are not depicted for purposes of clearly showing the
array of stretch zones of the present invention. In one embodiment,
a thermoplastic elastomer may be disposed on a standard liquid
impermeable backsheet material in a way which creates different
arrays of stretch zones in regions 252, 254, 256, 258 and 260. By
way of example, an array in region 252 may comprise a first
thermoplastic elastomer composition, while arrays in regions 254,
256, 258 and/or 260 may comprise a different composition or
comprise the first composition disposed in a different
configuration (thickness, width, pattern, etc.). In certain cases
for purposes of enhancing fit on a wearer, the various stretch zone
properties are symmetrical in that arrays in regions 252 and 260
have similar properties, arrays in regions 254 and 258 also have
similar properties while an array in region 256 has a third type of
elastic property. It should be understood, however, that this is
not necessary and the individual arrays in regions 252, 254, 256,
258 and 260 may vary individually and widely in terms of elastic
properties, size, shape, and composition without deviating from the
scope of the invention.
[0062] Reference is now made to FIGS. 3, 4 and 5A-B which show a
pant 370. The term "pant", as used herein, refers to disposable
garments having a waist opening and leg openings designed for
infant or adult wearers. A pant may be preformed by any suitable
technique including, but not limited to, joining together portions
of the article using refastenable and/or non-refastenable bonds
(e.g., seam, weld, adhesive, cohesive bond, fastener, etc.). A pant
may be preformed anywhere along the circumference of the article
(e.g., side fastened, front waist fastened). While the term "pant"
is used herein, pants are also commonly referred to as "closed
diapers", "prefastened diapers", "pull-on diapers", "training
pants" and "diaper-pants". Suitable pants are disclosed in U.S.
Pat. No. 5,246,433, U.S. Pat. No. 5,569,234, U.S. Pat. No.
6,120,487, U.S. Pat. No. 6,120,489, U.S. Pat. No. 4,940,464, U.S.
Pat. No. 5,092,861, U.S. patent application Ser. No. 10/171,249,
entitled "Highly Flexible And Low Deformation Fastening Device",
filed on Jun. 13, 2002; U.S. Pat. No. 5,897,545, U.S. Pat. No.
5,957,908.
[0063] Pant 370 may include stretch zones to impart the desired
elastic properties so that it can be donned easily and sustain
better fit and comfort. Similar to the diaper 10, stretch zones may
be included anywhere on the pant 370. FIG. 3 is a perspective view
of pant 370 and FIG. 4 shows pant 370 in a plan view. As shown
therein, pant 370 has a longitudinal centerline 360, lateral
centerline 362, a front waist region 364 (adjacent front waist edge
365), a crotch region 366 and a rear waist region 368 (adjacent
rear waist edge 369). As can be seen most clearly in FIGS. 5A-B,
pant 370 may include an absorbent assembly including liquid
permeable topsheet 372, a liquid impermeable backsheet 374, and an
absorbent core 376 disposed between the topsheet 372 and the
backsheet 374. An outer cover 378 (typically comprising a nonwoven)
is disposed on the outer surface of the pant 370. Two pair of side
panels 380, 382 and 384, 386 are attached to the outer cover 378 in
the front waist region 364 and the rear waist region 368, which in
turn, is attached to the backsheet 374 of the absorbent assembly so
as to form a pair of leg openings and a waist opening for the
wearer. Preferably, stretch zones areas are disposed in at least
one of the side panels 380, 382, 384 and/or 386. The stretch zones
of pant 370 may also comprise the waist regions 364, 366, barrier
leg cuffs 388 and 390. For example either or both of the leg
elastics 392, 394, and/or the barrier leg cuff elastics 396, 398
could comprise an elastomeric composition where the composition is
disposed on a substrate so as to form a stretch zone in one of the
features shown in FIGS. 5A and 5B.
[0064] Belt structures (not shown) may also comprise the stretch
zones of the present invention. One such alternative structure
comprises the ear and/or side panel and at least a portion of the
waist functionality. In another alternative belt structure, a belt
completely encircling a wearer's waist (i.e., a 360 degree belt)
may be formed, for example, by depositing one or more laterally
oriented stretch zones (or an array thereof) adjacent the front and
rear waist edges 365, 369 so as to form a band of tension about the
wearer's waist. Such stretch zones could also comprise those shown
in FIGS. 7A, 7B and 8A-D.
[0065] Reference is made to FIGS. 6A-I in which various side panels
604, 606, 608, 610 are depicted for a closable open or taped diaper
612. As will be recognized, the side panels 604, 606, 608, 610 each
have an inner edge 634, 636, 638 and 640 disposed at a predefined
angle (usually parallel) with respect to longitudinal centerline
650. It should be understood that the side panels 604, 606, 608 and
610 as described herein are interchangeable with any of the side
panels or ears described in FIGS. 1-4 of the diapers 10 or 250 or
pant 370 and with any of side panels 605, 607, 609, 611, 613, 615,
617, and 619 of FIGS. 6B-6I. The stretch zone arrows 614, 616 are
depicted to show exemplary force vectors desirable of typical side
panels in diapers. The size of a given stretch zone in a region of
the diaper 612 is dependent on the function of the stretch zone and
the desired tension/extension vectors 614, 616 in that given region
of the diaper 612. Each stretch zone may be smaller or larger than
the region of the diaper 612 in which it is primarily disposed. A
given stretch zone may also overlap other regions of the diaper
612.
[0066] Referring to FIGS. 6B-6I, various linear stretch zones 618
of side panel 605 may be configured as lines or strands generally
having widths less than about 2 mm and typically less than about 1
mm. Linear stretch zones 618 may also be configured as bands
generally having widths between about 2 mm and about 40 mm and
aspect ratios ranging from about 2:1 to about 100:1. Linear stretch
zones 618 may also be disposed at an angle with respect to the
lateral centerline 651 (FIGS. 6B and 6F). Preferred angles are in
the range 0.+-.70.degree.. Stretch zones having a predominately
lateral orientation are generally wider and have a higher modulus
than those having a generally longitudinal orientation. Curved
stretch zones 620 may be either concave or convex with respect to
the longitudinal or lateral centerlines 650, 651, or both and may
have radii of curvature greater than about 1 mm, preferably greater
than about 10 mm, more preferably greater than about 50 mm. The
curvature may optionally be variable over the length or "path" of
the stretch zone 620. Typically, the thickness of stretch zones 618
and/or 620 may be in the range of about 0.02 mm to about 5 mm and
the basis weight is in the range of about 20 g/m.sup.2 to about 300
g/m.sup.2.
[0067] Additional exemplary embodiments of the invention are shown
in FIG. 6C with side panel 607, FIG. 6D with side panel 609, FIG.
6E with side panel 611, FIG. 6F with side panel 613, FIG. 6G with
side panel 615, FIG. 6H with side panel 617, and FIG. 6I with side
panel 619. All of the side panels 609, 611, 613, 615, 617, 619 may
be integral with or separately attached to the diaper chassis of
the diaper 10 or pant 370 described previously. Also all of the
stretch zones 618 and 620 comprise an elastomeric composition as
described herein. FIGS. 6D-6I show additional stretch zones 622
applied to or formed as part of the fastener element 624 to impart
other desired elastic properties of the present invention.
[0068] Alternatively, one or more, but not all, of stretch zones
618, 620 may comprise an elastomeric composition that differs from
the composition used to form the remainder of the stretch zones
618, 620. For example, referring to FIGS. 6B and 6C, certain
stretch zones 618 that lie longitudinally outboard (i.e., closer to
rear waist end 635) of the remainder of stretch zones 618 may
comprise an elastomeric composition with a higher elastic modulus
so as to provide a larger elastic resistance around the
circumference of a wearer's waist. Alternatively (FIG. 6B), stretch
zones 618 may comprise a first elastomeric composition and stretch
zones 620 may comprise a second elastomeric composition. Again,
stretch zones 618 lie longitudinally outboard of stretch zones
620.
[0069] Alternatively, an array of linear stretch zones 618 or
curved stretch zones 620 or both may comprise a spiral or an
overlapping or entangled configuration, for example a cross hatch
array. Suitable stretch zone shapes (not shown) include rectangles,
circles, ellipses, diamonds, triangles, parallelograms, trapezoids,
wedges or other sections of circles or ellipses, other polygons, or
other irregular enclosed shapes.
[0070] One particularly preferred embodiment of an array of stretch
zones is shown in FIG. 6I where side panel 619 comprises a pair of
cross hatch arrays 625, 627. As shown therein, both of arrays 625,
627 comprise a plurality of linear stretch zones 618 in an
overlapping, cross hatch pattern where the individual stretch zones
618 have either a predominately lateral orientation or a
predominately longitudinal orientation. As will be recognized and
described herein, the stretch zones 618 can also be at an angle
other than 0.degree. or 90.degree. with respect to the
centerlines.
[0071] In one embodiment of side panel 619 shown in FIG. 6I, array
625 has different mechanical properties than array 627. In
particular, first array 625 has a lower available strain than
second array 625. As used herein, "available strain" is the strain
at which there is an abrupt increase in elastic resistive force in
response to an applied elongation. Such change typically occurs
when the applied elongation has reached the point where a
meaningful portion of the resistive force is provided to a stretch
zone by the substrate. At applied elongations less than the
available strain the elastic resistive force is substantially
provided to the stretch zone by the elastomeric composition. This
difference in available strain is because array 627 must be able to
stretch to a greater extent in order to conform to the full range
of movement of a wearer's legs. Similarly, first array 625 has
different elastic resistance than second array 627. Suitably, array
625 has an elastic resistance at 25% strain of between about 0.05
N/cm and about 50 N/cm, preferably between about 0.1 N/cm and about
40 N/cm, more preferably between about 1 N/cm and about 30 N/cm.
The ratio of elastic resistance at 25% elongation of array 625 to
the elastic resistance at 25% elongation of array 627 is suitably
greater than about 1.25:1, preferably greater than about 1.5:1,
more preferably between about 2.0:1 and about 6.0:1. The difference
between available strains of arrays 625 and 627 is suitably at
least about 25% (i.e., if array 625 has an available strain of
about 25%, then the available strain of array 627 would be at least
about 50%), preferably the difference is at least about 50%.
[0072] Referring to FIGS. 7A and 7B, a diaper 730, similar to
diaper 10 and having a longitudinal centerline 738, a lateral
centerline 739, a rear waist end 735 and a front waist end 737, is
depicted in which the waist and thigh portions of the side panel
732, 733 preferably comprise different stretch zones 734 and 736,
varying in tension and/or angle as shown. Preferably, the side
panel stretch zone 734 nearer the rear waist end 735 of diaper 730
may be oriented at an angle of about 0 to about minus 50 degrees
from the lateral centerline 739, more preferably between about -5
degrees and about -40 degrees from the lateral centerline 739.
Preferably, the stretch zone 736 may be oriented at an angle of
about 0 to about plus 70 degrees from the lateral centerline 739,
more preferably between about +20 degrees and about +60 degrees
from the lateral centerline 739. One preferred side panel 732
stretch zone embodiment includes a stretch zone 734 oriented at
about -10 to -20.degree. from the lateral centerline 739 and a
stretch zone 736 oriented at about +20.degree. to +50.degree. from
the lateral centerline 739.
[0073] In certain preferred embodiments, at least one of the side
panel stretch zones 736 may be aligned with the end of the outer
leg cuff elastics 740, 742 in order to provide an effective
extension of the leg cuff elastic, thereby encircling a wearer's
leg with a combination of stretch zone 736 and 740, 742 shown in
FIG. 7B. That is, the outer leg cuff elastics 740, 742 and the side
panel stretch zones cooperate to provide a substantially continuous
line of force to encircle a wearer's legs.
[0074] In other preferred embodiments, at least one of the waist
regions adjacent rear waist end 735 or front waist end 737 is also
provided with one or more waist stretch zones 744, 745, 746, 747.
In such embodiments the waist stretch zones 744, 745, 746, 747 may
be aligned with the ear stretch zones 734 that are disposed
adjacent to the rear waist end 735 so as to provide a substantially
continuous line of force encircling a wearer's waist. Depending on
the design of diaper 730, such a line of force may follow the low
motion zone of a wearer (see below) or be juxtaposed with another
portion of a wearer's anatomy while encircling the waist.
[0075] Regardless of the specific construction, composition, or
geometry, or stretch properties of the side panel 732, the stretch
zones 734 and 736 in the waist and thigh portions are preferably
capable of substantially independent action with respect to one
another. Certain embodiments may include an additional side panel
stretch zone (not shown) functioning as a transition between the
leg and thigh portions, i.e., a "transition zone". The transition
zone may have distinctly different stretch properties (or even not
be elastic at all) than either the leg or waist zones and functions
to decouple or separate the deformations caused by the leg and
waist panels, allowing them to act independently without
interaction with each other. In embodiments comprising a side panel
transition zone, the transition zone may be substantially
extensible to further promote independent action between the waist
and thigh zones of the side panel, while still providing sufficient
stretch to accommodate the relative movements of the waist and
thigh zones while being worn by a wearer, helping to control
buckling and/or folding of the transition region.
[0076] Referring to FIGS. 8A-D, at least one array 850 of stretch
zones 851 may be included in the waist region of the diaper 830.
The array 850 of stretch zones 851 may have similar or varying
degrees of elasticity or extensibility and may assume any geometry
or orientation. For example, in FIG. 8A the array 850 of stretch
zones 851 is located at the waist end 835 of diaper 830, whereas
FIG. 8B shows another embodiment in which the array 850 is offset
from waist end 835. It may be preferable to have array 850 located
generally in the lower back waist area as shown on a partial side
view of wearer 852 in FIG. 8C. In this way, the maximum fit and
comfort will be experienced by the wearer 852 as the tension is
applied by the article to the wearer's body at or immediately above
the convexity of the buttocks (i.e., the "buttocks shelf"),
contributing to the overall anchoring capability of the article
(i.e., its ability to resist sagging). Said another way, the array
850 and stretch zones 862, 864, 866, 868 and 870 (shown in FIG. 8D)
co-operate to maintain diaper 830 in an optimal fit configuration
with respect to the low motion zone 853 (i.e., the line or zone
connecting the lumbar curve of the back over the hips to under the
abdominal crease of a wearer's body 852) so as to maximize the
performance thereof. For a more detailed discussion of low motion
zones see U.S. Pat. No. 5,358,500.
[0077] In certain preferred embodiments as shown in the partial
plan view of diaper 830 in FIG. 8D, array 850 comprises one or more
stretch zones 854 having higher localized elastic resistances
(i.e., a "high tension" stretch zone 854) aligned with the waist
end 835. The high-tension stretch zones 854 may be adjacent the
waist end 835 or may be disposed inboard thereof. Typically, the
high-tension stretch zones 854 are disposed between about zero and
30 mm from the waist end 835 of the diaper 830. Preferably, the
high-tension stretch zones 854 are disposed less than about 20 mm
from the waist end 835. Generally, an array 850 of the high-tension
stretch zones 854 may correspond to an area 856 on the wearer 852
body immediately above or at the upper curvature of the buttocks
858 where the high-tension stretch zone 854 functions to provide
additional anchoring capability for the diaper 830 by applying a
normal force to the geometric "shelf" created by the buttocks 858.
The high tension stretch zones 854 additionally hold the waist end
835 of the diaper 830 against the wearer's back 860 preventing back
waist gapping.
[0078] In embodiments comprising an array 850 of stretch zones 854
at or near the waist end 835 of diaper 830 and extending through
multiple regions of the back waist and crotch of the article, the
remaining area of the waist end 835 may have either a lower elastic
resistance, may be primarily extensible, or may comprise areas with
either property. In any case, this waist end 835 area (i.e., the
area not including the stretch zones 850 or 854) may be a
low-tension zone.
[0079] Referring again to FIG. 8D, stretch zones 862 may be
substantially parallel to the proximal edges 864 and 866 of side
panels 832 and 833, respectively. Optionally, transition stretch
zones 868 and 870 may be disposed intermediate stretch zones 854
and 868, 870. The stretch zone 854 may provide a primary anchoring
function and stretch zones 862, 868 and 870 may provide a dynamic
leg motion accommodation function. While stretch zones 854, 868 and
870 all provide an elastic resistance, the present invention allows
tailoring such forces in both to degree and direction to meet the
different needs of the anchoring and motion accommodation
functions. Referring again to FIG. 8C, preferably, the region
covering a wearer's buttocks 858 comprises at least one extensible
stretch zone so as to provide adequate coverage thereof, conform to
the wearer 852 shape, and relieve stress in the transition region
between the crotch as and the waist end 835 region of the diaper
830 (FIGS. 8A, B and D) as it goes between the wearer 852 legs. As
described previously, side panels 832 and 833 may comprise distinct
stretch zones 854, 862, 868 and 870 having different functions and
may be single stretch elements having different properties
throughout the stretch zone or have physical delineations between
stretch zones 854, 862, 868 and 870 such as slits, holes, or other
deformation. However, stretch zones 854 and 862 preferably comprise
stretch elements, or arrays of stretch elements, having different
properties, geometry, and/or dimensions from each other
[0080] Typically, stretch zones 854 exhibit an elastic resistance
of at least about 0.05 N/cm when strained to 25% elongation.
Preferably, stretch zone 854 exhibits an elastic resistance of
between about 0.05 N/cm and about 50 N/cm when strained to 25%
elongation, more preferably between 0.1 N/cm and about 40 N/cm and
most preferably between 1 N/cm and about 30 N/cm. Preferably,
stretch zones 854 experience less than about 40% force relaxation
and less than about 15% set. Typically, stretch zones 854 will have
a maximum elongation of at least about 25%, preferably between
about 50% and about 300%. Typically, stretch zones 862 exhibit an
elastic resistance of at least about 0.05 N/m when strained to 25%
elongation. Preferably, the stretch zones 862 exhibits an elastic
resistance of between about 0.1 N/cm and about 8 N/cm when strained
to 25% elongation. Preferably, stretch zones 862 experience less
than about 40% force relaxation and less than about 15% set.
Typically, stretch zones 862 may have a maximum elongation of at
least about 25%, preferably between about 50% and about 200%.
Additionally, stretch zones 868 and 870 may exhibit a lower
resistive force upon elongation than either stretch zones 854 and
862 at a given extension. Typically, the ratio of elastic
resistance of stretch zone 854 to stretch zone 868 or 870 is at
least 1.25:1, preferably at least 1.5:1, and most preferably
between about 2.0:1 and 6.0:1. Regardless of the stretch properties
of the individual stretch zones 854, 862, 68 and 870, the overall
tension of the side panels 832 and 833 region when extended to 25%
is preferably less than 20 N, and the force relaxation is less than
40%.
[0081] Referring to FIG. 9, showing diaper 910 is depicted in which
the front waist region 926 may comprise at least one stretch zone
972 The function of stretch zone 972 is to dynamically accommodate
the contraction and expansion cycles of the wearer's abdomen as the
wearer moves and/or changes position, preventing front waist
sagging. Stretch zone 972 is preferably substantially aligned with
the front waist end 918 of the diaper 910. In closable versions of
diaper 910 including a fastening landing zone 927 disposed in or
near the front waist end 918, the landing zone 927 may be shaped in
a configuration presenting a concavity 928 to the front waist end
918 of the diaper 910. In these embodiments, stretch zone 972 may
at extend into the landing zone concavity 928, as shown in FIG.
9.
[0082] While the buttocks region 974 located in the back waist
region in proximity to the crotch region 976 as shown on diaper 910
may comprise either elastic or extensible portions, or a
combination thereof, in preferred embodiments, the buttocks region
974 may be provided with a pattern of thermoplastic elastomer so as
to provide a low level of elastic resistance to a stretch zone
therein causing the buttocks region 974 to better conform to a
wearer's anatomy so as to accommodate the largest wearer
circumference (i.e., the buttocks), including the volume of the
absorbent core 950, allowing the buttocks region 974 to have a
lower on-wearer tension than the rear waist end 916 region. The
buttocks region 974 may have stretch zones with extensibility that
allows for a smoother geometric transition from the constricted
crotch region 976 between the wearer's legs to the side panels 934
and 936 which may have stretch zones similar to those described in
FIG. 9D for anchoring. The buttocks region 974 preferably may
elongate further than the waist end 916 region to accommodate the
wearer's anatomic shape.
[0083] Referring to FIG. 10, another embodiment, diaper 1030, is
shown in which a stretch zone 1078 in the waist region may be
preferably aligned with the side panels 1032 and 1033 and/or the
fasteners 1080 and 1082 disposed on side panels 1032 and 1033 in
order to create a substantially continuous line of tension around
the waist to promote conforming sustained fit. As shown in FIG. 10,
the stretch zone 1078 preferably at least partially overlaps one of
the two imaginary lines 1084 and 1086 that connect the
longitudinally outboard edges 1092, 1094 of fasteners 1082.
[0084] Referring to FIG. 11, an array 1104 of stretch zones is
shown on diaper 1110 in the front crotch region 1128 spanning into
the front waist region 1126. The stretch zones comprising array
1104 may be primarily parallel to longitudinal centerline 1112 of
the diaper 1110 allowing better fit in the front crotch region 1128
by providing an elastic resistance along the centerline 1112 as
depicted by arrow 1106. Array 1104 should only have a low elastic
resistance so as not to pull the front of diaper 1110 down,
resulting in sagging. Also, array 1104 should have low available
strain so that it hits a force wall after straining a small amount
in the machine direction for improved coverage in the front waist
area. Typically, array 1104 provides an elastic resistance at 25%
strain of between about 0.005 N/cm and about 5 N/cm preferably
between about 0.01 N/cm and about 2 N/cm. In certain embodiments
the elastic resistance ranges from about 0.1N to about 1 N/cm.
[0085] The available strain of the array 1104 in the machine
direction is less than about 100%, preferably less than about 50%
and more preferably less than about 25%. For the whole diaper, the
maximum extension in the machine direction at a load of 5 N is less
than about 20 cm, preferably less than about 10 cm, and more
preferably less than about 5 cm. Preferably, the area of greatest
extensibility is substantially aligned with and overlapping the
longitudinal centerline 1112. In another embodiment, array 1104 can
be replaced by an individual stretch zone (not shown) providing an
equivalent elastic resistance. Preferably, the area of greatest
extensibility is substantially aligned with and overlapping the
longitudinal centerline 1112. In another embodiment, array 1104 can
be replaced by an individual stretch zone (not shown) providing an
equivalent elastic resistance. Alternatively, array 1104 may also
comprise stretch zones laterally outboard of and at an angle to the
longitudinal centerline 1112 and diverging toward the front corners
of diaper 1110 as shown by arrows 1108 and 1109 in FIG. 11. These
lines or arcs of tension may be primarily elastic so as to provide
suitable suspension for the absorbent core and wearers' waist held
therein by "connecting" these loads to the anchoring zones of the
article via suitable lines, or "paths" of tension. Alternatively,
these "load distribution elements" may comprise lines, arcs, bands,
or other geometric regions of inextensibility in the surrounding
areas of crotch region 1128 and front waist region 1126 and may
extend to accommodate the wearer's rise, while the outboard
inextensible load distribution elements provide support for a waste
load.
[0086] Referring to FIG. 12, another embodiment, diaper 1210 is
shown in which leg regions 1230 may comprise stretch zones 1212 and
1214. Preferably, stretch zones 1212 and 1214 are substantially
parallel to longitudinal centerline 1205 and are highly elastic.
Alternatively, stretch zones 1212 and 1214 may also be curvilinear
or at an angle to the longitudinal centerline 1205. Portions of the
leg regions 1232 may comprise one or more additional extensible
stretch zones 1216 and 1218 that are oriented at an angle to the
longitudinal centerline 1205 of diaper 1210. Typically, stretch
zones 1216 and 1218 may be at an angle of about 45 degrees to about
90 degrees, and preferably at an angle of 45 to 60 degrees, from
the longitudinal centerline 1205.
[0087] In yet another embodiment of the present invention, the
stretch zones described herein can also be provided to a topsheet.
For example, diaper 1310 is shown in FIG. 13. Diaper 1310 comprises
a topsheet 1324, a backsheet 1326 and core 1328 therebetween.
Topsheet 1324 has also been provided with aperture 1330 which has a
periphery 1340. As can be seen in FIG. 13, topsheet 1324 is further
provided with a pair of laterally opposed stretch zones 1343, 1344
which also comprise a portion of periphery 1340. Stretch zones
1343, 1344 extend from front waist region 1336 through crotch
region 1337 to rear waist region 1338. Stretch zones 1343, 1344
provide an elastic resistance causing diaper 1310 to assume a
cup-like configuration in the relaxed state shown in FIG. 13. This
elastic resistance helps insure desirable bodily contact between
topsheet 1324 and a wearer's body. In the preferred embodiment
shown in FIG. 13, this bodily contact helps insure that aperture
1330 and topsheet 1326 combine to create a sag tolerable anal cuff
to help isolate bodily waste from contact with the wearer's body.
Such cuffs are described in greater detail in copending US Patent
Application Publication No. 2004/0193134 A1 entitled "Articles with
Cuffs", filed in the name of Mueller, et al., published on Sep. 30,
2004.
Diaper Component Description Applicable to All Embodiments of
Present Invention
[0088] All of the embodiments in FIGS. 1-13 have diaper components
which may take any one or more of the materials, designs, and
methods of assembly described hereinafter without departing from
the scope of the present invention. While any of the article
components may be assembled in a variety of well known
configurations, exemplary diaper configurations are described
generally in U.S. Pat. No. 3,860,003; U.S. Pat. No. 5,151,092; and
U.S. Pat. No. 5,221,274; and U.S. Pat. No. 5,554,145; U.S. Pat. No.
5,569,234; U.S. Pat. No. 5,580,411; and U.S. Pat. No.
6,004,306.
[0089] Exemplary breathable materials may include materials such as
woven webs, nonwoven webs, composite materials such as film-coated
nonwoven webs, microporous films such as manufactured by Mitsui
Toatsu Co., of Japan under the designation ESPOIR NO and by Exxon
Chemical Co., of Bay City, Tex., under the designation EXXAIRE, and
monolithic films such as manufactured by Clopay Corporation,
Cincinnati, Ohio under the name HYTREL blend P18-3097 Some
breathable composite materials are described in greater detail in
U.S. Pat. No. 6,187,696; U.S. Pat. No. 5,938,648; U.S. Pat. No.
5,865,823; and U.S. Pat. No. 5,571,096.
[0090] The article may include a structural elastic-like film web
is an extensible material that exhibits an elastic-like behavior in
the direction of elongation without the use of added elastic
materials and is described in more detail in U.S. Pat. No.
5,518,801. In alternate embodiments, the backsheets may comprise
elastomeric films, foams, strands, or combinations of these or
other suitable materials with nonwovens or synthetic films.
[0091] Exemplary absorbent structures for use as the absorbent core
are described in U.S. Pat. No. 4,610,678; U.S. Pat. No. 4,673,402;
U.S. Pat. No. 4,834,735; U.S. Pat. No. 4,888,231; U.S. Pat. No.
5,137,537; U.S. Pat. No. 5,147,345; U.S. Pat. No. 5,342,338; U.S.
Pat. No. 5,260,345; U.S. Pat. No. 5,387,207; and U.S. Pat. No.
5,625,222.
[0092] Suitable absorbent and nonabsorbent sublayers are described
in European Patent Application No. EP 0 847 738 A1 and U.S. Pat.
No. 5,941,864. Further, the sublayer, or any portion thereof, may
include or be coated with a lotion or other known substances to
add, enhance or change the performance or other characteristics of
the element.
[0093] Some exemplary surface fastening systems are disclosed in
U.S. Pat. No. 3,848,594; U.S. Pat. No. B1 4,662,875; U.S. Pat. No.
4,846,815; U.S. Pat. No. 4,894,060; U.S. Pat. No. 4,946,527; the
herein before referenced U.S. Pat. No. 5,151,092; and U.S. Pat. No.
5,221,274. An exemplary interlocking fastening system is disclosed
in U.S. Pat. No. 6,432,098. The fastening system may also: provide
a means for holding the article in a disposal configuration as
disclosed in U.S. Pat. No. 4,963,140; include primary and secondary
fastening systems, as disclosed in U.S. Pat. No. 4,699,622; means
to reduce shifting of overlapped portions or to improve fit as
disclosed in U.S. Pat. No. 5,242,436; means to resist gapping at a
wearer's belly as disclosed in U.S. Pat. No. 5,499,978 in U.S. Pat.
No. 5,507,736 and in U.S. Pat. No. 5,591,152.
[0094] Suitable training pants and pull-on diapers are disclosed in
U.S. Pat. No. 5,246,433; U.S. Pat. No. 5,569,234; U.S. Pat. No.
6,120,487; U.S. Pat. No. 6,120,489;U.S. Pat. No. 4,940,464; and
U.S. Pat. No. 5,092,861.
[0095] Examples of diapers with elasticized side panels are
disclosed in U.S. Pat. No. 4,857,067; U.S. Pat. No. 4,381,781; U.S.
Pat. No. 4,938,753; the herein before referenced U.S. Pat. No.
5,151,092; U.S. Pat. No. 5,221,274; U.S. Pat. No. 5,669,897; U.S.
Pat. No. 6,004,306, and the aforementioned U.S. Pat. No.
6,300,208.
[0096] U.S. Pat. No. 3,860,003 describes a disposable diaper which
provides a contractible leg opening having a side flap and one or
more elastic members to provide an elasticized leg cuff (a
gasketting cuff). U.S. Pat. Nos. 4,808,178 and 4,909,803 describe
disposable diapers having "stand-up" elasticized flaps (barrier
cuffs) which improve the containment of the leg regions. U.S. Pat.
Nos. 4,695,278 and 4,795,454 describe disposable diapers having
dual cuffs, including gasketting cuffs and barrier cuffs.
[0097] Embodiments of the present invention may also include
pockets for receiving and containing waste, spacers which provide
voids for waste, barriers for limiting the movement of waste in the
article, compartments or voids which accept and contain waste
materials or any combinations thereof. Examples of pockets and
spacers for use in absorbent products are described in U.S. Pat.
No. 5,514,121; U.S. Pat. No. 5,171,236; U.S. Pat. No. 5,397,318;
U.S. Pat. No. 5,540,671; U.S. Pat. No. 6,168,584; U.S. Pat. No.
5,306,266; and U.S. Pat. No. 5,997,520. Examples of compartments or
voids are disclosed in U.S. Pat. No. 4,968,312; U.S. Pat. No.
4,990,147; U.S. Pat. No. 5,062,840; and U.S. Pat. No. 5,269,755.
Examples of suitable transverse barriers are described in U.S. Pat.
No. 5,554,142; U.S. Pat. No. 6,010,490; and U.S. Pat. No.
5,653,703. Examples of other structures especially suitable for
management of low viscosity feces are disclosed in U.S. Pat. Nos.
5,941,864; 5,977,430 and 6,013,063.
[0098] The diaper 10 of FIG. 1 is preferably applied to a wearer by
positioning one of the waist regions under the wearer's back and
drawing the remainder of the diaper between the wearer's legs so
that the other waist region is positioned across the front of the
wearer. The fastener elements are then used by the caregiver to
join the front and rear waist regions so as to encircle the
wearer's waist. The elasticized side panels will typically be
extended and tensioned during this operation so as to conform to
the size and shape of the wearer. A pant, such as that shown in
FIG. 3, may be placed in position on the wearer by inserting the
wearer's legs into the leg openings and sliding the pant into
position about the wearer's lower torso.
Test Methods
Hysteresis Test for Elastic Properties
Overview
[0099] This test measures: a) elastic resistance (load at 25%
elongation), b) force relaxation, and c) percent set of an
individual stretch zone or an array of stretch zones. The stretch
zones can either be intersecting or non-intersecting.
Non-intersecting stretch zones can be either parallel or
non-parallel. Ideally, the sample dimension should be 2.54 cm
wide.times.5.08 cm long, with the direction of stretch being the
long dimension. Furthermore, ideally, the gage length should be
2.54 cm. Because of the variety of patterns that the stretch can be
in, it is necessary to define different sample preparation
procedures for different classes of stretch zones. Once a sample
has been prepared, it is stretched according to a predefined
regimen to provide data for property determination.
Apparatus
[0100] Tensile Tester: A commercial constant rate of extension
tensile tester from Instron Engineering Corp., Canton, Mass. or
SINTECH-MTS Systems Corporation, Eden Prairie, Minn. (or a
comparable tensile tester) may is suitable. The instrument is
interfaced with a computer for controlling the test speed and other
test parameters, and for collecting, calculating and reporting the
data. [0101] Load Cell Choose the jaws and load cell suitable for
the test; the jaws should be wide enough to fit the sample,
typically 2.54 cm jaws are used; the load cell is chosen so that
the expected tensile response from the sample tested will be
between 25% and 75% of the capacity of the load cells or the load
range used, typically a 1 kN load cell is used; [0102] Sample
Cutter The specific sample cutter is defined by the desired sample
width. Suitable cutters are available from Thwing-Albert Instrument
Co. of Philadelphia, Pa. For a 2.54 cm wide sample a Model JDC 1-10
is suitable.
Sample Preparation
(i) Sample Preparation for Linear, Non-intersecting Stretch
Zones
[0103] Cut a sample that is 2.54 cm wide by 5.08 cm long from
within an individual stretch zone. If an individual stretch zone is
smaller than these dimensions, the sample should comprise the
entire stretch zone. Orient the sample in the jaws to ensure that
the sample is stretched in the longitudinal direction of the
stretch zone. If the force from an individual stretch zone is too
small to measure on the tensile tester, several samples from
identical stretch zones taken from multiple products can be pulled
collectively in between the grips of the tensile tester, and the
data normalized to an individual stretch zone. In the special case
when all the stretch zones are uniformly spaced apart and parallel
to one another, and also have the same dimensions and basis weight
of elastomer, a 2.54 cm sample spanning multiple stretch zones can
be tested. The load can then be normalized to an individual stretch
zone by dividing the total force by the number of stretch
zones.
(ii) Sample Preparation for Non-Linear, Non-intersecting Stretch
Zones
[0104] The sample dimensions are 6.3 mm width.times.5.08 cm length.
The length is measured along the curved path. The width of the
sample is small so that the curved stretch zone can be approximated
as a linear stretch zone. The gage length in the tensile tester is
set at 2.54 cm. As mentioned earlier, if it is not possible to
obtain a sample of the above dimensions, then the sample dimensions
can be decreased to the largest possible and the gage length
adjusted according.
(iii) Sample Preparation for an Array of Intersecting Stretch
Zones
[0105] The test sample is 2.54 cm wide.times.5.08 cm long. If the
array is smaller than these dimensions, the sample should comprise
the entire array. The array needs to be pulled in the direction
close to the direction of maximum stretch. This can generally be
determined by pulling the sample in several directions (e.g., CD,
MD and 45 degrees to CD). If such a direction is not easily
discernible, the default direction of pull is the cross machine
direction.
Method
[0106] The hysteresis is measured under standard laboratory
conditions (25.degree. C..+-.2.degree. C. and relative humidity of
about 50%.+-.2.0%).
[0107] The procedure for determining hysteresis of an elastomeric
member involves the following steps: [0108] 1. Calibrate the tester
according to the manufacturer's instructions; [0109] 2. Set the
gauge length at 2.54 cm or as appropriate for the sample being
tested; set the slack preload at 0.05 N. [0110] 3. Place the sample
in the flat surface of the jaws such that the longitudinal
centerline of the sample is substantially parallel to the gauge
length direction. [0111] 4. Set the crosshead speed at a constant
speed of 25.4 cm/min. [0112] 5. Initiate crosshead motion, the
tester begins to record load and strain data simultaneously.
[0113] The hysteresis test specifically involves the following
steps: [0114] a) elongate the sample to 25% strain at a constant
rate of 25.4 cm/min-record the force at 25% elongation; [0115] b)
allow the sample to remain at this strain for 2 minutes-record the
force at the start and end of the 2 minute period; [0116] c) return
the sample to 0% strain at a constant rate of 25.4 cm/min; [0117]
d) allow sample to remain at this strain for 1 minute; and [0118]
e) elongate the sample to 0.1 N load at a constant rate of 5.08
cm/min-record the strain at 0.1 N (i.e., a force sufficient to
remove slack but low enough to impart, at most, insubstantial
stretch to the sample).
Calculations and Reported Results
[0118] [0119] 1. From the data collected in step 5(a), the load at
25% strain is reported as the elastic resistance of the material.
[0120] 2. From the data collected in step 5(b), the force
relaxation is determined by the load at the beginning and at the
end of the 2 minutes hold time using the following formula:
[0120] % Stress Relaxation at time , t = [ ( initial load ) - (
load at time , t ) ] initial load .times. 100 ##EQU00001## [0121]
3. From the data collected in step 5(e), the % set is calculated
using the following formula:
[0121] Percent Set = [ ( Strain Recorded at 5 ( e ) Gage Length ) -
1 ] .times. 100 ##EQU00002## [0122] 4. Report the average results
from three replicate samples for each material tested.
Available Strain
[0123] This is intended to determine the Available Strain of a
sample. The Available Strain 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. An exemplary force (F (N/cm))-elongation (E (%))
curve is shown as FIG. 14. As shown therein, available strain is
determined from force elongation curve 720 as the intersection
point 720b of linear extrapolations of the stage 1 portion of the
curve 720a and the stage 2 portion of the curve 720c.
Method
[0124] 1. Samples are prepared according to the Hysteresis Test
described above. [0125] 2. Repeat steps 1-4 of the Hysteresis Test.
[0126] 3. Initiate crosshead motion. The tester begins to record
load versus strain (percent elongation) data simultaneously; [0127]
4. Continue elongating the sample until either: [0128] a) the
sample breaks; or [0129] b) the force limit of the load cell is
reached. [0130] 5. Plot the force/elongation data to create a curve
similar to that shown in FIG. 14. [0131] 6. Extrapolate the stage 1
and stage 2 portions as shown to determine the available strain.
[0132] 7. Report the average results from three replicate samples
for each material tested.
[0133] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention.
[0134] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
* * * * *