Note: Descriptions are shown in the official language in which they were submitted.
CA 02345756 2001-03-29
WO 00/20206 PCT/US99122471
ELASTIC LAMINATE INCLUDING NONWOVEN LAYER
FORMED FROM HIGHLY ORIENTED COMPONENT FIBERS
AND DISPOSABLE GARMENT EMPLOYING THE SAME
10 FIELD
The present invention relates to elastic laminates. More specifically, the
present invention relates to elastic laminates which includes a nonwoven layer
formed from highly oriented component fibers. The present invention also
relates
to disposable garments employing such elastic laminates. Examples of such
disposable garments include disposable underwear, disposable diapers including
pull-on diapers and training pants, and disposable panties for menstrual use.
BACKGROUND
Elastic laminates have previously been used in a variety of disposable
products, including sweat bands, bandages, body wraps, and disposable garments
including disposable diapers and incontinence devices. Herein, "elastic
laminate"
refers to an elastically stretchable two or more layered materials including
at least
one elastically stretchable single layer material. It is generally expected
that these
products provide good fit to the body andlor skin of the user by using
suitable
elastic members during the entire use period of products.
A "zero strain" stretch laminate is one type of elastic laminate which is
preferably used for such disposable products. For example, methods for making
"zero strain" stretch laminate webs are disclosed in U.S. Patent No. 5,167,897
issued to Weber et al. on December 1, 1992; U.S. Patent No. 5,156,793 issued
to
Buell et al. on October 20, 1990; and U.S. Patent No. 5,143,679 issued to
Weber
et al. on September 1, 1992. In a manufacturing process for such "zero strain"
stretch laminate, the elastomeric material is operatively joined to at least
one
component material in a substantially untensioned (zero strain) condition. At
least
a portion of the resultant composite stretch laminate is then subjected to
mechanical stretching sufficient to permanently elongate the non-elastic
components. The composite stretch laminate is then allowed to return to its
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/224~1
2
substantially untensioned condition. Thus, the elastic laminate is formed into
a
"zero strain" stretch laminate. Herein, "zero strain" stretch laminate refers
to a
laminate comprised of at least two plies of material which are secured to one
another along at least a portion of their coextensive surfaces while in a
substantially untensioned ("zero strain") condition; one of the plies
comprising a
material which is stretchable and elastomeric (i.e., will return substantially
to its
untensioned dimensions after an applied tensile force has been released) and a
second ply which is elongatable (but not necessarily elastomeric) so that upon
stretching the second ply will be, at least to a degree, permanently elongated
so
that upon release of the applied tensile forces, it will not fully return to
its original
undeformed configuration. The resulting stretch laminate is thereby rendered
elastically extensible, at least up to the point of initial stretching, in the
direction of
initial stretching.
As is noted in the above, the manufacturing process of such "zero strain
stretch laminate includes the step of subjecting the non-elastic composite
stretch
laminate to mechanical stretching sufficient to permanently elongate the non-
elastic
components. This step is additional to normal elastic lamination processes and
gives limitations to materials to be used in the elastic laminate. For
example, the
elastomeric material and other composite materials) used in the elastic
laminate
need to have enough physical strength or toughness since those materials tend
to
be mechanically damaged by the process. If the elastomeric material, for
example,
does not have enough strength or toughness, the elastomeric material tends to
be
easily shred or torn by the stress which is applied to the elastomeric
material during
the mechanical stretching in the manufacturing process and during the use of
products.
Based on the foregoing, there is a need for an elastic laminate that does not
have such limitations to the efastomeric material to be used therein.
Infants and other incontinent individuals wear disposable garments such as
diapers to receive and contain urine and other body exudates. One type of the
disposable garments, which is often called as "tape type", has a fastener
system to
hold the disposable garment at the wearer's waist area. As the fastener
system,
either an adhesive tape system or a mechanical fastener system is often used.
Recently, elastically stretchable ear panels tend to be preferably used in
this type
of disposable garment, because they can provide a better fit to the wearer's
waist
area by jointly working with the fastener system. Another type of disposable
garments, which is often called as "pant type" or "pull-on", has fixed sides
and has
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
3
become popular for use on children able to walk and often who are toilet
training.
This type of pull-on garments has ear panels the edges of which are seamed
together to form two leg openings and a waist opening. They also has a
stretchable waistband disposed along at least one of the end edges of the
disposable garments. These pull-on garments need to fit snugly about the waist
and legs of the wearer without drooping, sagging or sliding down from position
on
the torso to contain body exudates. Examples of these pull-on garments are
disclosed, for example, in U.S. Patent No. 5,171,239 to Igaue et al., U.S.
Patent
No. 4,610,681 to Strohbeen et al., WO 93/17648 published on September 16,
1993, U.S. Patent No. 4,940,464 to Van Gompel et al., U.S. Patent No.
5,246,433
to Hasse et al., and U.S. Patent No. 5,569,234 to Buell et ai.
Good performance characteristics of such stretchable ear panels and
waistband are important for these types of disposable garments. More
specifically,
the extension properties including the extension forces, recovery forces,
retention
forces, and available stretch (extension) of the ear panels and waistband are
important considerations in the performance of the fitness for pull-on
garments.
The extension properties provide the applicator and the wearer with the
overall
perceived "stretchiness" during use. They also effect the ability of the
applicator to
achieve a suitable degree of application stretch (i.e., for a "normally"
perceived
tensioning of the diaper during application, the total amount of resultant
stretch is
that desired to achieve/maintain good conformity of fit).
To provide good performance characteristics in stretchable ear panels and
waistband of disposable garments, elastic laminates which include an elastic
material which has suitable properties have been studied and applied to
disposable
garments. For example, a PCT application No. PCT/US98/05895 entitled "Elastic
Member And Disposable Garment Having Improved Fitness To Body During Entire
Use" filed on March 26, 1998, discloses such elastic materials for disposable
garments. It is generally expected that disposable garments provide good fit
to the
body andlor skin of the user by using suitable elastic laminates during the
entire
use period of products. Typical examples of such elastic laminates that have
been
previously used include composites formed from an elastic material joined to a
non(or less)-elastic material such as nonwoven fabrics and plastic films.
These
non(or less)-elastic materials tend to affect expected elastic properties of
elastic
laminates. For example, those materials tend to decrease elastic
"stretchiness" of
the stretchable ear panels during use.
CA 02345756 2001-03-29
WO 00/20206 PCTNS99/22471
4
Based on the foregoing, there is also a need for disposable garments which
employ an elastic laminate that does not decrease elastic "stretchiness"
thereof.
SUMMARY
The present invention is directed to an elastic laminate which is elastically
extensible in at least one direction. The elastic laminate includes an
elastomeric
material having a first surface and a second surface opposing the first
surface; and
a first nonwoven layer joined to the first surface of the elastomeric
material. The
first nonwoven layer is formed from component fibers having a primary fiber
direction. The first nonwoven layer has a Fiber Orientation Ratio within about
~20
degrees from the primary fiber direction of at least about 65%.
The present invention is also directed to a disposable garment having a front
region, a back region and a crotch region between the front region and the
back
region. The disposable garment comprises a chassis provided in the front, back
and crotch regions and having edge lines in the front and back regions. The
chassis includes a liquid pervious topsheet, a liquid impervious backsheet
associated with the topsheet, and an absorbent core disposed between the
topsheet and the backsheet.
In one aspect of the present invention, the disposable garment further
comprises at least one pair of extensible side panels extending laterally
outward
from the chassis in the front or back region. At least one of the side panels
includes an elastic laminate elastically extensible at least in the lateral
direction.
The elastic laminate includes an elastomeric material having a first surface
and a
second surface opposing the first surface; and a first nonwoven layer joined
to the
first surface of the elastomeric material. The first nonwoven layer is formed
from
component fibers having a primary fiber direction. The first nonwoven layer
has a
Fiber Orientation Ratio within about ~20 degrees from a primary fiber
direction of at
least about 65%.
In another aspect of the present invention, the disposable garment further
comprises a waistband disposed along at least one of the end edges of the
disposable garment. The waistband includes an elastic laminate elastically
extensible at least in the lateral direction. The elastic laminate includes an
elastomeric material having a first surface and a second surface opposing the
first
surface; and a first nonwoven layer joined to the first surface of the
elastomeric
material. The first nonwoven layer is formed from component fibers having a
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
primary fiber direction. The first nonwoven layer has a Fiber Orientation
Ratio
within about ~20 degrees from a primary fiber direction of at least about 65%.
These and other features, aspects, and advantages of the present invention
will become evident to those skilled in the art from reading of the present
5 disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims particularly pointing out and
distinctly claiming the invention, it is believed that the invention will be
better
understood from the following description of preferred embodiments which is
taken
in conjunction with the accompanying drawings and which like designations are
used to designate substantially identical elements, and in which:
Fig. 1 is a fragmentary enlarged perspective view of an elastic laminate of
one preferred embodiment of the present invention, prior to being formed into
the
elastic laminate;
Fig. 2 is a simplified cross-sectional view of an elastic laminate of another
preferred embodiment;
Fig. 3 is a enlarged perspective view of an elastic laminate of yet another
embodiment of the present invention, wherein a portion of the nonwoven layer
has
been removed to show the bonded structure;
Fig. 4 is a fragmentary enlarged perspective view of an alternative
embodiment of the elastomeric material;
Fig. 5 is a schematic representation of a lamination device for forming the
elastic laminate shown in Fig. 3;
Fig. 6 is a perspective view of one preferred embodiment of the disposable
pull-on garment of the present invention in a typical in use configuration;
Fig. 7 is a perspective view of another preferred embodiment of the
disposable pull-on garment of the present invention in a typical in use
configuration;
Fig. 8 is a simplified plan view of the embodiment shown in Fig. 7 in its flat
uncontracted condition showing the various panels or zones of the garment;
Fig. 9 is a cross-sectional view of a preferred embodiment taken along the
section line 9-9 of Fig. 8;
Fig. 10 is a cross-sectional view of a waistband 50 of a preferred
embodiment taken along the section line 10-10 of Fig. 8;
CA 02345756 2001-03-29
WO 00/20206 PCT/L'S99/22a71
6
Fig. 11 is a cross-sectional view of a waistband 50 of another preferred
embodiment; and
Fig. 12 is a graph showing the two-cycles of hysteresis curves of an
elastomeric material, in a preferred embodiment.
DETAILED DESCRIPTION
All cited references are incorporated herein by reference in their entireties.
Citation of any reference is not an admission regarding any determination as
to its
availability as prior art to the claimed invention.
Herein, "comprise", "include" and "have" mean that other elements) and
steps) which do not affect the end result can be added. These terms encompass
the terms "consisting of and "consisting essentially of'.
Herein, "gf' stands for gram force.
Herein, "joined" or "joining" encompasses configurations whereby af~
element is directly secured to another by affixing the element directly to the
other
element, and configurations whereby the element is indirectly secured to the
other
element by affixing the element to intermediate members) which in turn are
affixed
to the other element.
Herein, "layer" does not necessarily limit the element to a single stratum of
material in that a layer may actually comprise laminates or combinations of
sheets
or webs of materials.
Herein, "nonwoven" may include any material which has been formed
without the use of textile weaving processes which produce a structure of
individual
fibers which are interwoven in an identifiable manner. Methods of making
suitable
nonwovens includes a spunbonded nonwoven process, a meltblown nonwoven
process, a carded nonwoven process, or the like.
A. Laminate Structure
The present invention relates to an elastic laminate which does not have a
(imitation(s) to an elastomeric material to be used therein. This and other
advantages of the invention are described in more detail herein.
Fig. 1 is a fragmentary enlarged perspective view of an elastic laminate 70
of one preferred embodiment, prior to being formed into the elastic laminate.
(Preferred embodiments of the elastic laminate 70 after the formation are
shown in
Figs. 2 and 3.) Referring to Fig. 1, the elastic laminate 70 of the present
invention
includes an elastomeric layer 124 having a first surface 150 and a second
surface
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
7
152 opposing the first surface 150; and a first nonwoven layer 122 which is
joined
to the first surface 150 of the elastomeric layer 124. In a preferred
embodiment,
the first surface 150 and second surface 152 of the elastomeric layer 124 are
substantially parallel with the plane of the 1'Irst nonwoven layer 122. The
first
nonwoven layer 122 has an inner surface (or a first surface) 142 and an outer
surface (or a second surface) 144. The inner surface 142 of the first nonwoven
layer 122 is the surface that is positioned facing the elastomeric layer 124.
In a preferred embodiment, the elastic laminate 70 further comprises a
second nonwoven layer 126 joined to the second surface 152 of the elastic
material 70. The second nonwoven layer 126 also has an inner surface 146 and
an outer surface 148. The inner surface 146 of the second nonwoven layer 126
is
the surface that is positioned facing the elastomeric layer 124. The second
surface
152 of the elastomeric layer 124 is substantially parallel with the plane of
the
second nonwoven layer 126. In a preferred embodiment, the nonwoven layer 12~
is formed by an identical nonwoven material with that is employed in the first
nonwoven layer 122. Alternatively, the nonwoven layer 126 may be formed by a
different material from that is employed in the first nonwoven layer 122.
The elastic laminate 70 of the present invention is elastically extensible in
at
least one direction (first direction). For example, the elastic laminate 70
shown in
Fig. 1 is elastically extensible in the structural direction D. Herein,
"structural
direction" (e.g., D and B) is intended to mean a direction which extends
substantially along and parallel to the plane of the first nonwoven layer 122.
In a
preferred embodiment, the elastic laminate 70 is also elastically extensible
in the
second direction which is perpendicular to the first direction. For example,
the
elastic laminate 70 shown in Fig. 1 is also elastically extensible in the
structural
direction B.
B. Nonwoven Layers
The first nonwoven layer 122 of the present invention is formed from
component fibers which are joined together. The component fibers have a
primary
fiber direction. The first nonwoven layer 122 has a Fiber Orientation Ratio
within
about ~20 degrees from the primary fiber direction (FOR20) of at least about
65%;
more oreferably at least about 75%; more preferably still at least about 85%.
In a
more preferred embodiment, the first nonwoven layer 122 additionally has a
Fiber
Orientation Ratio within about ~10 degrees from the primary fiber direction
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
8
(FOR10) of at least about 45%; more preferably at least about 60%; more
preferably still at least about 70%.
"FOR#" (e.g., FOR10) indicates the ratio of the number of the component
fibers whose directions are within about ~# degrees, (e.g., ~10 degrees) from
the
primary fiber direction to the total number of component fibers. Herein,
"primary
fiber direction" refers to an average direction of component fibers in the
nonwoven
layer. One preferred method for measuring the Fiber Orientation Ratio of
nonwoven layers is explained in more detail below.
In a preferred embodiment, the first nonwoven layer 122 has a Tensile
Strength Ratio (TSR) of at least about 15, more preferably at least about 60.
The
TSR is defined by the following calculation:
TS R = TS 1 / TS2
wherein,
TS1 (gf/inch): a tensile strength (TS) at the breaking point in the primary
fiber direction; and
TS2 (gf/inch): a tensile strength (TS) at the breaking point in the
perpendicular direction which is perpendicular to the primary fiber direction.
Tensile Strength (ST) is measured as the maximum tensile strength value
recorded while the first nonwoven layer 122 is stretched at a rate of about 20
inches/min (about 50 cm/min) to its breaking point. The tensile strength of
the first
nonwoven layer 122 is measured before the first nonwoven layer 122 is joined
to
the elastomeric layer 124.
In a preferred embodiment, the first nonwoven layer 122 has a tensile
strength of less than about 200 gf/inch (about 80 gf/cm) at 30% elongation to
the
direction which is perpendicular to the primary fiber direction; more
preferably less
than about 100 gf/inch (about 40 gf/cm), more preferably still less than about
50
gflinch (about 20 gf/cm).
The first nonwoven layer 122 may be manufactured from a wide range of
component fibers including, e.g., natural fibers (e.g., wool and cotton
fibers),
synthetic fibers (e.g., polyolefin, polyester, nylon, and rayon fibers), or a
mixture of
natural fibers andlor synthetic fibers. For ease of manufacture and cost
efficiency,
the first nonwoven layer 122 is preferably formed from synthetic continuous
fibers.
More preferably, such synthetic continuous fibers are formed from a polyolefin
(e.g., polyethylene and polypropylene) or a polyester. Preferred polyester
material
includes a polyethylene terephthalate, a polybutylene terephthalate and a
polypropylene terephthalate, or mixtures thereof. In a preferred embodiment,
the
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
9
first nonwoven layer 122 additionally includes component fibers formed from
the
other materials (i.e., non-polyester materials) such as polyolefin and nylon.
In a preferred embodiment, the individual component fibers are formed from
a single type of material which is selected from the above materials (i.e.,
the
individual fiber is not made from polyolefin and nylon). Preferably, the
component
fibers are formed from a polyester, more preferably a polyethylene
terepthalate, or
one of its relatives which has an average molecular weight from about 5,000 to
about 60,000, preferably from about 10,000 to about 40,000, more preferably
from
about 14,000 to about 23,000. Alternatively, the component fibers may be
formed
from a mixture of two (or more) materials which are selected from the above
materials.
In one embodiment, the component fiber has a bi-component fiber structure
formed from two distinct materials of a polyester and a polyolefin. In an
alternative
embodiment, the component fiber has a bi-component fiber structure formed
frorrE
two distinct molecular weight materials of one identical material, for
example, a
polyester. Preferred bi-component fiber structures may include a side-by-side
bi-
component fiber structure and a sheath-core bi-component fiber structure known
in
the art. In one embodiment, the component fiber has a bi-component fiber
structure having a core of polyolefin and a sheath of a polyester.
In a preferred embodiment, the first nonwoven layer 122 has a basis weight
of less than about 60 g/m2, and comprises fibers having a fiber diameter of
less
than about 50 ~.m. More preferably, for products such as disposable garment
and
the like, the first nonwoven layer 122 has a basis weight of from about 3 g/m2
to
about 50 g/m2, more preferably from about 10 g/m2 to about 25 g/m2, and a
fiber
diameter of from about 1 ~,m to about 30 Vim, more preferably from about 3 wm
to
about 20 wm.
The component fibers may be joined together by adhesives, thermal
bonding, water-jetting, needling/felting, or other methods known in the art to
form
nonwoven fabrics. In a preferred embodiment, the first nonwoven layer 122 is
formed from a nonwoven manufacturing process handling continuous component
fibers or filaments known in the art. Preferred manufacturing process are
described in, for example, EP 0843036A1 (Kurihara et al.) published on May 20,
1998; U.S. Patent No. 5,312,500, entitled "Non-Woven Fabric and Method and
Apparatus for Making The Same", issued to Kurihara et al. on May 17, 1994;
Japanese Laid-Open Patent Publication (Kokai) No. H2-269859 published on
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
November 5, 1990; and Japanese Patent Publication (Kokoku) No. S60-25541
published on June 19, 1985.
Preferred nonwoven fabrics which are suitably applicable to the first
nonwoven layer 122 are available from Nippon Petrochemicals Co., Ltd., Tokyo,
5 Japan, under Code Nos. MBE8202-3-2; MBE8202-3-1; MBE7711-2; MBE6515-10;
and MBE7922-1 which have the following properties.
Table
Code No. Basis WeightFOR10 FOR20 TSR at TS at 30%
(g/m2) (%) (%) Break Point elongation
MBE8202-3- 15 77 93 106 10
2
MBE8202-3- 20 82 94 68 20
1
MBE7711-2 21 69 92 76 133
MBE6515-10 8 60 85 104 21
MBE7922-1 29 58 80 33 157
C. Elastomeric Material
10 The elastomeric layer 124 may be formed in a wide variety of sizes, forms
and shapes. In a preferred embodiment, the elastomeric layer 124 is in the
form of
a continuous plane layer such as shown in, for example, Fig. 1. Preferred
forms of
a continuous plane layer include a scrim, a perforated {or apertures formed)
film,
an elastomeric woven or nonwoven, and the like. Preferably, the elastomeric
layer
124 has a thickness of from about 0.05 mm to about 1 mm (about 0.002 inch -
about 0.039 inch). The continuous plane layer may take any shape which can be
suitably provided in products. Preferred shapes of a continuous plane layer
include
a quadrilateral including a rectangle and a square, a trapezoid, and the other
polygons. In an alternative embodiment, the elastomeric layer 124 is in the
form of
discrete strands (or strings) which are not connected each other.
The elastomeric material of the present invention may include all suitable
elastic materials known in the art. Elastomeric materials suitable for use
herein
include synthetic or natural rubber materials known in the art. Preferred
elastomeric materials include the diblock and triblock copolymers based on
polystyrene and unsaturated or fully hydrogenerated rubber bolcks, and their
blends with other polymers such as polyolefin polymers.
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
11
In a preferred embodiment, the elastomeric material is made from a
polystyrene thermoplastic elastomer including styrene block copolymer based
materials. A preferred styrenic block copolymer based material contains from
about 1 wt% to about 70 wt% of polystyrene, more preferably from about 10 wt%
to
about 50 wt% of polystyrene.
Preferably, the polystyrene thermoplastic elastomer is selected from the
group consisting of a styrene-butadiene-styrene thermoplastic elastomer, a
styrene-isopren-styrene thermoplastic elastomer, a styrene-ethylene/butylene-
styrene thermoplastic elastomer, a styrene-ethylene/propylene-styrene
thermoplastic elastomer, a styrene-ethylene/propylene thermoplastic elastomer,
a
hydrogenated styrene butadiene rubber, and a mixture thereof.
A preferred styrenic block copolymer based material contains from about 1
wt% to about 70 wt% of polystyrene, more preferably from about 10 wt% to about
50 wt% of polystyrene.
In an alternative preferred embodiment, the elastomeric material 124 is a
porous, macroscopically-expanded, three-dimensional elastomeric web 172 as
shown in Fig. 4. The web 172 has a continuous first surface 174 and a
discontinuous second surface 176 opposing to the first surface 174. The
elastomeric web 172 preferably comprises a formed film interconnecting member
186 including at least two polymeric layers 178 and 182. The first layer 178
is
substantially elastic and the second Layer 182 is substantially less elastic
than the
first layer 178. At least one of the two polymeric layers 178 and 182 is
formed from
a polystyrene thermoplastic elastomer. The elastomeric web 172 exhibits a
multiplicity of primary apertures 184 in the first surface 174 of the web 172.
The
primary apertures 184 are defined in the plane of the first surface 174 by a
continuous network of the interconnecting member 186. The interconnecting
member 186 exhibits an upwardly concave-shaped cross-section along its length.
The interconnecting member 186 also forms secondary apertures 188 in the plane
of the second surface 176 of the web 172. The apertures 184 and 188 may take
any shape. A preferred elastomeric web is disclosed in U.S. Patent application
serial number 08/816,106, filed on March 14, 1997. A preferred porous
elastomeric material for the elastomeric layer 124 is available from Tredegar
Film
Products under the designation X-25007.
In one preferred embodiment, the elastomeric layer 124 is in the form of a
scrim 130 as shown in Fig. 1. The elastomeric scrim 130 comprises a plurality
of
first strands 125 which intersect or cross (with or without bonding to) a
plurality of
CA 02345756 2001-03-29
WO 00/20206 PCT/US99I22471
12
second strands 127 at nodes 128 at a predetermined angle a, thereby forming a
net-like open structure having a plurality of apertures 132. Each aperture 132
is
defined by at least two adjacent first strands 125 and at least two adjacent
second
strands 127 such that apertures 132 are substantially rectangular (preferably
square) in shape. Other aperture configurations, such as parallelograms or
circular
arc segments, can also be provided. Such configurations could be useful for
providing non-linear elastic structural directions. Preferably, the first
strands 125
are substantially straight and substantially parallel to one another; and,
more
preferably, the second strands 127 are also substantially straight and
substantially
parallel to one another. More preferably, first strands 125 intersect second
strands
127 at nodes 128 at a predetermined angle a of about 90 degrees. Each node 128
is an overlaid node, wherein first strands 125 and second strands 127 are
preferably joined or bonded (although it is contemplated that joining or
bonding
may not be required) at the point of intersection with the strands stilt
individually
distinguishable at the nodes 128. However, it is believed that other node
configurations such as merged or a combination of merged and overlaid would be
equally suitable.
Although it is preferred that first and second strands 125 and 127 be
substantially straight, parallel, and intersect at an angle a of about 90
degrees, it is
noted that first and second strands 125 and 127 can intersect at other angles
a,
and that first strands 125 and/or second strands 127 can be aligned in
circular,
elliptical or otherwise nonlinear patterns relative to one another. Although
for ease
of manufacture it is contemplated that first strands 125 and second strands
127
have a substantially circular cross-sectional shape prior to incorporation
into elastic
laminate 70 (as shown in Fig. 1 ), the first and second strands 125 and 127
can also
have other cross-sectional shapes such as elliptical, square, triangular or
combinations thereof.
Preferably, the material for the first strands 125 is chosen so that the first
strands 125 can maintain the second strands 127 in relative alignment prior to
forming elastic laminate 70. It is also desirable that the materials for the
first and
second strands 125 and 127 are capable of being deformed (or initially formed)
into
predetermined shapes upon application of a predetermined pressure or a
pressure
in combination with a heat flux prior to forming elastic laminate 70. These
deformed shapes (e.g., elliptical second strands, substantially flat first
strands and
the like) can provide an elastic laminate 70 which can be comfortably worn
about
the body without irritation or other discomfort.
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
13
In a preferred embodiment, the first and second strands 125 and 127 are
formed from an identical elastomeric material. For example, the first and
second
strands 125 and 127 are formed from an identical polystyrene thermoplastic
elastomer which is selected from the group consisting of a styrene-butadiene-
styrene thermoplastic elastomer, a styrene-isopren-styrene thermoplastic
elastomer, a styrene-ethylene/butyiene-styrene thermoplastic elastomer, a
styrene-
ethylene/propylene-styrene thermoplastic elastomer, a styrene-
ethylene/propylene
thermoplastic elastomer, a hydrogenated styrene butadiene rubber or an
unsaturated styrene butadiene rubber, and a mixture thereof. A preferred
elastomeric scrim 124 which containes a styrene-butadiene-styrene
thermoplastic
elastomer is manufactured by the Conwed Plastics Company (Minneapolis, Minn.,
U.S.A.) under the designation X02514. This material has about 12 elastic
strands
per inch (about 5 strands/cm) in the structural direction B (i.e., the first
strands 125)
and about 7 elastic strands per inch (about 3 strands/cm) in the structural
directiorf
D (i.e., the second strands 127) before lamination.
Alternatively, the first and second strands 125 and 127 are formed from two
different material. For example, one of the first and second strands 125 and
127 is
formed from one of the above described polystyrene thermoplastic elastomer,
while
the other of the first and second strands 125 and 127 is formed from
materials)
other than the above described polystyrene thermoplastic elastomer. Such other
materials) may be either elastic or non-elastic, and selected from suitable
materials known in the art.
D. Joinin4 Nonwoven to Elastomeric Material
The first nonwoven layer 122 of the present invention can be joined to the
elastomeric layer 124 by any means known in the art. In a preferred
embodiment,
the first nonwoven layer 122 is joined to the first surface 150 of the
elastomeric
layer 124 by an adhesive means such as those well known in the art. For
example,
the first nonwoven layer 122 may be secured to the first surface 150 of the
elastomeric layer 124 by a uniform continuous layer of adhesive, a patterned
layer
of adhesive, or an array of separate lines or spots of adhesive. One preferred
laminate structure formed by an adhesive means is shown in Fig. 2.
Fig. 2 shows a simplified fragmentary enlarged side view looking into the
structural direction B of the elastic laminate 70. In this embodiment, the
elastic
laminate 70 includes the second nonwoven layer 126. Referring to Fig. 2, a
first adhesive 170 is applied to the inner surface 142 of the first nonwoven
layer
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
14
122 in positions that correspond to each of the outer edges 180 of the
laminate
structure 120. The first adhesive 170 may alternatively or additionally be
applied to
the inner surface 146 of the second nonwoven layer 126. For ease of
illustration,
the description and Figs. refer to application to the first nonwoven layer 122
only.
This pattern creates side anchor zones A, which substantially eliminate the
delamination and creep associated with previously known laminates and which
allows the elastic laminate 70 to experience higher strains without creeping
or
delaminating. It has also been found that confining the first adhesive 170 to
the
edge areas 180 of the laminate structure 120 avoids impeding the extensibility
of
the elastic laminate 70 and also avoids tears in the nonwoven layers 122 and
126.
Preferably, the first adhesive 170 is applied as a plurality of beads 168, as
shown
in Fig. 2. Preferably, the first adhesive 170 is a flexible adhesive with an
amorphous and crystallizing component. Such a preferred adhesive is made b~
Ato Findley Inc., WI, U.S.A., under the designation H9224.
The side anchoring is preferably performed by side gluing with adhesive
beads to anchor the elastomeric layer 124 between the nonwoven layers 122 and
126 as a part of the lamination process. Alternatively, side anchoring may be
performed by sewing, heat sealing, ultrasonic bonding, needle punching,
alternative gluing processes, or by any other means known to those skilled in
the
art.
More preferably, the elastic laminate 70 includes a second adhesive 164.
Preferably, the second adhesive 164 is an elastomeric adhesive. The second
adhesive 164 is preferably applied to the first surface 150 of the elastomeric
layer
130. The second adhesive 164 is preferably applied in a spiral spray pattern
166,
thereby forming bond points 167b that are more discrete than would be formed
by
a linear spray application. Without being bound by theory, it is believed that
most
of the second adhesive 164 is sprayed in the structural direction D (Fig. 1 ).
Preferably, the layer of second adhesive 164 is directly applied onto the
first
surface 150 of the elastomeric layer 124 in the lamination process.
A third adhesive 160 may also preferably be applied to the inner surface 146
of the second nonwoven layer 126. Preferably, the third adhesive 160 is an
elastomeric adhesive. In a manner similar to that described with reference to
the
second spiral adhesive application 166, the third adhesive 160 is preferably
applied
in a spiral spray pattern 162, thereby forming bond points 167a that are more
discrete than would be formed by a linear spray application. Preferably, the
layer
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
of third adhesive 160 is directly applied onto the second surface 152 of the
elastomeric layer 124 in the lamination process.
Preferably, second and third adhesives 160 and 164 are the same
elastomeric adhesive. A preferred adhesive for use in the second and third
5 adhesive spiral sprays 162 and 166 is made by Ato Findley Inc., WI, U.S.A.,
under
the designation H2120. Preferably, the add-on level for each of the second and
third spiral sprays 162 and 166 is about 4 mg/inch (about 1.6 mg/cm) to about
12
mglinch (about 4.8 mg/cm), more preferably about 8 mg/inch (about 3.2 mg/cm).
In an alternative preferred embodiment, the first nonwoven layer 122 is
10 bonded to the first surface 150 of the elastomeric layer 124 by forming a
heat/pressure bond between the first nonwoven layer 122 and the elastomeric
layer 124. Herein, "heat/pressure bond" is either a physical or chemical bond
formed by an application of appropriate heat and pressure to two different
members so that the two members can have a portion which has an increased pe~i
15 strength by the formation of the bond. Herein, "peel strength" refers to
the amount
of force required to separate the two members from each other. Higher peel
strengths typically equate to less chance of de-lamination of the elastic
laminates in
use of products. To form such heat/pressure bonds) between the first nonwoven
layer 122 and the elastomeric layer 124, any pressure can be applied to the
first
nonwoven layer 122 and the elastomeric layer 124 at a certain temperature as
long
as it does not substantially damage the physical and/or chemical properties of
the
resulting elastic laminate.
Fig. 3 is a partial perspective view of an elastic laminate 70 of yet another
embodiment, wherein a portion of the first nonwoven layer 122 has been removed
to show the heat/pressure bond structure. In Fig. 3, the elastomeric scrim 130
which is formed by the first and second strands 125 and 127 is used as an
example for the elastomeric layer 124. Referring to Fig. 3, the first nonwoven
layer
122 is bonded to the first surface 150 of the elastomeric layer 124 by forming
a
heat/pressure bond between the first nonwoven layer 122 and the elastomeric
layer 124. In a preferred embodiment, the elastic laminate further includes a
second nonwoven layer (not shown in Fig. 3) which is bonded to the second
surface 152 of the elastomeric layer 124 by forming another heat/pressure bond
therebetween.
The heat/pressure bond is formed by softening only the material of the
elastomeric layer 124 (i.e., without melting the component fibers of the first
nonwoven layer 122). This heat/pressure bond is preferably formed by
application
CA 02345756 2001-03-29
WO 00/20206 PCT/US99i22471
16
of a bonding temperature which is lower than the melting point of the material
of
the first nonwoven layer 122. This generally results in a decrease in the
viscosity
of the material which may or may not involve a "melting" of the material. As a
result, the component materials of the elastomeric layer 124 are softened to
form
the heat/pressure bond. In a more preferred embodiment wherein the elastomeric
layer 124 is formed from a polystyrene thermoplastic elastomer including a
polystyrene segment, a bonding temperature which is higher than the glass
transition temperature of the polystyrene segment is applied for forming the
heat/pressure bond.
Fig. 5 shows one preferred example of a lamination device for forming the
elastic laminate 70 shown in Fig. 3. Referring to Fig. 5, the lamination
device 800
includes a first pressure plate 801 having a first surface 803, and a second
plate
802 having a second surface 804. The second pressure plate 802 is fixed, while
the first pressure plate 801 is movable to apply a pressure P to the first
nonwove~
layer 122 and the elastomeric layer 124 in cooperation with the second
pressure
plate 802. Preferably, the first and second surfaces 803 and 804 are
substantially
plane and are substantially parallel each other. The first nonwoven layer 122
is
juxtaposed with the elastomeric layer 124 such that the first nonwoven layer
122 is
immediately adjacent the elastomeric layer 124. The juxtaposed two layers 122
and 124 are manually supplied to the lamination device 800. A preferred
lamination device 800 is available from Toyo Tester Industry Co., Ltd., Osaka,
Japan, under a trade name "Heat Sealer".
In the lamination process, the first surface 803 is heated to a temperature
T1, while the second surface 804 is heated to a temperature T2. Preferably,
the
temperature T1 is from about 80°C to about 160°C, more
preferably from about
100°C to about 130°C. The temperature T2 is preferably from
about 30°C to about
60°C, more preferably from about 45°C to about 55°C. The
pressure P is
preferably from about 6 kg/cm2 to about 15 kg/cm2, more preferably from about
9
kg/cm2 to about 11 kg/cm2. The time period of the application of the pressure
P is
preferably from about 1 second to about 20 seconds, more preferably from about
5
seconds to about 15 seconds. Preferably, the application of pressure P can be
performed two (or more) times to increase the peel strength of the resulting
laminate 70. By the application of the temperatures T1 and T2 at the pressure
P,
the elastomeric layer 124 is bonded to the first nonwoven layer 122 through a
heat/pressure bond which is formed by softening the material of the
elastomeric
layer 124 (e.g., the polystyrene thermoplastic elastomer).
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/224?1
17
The elastic laminate 70 of the present invention can be incorporated into a
variety of products wherein it is desired to provide an elastic stretchability
in at least
one structural direction either partially or entirely. Examples of such
products
include disposable products, including sweat bands, bandages, body wraps, and
disposable garments including disposable diapers and incontinence products.
E. Test Methods
1. Test Method for Fiber Orientation
The following method is preferably used to determine the Fiber Orientation
Ratio (FOR) of nonwoven material.
A sample nonwoven fabric (or layer) is placed on a specimen stub. The
sample nonwoven fabric is fixed on the specimen stub at a flat condition so
that the
primary fiber direction (to be defined hereinafter) of the sample nonwoven
fabric
can be roughly aligned with the longitudinal direction of the photograph to be
taken
A scanning electron microscope (SEM) is used to take a photograph at 50X
magnification. A preferred SEM is available from Japan Electron Optics
Laboratory
(JEOL) Ltd., Tokyo, Japan, under Code No. JSM-5310
The following analysis is conducted on the photograph by using a digitizer.
A preferred digitizer is available from Graphtec Co., Ltd., Tokyo, Japan,
under
Code No. KD9600. A photograph is placed on the digitizer. A square area (500
pm x 500 Vim) is chosen at will in the photograph on the digitizer. The both
ends of
every component fiber which can be seen in the square area are manually
identified by an operator and the coordinates thereof are detected and
recorded by
the digitizer. This work is conducted on three different square areas (each
having
500 pm x 500 pm) which are chosen at will in the photograph to obtain
coordinate
data on the all fibers in the three different square areas. The orientation
angle of
each fiber is calculated based on the coordinate data. The primary fiber
direction
of the sample nonwoven fabric is determined by the average orientation angle,
which is an average value of the all orientation angle data obtained from the
three
different square areas.
The Fiber Orientation Ratio within about ~10 degrees (FOR10) is
determined by the following calculation:
FOR10 = NF10 / TNF x 100 (2)
wherein,
NF10: the number of fibers which have orientation angles within about ~10
degrees from the primary fiber direction; and
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22:1?t
18
TNF: the total number of fibers measured within the three different square
areas.
Similarly, the Fiber Orientation Ratio within about ~20 degrees (FOR20) is
determined by the following calculation:
FOR20 = NF20 / TNF x 100 1:~1
wherein,
NF20: the number of fibers which have orientation angles within about ~20
degrees from the primary fiber direction.
2. Test Method for Tensile Strenath
The following method is preferably used to measure the tensile strength of
materials.
A tensile tester is prepared. The tensile tester has an upper jaw and a lowed
jaw which is located below the upper jaw. The upper jaw is movable and is
connected to an extension force measuring means. The lower jaw is fixed in the
tester. A test specimen (i.e., a nonwoven fabric to be measured) which has
about
2.5 cm (about 1 inch) in width and about 10.2 cm (about 4 inches) in length is
prepared and clamped with the upper jaw and the lower jaw so that the
effective
specimen length (L) (i.e., gauge length) is about 5.1 cm (about 2 inch). An
extension force is continuously applied to the test specimen through the upper
jaw
at a cross-head speed of about 50 cm (about 20 inches) per minute, until the
test
specimen is physically broken. The applied extension force is recorded by a
recorder (e.g., a computer system). The tensile strength at the breaking point
is
determined at the maximum tensile strength value. A tensile tester suitable
for use
is available from Instron Corporation (100 Royall Street, Canton, MA02021,
U.S.A.)
as Code No. Instron 5564.
F. DISPOSABLE GARMENTS
Herein, "pull-on garment" refers to articles of wear which have a defined
waist opening and a pair of feg openings and which are pulled onto the body of
the
wearer by inserting the legs into the leg openings and pulling the article up
over the
waist. Herein, "disposable" describes garments which are not intended to be
laundered or otherwise restored or reused as a garment (i.e., they are
intended to
be discarded after a single use and, preferably, to be recycled, composted or
otherwise disposed of in an environmentally compatible manner). A "unitary"
pull-
on garment refers to pull-on garments which are formed of separate parts
united
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
19
together to form a coordinated entity, but the ear panels are not separate
elements
joined to a separate chassis; rather, the ear panels are formed by at least
one layer
which also forms the chassis of the garment (i.e., the garment does not
require
separately manipulative panels such as a separate chassis and separate ear
panels). The pull-on garment is also preferably "absorbent" to absorb and
contain
the various exudates discharged from the body. A preferred embodiment of the
pull-on garment of the present invention is the unitary disposable absorbent
pull-on
garment, pull-on garment 120, shown in Fig. 6. Herein, "pull-on diaper" refers
to
pull-on garments generally worn by infants and other incontinent individuals
to
absorb and contain urine and feces. It should be understood, however, that the
present invention is also applicable to other pull-on garments such as
training
pants, incontinent briefs, feminine hygiene garments or panties, and the like.
Herein, "panel" denotes an area or element of the pull-on garment. (While a
panel
is typically a distinct area or element, a panel may coincide (functionally
correspond) somewhat with an adjacent panel.) Herein, "uncontracted state" is
used herein to describe states of pull-on garments in its unseamed (i.e.,
seams are
removed), flat and relaxed condition wherein all elastic materials used are
removed
therefrom.
Fig. 6 shows one preferred embodiment of a disposable pull-on garment of
the present invention (i.e., a unitary disposable pull-on diaper 120).
Referring to
Fig. 6, the disposable pull-on garment 120 has a front region 26; a back
region 28
and a crotch region 30 between the front region 26 and the back region 28. A
chassis 41 is provided in the front, back and crotch regions 26, 28 and 30.
The
chassis 41 includes a liquid pervious topsheet 24, a liquid impervious
backsheet 22
associated with the topsheet 24, and an absorbent core 25 (not shown in Fig.
6)
disposed between the topsheet 24 and the backsheet 22. The chassis 41 has side
edges 220 which form edge fines 222 in the front region 26.
The pull-on garment 120 further includes at least one pair of extensible ear
panels 45 each extending laterally outward from the corresponding sides of the
chassis 41. Each of the ear panels 45 has an outermost edge 240 which forms an
outermost edge line 242. At least one of the outermost edge lines 242 has a
nonuniform lateral distance from the longitudinal center line 100 (not shown
in Fig.
6) in the uncontracted state of the garment 120.
In a preferred embodiment, the ear panels 45 continuously extend from the
corresponding sides of the chassis 41 in the back region 28 to the
corresponding
side edges 220 of the chassis 41 in the front region 26 as shown in Fig. 6.
CA 02345756 2001-03-29
WO 00/20206 PCT/C,'S99/224~1
Alternatively, the ear panels 45 may continuously extend from the
corresponding
sides of the chassis 41 in the front region 26 to the corresponding side edges
of
the chassis 41 in the back region 28 (not shown in Fig. 6).
The pull-on garment 120 has the ear panels 45 joined to the chassis 41 to
5 form two leg openings 34 and a waist opening 36. Preferably, the pull-on
garment
120 further includes seams 232 each joining the chassis 41 and the ear panels
45
along the corresponding edge lines 222 and 242 to form the two leg openings 34
and the waist opening 36.
Fig. 7 shows another preferred embodiment of a disposable pull-on garment
10 of the present invention (i.e., a unitary disposable pull-on diaper 20).
Referring to
Fig. 7, the disposable pull-on garment 20 includes a pair of extensible front
ear
panels 46 each extending laterally outward from the corresponding sides of the
chassis 41 in the front region 26, and a pair of extensible back ear panels 48
each
extending laterally outward from the corresponding sides of the chassis 41 in
tffe
15 back region 28. Each of the ear panels 46 and 48 has an outermost edge 240
which forms an outermost edge line 242. At least one of the outermost edge
lines
242 has a nonuniform lateral distance LD from the longitudinal center line 100
(not
shown in Fig. 7 but in Fig. 8) in the uncontracted state of the garment 20.
The pull-
on garment 20 further includes seams 32 each joining the front and back ear
20 panels 46 and 48 along the corresponding edge lines 242 to form the two leg
openings 34 and the waist opening 36.
In a preferred embodiment, at least one of, more preferably both of, the
pairs of the ear panels 45, 46 and 48 are elastically extensible in at least
the lateral
direction. In alternative embodiments, the ear panels 45, 46 and 48 are
elastically
extensible both in the lateral and longitudinal directions. Herein,
"extensible" refers
to materials that are capable of extending in at least one direction to a
certain
degree without undue rupture. Herein, "elasticity" and "elastically
extensible" refer
to extensible materials that have the ability to return to approximately their
original
dimensions after the force that extended the material is removed. Herein, any
material or element described as "extensible" may also be elastically
extensible
unless otherwise provided. The extensible ear panels 45, 46 and 48 provide a
more comfortable and contouring fit by initially conformably fitting the pull-
on
garment to the wearer and sustaining this fit throughout the time of wear well
past
when the pull-on garment has been loaded with exudates since the ear panels
45,
46 andlor 48 allow the sides of the pull-on garment to expand and contract.
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/224?1
21
The ear panels 45, 46 and 48 may be formed by unitary elements of the
pull-on garment 20 or 120 (i.e., they are not separately manipulative elements
secured to the pull-on garment 20 or 120, but rather are formed from and are
extensions of one or more of the various layers of the pull-on garment). In a
preferred embodiment, each of the ear panels 45, 46 and 48 is a projected
member
of the chassis 41 (more clearly shown in Fig. 8). Preferably, the ear panels
45, 46
and 48 include at least one unitary element or a continuous sheet material
(e.g. the
nonwoven outer cover 74 in Fig. 9) that forms a part of the chassis 41 and
continuously extends into the ear panels 45, 46 and 48. Alternatively, the ear
panels 45, 46 and 48 may be discrete members (not shown in Figs.) which do not
have any unitary element that forms a part of the chassis 41, and may be
formed
by joining the discrete members to the corresponding sides of the chassis 41.
In a preferred embodiment, the pull-on garment 20 or 120 further includes
seam panels 66 each extending laterally outward from each of the ear panels
45,'
46 and 48; and tear open tabs 31 each extending laterally outward from the
seam
panel 66. In a preferred embodiment, each of the seam panels 66 is an
extension
of the corresponding ear panels 45, 46 and 48, or at least one of the
component
elements used therein, or any other combination of the elements. More
preferably,
each of the tear open tabs 31 is also an extension of the corresponding seam
panel 66 or at least one of its component elements used therein, or any other
combination of its elements.
In a preferred embodiment, the corresponding edge portions of the chassis
41 and/or the ear panels 45, 46 and 48 are seamed directly or indirectly
(e.g.,
through the seam panels 66), in an overlaying manner to make an overlapped
seam structure. Alternatively, the front and ear panels 46 and 48 can be
seamed
in a butt seam manner (not shown in Figs.). The bonding of the seams 32 can be
performed by any suitable means known in the art appropriate for the specific
materials employed in the chassis 41 and/or the ear panels 45, 46 and 48.
Thus,
sonic sealing, heat sealing, pressure bonding, adhesive or cohesive bonding,
sewing, autogeneous bonding, and the like may be appropriate techniques.
Preferably, the seam panels 66 are joined by a predetermined pattern of
heat/pressure or ultrasonic welds which withstands the forces and stresses
generated on the garment 20 or 120 during wear.
A continuous belt 38 is formed by the ear panels 45, 46 and 48, and a part
of the chassis 41 about the waist opening 36 as shown in Figs. 6 and 7.
Preferably, elasticized waist bands 50 are provided in both the front region
26 and
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22:171
22
the back region 28. The continuous belt 38 acts to dynamically create fitment
forces in the pull-on garment 20 or 120 when positioned on the wearer, to
maintain
the pull-on garment 20 or 120 on the wearer even when loaded with body
exudates
thus keeping the absorbent core 25 (not shown in Fig. 7) in close proximity to
the
wearer, and to distribute the forces dynamically generated during wear about
the
waist thereby providing supplemental support for the absorbent core 25 without
binding or bunching the absorbent core 25.
Fig. 8 is a partially cut-away plan view of the pull-on garment 20 of Fig. 7
in
its uncontracted state (except in the ear panels 46 and 48 which are left in
their
relaxed condition) with the topsheet 24 facing the viewer, prior to the ear
panels 46
and 48 being joined together by the seams 32. The pull-on garment 20 has the
front region 26, the back region 28 opposed to the front region 26, the crotch
region 30 positioned between the front region 26 and the back region 28, and a
periphery which is defined by the outer perimeter or edges of the pull-on
garment
20 in which the side edges are designated 150 and 240, and the end edges or
waist edges are designated 152. The topsheet 24 has the body-facing surface of
the pull-on garment 20 which is positioned adjacent to the wearer's body
during
use. The backsheet 22 has the outer-facing surface of the pull-on garment 20
which is positioned away from the wearer's body. The pull-on garment 20
includes
the chassis 41 including the liquid pervious topsheet 24, the liquid
impervious
backsheet 22 associated with the topsheet 24, and the absorbent core 25
positioned between the topsheet 24 and the backsheet 22. The garment 20
further
includes the front and back ear panels 46 and 48 extending laterally outward
from
the chassis 41, the elasticized leg cuffs 52, and the elasticized waistbands
50. The
topsheet 24 and the backsheet 22 have length and width dimensions generally
larger than those of the absorbent core 25. The topsheet 24 and the backsheet
22
extend beyond the edges of the absorbent core 25 to thereby form the side
edges
150 and the waist edges 152 of the garment 20. The liquid impervious backsheet
22 preferably includes a liquid impervious plastic film 68.
The pull-on garment 20 also has two centerlines, a longitudinal centerline
100 and a transverse centerline 110. Herein, "longitudinal" refers to a line,
axis, or
direction in the plane of the pull-on garment 20 that is generally aligned
with (e.g.
approximately parallel with) a vertical plane which bisects a standing wearer
into
left and right halves when the pull-on garment 20 is worn. Herein,
"transverse" and
"lateral" are interchangeable and refer to a line, axis or direction which
lies within
the plane of the pull-on garment that is generally perpendicular to the
longitudinal
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22d71
23
direction (which divides the wearer into front and back body halves). The pull-
on
garment 20 and component materials thereof also have a body-facing surface
which faces the skin of wearer in use and an outer-facing surface which is the
opposite surface to the body-facing surface.
Each of the ear panels 45, 46 and 48 has the outermost edge line 242.
Herein, "edge line" refers to lines which define the outlines of the ear
panels 45, 46
and 48 or the chassis 41. Herein, "outermost" refers to portions which are
farthest
from the longitudinal centerline 100. At least one of the edge lines 242 has a
nonuniform lateral distance LD from the longitudinal center line 100 in the
uncontracted state of the garment 20.
While the topsheet 24, the backsheet 22, and the absorbent core 25 may be
assembled in a variety of well known configurations, exemplary chassis
configurations are described generally in U.S. Patent 3,860,003 entitled
"Contractible Side Portions for Disposable Diaper" which issued to Kenneth B =
Buell on January 14, 1975; and U.S. Patent 5,151,092 entitled "Absorbent
Article
With Dynamic Elastic Waist Feature Having A Predisposed Resilient Flexural
Hinge" which issued to Kenneth B. Buell et al., on September 29, 1992.
Fig. 9 is a cross-sectional view of a preferred embodiment taken along the
section line 9-9 of Fig. 8. The pull-on garment 20 includes the chassis 41
including
the liquid pervious topsheet 24, the liquid impervious backsheet 22 associated
with
the topsheet 24, and the absorbent core 25 positioned between the topsheet 24
and the backsheet 22. The pull-on garment further includes the front ear
panels 46
each extending laterally outward from the chassis 41, and an inner barrier
cuffs 54.
Although Fig. 9 depicts only the structure of the front ear panel 46 and the
chassis
41 in the front region 26, preferably a similar structure is also provided in
the back
region 28. In a preferred embodiment, each of the front ear panels 46 is
formed by
a lamination of an extended part 72 of the barrier flap 56, an elastic
laminate 70
and the nonwoven outer cover 74. The elastic laminate 70 includes a plane
elastomeric material 124 (not shown in Fig. 9 but in Fig. 11 ). Herein, "plane
elastomeric material" refers to elastomeric materials which continuously
extend in
two dimensional directions. Preferred plane elastomeric materials include a
scrim,
a perforated (or apertures formed) film, an elastomeric woven or nonwoven, and
the like. In a preferred embodiment, the plane elastomeric material 124
includes at
least a portion that has a nonuniform lateral width.
The absorbent core 25 can be any absorbent member which is generally
compressible, conformable, non-irritating to the wearer's skin, and capable of
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/2241
24
absorbing and retaining liquids such as urine and other certain body exudates.
The absorbent core 25 may be manufactured in a wide variety of sizes and
shapes
(e.g., rectangular, hourglass, "T"-shaped, asymmetric, etc.) and from a wide
variety
of liquid-absorbent materials commonly used in disposable pull-on garments and
other absorbent articles such as comminuted wood pulp which is generally
referred
to as airfelt. Examples of other suitable absorbent materials include creped
cellulose wadding; meltblown polymers including coform; chemically stiffened,
modified or cross-linked cellufosic fibers; tissue including tissue wraps and
tissue
laminates; absorbent foams; absorbent sponges; superabsorbent polymers;
absorbent gelling materials; or any equivalent material or combinations of
materials.
The configuration and construction of the absorbent core 25 may vary (e.g.,
the absorbent core 25 may have varying caliper zones, a hydrophilic gradient,
a~
a
superabsorbent gradient, or lower average density and lower average basis
weight
acquisition zones; or may include one or more layers or structures). Further,
the
size and absorbent capacity of the absorbent core 25 may also be varied to
accommodate wearers ranging from infants through adults. However, the total
absorbent capacity of the absorbent core 25 should be compatible with the
design
loading and the intended use of the garment 20.
A preferred embodiment of the garment 20 has an asymmetric, modified
hourglass-shaped absorbent core 25 having ears in the front and back waist
regions 26 and 28. Other exemplary absorbent structures for use as the
absorbent
core 25 that have achieved wide acceptance and commercial success are
described in U.S. Patent No. 4,610,678 entitled "High-Density Absorbent
Structures" issued to Weisman et al. on September 9, 1986; U.S. Patent No.
4,673,402 entitled "Absorbent Articles With Dual-Layered Cores" issued to
Weisman et al. on June 16, 1987; U.S. Patent No. 4,888,231 entitled "Absorbent
Core Having A Dusting Layer" issued to Angstadt on December 19, 1989; and U.S.
Patent No. 4,834,735, entitled "High Density Absorbent Members Having Lower
Density and Lower Basis Weight Acquisition Zones", issued to Alemany et al. on
May 30, 1989.
The chassis 41 may further include an acquisition/distribution core 84 of
chemically stiffened fibers positioned over the absorbent core 25, thereby
forming a
dual core system. In a preferred embodiment, the fibers are hydrophilic
chemically
stiffened celluiosic fibers. Herein, "chemically stiffened fibers" means any
fibers
which have been stiffened by chemical means to increase stiffness of the
fibers
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
under both dry and aqueous conditions. Such means include the addition of
chemical stiffening agents which, for example, coat and/or impregnate the
fibers.
Such means also include the stiffening of the fibers by altering the chemical
structure of the fibers themselves, e.g., by cross-linking polymer chains.
5 The fibers utilized in the acquisition/distribution core 84 can also be
stiffened
by means of chemical reaction. For example, crosslinking agents can be applied
to
the fibers which, subsequent to application, are caused to chemically form
intrafiber
crosslink bonds. These crosslink bonds can increase stiffness of the fibers.
Whereas the utilization of intrafiber crosslink bonds to chemically stiffen
the fibers
10 is preferred, it is not meant to exclude other types of reactions for
chemical
stiffening of the fibers.
In the more preferred stiffened fibers, chemical processing includes
intrafiber
crosslinking with crosslinking agents while such fibers are in a relatively
dehydrated, defibrated (i.e. individualized), twisted, curled condition.
Suitably
15 chemical stiffening agents include monomeric crosslinking agents including,
but not
limited to, C2 Ce dialdehydes and CZ Ce monoaldehydes having an acid
functionality
can be employed to form the cosslinking solution. These compounds are capable
of reacting with at least two hydroxyl groups in a single cellulose chain or
on
proximately located cellulose chains in a single fiber. Such crosslinking
agents
20 contemplated for use in preparing the stiffened cellulose fibers include,
but are not
limited to, giutaraldehyde, glyoxal, formaldehyde, and glyoxylic acid. Other
suitable
stiffening agents are polycarboxylates, such as citric acid. The
polycarboxylic
stiffening agents and a process for making stiffened fibers from them are
described
in U.S. Patent No. 5,190,563, entitled "Process for Preparing Individualized,
25 Polycarboxylic Acid crosslinked Fibers" issued to Herron, on March 2, 1993.
The
effect of crosslinking under these conditions is to form fibers which are
stiffened
and which tend to retain their twisted, curled configuration during use in the
absorbent articles herein. Such fibers, and processes for making them are
cited in
the above incorporated patents.
Preferred dual core systems are disclosed in U.S. Patent No. 5,234,423,
entitled "Absorbent Article With Elastic Waist Feature and Enhanced
Absorbency"
issued to Alemany et al., on August 10, 1993; and in U.S. Patent No.
5,147,345,
entitled "High Efficiency Absorbent Articles For Incontinence Management"
issued
to Young, LaVon and Taylor on September 15, 1992. fn a preferred embodiment,
the acquisition/distribution core 84 includes chemically treated stiffened
cellulosic
fiber material, available from Weyerhaeuser Co. (U.S.A.) under the trade
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
26
designation of "CMC". Preferably, the acquisition/distribution core 84 has a
basis
weight of from about 40 g/m2 to about 400 g/m2, more preferably from about 75
g/m2 to about 300 g/m2.
More preferably, the chassis 22 further includes an acquisition/distribution
layer 82 between the topsheet 24 and the acquisition/distribution core 84 as
shown
in Fig. 9. The acquisition/distribution layer 82 is provided to help reduce
the
tendency for surface wetness of the topsheet 24. The acquisition/distribution
layer
82 preferably includes carded, resin bonded hiloft nonwoven materials such as,
for
example, available as Code No. FT-6860 from Polymer Group, Inc., North America
(Landisiville, New Jersey, U.S.A.), which is made of polyethylene
telephthalate
fibers of 6 dtex, and has a basis weight of about 43 g/m2. A preferable
example
for the acquisition/distribution layer 82 and the acquisition/distribution
core 84 is
disclosed in EP 0797968A1 (Kurt et al.) published on October 1, 1997.
The topsheet 24 is preferably compliant, soft feeling, and non-irritating to
the
wearer's skin. Further, the topsheet 24 is liquid pervious permitting liquids
(e.g.,
urine) to readily penetrate through its thickness. A suitable topsheet 24 may
be
manufactured from a wide range of materials such as woven and nonwoven
materials; polymeric materials such as apertured formed thermoplastic films,
apertured plastic films, and hydroformed thermoplastic films; porous foams;
reticulated foams; reticulated thermoplastic films; and thermoplastic scrims.
Suitable woven and nonwoven materials can be included of natural fibers (e.g.,
wool or cotton fibers), synthetic fibers (e.g., polymeric fibers such as
polyester,
polypropylene, or polyethylene fibers) or from a combination of natural and
synthetic fibers. The topsheet 24 is preferably made of a hydrophobic material
to
isolate the wearer's skin from liquids which have passed through the topsheet
24
and are contained in the absorbent core 25 (i.e., to prevent rewet). If the
topsheet
24 is made of a hydrophobic material, at least the upper surface of the
topsheet 24
is treated to be hydrophilic so that liquids will transfer through the
topsheet more
rapidly. This diminishes the likelihood that body exudates will flow off the
topsheet
24 rather than being drawn through the topsheet 24 and being absorbed by the
absorbent core 25. The topsheet 24 can be rendered hydrophilic by treating it
with
a surfactant. Suitable methods for treating the topsheet 24 with a surfactant
include spraying the topsheet 24 material with the surfactant and immersing
the
material into the surfactant. A more detailed discussion of such a treatment
and
hydrophilicity is contained in U.S. Patent No. 4,988,344 entitled "Absorbent
Articles
with Multiple Layer Absorbent Layers" issued to Reising, et al. on January 29,
1991
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
27
and U.S. Patent No. 4,988,345 entitled "Absorbent Articles with Rapid
Acquiring
Absorbent Cores" issued to Reising on January 29, 1991.
In a preferred embodiment, the topsheet 24 is a nonwoven web that can
provide reduced tendency for surface wetness; and consequently facilitate
maintaining urine absorbed by the core 25 away from the user's skin, after
wetting.
One of the preferred topsheet materials is a thermobonded carded web which is
available as Code No. P-8 from Fiberweb North America, Inc. (Simpsonville,
South
Carolina, U.S.A.). Another preferred topsheet material is available as Code
No. S-
2355 from Havix Co., Japan. This material is a bi-layer composite material,
and
made of two kinds of synthetic surfactant treated bicomponent fibers by using
carding and air-through technologies. Yet another preferred topsheet material
is a
thermobonded carded web which is available as Code No. Profleece Style
040018007 from Amoco Fabrics, Inc. (Gronau, Germany).
Another preferred topsheet 24 includes an apertured formed film. Aperturecf
formed films are preferred for the topsheet 24 because they are pervious to
body
exudates and yet non-absorbent and have a reduced tendency to allow liquids to
pass back through and rewet the wearer's skin. Thus, the surface of the formed
film which is in contact with the body remains dry, thereby reducing body
soiling
and creating a more comfortable feel for the wearer. Suitable formed films are
described in U.S. Patent No. 3,929,135, entitled "Absorptive Structures Having
Tapered Capillaries", issued to Thompson on December 30, 1975; U.S. Patent No.
4,324,246 entitled "Disposable Absorbent Article Having A Stain Resistant
Topsheet", issued to Mullane, et al. on April 13, 1982; U.S. Patent No.
4,342.314
entitled "Resilient Plastic Web Exhibiting Fiber-Like Properties", issued to
Radel. et
al. on August 3, 1982; U.S. Patent No. 4,463,045 entitled "Macroscopically
Expanded Three-Dimensional Plastic Web Exhibiting Non-Glossy Visible Surface
and Cloth-Like Tactile Impression", issued to Ahr et al. on July 31, 1984; and
U.S.
5,006,394 "Muftilayer Polymeric Film" issued to Baird on April 9, 1991.
In a preferred embodiment, the backsheet 22 includes the liquid impervious
film 68 as shown in, for example, Fig. 9. Preferably, the liquid impervious
film 68
longitudinally extends in the front, back and crotch regions 26, 28 and 30.
More
preferably, the liquid impervious film 68 does not laterally extend into the
at least
one of the ear panels 46 or 48. The liquid impervious film 68 has a body-
facing
surface 79 and an outer-facing surface 77. The liquid impervious film 68 is
impervious to liquids (e.g., urine) and is preferably manufactured from a thin
plastic
film. However, more preferably the plastic film permits vapors to escape from
the
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22.~''1
28
garment 20. In a preferred embodiment, a microporous polyethylene flm is used
for the liquid impervious film 68. A suitable microporous polyethylene film is
manufactured by Mitsui Toatsu Chemicals, Inc., Nagoya, Japan and marketed in
the trade as PG-P. In a preferred embodiment, a disposable tape (not shown in
Figs.) is additionally joined to the outer surface of the backsheet 22 to
provide a
convenient disposal after soiling.
A suitable material for the liquid impervious film 88 is a thermoplastic film
having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 mm (2.0
mils),
preferably including polyethylene or polypropylene. Preferably, the liquid
impervious film has a basis weight of from about 5 g/m2 to about 35 g/m2.
However, it should be noted that other flexible liquid impervious materials
may be
used. Herein, "flexible" refers to materials which are compliant and which
will
readily conform to the general shape and contours of the wearer's body.
Preferably, the backsheet 22 further includes the nonwoven outer cover 7~
which is joined with the outer-facing surface of the liquid impervious ~Im 68
to form
a laminate (i.e., the backsheet 22). The nonwoven outer cover 74 is positioned
at
the outermost portion of the garment 20 and covers at least a portion of the
outermost portion of the garment 20. In a preferred embodiment, the nonwoven
outer cover 74 covers almost all of the area of the outermost portion of the
garment
20. The nonwoven outer cover 74 may be joined to the liquid impervious film 68
by
any suitable attachment means known in the art. For example, the nonwoven
outer cover 74 may be secured to the liquid impervious film 68 by a uniform
continuous layer of adhesive, a patterned layer of adhesive, or an array of
separate
lines, spirals, or spots of adhesive. Suitable adhesives include a hotmelt
adhesive
obtainable from Nitta Findley Co., Ltd., Osaka, Japan as H-2128, and a hotmelt
adhesive obtainable from H.B. Fuller Japan Co., Ltd., Osaka, Japan as JM-6064.
In a preferred embodiment, the nonwoven outer cover 74 is a carded
nonwoven web, for example, obtainable from Havix Co., LTD., Gifu, Japan as E-
2341. The nonwoven outer cover 74 is made of bi-component fibers of a
polyethylene (PE) and a polypropylene (PP). The ratio of PE/PP is about 50150.
The PE/PP bi-component fiber has the dimension of 2d x 51 mm. Another
preferred carded nonwoven web is obtainable from Chisso Corp., Moriyama,
Japan. The nonwoven outer cover 74 is also made of bi-component fibers of a
polyethylene (PE) and a polypropylene (PP). The ratio of PEIPP is about 50/50.
In another preferred embodiment, the nonwoven web is a spunbonded
nonwoven web, for example, obtainable from Mitsui Petrochemical Industries,
Ltd.,
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
29
Tokyo, Japan. The nonwoven web is made of bi-component fibers of a
polyethylene (PE) and a polypropylene (PP). The ratio of PE/PP is about 80/20.
The PE/PP bi-component fiber has the thickness is approximately 2.3d. Another
spunbonded nonwoven web is obtainable from Fiberweb France S.A., under Code
No. 13561 DAPP.
The backsheet 22 is preferably positioned adjacent the outer-facing surface
of the absorbent core 25 and is preferably joined thereto by any suitable
attachment means known in the art. For example, the backsheet 22 may be
secured to the absorbent core 25 by a uniform continuous layer of adhesive, a
patterned layer of adhesive, or an array of separate lines, spirals, or spots
of
adhesive. Adhesives which have been found to be satisfactory are manufactured
by H. B. Fuller Company of St. Paul, Minnesota, U.S.A., and marketed as
HL-1358J. An example of a suitable attachment means including an open pattern
,
network of filaments of adhesive is disclosed in U.S. Patent No. 4,573,986
entitled ~
"Disposable Waste-Containment Garment", which issued to Minetola et al. on
March 4, 1986. Another suitable attachment means including several lines of
adhesive filaments swirled into a spiral pattern is illustrated by the
apparatus and
methods shown in U.S. Patent No. 3,911,173 issued to Sprague, Jr, on October
7,
1975; U.S. Patent No. 4,785,996 issued to Ziecker, et al. on November 22,
1978;
and U.S. Patent No. 4,842,666 issued to Werenicz on June 27, 1989.
Alternatively, the attachment means may include heat bonds, pressure bonds,
ultrasonic bonds, dynamic mechanical bonds, or any other suitable attachment
means or combinations of these attachment means as are known in the art.
In an alternative embodiment, the absorbent core 25 is not joined to the
backsheet 22, and/or the topsheet 24 in order to provide greater extensibility
in the
front region 26 and the back region 28.
The pull-on garment 20 preferably further includes elasticized leg cuffs 52
for providing improved containment of liquids and other body exudates. The
elasticized leg cuffs 52 may include several different embodiments for
reducing the
leakage of body exudates in the leg regions. (The leg cuffs can be and are
sometimes also referred to as leg bands, side flaps, barrier cuffs, elastic
cuffs or
gasketing cuffs.) U.S. Patent 3,860,003 entitled "Contractible Side Portions
for
Disposable Diaper" issued to Buell on January 14, 1975, describes a disposable
diaper which provides a contractible leg opening having a side flap and one or
more elastic members to provide an elasticized leg cuff. U.S. Patent 4,909,803
entitled "Disposable Absorbent Article Having Elasticized Flaps" issued to
Aziz et
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
al. on March 20, 1990, describes a disposable diaper having "stand-up"
elasticized
flaps (barrier cuffs) to improve the containment of the leg regions. U.S.
Patent
4,695,278 entitled "Absorbent Article Having Dual Cuffs" issued to Lawson on
September 22, 1987; and U.S. Patent 4,795,454 entitled "Absorbent Article
Having
5 Leakage-Resistant Dual Cuffs" issued to Dragoo on January 3, 1989, describe
disposable diapers having dual cuffs including a gasketing cuff and a barrier
cuff.
U.S. Patent 4,704,115 entitled "Disposable Waist Containment Garment" issued
to
Buell on November 3, 1987, discloses a disposable diaper or incontinence
garment
having side-edge-leakage-guard gutters configured to contain free liquids
within the
10 garment.
While each elasticized leg cuff 52 may be configured so as to be similar to
any of the leg bands, side flaps, barrier cuffs, or elastic cuffs described
above, it is
preferred that the elasticized leg cuff 52 includes an elastic gasketing cuff
62 with
one or more elastic strands 64 as shown in Fig. 8, which is described in the
above-
15 referred U.S. Patent Nos. 4,695,278 and 4,795,454. It is also preferred
that each
elasticized leg cuff 52 further includes inner barrier cuffs 54 each including
a barrier
flap 56 and a spacing means 58 which are described in the above-referenced
U.S.
Patent No. 4,909,803.
The pull-on garment 20 of the present invention further includes an
20 elasticized waistband 50 that provides improved fit and containment. The
elasticized waistband 50 is that portion or zone of the pull-on garment 20
which is
intended to elastically expand and contract to dynamically fit the wearer's
waist.
The waistband 50 of the present invention includes an elastic laminate 70
which
will be described in detail hereinafter. The waistband 50 is disposed along at
least
25 one, preferably both of the end edges 152 of the disposable garment 20. The
elasticized waistband 50 preferably extends longitudinally inwardly from the
end
edge 152 of the pull-on garment 20 toward the waist edge 154 of the absorbent
core 25. Preferably, the pull-on garment 20 has two elasticized waistbands 50,
one
positioned in the back region 28 and one positioned in the front region 26,
although
30 other pull-on diaper embodiments can be constructed with a single
elasticized
waistband. The elasticized waistband 50 may be constructed in a number of
different configurations including those described in U.S. Patent 4,515,595
entitled
"Disposable Diapers with Elastically Contractible Waistbands" issued to Kievit
et al.
on May 7, 1985 and the above referenced U.S. Patent 5,151,092 issued to Buell.
Fig. 10 is a cross-sectional view of one preferred embodiment taken along
the section line 10-10 of Fig. 8. As shown in Fig. 10, both the backsheet 22
and
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
31
the topsheet 24 extend beyond the waist edge 154 of the absorbent core 25 to
define a waist flap 156. Preferably, the juxtaposed areas of the backsheet 22
and
the topsheet 24 are joined together by an adhesive (not shown in Figs.). In a
preferred embodiment, the waistband 50 is joined to the waist flap 156.
Preferably,
the waistband 50 is disposed on and joined to the topsheet 24 as shown in Fig.
10.
Alternatively, the waistband 50 can be disposed and joined between the
backsheet
22 and the topsheet 24 as shown in Fig. 11. The waistband 50 can be joined to
the topsheet 24 (and the backsheet 22) by an adhesive means (not shown in
Figs.)
such as those well known in the art. For example, the waistband 50 may be
secured to the waist flap 156 by a uniform continuous layer of adhesive, a
patterned layer of adhesive, or an array of separate lines or spots of
adhesive. A
preferred adhesive for use is available from Ato Findley Inc., WI, U.S.A.,
under the
designation H2085.
In a preferred embodiment, the waistband 50 is secured to the waist fla~
156 in an elastically contractible condition so that in a normally
unrestrained
configuration the waistband 50 effectively contract or gather the waist flap
156.
The waistband 50 can be secured to the waist flap 156 in an elastically
contractible
condition in at least two ways. For example, the waistband 50 may be stretched
and secured to the waist flap 156 while the waist flap 156 is in an
uncontracted
condition. Alternatively, the waist flap 156 may be contracted, for example by
pleating, and the waistband 50 is secured to the contracted waist flap 156
while the
waistband 50 in its relaxed or unstretched condition.
Yet alternatively, the waistband 50 is joined, in its relaxed or unstretched
condition, to the waist flap 156 which is in an uncontracted condition,
thereby
forming a composite laminate with the materials of the backsheet 22 and the
topsheet 24. At least a portion, preferably the entire portion of the
composite
laminate is then subjected to mechanical stretching sufficient to permanently
elongate the non-elastic components which are the backsheet 22 and the
topsheet
24. The composite laminate is then allowed to return to its substantially
untensioned condition. Thus, the composite laminate is formed into a "zero
strain"
stretch laminate which works as elasticized waistband 50.
Herein, "zero strain" stretch laminate refers to a laminate included of at
least
two plies of material which are secured to one another along at least a
portion of
their coextensive surfaces while in a substantially untensioned ("zero
strain")
condition; one of the plies including a material which is stretchable and
elastomeric
(i.e., will return substantially to its untensioned dimensions after an
applied tensile
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
32
force has been released) and a second ply which is elongatable (but not
necessarily elastomeric) so that upon stretching the second ply will be, at
least to a
degree, permanently elongated so that upon release of the applied tensile
forces, it
will not fully return to its original undeformed configuration. The resulting
stretch
laminate is thereby rendered elastically extensible, at least up to the point
of initial
stretching, in the direction of initial stretching. Particularly preferred
methods and
apparatus used for making stretch laminates utilize meshing corrugated rolls
to
mechanically stretch the components. Particularly preferred apparatus and
methods are disclosed in U.S. Patent No. 5,167,897 issued to Weber et al. on
December 1, 1992; U.S. Patent No. 5,156,793 issued to Buell et al. on October
20,
1990; and U.S. Patent No. 5,143,679 issued to Weber et al. on September 1,
1992.
In a preferred embodiment, the waistband 50 extends across essentially the
entire lateral width of the absorbent core 25. Herein, "lateral width" refers
to the
dimension between the side edges of components of disposable garments
Herein, "across essentially" is used in this context to indicate that the
waistband 50
does not need to extend absolutely across the entire width of the absorbent
core
so long as it extends sufficiently far across the width thereof to provide the
elasticized waistband. Preferably, the waistband 50 extends across only a
portion
of the lateral width of the absorbent core 25, more preferably at least
between
20 portions in the ear panels 46 and 48 {as shown in Fig. 8). In one preferred
embodiment, the waistband 50 extends across the entire lateral width of the
garment 20 (not shown Figs.).
The extent to which the waistband 50 extends inboard from the end edge
152 of the garment 20, and thus the longitudinal span of the resultant
waistband,
25 can vary according to the particular construction of the garment 20. The
longitudinal span of the waistband 50 is at least about 5 mm, preferably from
about
6 mm to about 60 mm, more preferably from about 15 mm to about 30 mm.
At least one of the ear panels 45, 4fi and 48 includes the elastic laminate 70
of the present invention. For example, each of the front ear panels 46 shown
in
Fig. 9 includes the elastic laminate 70 which includes the elastomeric
material 124
(not shown in Fig. 9) which preferably extends laterally outward from the
chassis
41 to provide good fitness by generating the optima! retention (or sustained)
force
at the waist and side areas of the wearer. Preferably, the elastomeric
material 124
is extensible in at least one direction, preferably in the lateral direction
to generate
a retention (or sustained) force that is optimal to prevent the pull-on
garment 20
from drooping, sagging, or sliding down from its position on the torso without
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22471
33
causing the red marking on the skin of the wearer. In a preferred embodiment,
each of the ear panels 45, 46 and 48 includes the elastomeric material 124.
The elastic laminate 70 is operatively joined to at least one of the nonwoven
webs 72 and 74 in the ear panels 45, 46 and 48 to allow the elastic laminate
70 to
be elastically extensible in at least the lateral direction. In a preferred
embodiment,
the elastic laminate 70 is operatively joined to the nonwoven webs 72 and 74
by
securing them to at least one, preferably both of the nonwoven webs 72 and 74
while in a substantially untensioned (zero strain) condition.
The elastic laminate 70 can be operatively joined to the nonwoven webs 72
and 74, by using either an intermittent bonding configuration or a
substantially
continuous bonding configuration. Herein, "intermittently" bonded laminate web
means a laminate web wherein the plies are initially bonded to one another at
discrete spaced apart points or a laminate web wherein the plies are
substantially
unbonded to one another at discrete spaced apart areas. Conversely, a
"substantially continuously" bonded laminate web means a laminate web wherein
the plies are initially bonded substantially continuously to one another
throughout
the areas of interface. It is preferred that the stretch laminate be bonded
over all or
a significant portion of the stretch laminate so that the inelastic webs
(i.e., the
nonwoven webs 72 and 74) elongate or draw without causing rupture, and the
layers of the stretch laminates are preferably bonded in a configuration that
maintains all of the layers of the stretch laminate in relatively close
adherence to
one another after the incremental mechanical stretching operation.
Consequently,
the elastic panel members and the other plies of the stretch laminate are
preferably
substantially continuously bonded together using an adhesive. In a
particularly
preferred embodiment, the adhesive selected is applied with a control coat
spray
pattern at a basis weight of about 7.0 grams/square m. The adhesive pattern
width
is about 6.0 cm. The adhesive is preferably an adhesive such as is available
from
Nitta Findley Co., Ltd., Osaka, Japan, under the designation H2085F.
Alternatively, the elastic panel member and any other components of the
stretch
laminates may be intermittently or continuously bonded to one another using
heat
bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or
any other method as is known in the art.
After the elastic laminate 70 is operatively joined to at least one of the
nonwoven webs 72 and 74, at least a portion of the resultant composite stretch
laminate is then subjected to mechanical stretching sufficient to permanently
elongate the non-elastic components which are, for example, the nonwoven webs
CA 02345756 2001-03-29
WO 00/20206 PCT/US99/22d71
34
72 and 74. The composite stretch laminate is then allowed to return to its
substantially untensioned condition. At least one pair of, preferably both of
the ear
panels 45, 46 and 48 is thus formed into "zero strain" stretch laminates.
(Alternatively, the elastic laminate 70 could be operatively joined in a
tensioned
condition and then subjected to mechanical stretching; although this is not as
preferred as a "zero strain" stretch laminate.)
The elastic laminate 70 is preferably joined to, more preferably directly
secured to the respective edges 78 of the liquid impervious film (i.e., the
liquid
impervious film 68) through an adhesive 76 as shown in Fig. 9. In a preferred
embodiment, while liquid impervious film 68 longitudinally extends in the
front, back
and crotch regions 26, 28 and 30, it does not laterally extend into at least
one of,
preferably each of the extensible ear panels 45, 46 and 48. In a more
preferred
embodiment, the elastic laminate 70 is joined to the respective edges 78 of
the
liquid impervious film 68 at the outer-facing surface 77 as shown in Fig. 9.
In an
alternative embodiment, the elastic laminate 70 may be joined to the
respective
edges 78 of the liquid impervious film 68 at the body-facing surface 79 (not
shown
in Figs.). Preferably, the adhesive 76 is applied in a spiral glue pattern. In
a
preferred embodiment, the adhesive 76 is a flexible adhesive with an amorphous
and crystallizing component. Such a preferred adhesive is made by Nitta
Findley
Co., Ltd., Osaka, Japan, under the designation H2085F. Alternatively, the
elastic
laminate 70 may be joined to the respective edges 78 of the liquid impervious
film
68 by any other bonding means known in the art which include heat bonds,
pressure bonds, ultrasonic bonds, dynamic mechanical bonds, or combinations of
these attachment means.
It is understood that the examples and embodiments described herein are
for illustrative purpose only and that various modifications or changes will
be
suggested to one skilled in the art without departing from the scope of the
present
invention.
