Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE: STRETCH LAMINATE MATERIAL AND METHODS OF MAKING
SAME
FIELD
[0001] The embodiments disclosed relate to several variants of a
stretch laminate material and to methods of making such stretch laminate
materials and to absorbent articles comprising a stretch laminate.
BACKGROUND
[0002] Absorbent articles such as diapers and training pants Are
desirably configured for fit wearers snugly and to conform to the shape of the
wearers body while the wearer moves about. In recent years, such absorbent
articles have included various elastic components to facilitate such
conformation.
SUMMARY
[0003] The following summary is intended to introduce the reader to
this specification but not to define any invention_ In general, this
specification
discusses one or more methods or apparatuses related to stretch laminates,
method of making stretch laminates, and articles such as diapers
incorporating stretch laminates.
[0004] According to one aspect, a stretch laminate comprises a carrier
web extending lengthwise in a machine (or longitudinal) direction and
widthwise in a cross (or lateral) direction between opposed side edges, the
carrier web including an extensible zone and an inextensible zone disposed
side-by-side across the width of the carrier web; and an elastomeric element
laminated to the nonwoven layer over at least a portion of the extensible
zone.
[0005] In some embodiments, the carrier web comprises a nonwoven
layer carded in the machine direction at least in the extensible zone. In some
embodiments, the nonwoven layer is also carded in the inextensible zone.
The laminate can comprise a reinforcement applied to the carrier web in the
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inextensible zone. The reinforcement can comprise a reinforcing layer
laminated to the inextensible zone of the carrier web. The reinforcement can
comprise embossing applied to the inextensible zone of the carrier web.
[0006] According to another aspect, a diaper comprises a shell having
a front waist end and a rear waist end and a crotch portion extending between
the front and rear waist ends, the shell configured to hold an absorbent
assembly against the crotch of a wearer, the shell Including ears extending
laterally outwardly from at least one of the front and rear waist ends, the
ears
comprising a stretch laminate, the stretch laminate comprising a carrier web
extending lengthwise in a machine direction and widthwise in a cross direction
between opposed side edges, the carrier web including an extensible zone
and an inextensible zone disposed side-by-side across the width of the carrier
web; and an elastomeric element laminated to the nonwoven layer over at
least a portion of the extensible zone.
[0007] According to another aspect, a method making a stretch
laminate having an elastic region and a non-elastic region comprises:
providing a non-woven material carded in a machine direction; applying an
elastic material in a first region of the non-woven material; and reinforcing
a
second region of the of the non-woven material, the second region
overlapping a portion of the elastic material, the second region generally
corresponding to the non-elastic region of the laminate and the first region
. non-overlapped by the second region generally corresponding to the
elastic
region. The stretch laminate is stretchable transversely of the machine
direction in the elastic region and is substantially unstretchable in the non-
elastic region.
[0008] In some embodiments, the non-elastic region is reinforced by
applying a substantially non-stretchable film to the non-elastic region. The
film
and the elastic material can be bonded together in the overlap region. In
some embodiments, the non-elastic region can be reinforced by embossing
the non-elastic region. The non-elastic region can be reinforced by heating
the non-elastic region to a temperature sufficient to at least partially melt
at
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least some of the carded fibers in the non-elastic region_ The elastic
material
can be applied to the non-woven material by bonding the elastic material to
the non-woven material. The elastic material can be an elastic film applied to
the non-woven material by bonding the elastic film to the non-woven material.
The elastic film can be bonded to the non-woven material across substantially
the entire surface of the elastic film. The elastic film can be bonded to the
non-woven web with an adhesive, The elastic film can be bonded to the non-
woven web with a stretchable adhesive_ The elastic film can be intermittently
bonded to the non-woven material with an adhesive. The elastic film can be
point-bonded to the non-woven material. The elastic film can be extrusion-
bonded to the non-woven material. The elastic material can be applied to the
non-woven material by spraying the elastic material onto the non-woven
material. The elastic material can be an elastic film applied to the non-woven
material by forming the elastic film on the non-woven material.
[0009] According to
another aspect, a method making a stretch
laminate having an elastic region and a non-elastic region comprises:
providing a non-woven material carded in a machine direction; applying an
elastic material in a first region of the non-woven material corresponding to
the elastic region; and reinforcing a second region of the of the non-woven
material corresponding to the non-elastic region. The non-elastic region is
spaced apart from the elastic region by gap region, and the stretch laminate
is
stretchable in the elastic region except for the gap region in a cross-
direction
that generally perpendicular to the machine direction and is Substantially not
stretchable in the non-elastic region.
WM Other aspects
and features of the present specification will
become apparent, to those ordinarily skilled in the art, upon review of the
following description of the specific examples of the specification.
BRIEF DESCRIPTION OF THE DRAWINGS
10011] The
drawings included herewith are for illustrating various
examples of articles, methods, and apparatuses of the present specification
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and are not intended to limit the scope of what is taught in any way. In the
drawings:
[0012] Figure 1 is a top cut-away view of a first exemplary laminate
material;
[0013] Figure 2a is a cross-sectional view of the laminate material of
Figure 1 taken along the lines 2-2;
[0014] Figure 2b is an enlarged view of a portion of the material of
Figure 1;
[0015] Figure 3 is a schematic view of a system and process for
manufacturing a laminate material;
[0016] Figure 4 is a top view of a diaper including an ear comprising
the
laminate material of Figure 1;
[0017] Figures 5a and 5b are perspective view of the diaper of Figure
4
prior to and after, respectively, the diaper being fastened on a wearer; and
[0018] Figures 6 and 7 illustrate additional embodiments of stretch
laminate materials.
DETAILED DESCRIPTION
[0019] Various apparatuses or processes will be described below to
provide an example of an embodiment of each claimed invention. No
embodiment described below limits any claimed invention and any claimed
invention may cover processes or apparatuses that are not described below.
The claimed inventions are not limited to apparatuses or processes having all
of the features of any one apparatus or process described below or to
features common to multiple or all of the apparatuses described below. It is
possible that an apparatus or process described below is not an embodiment
of any claimed invention. The applicants, inventors or owners reserve all
rights that they may have in any invention disclosed in an apparatus or
process described below that is not claimed in this document, for example the
right to claim such an invention in a continuing application and do not intend
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to abandon, disclaim or dedicate to the public any such invention by its
disclosure in this document.
[0020] Reference is first made to Figure 1, which illustrates a first
exemplary stretch laminate material 100. Laminate material 100 includes first
and second non-woven layers 102 and 104, an elastic element 106 and
reinforcing elements 108 and 109.
[0021] Laminate 100 has a first non-elastic region 110, a second non-
elastic region 111 and an elastic region 112. Laminate 100 is formed in a
longitudinal direction (also called machine direction) 114 and elastic region
112 is stretchable and resilient across its width in a transverse direction
also
called cross direction) 116. Elastic region 112 may also be stretchable in
other directions, such as the machine direction 114 or any other direction at
an angle to machine direction 114.
[0022] Referring now also to Figures 2a and 2b, first and second non-
woven layers 102 and 104 are, in the example illustrated, formed of a carded
non-woven material. Fibers 120 in the non-woven layers are generally
oriented in the machine direction 114. The degree of carding may vary and
the non-woven layers can also include fibers 122 oriented at an angle to the
machine direction. In the example illustrated, the non-woven layers have
much greater resistance to tension in the machine direction 114 than in the
cross direction 116. The machine direction tensile strength can facilitate
transporting webs of the non-wbven layers 102 and 104 in the machine
direction during processing. The weakened tensile strength in the cross-
direction 116 can facilitate lateral straining (i.e. extension of the width)
of the
non-woven layers in the cross-direction when stressed laterally by a user,
examples of which are provided hereinafter.
[0023] In the example illustrated, the non-woven layers 102 and 104
are carded generally uniformly across the width of the layers 102, 104, such
that the non-woven layers 102, 104 have a generally uniform cross-directional
strength across the width of the non-woven layers 102, 104. In other
examples, the non-woven layers 102, 104 can be carded only in a laterally
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central region of the layers 102, 104, corresponding to where the elastic
region 112 is provided in the laminate 100. Alternatively or additionally, the
non-woven layers 102, 104 can have a central region that is carded to a
greater extent than the marginal regions. Non-woven layers 102, 104 having
cross-directionally weakened central portions and cross-directionally stronger
side marginal portions can thus be provided. In other examples, providing
cross-directional weakened non-woven layers 102, 104 can be effected by
means other than carding, such as, for example, mechanically weakening a
non-carded non-woven layer to reduce cross-directional strength thereof,
10024] In the
illustrated example of the laminate material 100, the
elastic element 106 and reinforcing element 108 and 109 are sandwiched
between the non-woven layers. The elastic elements 106 is, in the example
illustrated, disposed in a generally lateral (or transverse) central portion
of the
laminate 100, and the reinforcing elements 108 and 109 are disposed
16 adjacent respective sides of the elastic element 106. The elastic
element 106
extends transversely between left and right lateral edges 106a, 106b,
respectively. The reinforcing elements 108 and 109 each extend transversely
between respective proximal and distal lateral edges 108a, 108b and 109a,
109b.
[0029 The elastic
element 106 may be formed of any stretchable or
elastic (elastic also generally referred to as elastomeric herein) sheet,
film,
scrim or other material that is flexible, stretchable and resilient. The
elastic
element is stretchable and resilient in at least the cross-direction, although
it
may also be stretchable and resilient in other directions. In one embodiment,
the elastic element 106 is an elastomeric film. The elastomeric film is bonded
to the first non-woven layer 102 with an adhesive 124 and to the second non-
woven layer with an adhesive 125.
f0026] The
reinforcing elements 108 and 109 are substantially non-
stretchable in at least the cross direction 116. By "substantially" non-
stretchable, it is meant that the reinforcing elements will be less than about
10% as stretchable as the elastic element 106 in the Cross direction 116. The
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reinforcing elements 108, 109 may also be substantially non-stretchable in
other directions, although they may optionally exhibit some stretchability in
directions at an angle to the cross-direction. In this exemplary embodiment,
the reinforcing elements 108, 109 comprise polyethylene films. In other
embodiments, the reinforcing elements may be polypropylene films, plastic
films, or other flexible, substantially non-stretchable sheets, films, scrims
Or
other material.
[0027] The reinforcing elements 108 and 109 are, in the example
illustrated, significantly stronger in the cross-direction 116 than are the
non-
woven layers 102 and 104. For example, the reinforcing elements 108, 109
can have a resistance to a cross-direction tensile force that is about two
times, four times, or ten times (or more) greater than that of the non-woven
layers 102, 104. This means that to obtain a particular unit of strain in the
reinforcing layer 108, 109, a force of two times, four times, or ten times (or
more) must be applied to the reinforcing layer 108, 109 as compared to the
cross-direction force required to obtain the same unit of strain in the non-
woven layers 102, 104.
[0028] The reinforcing elements 108 and 109 are bonded to the first
non-woven layer 102 with an adhesive 126, which may be the same or a
different adhesive than adhesive 124. In this embodiment, elastic element
106 extends beyond the longitudinally extending, cross-direction edges of
elastic regions 112 into overlap regions 128, 130 within the non-elastic
regions 110 and 111. In the overlap regions 128, 130, elastic element 106
overlaps and is bonded to reinforcement elements 108,109 using adhesive
126. In another embodiment, a different adhesive may be used in the overlap
regions 128 to adhere the reinforcement elements to the elastic element. For
example, an adhesive that is particularly suited to bonding the materials from
which those elements are formed may be used. Adhesive 126 adheres
elastic element 106 and reinforcing element 108 such that they remain
attached during use of the stretch laminate material 100, as is further
described below.
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[0029] The second non-woven layer 104 is bonded to the reinforcing
elements 108 and 109 and to the elastic element 106 with adhesive 125.
Optionally, different adhesives may be used to bond the second non-woven
layer 104 to the reinforcing elements and to the elastic element. The laminate
100 in the illustrated example has an elastic region 112 generally
corresponding to the central region comprising the elastic element 106 and
free of the reinforcing elements 108, 109. While the carded non-woven layers
102, 104 may provide some resistance to a cross-direction force applied over
the width of the laminate 100, due for example to some fiber bonding in the
cross-direction, these bonds and/or fibers can easily be broken so that after
a
single, first cycle extension in the cross-direction, the central
elasticizable
region behaves as an elastic region, and from a user's experience, behaves
similar to the behaviour of the laminate 100 prior to the first cycle
extension.
[0030] The co-operation of the reinforcement elements 108, 109 and
the non-woven layers 102, 104 generally provides a carrier web having a
highly extensible central zone (generally corresponding to elastic zone 112),
and relatively inextensible marginal zones on either side of the extensible
central zone (generally corresponding to inelastic zones 110, 111). These
relative measures of extensibility are considered in relation to forces that
may
be expected to be exerted by a caregiver when stretching a diaper around the
waist of an infant. Such forces can be, for example, in the range of 100N or
less. Under such forces, the highly extensible central zone is configured to
extend to at least about 50%, and in some embodiments to 100%, 200%, or
more of its original cross-directional extent. In some embodiments, such
forces would be sufficient to sever the non-woven layers 102, 104, were it not
for the elastic member 106 laminated thereto. In the embodiment illustrated,
the elastic member 106 maintains the integrity of the laminate 100 in the
central elastic zone 112, and provides resilient elasticity to the laminate
100.
The reinforcement members 108, 109 maintain the integrity of the laminate
100 in the marginal regions 110, 111 and can facilitate providing a robust
attachment zone for reliably securing the laminate 100 to other products, such
as, for example, a diaper or other garment.
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[0031] Other
examples of a carrier web adapted to receive an elastic
element laminated thereto and having a highly extensible central region and
inextensible marginal regions can also be provided within the scope of the
applicant's teaching. For example, a carrier web having a non-woven layer
that is preferentially or only carded in the central region thereof can be
provided. In such an example, the elastic member 106 can maintain the
integrity of the laminate in the carded central region, and the marginal
regions
can be free of an additional reinforcing member since the less carded or non-
carded marginal regions can generally possess sufficient cross-directional
strength to maintain integrity of the laminate and in some example to provide
robust attachment zones.
[0032] Reference
is next made to Figure 3, which illustrates an
example system 300 for assembling laminate material 100 in a continuous
manufacturing process. System 300 includes a first non-woven layer unwind
roll 302, a second non-woven layer unwind roll 304, an elastic element unwind
roll 306 and a pair of reinforcing element unwind roll 308 and 309 (which is
hidden behind unwind roll 308 in Figure 3). A roll of the corresponding
material, element or layer is placed on each of the unwind rolls and is drawn
from the roll as the laminate material is formed.
[0033] System 300
also includes adhesive spray heads 324. 325 and
326. In the operation of system 300, laminate material 100 is continuously
assembled with the various components of the laminate material traveling in
the machine direction 114 as they are drawn from their respective unwind
rolls.
[0034] The apparatus
300 (for example) can be used to make the
laminate material 100 according to a method as follows. Elastic element 106
can be drawn from unwind roll 306 and adhesive 124 is sprayed onto elastic
element 106 by adhesive spray head 324. Non-woven layer 102 and elastic
element 106 are pressed by pressure rollers 330a and 330b, bonding them
together with adhesive 124. In this embodiment, adhesive 124 is not sprayed
over the entire width of the elastic element 106. Instead, edge margins 136
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(Figure 2) are provided free of adhesive 124. Leaving the edge margins 136
of the elastic element 106 free of adhesive can reduce overspray onto the
components of system 300. Alternatively, adhesive 124 may be sprayed to
the edges 106a, 106b Of elastic element 106, which can in some
embodiments help to ensure that the elastic element 106 is bonded to the first
non-woven layer 102 across the width of the elastic element.
[0035] Reinforcing elements 108 and 109 are drawn from their
respective unwind rolls 308 and 309 and adhesive 126 is sprayed onto them
using adhesive spray heads 326. The reinforcement elements 108 and 109
are bonded to non-woven layer 102 and to elastic element 106 by pressing
them together through pressure rollers 332a and 332b. In this embodiment,
an edge margin 140 free of adhesive 126 is provided at the cross direction
edges of the laminate material as well as at the inboard edges 108a, 109a of
the reinforcing elements 108, 109. In the overlap regions 128 and 130, the
reinforcing elements are adhered to elastic element 106 with adhesive 126.
[0036] The second non-woven layer 104 is drawn from its unwind roll
304 and adhesive 125 is sprayed onto the non-woven layer 104 using
adhesive spray head 325_ The second non-woven layer 104 is bonded to the
reinforcing elements 108 and 109 and to the elastic element 106 by pressing
them together through pressure rollers 334a and 334b.
[0037] Reference is next made to Figure 4, which illustrates an
exemplary diaper 400 incorporating the stretch laminate material 100. Diaper
400 has a central chassis 402 that includes a liquid permeable topsheet 404,
a liquid impermeable backsheet 406 and an absorbent core 406 sandwiched
26 between the topsheet and backsheet. The illustrated diaper 400 has a
rectangular chassis 402. In alternative embodiments the chassis of the diaper
may have an hourglass shape or may have one or more contoured sides or
may have any other shape. The diaper 400 has a longitudinal or machine
direction 401 and a transverse or cross direction 403.
[0038] The chassis 402 has a rear waist region 407 and a front waist
region 408 separated by a central region 410. Each one of a pair of ears 412
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and 414 is mounted to a respective outboard side edge 416 and 418 of the
rear waist region 407. Ears 412 and 414 are cut from laminate material 100.
Each ear has a proximal non-elastic region 432, a distal non-elastic region
434 and an elastic region 436 disposed between the proximal and distal non-
elastic regions. In each ear, the proximal non-elastic region corresponds to
one of the first or second non-elastic regions 110, 111 in stretch laminate
material 100, the distal non-elastic region corresponds to the other one of
the
first or second non-elastic region 110, 111 in the stretch laminate material
and
the elastic region 436 corresponds to the elastic region 106 of the stretch
laminate material 100.
[0039] Ear 412 has
a proximal edge 420 that is mounted to chassis 402
adjacent outboard edge 416. Ear 412 also has a distal edge 422 to which a
tab 424 is mounted. Tab 424 includes a base layer 426 that is bonded to the
distal edge 422 of the ear 412. Tab 424 also includes a fastening element
428 that cooperates with a complementary fastening element 430 on the
exterior of the front waist region 408 of the diaper 400 to allow the diaper
to
be fastened on a wearer when the diaper is in use.
[0040] Ear 414
similarly has a proximal edge 420 mounted to the
chassis of diaper 400 and a distal edge 422 to which a tab 424 is mounted.
[0041] Reference is
next made to Figures 5a and 5b. Figure 5a
illustrates diaper 400 prior to placing it on a wearer. Figure 5b illustrates
diaper 400 in its configuration when worn by a wearer (who is not
illustrated).
Typically, diaper 400 will be worn by a child and will be placed on the child
by
a parent or other caregiver. To fasten the diaper 400 on the child, the
caregiver can lay the child on the open diaper 400 (Fig. 4) with the rear
waist
region 407 of the child's lower back, and the front waist region 408 between
the child's legs. The front waist region 408 can be pulled through the child's
legs to overlie the child's lower tummy. The caregiver can then grasp the tab
424 and pull the ears 412 and 414 in the cross direction 116 of the ears with
sufficient force to extend the ears by stretching the elastic region 436 of
the
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ear (i.e. by extending the cross-directional extent of the laminate 100
between
the overlap regions 128 and 130).
10042] This
stretching of the elastic region 436 of the ears 412,414 (i.e.
elastic region 112 of the laminate 100) effects a first cycle stretch of the
laminate 100 that strains the non-woven layers 102, 104, The weakening of
the central regions of the nonwoven layers 102, 104 facilitates the straining
of
the nonwoven layers 102, 104 when the ears 412, 414 are stretched for the
first time. In the example illustrated, the nonwovens are weakened in the
cross direction by carding in the machine direction, providing nonwoven layers
in which cross direction inter-fiber bonds of the non-woven layers can be
broken relatively easily, allowing the non-woven layers to be extended more
easily. The caregiver is able to extend the elastic regions 436 of the ears
412
and 414 of the example illustrated with less force than if the non-woven
layers
102 and 104 were not carded,
[0043] Once the elastic
region 436 of the ears have been extended, the
caregiver affixes the fastening element 428 onto the complementary fastening
element 430. When the diaper has been fastened in this fashion, the elastic
element 106 in the elastic region 436 of the ears 412 and 414 provides
tension in the elastic region.
[0044] The
reinforcement elements 108, 109 substantially prevent
extension of the non-elastic regions 432 and 434 of the ear 412, thereby
ensuring that the non-woven layers 102 and 104 do not tear when the ear is
stretched by caregiver and subsequently when the diaper is in use On a child.
[0045] By bonding
the reinforcement elements 108 and 109 with the
elastic element 106 in the overlap regions 128,130 the tensile force applied
to
the ears 412 or 414 when the diaper 400 is installed on a child is applied
through the reinforcing elements 108, 109 to the elastic element 106 between
the overlap regions 128 and 130. As can be understood with reference to
Figure 2a, the laminate 100 (in its thickness) includes at least one of the
reinforcing elements 108, 109 or the elastic member 106 in addition to the
nonwoven layers 102, 104 anywhere along its width between the distal edges
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108b, 109b. Thus the cross direction strength of the laminate does not at any
point rely only on the highly extensible, but cross-directionally weak, non-
woven layers 102, 104, and so rupture or tearing apart of the laminate 100 is
generally inhibited.
(0046) In other embodiments of a stretch laminate material, the non-
elastic regions may include different reinforcement elements 108,109. For
example, the non-woven layers May be bonded together with an adhesive
between them in a bilaminate construction. The interfiber bonds between the
carded non-woven layers are enhanced by the adhesive layer between the
non-woven layers and the adhesive functions as a reinforcement element. To
manufacture a stretch laminate material according to this embodiment, an
adhesive is applied to adhesive element, which is then bonded to the first
non-woven layer. The reinforcement element adhesive is then applied to the
second non-woven layer (or to the first non-woven layer) and the two non-
woven layers are bonded together with the elastic element sandwiched
between them.
[0047] In another
embodiment, an oriented fiber adhesive may be used
as the reinforcement element 108,109. The adhesive is disposed in fibers
oriented in the cross-direction to enhance the cross-direction reinforcement
provided by the adhesive. During manufacturing, the reinforcement adhesive
may be laid in strands generally in the cross-direction or may be blown onto
the first or second non-woven layer so that it is generally oriented in cross-
directions fibers or strands.
[0048] In another
embodiment of a stretch laminate material, the non-
woven layers may not be carded in the machine direction. The non-woven is
selected or configured such that the interfiber bonds between fibers in the
non-women layers, at least in the elastic region, are sufficiontly wok to
Qii0W Cl=
caregiver to stretch the laminate in the elastic region.
[0049] Reference
is next made to Figure 6, which illustrates a second
embodiment of a stretch laminate material 600. Elements of stretch laminate
material 600 that correspond to elements of stretch laminate material 100 are
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identified with similar reference numerals, incremented by 500, Stretch
laminate material 600 includes first and second non-woven layers 602 and
604. Stretch laminate material 600 has an elastic element 606 sandwiched
between the non-woven layers 602, 604 in an elastic region 612. Elastic
region 612 is transversely disposed between first and second non-elastic
regions 610 and 611. First and second non-woven layers 602, 604 are
bonded together across the non-elastic regions 610, 611 and may be bonded
together with an adhesive. The non-woven layers are modified to reinforce
them in the cross direction 616. In this embodiment, the non-woven layers
602, 604 are embossed across the non-elastic region 610, 611 following
assembly of the non-woven layers 602, 604 and the elastic element 606.
Embossing the non-woven layers can increase the interfiber bonds within
each of the non-woven layers allowing the non-woven layer to resist tearing in
the machine direction 614 when a cross direction force is applied to an ear
cut
16 (illustrated by dotted-line region 650) from the stretch laminate
material 600.
[0050] In other embodiments, the non-woven layers may be reinforced
by hydroentangling or by needlepunching fibers within the non-woven layers
such that they become intermeshed with one another and have a stronger
interfiber coupling (which may be a physical entangling in addition to any
bonding between the fibers resulting form the manufacturing of the non-woven
layer). These processes may also be used to entangle fibers in one or both of
the non-woven layers with fibers in the other non-woven layer, which may
further enhance the resistance of the non-elastic regions to tearing.
[0051] In other embodiments, the non-elastic regions may be reinforced
by thermal bonding (with or without the use of a pressure or calendar roll)
heating the non-woven layers in the non-elastic regions such that the fibers
within the non-woven layers melt and form stronger bonds with one another
and with fibers in the other non-woven layer. In other embodiments, the non-
elastic regions may be reinforced by ultrasonic bonding (which is a form of
thermal bonding). The embossing of the non-elastic regions in laminate 600
can comprise another example of thermal bonding.
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[0052] The non-elastic
regions may be reinforced across their entire
area or may be reinforced at discrete or localized areas, lines, or at
particular
points, such as, for example, with a point bonding or embossing process. The
reinforcement of the non-elastic regions may reinforce One or both non-woven
layers individually or may reinforce the non-elastic region by bonding
(thermally or mechanically) the non-woven layers to one another. The
reinforcement may also operate on one or both non-woven layer separately
and on the non-woven layers together.
[0053] Laminate 600 and the
variations described above involve
reinforcement of the non-elastic regions after the laminate 600 has been
assembled. Alternatively, or in addition, the non-woven layer could be
reinforced prior to assembly with an elastic element such that the non-woven
layers are reinforced in at least the non-elastic regions of the finished
laminate.
[0054] In another embodiment,
the non-woven layers may be
processed (before or after assembly with the elastic element) to reinforce
them, and a reinforcement element may also be provided in the non-elastic
regions.
[0055] Reference is next
made to Figure 7, which illustrates another
stretch laminate material
700. Elements of stretch laminate 700 that
correspond to stretch laminate material 100 are identified by similar
reference
numerals, incremented by 600. Stretch laminate material 700 includes first
and Second non-woven layers 702 and 704. An elastic element 706 and
reinforcement elements 708 and 709 are sandwiched between the non-woven
layer 702 and 704. The first and second non-woven layers 702 and 704 are
formed of a carded non-woven material.
[0056] Laminate 700 has an
elastic region 712 disposed between first
and second non-elastic regions 710 and 711.
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[0057] The elastic region 712 is spaced apart from the first and
second
non-elastic regions by gap regions 740 and 742. Neither the elastic element
706 or the reinforcement elements 708 and 709 extend into the gap regions.
[0058] The non-woven layers 702 and 704 are carded with their fibers
oriented to some degree in the machine direction 716 of the laminate. To
prevent the non-woven layers from tearing in the machine direction in the gap
regions when a cross-direction force is applied to a diaper ear cut
(illustrated
in shaded region 750) from laminate material, the non-woven layers are
reinforced between the elastic region 712 and the non-elastic regions 710 and
711. In this embodiment, the non-woven layers are embossed in at least the
gap regions 740, 742 after the components of laminate 700 are assembled
together. Alternatively, the gap regions could be reinforced in any of the
manners discussed above in relation to laminate 600 for reinforcing the non-
elastic regions 610,611. In other embodiments, the non-woven layers may be
reinforced prior to assembly with the elastic element 706 and the
reinforcement elements.
[0059] In other embodiments, the edges 706a, 706b of the elastomeric
element 706 can abut the proximal edges 708a, 709a, respectively of the
reinforcing members so that neither a gap region nor an overlap region are
provided therebetween. The outboard edges of the nonwoven layers 702,
704 can, in some examples, be positioned inboard of the distal edges 708b,
709b of the reinforcement members 708, 709.
[0060] In other embodiments of a stretch laminate, the elastic element
may be extrusion bonded with one or both of the non-woven layers.
Optionally, an adhesive may be applied to assist the bond between an elastic
element and a non-woven layer to which the elastic element is extrusion
bonded.
[0061] The present invention has been described here by way of
example only. Various modification and variations may be made to these
exemplary embodiments without departing from the scope of the invention.
CA 02602991 2007-09-19
- 17 ¨
EXAMPLE
[0062] A laminate
100 has a construction generally as described in
Figure 1. The nonwoven layers 102, 104 are of a 21 gsm carded non-woven,
uniform across its width. The elastic element 106 is in the form of an
elastomeric film adhesively bonded to the nonwoven layers 102, 104. The
reinforcement members 108, 109 are a non-carded non-woven of about 30
gsm. The cross-directional extent of the elastic region 112 (i.e. the spacing
between the edges 108b and 109b is about 5cm.
[0063] On the
first cycle extension (during which the central regions of
the non-woven layers are strained), a load of about 20-22 N is applied across
the width of the laminate 100, causing no cross-direction extension of the
inelastic regions 110, 111, and causing a 150% elongation in the cross-
direction of the elastic region 112 (i.e. causing the 5cm distance to extend
to
about 12.5cm). On the second cycle, a force of about 10-12N is applied
across the laminate 100 to achieve an equal extension (about 150%) as for
the first cycle.
[0054] The first
cycle force is that which actually strains the highly
extensible, non-reinforced region of the carded nonwovens 102, 104 of the
example illustrated. During subsequent cycles, the nonwoven layers 102, 104
generally offer no resistance to a force re-extending the laminate to the
extension reached in the first cycle. By providing a highly extensible non-
woven, the 'first cycle force required to achieve 150% extension of elastic
region 112 is not more than about twice that as required for the second cycle.
In the third and subsequent cycles, the laminate 100 behaves similar as the
first cycle.
