U.S. patent application number 11/771572 was filed with the patent office on 2008-01-03 for embossed stretchable elastic laminate and method of production.
Invention is credited to Martin F. Hoenigmann, Jeffrey Alan Middlesworth, Amiel Bassam Sabbagh.
Application Number | 20080003911 11/771572 |
Document ID | / |
Family ID | 38895350 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080003911 |
Kind Code |
A1 |
Sabbagh; Amiel Bassam ; et
al. |
January 3, 2008 |
Embossed Stretchable Elastic Laminate and Method of Production
Abstract
A stretchable embossed elastic laminate including at least one
nonwoven fabric layer, and at least one elastomeric material
extruded as a melt onto a major surface of the nonwoven fabric to
form an elastic layer bonded to the surface of the nonwoven fabric.
The elastic laminate is embossed with a deep embossing pattern to
provide an embossed laminate having good tensile strength and
excellent resistance to delamination. Also disclosed is a method of
forming a stretchable embossed laminate wherein at least one melted
elastic material is extruded onto a major surface of the nonwoven
fabric, and the elastic material and the nonwoven fabric are
conveyed through a nip formed by a layon roll and an embossing roll
having a deep embossing pattern.
Inventors: |
Sabbagh; Amiel Bassam;
(Williamsburg, VA) ; Hoenigmann; Martin F.;
(Chippewa Falls, WI) ; Middlesworth; Jeffrey Alan;
(Wauconda, IL) |
Correspondence
Address: |
MCANDREWS HELD & MALLOY, LTD
500 WEST MADISON STREET
SUITE 3400
CHICAGO
IL
60661
US
|
Family ID: |
38895350 |
Appl. No.: |
11/771572 |
Filed: |
June 29, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60818066 |
Jun 30, 2006 |
|
|
|
Current U.S.
Class: |
442/327 |
Current CPC
Class: |
B32B 27/30 20130101;
B32B 2305/20 20130101; B32B 3/30 20130101; B32B 2307/51 20130101;
B32B 37/144 20130101; Y10T 442/60 20150401; B32B 5/04 20130101;
B32B 2555/02 20130101; B32B 27/12 20130101; D04H 5/06 20130101;
B32B 27/08 20130101; B32B 5/26 20130101 |
Class at
Publication: |
442/327 |
International
Class: |
D04H 13/00 20060101
D04H013/00; D04H 1/00 20060101 D04H001/00 |
Claims
1. An embossed stretchable elastic laminate comprising: at least
one nonwoven fabric that is stretchable in at least one direction;
and an elastic material applied as a melt onto a major surface of
said nonwoven fabric; wherein the melt forms an elastic layer
bonded to said surface of said nonwoven fabric; and wherein said
nonwoven fabric has an embossing pattern applied to a major surface
of said nonwoven fabric opposite the major surface receiving the
elastic material, said embossing pattern comprising discontinuous
discrete shapes having a depth of at least about 0.008 inches.
2. The embossed stretchable elastic laminate of claim 1, wherein
the nonwoven fabric comprises a material selected from the group
consisting of polyethylene terephthalate, polybutylene
terephthalate, polypropylene terephthalate, polyamides,
polyacrylates, polyacrylonitrile, viscose, aramide,
polyvinylalcohol and rayon.
3. The embossed stretchable elastic laminate of claim 1, wherein
the elastic material comprises a styrene block copolymer.
4. The embossed stretchable elastic laminate of claim 3, wherein
the styrene block copolymer comprises SEBS.
5. The embossed stretchable elastic laminate of claim 1, wherein
the elastic layer is comprised of a plurality of layers formed by
co-extruding the elastic material and at least one other
material.
6. The embossed stretchable elastic laminate of claim 5, wherein
the at least one other material is a second elastic material.
7. The embossed stretchable elastic laminate of claim 5, wherein
the at least one other material is a tie layer material.
8. The embossed stretchable elastic laminate of claim 1, wherein
said laminate comprises a second nonwoven fabric and said elastic
material is applied to a major surface of said second nonwoven
fabric so that the elastic layer is sandwiched between and bonded
to said major surfaces of the nonwoven fabric and the second
nonwoven fabric.
9. The embossed stretchable laminate of claim 1, wherein the at
least one nonwoven fabric is a spunlace nonwoven fabric.
10. The embossed stretchable laminate of claim 8, wherein the
second nonwoven fabric is a spunlace nonwoven fabric.
11. The embossed stretchable laminate of claim 1, wherein the
embossing pattern comprises a series of discrete dots having a
depth in the range of about 0.010 to about 0.060 inches.
12. The embossed stretchable laminate of claim 1, wherein the
embossing pattern comprises a series of discrete perpendicular
rectangles having a depth in the range of about 0.008 to about
0.060 inches.
13. The embossed stretchable laminate of claim 1, wherein the
embossing pattern is imparted by a roll having embossing pattern
depth of about 0.008 inches to about 0.5 inches.
14. The embossed stretchable elastic laminate of claim 1, wherein
the at least one nonwoven fabric comprises natural fibers selected
from the group consisting of cellulose, cotton, hemp, wool and
flax.
15. The embossed stretchable elastic laminate of claim 5, wherein
the elastic layer comprises first and second outer layers and at
least one core layer.
16. The embossed stretchable elastic laminate of claim 15, wherein
the first and second outer layers are tie layers.
17. A method of forming an embossed stretchable elastic laminate
comprising the steps of: (a) providing a nonwoven fabric that is
stretchable in at least one direction; (b) heating an elastic
material to form an elastic melt; (c) applying said elastic melt to
a major surface of said nonwoven fabric; (d) applying a compressive
force to at least one of said elastic melt and said nonwoven fabric
to form an elastic layer bonded to said surface of said nonwoven
fabric; and (e) during the step of applying a compressive force
with a roller having a deep embossing pattern to form a deep
embossing pattern on a major surface of said nonwoven fabric
opposite the major surface receiving the elastic melt.
18. The method of claim 17, wherein a single elastic material is
applied to the surface of said nonwoven to form a single elastic
layer.
19. The method of claim 17, wherein the applying step comprises
co-extruding at least two materials, at least one of which is an
elastic material, onto the surface of the nonwoven fabric.
20. The method of claim 17, wherein the elastic melt and the
nonwoven fabric are conveyed through a nip formed by a layon roll
and an embossing roll to form the elastic layer bonded to the
surface of the nonwoven fabric.
21. The method of claim 17, wherein the compressive force is
generated by using at least one of an air knife, a vacuum box,
nonwoven web tension, or a static bar.
22. The method of claim 17, wherein the deep embossing pattern
comprises a series of discrete dots having a depth in the range of
about 0.010 to about 0.060 inches.
23. The method of claim 17, wherein the deep embossing pattern
comprises a series of discrete perpendicular rectangles having a
depth in the range of about 0.008 to about 0.060 inches.
24. A component for an absorbent article comprising; at least one
nonwoven fabric that is stretchable in at least one direction; and
an elastic material applied as a melt onto a major surface of said
nonwoven fabric, wherein the melt forms an elastic layer bonded to
said surface of said nonwoven fabric; wherein said nonwoven fabric
has an embossing pattern applied to a major surface of said
nonwoven fabric opposite the major surface receiving the elastic
material via a roller having a deep embossing pattern, said
embossing pattern comprising discontinuous, discrete shapes having
a depth of at least about 0.008 inches.
25. An absorbent article comprising the component of claim 24.
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application Ser. No. 60/818,066, filed on Jun. 30, 2006. The
disclosure of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The presently described technology relates generally to
stretchable elastic laminates. More specifically, the present
technology relates to embossed stretchable elastic laminates formed
from an elastic melt layer and a non-woven layer and having a deep
emboss pattern that allows for improved resistance to delamination
of the nonwoven from the elastic layer.
[0003] Disposable absorbent articles (e.g., disposable diapers for
children or adults) often include elastic features designed to
provide enhanced and sustainable comfort and fit to the wearer by
conformably fitting to the wearer over time. Examples of such
elastic features may include, for example, elastic waistbands,
elastic leg cuffs, elastic side tabs, or elastic side panels so
that the absorbent article can expand and contract to conform to
the wearer in varying directions. Additionally, such elastic
features are often required to be breathable to provide a desired
level of comfort to the wearer's skin.
[0004] Further, the elastic features of disposable absorbent
articles may be made of stretchable elastic laminates. A
stretchable elastic laminate typically includes an elastic film and
a non-woven fabric. More particularly, the elastic film is
typically bonded to the non-woven fabric to form the stretchable
elastic laminate.
[0005] A nonwoven elastomeric laminate is disclosed, for example,
in U.S. published application No. 2005/0287892 A1. According to the
disclosure, the nonwoven web is one in which the fibers are
thermally bonded to form the web material (see paragraph 0054). An
elastomeric film is directly bonded to the nonwoven web layer by
feeding the elastomeric film and the nonwoven web to the nip
between two calender rollers. Pressure between the calender rollers
ranges from about 0.25 to about 5 bar. Pressures at the lower end
of the range are stated as being preferred, in order to insure that
the elastomeric material does not become deeply embedded in the
nonwoven web (see paragraph 0042).
[0006] Bonding the elastic film to the non-woven fabric typically
requires a secondary bonding operation. For example, U.S. Pat. No.
6,069,097 (the '097 patent) describes a composite elastic material
comprising a non-woven fabric secured to an elastic member, wherein
the elastic member and the non-woven fabric are secured together at
a plurality of points in the stretchable direction of the non-woven
fabric (see Abstract). The '097 patent discloses using a heated
embossing roller and a chilled roller to bond a co-extruded elastic
film to a spunlace non-woven fabric to form the composite elastic
sheet, (see col. 14, lines 7-20). Further, the '097 patent
discloses that the composite sheet should be bonded in a particular
pattern, namely that the composite should be bonded in an
approximately perpendicular direction to the direction of
elongation, and also that the bond sites should be positioned on
either side of the elastic sheet so as not to overlap with bond
sites on the other side of the elastic sheet, (see col. 5, lines
60-65).
[0007] Additionally, for example, U.S. Pat. App. Pub. No.
2004/0121687 (the '687 publication) describes forming an extensible
laminate by laminating an extensible nonwoven web to an elastomeric
sheet to form a laminate and mechanically stretching the laminate
in a cross direction (see Abstract). The '687 publication discloses
that an extensible laminate can be formed using nip rolls 46, 48 to
bond an elastomeric sheet 14 to an extensible nonwoven web 12
(paragraph 0088). According to the '687 publication, "the
extensible nonwoven web 12 may be laminated to the elastomeric
sheet by a variety of processes including, but not limited to
adhesive bonding, thermal bonding, point bonding, ultrasonic
welding and combinations thereof" (paragraph 0090).
[0008] Furthermore, the '687 publication also describes the
extensible nonwoven web 12 as "a necked spunbonded web, a necked
meltblown web or a necked bonded carded web" (paragraph 0065).
Stretching the nonwoven web in one direction not only causes
necking in the other direction, but may also cause the nonwoven web
to become thicker. A variation in thickness may require more
complicated set-up procedures and additional processing equipment
when utilizing the nonwoven web in different manufacturing
operations, thus resulting in increased manufacturing costs.
Moreover, necking of the nonwoven web may cause orientation of the
fibers which may result in a striated appearance that may not be
aesthetically pleasing.
[0009] Employing a secondary bonding operation, such as those
described in the '097 patent and the '687 publication, to form the
stretchable laminate typically increases the production cost of the
stretchable elastic laminate.
[0010] Improving the elasticity of the stretchable elastic laminate
typically requires stretch activation, which typically requires a
secondary stretching operation. For example, U.S. Pat. No.
6,313,372 (the '372 patent) relates to a stretch-activated plastic
composite. According to the '372 patent, "it may be desirable that
such stretch activation be done either prior to or during
production of a product using the composite" (col. 4, lines
37-39).
[0011] Additionally, for example, the '687 publication describes
stretching a non-woven fabric with two pairs of rollers, each pair
of rollers operating at a different speed. More particularly, the
'687 publication describes necking an extensible nonwoven web 12
using a first nip 30, including nip rolls 32, 34 turning at a first
surface velocity, and a second nip 36, including nip rolls 38, 40
turning at a second surface velocity that is higher than the first
surface velocity (see paragraph 0085). The '687 publication also
describes mechanically stretching the laminate 50 using grooved
rolls 58, 60 (extensible paragraph 0091) or a tenter frame 66
(extensible paragraph 0092).
[0012] The use of such secondary stretching operations typically
increases the production cost of the stretchable elastic
laminate.
BRIEF SUMMARY OF THE INVENTION
[0013] The presently described technology is directed to a
stretchable laminate that has improved stretch properties such as
improved elongation to break and low permanent deformation, as well
as high tensile strength, high delamination resistance and
aesthetic appeal.
[0014] In one aspect, the present technology is directed to an
embossed stretchable laminate that includes a nonwoven fabric that
is stretchable in at least one direction and an elastic material
extruded or otherwise applied as a melt onto a major surface of the
non-woven fabric such that the melt forms an elastic layer bonded
to the surface of the nonwoven fabric.
[0015] In another aspect, the present technology is directed to an
embossed stretchable laminate that includes a nonwoven fabric that
is stretchable in at least one direction, and an elastic material
applied as a melt to a major surface of the nonwoven fabric via a
roll having a deep embossing pattern which is utilized during
formation of a laminate to give the laminate an improved resistance
to delamination.
[0016] For example, in at least one preferred embodiment, the
present technology provides an embossed stretchable elastic
laminate comprising at least one nonwoven fabric that is
stretchable in at least one direction, and an elastic material
applied as a melt onto a major surface of said nonwoven fabric. In
preferred embodiments, the melt forms an elastic layer bonded to
said surface of said nonwoven fabric. Additionally, it is preferred
that the nonwoven fabric has an embossing pattern applied to a
major surface of said nonwoven fabric opposite the major surface
receiving the elastic material, said embossing pattern comprising
discontinuous discrete shapes having a depth of at least about
0.008 inches.
[0017] In another aspect, the present technology is directed to a
method of making an embossed stretchable laminate which includes
heating an elastic material to form an elastic melt and applying
the melt to a major surface of at least one nonwoven fabric layer
wherein the fabric is stretchable in at least one direction, to
form an elastic layer bonded to the surface of the nonwoven fabric,
and applying a deep embossing pattern to the nonwoven fabric. For
example, in at least one embodiment, a method of forming an
embossed stretchable elastic laminate is provided that comprises
the steps of: (a) providing a nonwoven fabric that is stretchable
in at least one direction; (b) heating an elastic material to form
an elastic melt; (c) applying said elastic melt to a major surface
of said nonwoven fabric; (d) applying a compressive force to at
least one of said elastic melt and said nonwoven fabric to form an
elastic layer bonded to said surface of said nonwoven fabric; and
(e) during the step of applying a compressive force with a roller
having a deep embossing pattern to form a deep embossing pattern on
a major surface of said nonwoven fabric opposite the major surface
receiving the elastic melt.
[0018] In another aspect, the present technology is directed to a
method of perforating the laminate or film within the laminate to
improve its breathability.
[0019] In another aspect, the present technology is directed to a
method of minimizing the stretch in selected zones of the laminate
to facilitate a secure attachment to nonstretchy films, laminates
or hooks in a disposable garment.
[0020] In another aspect, the present technology is directed to a
method of increasing the elongation of the elastic laminate.
[0021] In a further aspect, the present technology is directed to a
component for an absorbent article, or an absorbent article
comprised of a component (for example, a side tab, a side panel, a
waistband or an elastic belt substrate), that comprises an embossed
stretchable laminate that includes a nonwoven fabric that is
stretchable in at least one direction, and an elastic material
applied as a melt to a major surface of the nonwoven fabric, by a
roll with a deep embossing pattern. In at least one such
embodiment, a component for an absorbent article is provided that
comprises at least one nonwoven fabric that is stretchable in at
least one direction, and an elastic material applied as a melt onto
a major surface of said nonwoven fabric, wherein the melt forms an
elastic layer bonded to said surface of said nonwoven fabric, and
wherein said nonwoven fabric has an embossing pattern applied to a
major surface of said nonwoven fabric opposite the major surface
receiving the elastic material via a roller having a deep embossing
pattern. The embossing pattern preferably comprises discontinuous,
discrete shapes having a depth of at least about 0.008 inches.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
[0022] While the specification concludes with claims particularly
pointing out and distinctly claiming the subject matter which is
regarded as the presently described technology of the present
invention; it is believed that the presently described technology
will be more fully understood from the following description taken
in conjunction with the accompanying figures, in which:
[0023] FIG. 1 is a schematic diagram showing a process for
manufacturing the stretchable elastic laminate of the present
technology;
[0024] FIG. 2 illustrates a laminate having a shallow embossing
pattern in accordance with the prior art;
[0025] FIG. 3 illustrates an embodiment of a laminate having a
rectangular deep embossing pattern in accordance with the present
technology;
[0026] FIG. 4 illustrates an embodiment of a laminate having a dot
deep embossing pattern in accordance with the present
technology;
[0027] FIG. 5 is a graphical illustration of hysteresis curves for
the laminates illustrated in FIGS. 2-4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0028] The stretchable elastic laminates, methods of producing such
laminates, and articles incorporating the stretchable elastic
laminates of the presently described technology are suited for a
variety of uses and applications, in particular for use in
garments, such as a disposable absorbent article.
[0029] As used herein, the term "absorbent article" refers to a
device which absorbs and contains body exudates, and more
specifically, refers to a device which is placed against the skin
of a wearer to absorb and contain the various exudates discharged
from the body. Examples of absorbent articles include diapers,
pull-on pants, training pants, incontinence briefs, diaper holders,
feminine hygiene garments, and the like.
[0030] The term "disposable" is used herein to describe absorbent
articles, which generally are not intended to be laundered or
otherwise restored or reused as absorbent articles, but rather
discarded after use by the wearer.
[0031] The term "elastic" refers herein to any material that upon
application of a force to its relaxed, initial length can stretch
or elongate without substantial rupture and breakage by at least
50% of its initial length, and which can recover at least 30% of
its initial length upon release of the applied force.
[0032] The term "spunlace nonwoven fabric" as used herein refers to
a structure of individual fibers or threads which are physically
entangled, without thermal bonding. Physical entanglement may be
achieved using a water entanglement process or alternatively, a
needling process or a combination of both processes. Spunlace
nonwoven fabric is distinguishable from "spun-bonded nonwoven
fabric" in that spun-bonded nonwoven fabric has thermal bonding
points between individual fibers in the nonwoven fabric, such that
the fibers are thermally bonded into a cohesive web.
[0033] The term "machine direction" for a nonwoven fabric, web or
laminate refers to the direction in which it was produced. The
terms "cross direction" or "transverse direction" refer to the
direction perpendicular to the machine direction.
[0034] The terms "stretchable" or "extensible" refer herein to a
material that can be stretched, without substantial breaking, by at
least 50% of its relaxed, initial length in at least one direction.
The term can include elastic materials, as well as nonwovens that
are inherently extensible, but do not recover. Such nonwovens can
be made to behave in an elastic manner by bonding them to elastic
films.
[0035] The term "delamination" refers to a failure of the bond
between the nonwoven and film after some amount of stretching.
Delamination typically is evident as a raised section of nonwoven
over 10 mm of the laminate in any direction.
[0036] The stretchable laminate of the present technology comprises
at least one nonwoven fabric and an elastic material extruded as a
melt onto a major surface of the nonwoven fabric, wherein the melt
forms an elastic layer bonded to the surface of the nonwoven
fabric. In a preferred embodiment, the laminate is a 3-layer
laminate in which an elastic layer is sandwiched between two
nonwoven fabric layers, with at least one of the nonwoven fabric
layers being formed from a spunlace nonwoven fabric.
[0037] The spunlace nonwoven fabric used herein is made from a
material having a melting point or softening point that is greater
than the temperature of the elastic melt at the time the elastic
melt contacts the spunlace nonwoven fabric. Selecting a spunlace
nonwoven fabric with a melting point or softening point greater
than the temperature of the elastic melt at the time of contact
insures that melting of the fibers in the spunlace nonwoven fabric
does not occur when the elastic melt is extruded onto the surface
of the nonwoven fabric.
[0038] Suitable materials for the spunlace nonwoven fabric include
high melting temperature materials, such as polyethylene
terephthalate (PET), polybutylene terephthalate (PBT),
polypropylene terephthalate (PPT), polyacrylonitrile (PAN),
polyamides, including polyamide 6 and polyamide 6.6, and
polyacrylate (PAC). Other suitable materials for the spunlace
nonwoven fabric include materials that do not have a true melting
point, but have a high softening temperature range or a high
decomposition temperature. Such materials include viscose, aramide
(known commercially as Nomex.TM.), polyvinylalcohol (PVA) (known
commercially as Vinylon.TM.), and rayon. Other polymeric materials,
such as polypropylene, may also be used for the spunlace nonwoven
fabric. A preferred material for the spunlace nonwoven fabric is
PET having a melting point of approximately 260.degree. C. A
suitable PET spunlace nonwoven fabric is commercially available
from Tomen America Inc. of New York, N.Y., under the product name
Tomiace PET. Other suppliers of PET spunlace nonwoven fabric
include Sandler Vliesstoffe of Germany and BBA Group of Brentwood,
Tenn.
[0039] The spunlace nonwoven fabric may have a basis weight of
about 20 to about 80 gsm and is stretchable in an amount of about
50% to about 200% of its initial length. In general, spunlace
nonwoven fabrics having a basis weight at the upper end of the
range have better strength and are more stretchable than lower
basis weight spunlace nonwovens, but are also more expensive. A
suitable spunlace nonwoven fabric for use herein has a basis weight
of about 30 grams per square meter (gsm) and is stretchable in the
cross-direction.
[0040] Use of a spunlace nonwoven fabric made from a material
having a high melting or decomposition temperature provides a
surprisingly high level of laminate elongation compared to other
nonwoven fabrics having thermal bonding points. Without wishing to
be bound by a particular theory, it is believed that there are
three attributes that help create the high level of elongation.
First, the high melting or decomposition temperature of the
nonwoven (for a PET nonwoven around 260.degree. C.) allows it to
retain its fiber integrity even when in contact with the melted
elastic material. Second, the relative incompatibility of the
nonwoven fabric with the polymers used to form the elastic layer
keeps the elastic melt from wetting out the nonwoven fibers and
causes the attachment of the nonwoven fabric to the melted elastic
material to be a physical trapping of the surface fibers rather
than a full chemical bond. This physical trapping helps to allow
some sliding of the nonwoven fibers, thereby contributing to the
level of elongation. Third, the spunlace nonwoven, being a
physically entangled nonwoven rather than a thermally bonded
nonwoven, may allow some fiber sliding without requiring much
physical separation between the nonwoven fabric and the elastic
layer.
[0041] The use of a spunlace nonwoven fabric in a stretchable
laminate provides additional advantages. For example, the spunlace
fabric lends itself to the addition of liquid absorbing natural
fibers to the spunlace fabric. Since manufacture of the present
laminate does not depend on nonwoven melting to achieve attachment
between the elastic layer and the nonwoven fabric, natural fibers
that are nonmelting can be added to the spunlace fabric without
detrimentally affecting the attachment between the elastic layer
and the spunlace fabric. Suitable natural fibers that may be added
include cellulose, cotton, wool, flax and hemp. Such added natural
fibers contribute to a level of comfort in hygiene applications
that cannot be achieved by other nonwoven materials. In addition,
natural fibers are biodegradable. By incorporating such fibers into
the spunlace nonwoven, or indeed, utilizing a spunlace nonwoven
fabric manufactured entirely from natural fibers, and selecting an
elastic material that is also biodegradable, the entire elastic
laminate structure may be made to be biodegradable, a desirable
property for disposable articles to have. A further advantage of
the spunlace technology is the furrowed appearance that it creates
in the finished elastic laminate. The furrows generally
corresponding to the channels created by the hydraulics creates an
aesthetically appealing laminate with a look that simulates the
appearance of incrementally stretched elastic laminates that are
popular in disposable absorbent garments.
[0042] The high temperature resistance of the spunlace fabric may
also be used to advantage for high speed "welding" applications
where the spunlace nonwoven layer of the laminate is in close
proximity to a hot bar or hot wire, and a more delicate, lower
melting temperature material on the opposite surface of the
laminate could be kept relatively cool. In such applications, the
spunlace fabric can withstand the heat from the hot bar or wire
without melting and can transfer some of the heat to the lower
layers.
[0043] Although a spunlace nonwoven is preferred for the nonwoven
layer or layers, other nonwoven fabrics are also suitable for use
in the present technology. Such nonwoven fabrics include, for
example, those formed by meltblowing processes, spunbonding
processes, air laying processes and bonded carded web processes.
One example of a suitable nonwoven fabric is a spunbond nonwoven
fabric made from fibers containing an elastic core and a
polylethylene or polypropylene sheath, which is available from BBA
Group under the trade name Dreamex.TM..
[0044] The elastic layer which is extruded onto the nonwoven fabric
is formed from one or more thermoplastic materials. Thermoplastic
materials suitable for use in the elastic layer or layers in the
laminates of the present technology are generally materials that
flow when heated sufficiently above their glass transition
temperature and become solid when cooled.
[0045] Thermoplastic materials that have elastomeric properties are
typically called elastomeric materials. Thermoplastic elastomeric
materials are generally defined as materials that exhibit high
resilience and low creep as though they were covalently crosslinked
at ambient temperatures, yet process like thermoplastic
nonelastomers and flow when heated above their softening point.
Thermoplastic elastomeric materials, in particular block
copolymers, useful in practicing the presently described technology
can include, for example, linear, radial, star, and tapered block
copolymers such as styrene block copolymers, which may include, for
example, Kraton.RTM. or Kraton.RTM.-based styrene block copolymers
available from Kraton Polymers, Inc., located in Houston, Texas;
styrene-isoprene block copolymers, styrene-(ethylene-butylene)
block copolymers, styrene-(ethylene-propylene) block copolymers,
and styrene-butadiene block copolymers; polyether esters such as
that available under the trade designation HYTREL.TM. G3548 from
E.I. DuPont de Nemours; and polyether block amides such PEBAX.TM.
available from Elf Atochem located in Philadelphia, Pa. Preferably,
styrene block copolymers are utilized in practicing the presently
described technology. Styrene-ethylene butylene block copolymers
are most preferred.
[0046] Non-styrene block copolymers (elastomers or plastomers)
suitable for use in accordance with the presently described
technology include, but are not limited to, ethylene copolymers
such as ethylene vinyl acetates, ethylene octane, ethylene butene,
and ethylene/propylene copolymer or propylene copolymer elastomers,
such as those available under the trade designation VISTAMAXX.RTM.
available from ExxonMobil, located in Irving, Texas, or
ethylene/propylene/diene terpolymer elastomers, and metallocene
polyolefins such as polyethylene, poly (1-hexane), copolymers of
ethylene and 1-hexene, and poly(1-octene); thermoplastic
elastomeric polyurethanes such as that available under the trade
designation MORTHANE.TM. PE44-203 polyurethane from Morton
International, Inc., located in Chicago, Ill. and the trade
designation ESTANE.TM. 58237 polyurethane from Noveon Corporation,
Inc., located in Cleveland, Ohio; polyvinyl ethers;
poly-.alpha.-olefin-based thermoplastic elastomeric materials such
as those represented by the formula --(CH2CHR)x where R is an alkyl
group containing about 2 to about 10 carbon atoms;
poly-.alpha.-olefins based on metallocene catalysis such as
ENGAGE.TM. 8200, ethylene/poly-.alpha.-olefin copolymer available
from Dow Plastics Co., located in Midland, Mich.; polybutadienes;
polybutylenes; polyisobutylenes such as VISTANEX NM L-80, available
from Exxon Chemical Co.; and polyether block amides such PEBAX.TM.
available from Elf Atochem located in Philadelphia, Pa. A preferred
elastomer or plastomer of the presently described technology is an
ethylene/propylene copolymer or polypropylene copolymer. It is also
preferable that the non-styrene block copolymer elastomer or
plastomer of the presently described technology comprise from about
10% to about 95% by weight of the elastomeric layer based upon the
total weight of the composition. For example, one embodiment of the
elastomer or plastomer of the presently described technology may be
comprised of a polypropylene copolymer containing from about 50% to
about 95% of propylene content.
[0047] Additional elastomers which can be utilized in accordance
with presently described technology also include, for example,
natural rubbers such as CV-60, a controlled viscosity grade of
rubber, and SMR-5, a ribbed smoked sheet rubber; butyl rubbers,
such as EXXON.TM. Butyl 268 available from Exxon Chemical Co.,
located in Houston, Texas; synthetic polyisoprenes such as
CARIFLEX.TM., available from Shell Oil Co., located in Houston,
Texas, and NATSYN.TM. 2210, available from Goodyear Tire and Rubber
Co., located in Akron, Ohio; and styrene-butadiene random copolymer
rubbers such as AMERIPOL SYNPOL.TM. 1101 A, available from American
Synpol Co., located in Port Neches, Texas.
[0048] The elastic layer can be extruded as a single layer onto the
surface of the nonwoven fabric. Alternatively, the elastic layer
can comprise a plurality of elastic layers which are formed by
co-extruding the melted elastic materials through a suitable
co-extrusion die. For example, the elastic layer can comprise a
three layer structure, which allows for a core layer sandwiched
between two outer layers.
[0049] The elastic material used for each of the different layers
of the co-extruded elastic layer can be selected from the
elastomeric materials described above in order to vary the level of
adhesion between the elastic layer and the nonwoven fabric.
Adjusting the level of adhesion between the elastic layer and the
nonwoven allows one to obtain a desired balance between laminate
stretch and delamination resistance. In one embodiment, the
multi-layer elastic layer comprises a KRATON.TM. styrene block
copolymer core layer sandwiched between two outer layers formed
from VISTAMAXX.TM. elastomer. Alternatively, the outer layers of
the multi-layer elastic layer may be tie layers formed from a
material that promotes adhesion between the elastic layer and the
nonwoven layer or layers. Such tie layers may be formed from
compositions known in the art to promote adhesion between
incompatible materials. For example, tie layers may be formed from
maleic anhydride grafted polyolefins, such as BYNEL.RTM. from
DuPont or PLEXAR.RTM. from Equistar.
[0050] The level of adhesion between the elastic layer and the
nonwoven may also be adjusted through the use of adhesive fibers,
which can provide adhesive bonding between the nonwoven fabric and
the elastic layer where a low level of stretch is desired. Such
adhesive fibers may include, for example, polyvinyl alcohol fibers,
alginic fibers, fibers made from hot melt adhesives, or fibers made
from thermoplastic materials having a low softening or melting
point.
[0051] It will be appreciated by those skilled in the art that
additives may be added to the one or more layers of the presently
described laminates in order to improve certain characteristics of
the particular layer. Preferred additives include, but are not
limited to, color concentrates, neutralizers, process aids,
lubricants, stabilizers, hydrocarbon resins, antistatics,
antiblocking agents and fillers. It will also be appreciated that a
color concentrate may be added to yield a colored layer, an opaque
layer, or a translucent layer. A suitable neutralizer may include,
for example, calcium carbonate, while a suitable processing aid may
include, for example, calcium stearate.
[0052] Suitable antistatic agents may include, for example,
substantially straight-chain and saturated aliphatic, tertiary
amines containing an aliphatic radical having from about 10 to
about 20 carbon atoms that are substituted by
.omega.-hydroxy-(C1-C4)-alkyl groups, and
N,N-bis-(2-hydroxyethyl)alkylamines having from about 10 to about
20 carbon atoms in the alkyl group. Other suitable antistatics can
include ethoxylated or propoxylated polydiorganosiloxanes such as
polydialkylsiloxanes and polyalkylphenylsiloxanes, and alkali metal
alkanesulfonates.
[0053] Antiblocking agents suitable for use with the presently
described laminates include, but are not limited to, calcium
carbonate, aluminum silicate, magnesium silicate, calcium
phosphate, silicon dioxide, and diatomaceous earth. Such agents can
also include polyamides, polycarbonates, and polyesters.
[0054] Additional processing aids that may be used in accordance
with the presently described technology include, for example,
higher aliphatic acid esters, higher aliphatic acid amides, metal
soaps, polydimethylsiloxanes, and waxes. Conventional processing
aids for polymers of ethylene, propylene, and other .alpha.-olefins
are preferably employed in the present technology. In particular,
alkali metal carbonates, alkaline earth metal carbonates, phenolic
stabilizers, alkali metal stearates, and alkaline earth metal
stearates can be used as processing aids.
[0055] Fillers may be added to the elastic material to promote a
microporous structure within the elastic layer when the layer is
stretched. Examples of useful fillers include, but are not limited
to, alkali metal and alkaline earth metal carbonates, such as
sodium carbonate (Na.sub.2CO.sub.3), calcium carbonate
(CaCO.sub.3), and magnesium carbonate (MgCO.sub.3), nonswellable
clays, silica (SiO.sub.2), magnesium sulfate, magnesium oxide,
calcium oxide, alumina, mica, talc, titanium dioxide, zeolites,
aluminum sulfate, barium sulfate, and aluminum hydroxide.
[0056] Turning now to FIG. 1, there is schematically illustrated an
extrusion lamination process for making a stretchable laminate of
the presently described technology. A nonwoven fabric 12 is unwound
from a supply roll (not shown) and travels from the supply roll
over a layon roll 14 to a nip 16 created between the layon roll 14
and an embossing roll 18. The layon roll 14, which is also known in
the art as a pressure roll, is coated with a silicone rubber
coating and is typically water cooled or heated. The embossing roll
18 is provided with raised embossing elements 19 that impart a deep
embossing pattern to the nonwoven, as will be explained further
below. The embossing roll 18 is also typically water cooled or
heated. Suitable temperatures for the layon roll and the embossing
roll may be from about 60.degree. F. to about 230.degree. F.,
preferably from about 70.degree. F. to about 180.degree. F. A
second nonwoven fabric 22 is unwound from a second supply roll (not
shown) and travels from the second supply roll over the embossing
roll 18 to the nip 16. Preferably, layon roll 14 travels
rotationally at the same surface speed as the embossing roll
18.
[0057] It has been found that improved resistance to delamination
can be achieved in the stretchable laminates if the embossing roll
is provided with a deep embossing pattern that imparts
discontinuous, discrete dots, dashes, crosses, or other
discontinuous discrete shapes. By a deep embossing pattern it is
meant that the engraving depth of the embossing roll is at least
about 0.008 inches. Preferably the engraving depth of the embossing
roll is in the range of about 0.008 inches to about 0.5 inches,
alternatively in the range of about 0.008 inches to about 0.4
inches, alternatively in the range of about 0.008 inches to about
0.3 inches, alternatively in the range of about 0.008 inches to
about 0.2 inches, alternatively in the range of about 0.008 inches
to about 0.1 inches, alternatively in the range of about 0.008
inches to about 0.060 inches. The depth of the pattern can vary
depending upon the shape selected. For example, if the dot pattern
is selected (illustrated in FIG. 4), the depth should be at least
about 0.010 inches, alternatively from about 0.010 inches to about
0.060 inches. If the rectangular pattern is selected (illustrated
in FIG. 3), the depth of the embossing should be at least about
0.008 inches, alternatively from about 0.008 inches to about 0.060
inches. One particularly preferred depth for the dot pattern is
about 0.031 inches, and one particularly preferred depth for the
rectangular pattern is about 0.023 inches.
[0058] Without being bound by a particular theory, it is believed
that the deep embossing pattern imparted to the nonwoven fabric
concentrates the compressive force in a small area to create
discrete bonding sites. These discrete bonding sites provide
improved resistance to delamination compared to typical shallow
embossing patterns, having substantially greater bonding areas,
such as male fine square taffeta (MFST) embossing patterns, which
are about 0.0013 inches in depth.
[0059] An elastic material 30 is extruded through a die tip 32 at a
temperature above the melting point of the elastic material so that
the elastic material is melted. The melted elastic material drops
down to the nip 16 between the layon roll 14 and the embossing roll
18 where it contacts the nonwoven fabric 12 and the nonwoven fabric
22. As the nonwoven fabrics 12 and 22 and the elastic material 30
travel through the nip 16, compressive force at the nip 16 causes
the nonwoven fabric 22 to be embossed by the embossing roll 18 and
causes the elastic material to physically entrap the fibers at the
surfaces of the nonwoven fabrics, resulting, upon cooling of the
elastic material, in an embossed stretchable laminate having an
elastic layer bonded to the surfaces of the nonwoven fabrics but
not embedded within them. A suitable compressive force at the nip
may be from about 10 to about 150 pounds per lineal inch (PLI). It
should also be appreciated by those skilled in the art that the
embossing can also be accomplished by lay on roll 14.
[0060] It will be appreciated by those skilled in the art that,
although a three-layer stretchable laminate is illustrated in FIG.
1, a similar process can be used to manufacture a two-layer
stretchable laminate or, alternatively, a stretchable laminate
having more than three layers. In the case of a two-layer
stretchable laminate, the nonwoven fabric can be delivered to the
nip 16 either via the layon roll 14 or via the embossing roll 18,
although preferably it would be delivered via the embossing roll 18
with the elastic melt traveling through the nip 16 adjacent to the
layon roll 14. Slip agents may be added to the elastic material to
minimize adherence of the elastic melt to the layon roll 14. Such
slip agents may be, for example, euracylamide, and are well known
to those of skill in the art.
[0061] It will also be appreciated by those skilled in the art that
the compressive force used to bond the elastic layer to the
nonwoven fabric may be generated using techniques other than
conveying the elastic melt and the nonwoven fabric through a nip.
Such alternative techniques may include, for example, using an air
knife to blow the nonwoven fabric into the elastic melt, using a
vacuum box to draw the elastic melt down into the nonwoven fabric,
using nonwoven web tension to pull the nonwoven fabric into the
elastic melt, using a static bar (static electric pressure), or
combinations of these alternative techniques.
[0062] It should be further appreciated by those skilled in the art
that according to the present technology, the elastic material 30,
nonwoven fabrics 12 and 22 and resultant embossed stretchable
laminate can be perforated. Such materials, nonwoven fabrics and
laminates of the present technology can be perforated by any
conventional means or processes known or utilized to perforate such
materials. Thus, those skilled in art will appreciate that the step
of perforation is included within the spirit and scope of the
present technology.
[0063] The stretchable laminate resulting from the extrusion
lamination and embossing process has sufficient adhesion between
the elastic layer and the nonwoven fabric that delamination of the
layers does not occur, yet the adhesion is not so strong that it
negatively impacts the stretch properties of the laminate. The
adhesion between the elastic layer and the nonwoven is such that no
additional downstream bonding steps are necessary to insure that
delamination between the layers does not occur.
[0064] An additional property achieved by the stretchable laminates
of the presently described technology is improved resistance to
stretching in the machine direction. This is an important property
because it allows the laminate to be easily converted on a
manufacturing line. Resistance to stretching is determined by
measuring the tensile force required to stretch the laminate 5% in
the machine direction. The greater the tensile force, the greater
the laminate resists stretching in the machine direction as the
laminate is processed through manufacturing equipment.
[0065] The improved tensile forces for the stretchable elastic
laminates made in accordance with the present technology are
achieved without utilizing additional processing techniques, such
as necking. The tensile forces at 5% machine direction stretch
(tensile at 5% MD) for the stretchable laminates of the presently
described technology may be as high as 150 grams, preferably 200
grams, more preferably 250 grams, and most preferably 300 grams or
higher, without necking.
[0066] For some applications, it may be desirable to have a low
stretch zone on the elastic laminate in order to assure a secure
bond or attachment between the elastic laminate and a nonstretchy
substrate. Such a low stretch zone or area can be achieved in the
present elastic laminate in a variety of ways. For example, a tie
layer coating can be applied to the surface of the nonwoven fabric
where a low level of stretch is desired prior to lamination with
the elastic melt. The tie layer would not cause appreciable
stiffening, but would assure such a complete bond between the
nonwoven fabric and the elastic layer that little stretch could
occur in the tie layer region. Alternatively, a heavy bonding
pattern could be applied to those areas of the laminate where a low
level of stretch is desired to insure that there is a complete bond
between the nonwoven fabric and the elastic layer. Alternatively,
heat could be applied to the nonwoven in zones which will at least
partially fuse the nonwoven or create a greater degree of bonding
to the elastic material. The heat could be applied to the nonwoven
before lamination. One particularly preferred approach is heating
the nonwoven web with IR heat directed to specific areas of the
nonwoven, but other approaches with hot contact rollers would also
achieve the desired result. Another approach to create the low
stretch areas would be to use selective prestretching of the
nonwoven in the zones where a low level of stretch is desired in
the finished elastic laminate. These prestrained regions of the
nonwoven would resist further elongation after being applied to the
nonwoven. The prestraining could be accomplished with bowing
techniques known to the industry. Approaches would include the use
of small casters or wide rollers a contoured surface or a fixed rod
or plate with a contoured surface. This prestraining approach would
have the additional benefit of creating areas of nonwoven between
the prestrained zones having a greater level of potential stretch
than it had originally. This would increase the level of final
laminate stretch. Another approach for creating low stretch zones
would be the use of heat after the laminate is formed by the
application of heat in lanes to partially fuse the nonwoven and/or
increase its bond with the elastic film. This heat could be applied
with radiative, convective or conductive heat. One particularly
preferred approach would the use of hot rollers applied to the web
at or close to the slitting station. With this approach the
increased fusion could be more precisely positioned with respect to
the edges of a slit laminate roll so that is positioned more
exactly where the end customer would desire it. The heated fusion
is not necessarily continuously applied along the machine direction
of the laminate as any fusion pattern that is generally aligned in
the transverse direction of the web would reduce the laminate
stretch. Particularly preferred patterns would include transverse
oriented line segments, bands or curved bands. Other approaches
known in the art for creating low stretch zones, which are also
known in the art as "deadened lanes," may also be utilized. One
such approach is to add strips of conventional polypropylene
nonwoven fabric in lanes where little stretch is desired. This
could be done on one or both sides of the stretchable laminate.
[0067] For some applications it may be desirable for the elastic
laminate to be perforated in at least some regions so that it has
improved porosity. This is especially useful in garment
applications where the porosity contributes to the wearer's
comfort. Since the nonwoven webs are inherently porous the desired
laminate porosity can be achieved even if only the film is
perforated. Approaches known in the art for creating perforations
include among others needle perforation (hot or cold), die cutting,
laser, water jet or hot air pulsing. Additional perforation
techniques are envisioned for use with the present technology. One
preferred method would be the use of fiber ends or segments lifted
out of the plan of the nonwoven web (in the z-direction) to
perforate the elastic melt upon contact. The number of the
protruding nonwoven ends or segments can be increased by techniques
such roughening the nonwoven with a sanding or abrasion action or
by perforating the nonwoven web with a spiked roll such as the
pinned shells produced by Robert A. Main & Sons, Inc., located
in Wyckoff, N.J. Another preferred method would be creation of
perforations during the lamination process while the elastic
material is quiescent and more easily perforated. The perforation
at this stage could be created by raised elements on one of the
lamination rolls and this impact could be enhanced if desired by
heating these raised elements. The perforation of the elastic melt
at the lamination stage of the process could also be created by
selective introduction of water or air with either of the
lamination rollers to disrupt the continuity of the elastic melt.
If desired the perforation could be accomplished subsequent to
lamination. Another preferred technique for this would be spark
induced perforation such as that developed in corona treatment.
Another preferred technique would be die cutting of the laminate.
The cutting could be accomplished with or without material removal.
A preferred die cutting approach would be use of cutting segments
generally aligned with the machine direction of the web which would
also increase the cross direction stretch capability of the
laminate. If desired these cutting segments may include smaller
cross direction elements that could blunt any tearing propagation
of the laminate when stretched in the cross direction. One example
cutting pattern would be an I-beam shaped cut repeated across the
web wherever porosity is desired.
[0068] For some applications it may be desirable to increase the
level of the elongation of the elastic laminate in the cross
direction. One preferred technique for increasing the elongation of
the laminate would be the addition of available stretch in the
nonwoven by creating a greater path length for regions of the
nonwoven by extending the nonwoven out of the plane of the nonwoven
web (in the z-direction) in lanes or discrete zones. These lanes or
zones can preferably be created by allowing the nonwoven to conform
to the pattern roll before the nonwoven makes contact with the
elastic melt in the lamination process. The additional loft is
expected to create channels where air flow is permitted to enhance
the comfort of the user. In applications where the loft is not
desired for aesthetic reasons it can be available on one side of
the laminate and not on the other and the lofty side can be
positioned so that it is hidden from view in use. In an especially
preferred embodiment of this approach the flat surface would be
comprised of a nonwoven having higher inherent elongation than the
nonwoven used for the lofty surface of the web.
[0069] Although it is generally recognized in the art that higher
elongation is an advantage for elastic laminates, it is not
generally recognized that there is an advantage to a laminate with
two stages of elongation. The first stage could be nonrecoverable
or less recoverable and the second stage elastically recoverable.
With a nonrecoverable first stage it is possible to reduce the
amount of elastic laminate employed in a garment. A shorter segment
of elastic laminate could be utilized to save cost. The user would
extend the laminate through its first nonrecoverable stage of
elongation till it is close to the desired minimum length for its
fit function. The second stage of recoverable elongation for the
laminate would correspond more closely with the desired fit range
of the garment. An elastic laminate with this desired two stages of
elongation could be created with the invented process through the
removal of laminate material or the selected rupturing of the
elastic sheet such that the initial elongation of the laminate is
directed toward partially closing up the voids created in the
laminate. One preferred technique would be the use of die cutting
to produce open spots in the laminate through material removal. A
preferred pattern for this approach would be an array of ovals or
parallelograms or the like with the long axis generally aligned in
the machine direction of the web. Another preferred technique would
be the use of die cutting to cut the web without removal. A
preferred pattern for this approach would be an array of slits
generally aligned with the machine direction of the web. The slits
would preferentially be interrupted with cross direction elements
designed to blunt any tear propagation in the machine direction as
the laminate is stretched in the cross direction. A die cut
resembling an I-beam is particularly preferred for this
purpose.
[0070] One skilled in the art will recognize that modifications may
be made in the presently described technology without deviating
from the spirit or scope of the invention. Various embodiments of
the presently described technology are also described in the
following illustrative examples, which are not to be construed as
limiting the invention or scope of the specific procedures or
compositions described herein.
EXAMPLE 1 (COMPARATIVE)
[0071] A three layer extrusion laminate was prepared by extruding a
melt of an elastic resin from a die, such as die 32 shown in FIG.
1, into the nip between a layon roll, and an embossing roll, such
as layon roll 14 and embossing roll 18 shown in FIG. 1. The surface
of the embossing roll has a male fine square taffeta (MFST)
embossing pattern, which is known in the art. The melted elastic
layer is a multi-layer structure formed from a co-extruded melt
wherein the outer layers of the co-extruded multi-layer structure
are tie layers and the core layer is a
styrene-ethylene/butylene-styrene resin available from Kraton
Polymers of Houston, Texas under the trade name Kraton G-1657. The
elastic layer comprises the following:
[0072] BYNEL.RTM. E418 5% by weight outer layer/KRATON G1657 90% by
weight core/BYNEL.RTM. E418 5% by weight outer layer.
[0073] A first nonwoven web made from a PET spunlace material
having a basis weight of about 30 gsm and available from Tomen
America, Inc. of N.Y., travels over the layon roll to the nip and a
second, nonwoven web made of the PET spunlace material travels over
the embossing roll to the nip where the first and second nonwoven
webs each make contact with the elastic melt. Pressure at the nip
causes the elastic melt to bond to the surfaces of the first and
second nonwoven webs, and cause the embossing roll to form the MFST
embossed pattern on the outer surface of the second nonwoven web,
thus forming a three layer embossed laminate in which the elastic
layer is sandwiched between the first and second nonwoven webs.
EXAMPLE 2
[0074] A three layer extrusion laminate was prepared in the same
manner, using the same elastic resin melt and the same PET spunlace
nonwoven material for the first and second nonwoven layers as the
laminate made in comparative Example 1, except that the embossing
roll is provided with a rectangular deep embossing pattern.
EXAMPLE 3
[0075] A three layer extrusion laminate was prepared in the same
manner as Example 2, using the same elastic resin melt and the same
PET spunlace nonwoven material for the first and second nonwoven
layers. Except that the embossing roll is provided with a dot deep
embossing pattern.
[0076] Each of the laminates made in Examples 1-3 have overall
thicknesses of about 2 mils and have approximately the same basis
weight. The laminates were tested to determine the extent of
delamination as a function of number of loading cycles using an
Instron mechanical testing machine. The test geometry is a
4''.times.1'' strip with a 2'' gauge length. The crosshead speed
was 20''/minute to 100% strain for 20 cycles. Three specimens of
each laminate were tested. After 20 cycles, pictures of the grip
boundary showing the untested region in the grip and a region that
was tested for 20 cycles were taken under a microscope. The results
for Examples 1-3 are illustrated in FIGS. 2-4, respectively.
[0077] As can be seen from FIG. 2, the laminate prepared in
accordance with Example 1, which was embossed with the prior art
male fine square taffeta (MFST) embossing pattern had extensive
delamination after 20 cycles of testing. Thus, the Example 1
laminate showed poor resistance to delamination.
[0078] The laminate made in accordance with Example 2, which was
embossed with the rectangular deep embossing pattern, showed
improved resistance to delamination compared to Example 1. As can
be seen from FIG. 3, there was some delamination between bonding
points, but the delamination is limited. The Example 2 laminate has
high stretch, high tensile strength, good delamination resistance,
and excellent softness and feel.
[0079] The laminate made in accordance with Example 3, which was
embossed with the dot deep embossing pattern, showed superior
resistance to delamination compared to Example 1. As can be seen
from FIG. 4, there was almost no delamination in the Example 3
laminate, showing that deeper but fewer bonding areas can still
achieve superior delamination resistance. The Example 3 laminate
had better resistance to delamination than the Example 2 laminate,
but the Example 2 laminate had better softness and feel
characteristics than the Example 3 laminate.
[0080] First cycle hysteresis curves for each of the laminates made
in accordance with Examples 1-3 are illustrated in FIG. 5. As can
be seen from FIG. 5, each of the laminates have similar hysteresis
curves, with comparable loading forces at 100% strain rate and
comparable permanent sets. The similar laminate properties further
indicate that the improved delamination resistance of the Example 2
and Example 3 laminates can be attributed to the deep embossing
patterns used for those laminates.
[0081] The invention has now been described in such full, clear,
concise and exact terms as to enable any person skilled in the art
to which it pertains, to practice the same. It is to be understood
that the foregoing describes preferred embodiments and examples of
the invention and that modifications may be made therein without
departing from the spirit or scope of the invention as set forth in
the claims.
* * * * *