U.S. patent application number 10/617458 was filed with the patent office on 2004-01-15 for stable web having enhanced extensibility and method for making same.
Invention is credited to Benson, Douglas Herrin, Curro, John Joseph.
Application Number | 20040007314 10/617458 |
Document ID | / |
Family ID | 27805684 |
Filed Date | 2004-01-15 |
United States Patent
Application |
20040007314 |
Kind Code |
A1 |
Benson, Douglas Herrin ; et
al. |
January 15, 2004 |
Stable web having enhanced extensibility and method for making
same
Abstract
The present invention provides a stable material having enhanced
extensibility and a method for making the same. A tensioning force
is applied to a neckable material to neck the material. The necked
material is then subjected to mechanical stabilization to provide a
stabilized extensible necked material. The stabilized extensible
necked material is easily extended in a direction parallel to the
direction necking.
Inventors: |
Benson, Douglas Herrin;
(West Harrison, IN) ; Curro, John Joseph;
(Cincinnati, OH) |
Correspondence
Address: |
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
Family ID: |
27805684 |
Appl. No.: |
10/617458 |
Filed: |
July 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10617458 |
Jul 11, 2003 |
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08916055 |
Aug 21, 1997 |
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6620485 |
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Current U.S.
Class: |
156/163 ;
156/209; 156/229; 264/171.24; 264/280; 264/284; 264/288.4 |
Current CPC
Class: |
D04H 3/14 20130101; Y10T
156/1023 20150115; B29C 55/06 20130101; D04H 3/02 20130101; Y10T
428/2848 20150115; B29C 55/18 20130101; Y10S 428/903 20130101; Y10T
428/24463 20150115; Y10T 428/24479 20150115; Y10T 428/24446
20150115; Y10T 428/24455 20150115; Y10T 428/2826 20150115 |
Class at
Publication: |
156/163 ;
264/280; 264/288.4; 264/284; 264/171.24; 156/209; 156/229 |
International
Class: |
B29C 055/06; B29C
059/04; B32B 031/08; B32B 031/12 |
Claims
What is claimed is:
1. A method of producing a stabilized extensible necked material
comprising the steps of: a) providing a neckable material; b)
applying a tensioning force to the neckable material to neck the
material; and c) subjecting the necked material to mechanical
stabilization to provide a stabilized extensible necked
material.
2. The method of claim 1 wherein step c) comprises subjecting the
necked material to incremental stretching.
3. The method of claim 2 wherein said incremental stretching
comprises feeding the necked material through a nip formed by a
pair of incremental stretching rollers.
4. The method of claim 3 wherein each said incremental stretching
roller comprises a plurality of teeth and a plurality of
grooves.
5. The method of claim 1 wherein said mechanical stabilization
comprises feeding the necked material through a nip formed by a
pair of patterned compression rollers.
6. The method of claim 5 wherein said patterned compression rollers
provide a continuous compression stabilizing embossment across the
entire width of the material.
7. The method of claim 1 wherein said neckable material is a web
selected from the group consisting of a bonded carded web of
fibers, a web of spunbonded fibers, a web of meltblown fibers, and
a multilayer material including at least one of said webs.
8. The method of claim 7 wherein said fibers comprise a polymer
selected from the group consisting of polyolefins, polyesters, and
polyamides.
9. The method of claim 8 wherein said polyolefin is selected from
the group consisting of one or more of polyethylene, polypropylene,
polybutene, ethylene copolymers, propylene copolymers, and butane
copolymers.
10. The method of claim 1 wherein said neckable material is a
composite material comprising a mixture of fibers and one or more
other materials selected from the group consisting of wood pulp,
staple fibers, particulates, and super-absorbent materials.
11. The method of claim 1 further comprising the additional step
of: d) joining the stabilized extensible necked material to an
elastic member.
12. The method of claim 11 wherein the elastic member comprises an
elastomeric polymer selected from the group consisting of elastic
polyesters, elastic polyurethanes, elastic polyamides, and elastic
A-B-A' block copolymers wherein A and A' are the same or different
thermoplastic polymer, and wherein B is an elastomeric polymer
block.
13. The method of claim 11 wherein said elastic member comprises an
elastomeric film.
14. The method of claim 11 wherein said elastic member comprises an
elastomeric scrim.
15. A method of producing a stabilized extensible necked nonwoven
web comprising the steps of: a) providing a neckable nonwoven web;
b) applying a tensioning force to the neckable nonwoven web to neck
the nonwoven web; and c) subjecting the necked nonwoven web to
mechanical stabilization to provide a stabilized extensible necked
nonwoven web.
16. The method of claim 15 wherein step c) comprises subjecting the
necked nonwoven web to incremental stretching.
17. The method of claim 16 wherein said stabilized extensible
necked nonwoven web comprises a plurality of linear embossments
extending continuously across the entire width of the stabilized
extensible necked nonwoven web.
18. The method of claim 15 wherein said neckable nonwoven web is a
web selected from the group consisting of a bonded carded web of
fibers, a web of spunbonded fibers, a web of meltblown fibers, and
a multilayer material including at least one of said webs.
19. The method of claim 15 further comprising the step of: d)
joining the stabilized extensible necked nonwoven web to an elastic
member.
20. The method of claim 19 wherein said elastic member comprises an
elastomeric scrim.
Description
CROSS REFERENCE
[0001] This application is a division of patent application Ser.
No. 08/916,055, filed Aug. 21, 1997.
FIELD OF THE INVENTION
[0002] The present invention relates to stable materials having
enhanced extensibility and a mechanical post-processing method for
making the same. High extension materials, such as nonwoven webs
and film webs are particularly well suited for use in disposable
absorbent articles such as diapers, incontinence briefs, training
pants, feminine hygiene garments, and the like, as they are able to
be used in portions of the article where high extensibility can aid
in the article's fit to the body.
BACKGROUND OF THE INVENTION
[0003] Nonwoven webs may be manufactured into products and
components of products so inexpensively that the product may be
viewed as disposable after only one or a few uses. Representatives
of such products include diapers, training pants, wipes, garments,
incontinence briefs, feminine hygiene garments and the like.
[0004] Nonwoven webs may be treated to provide the nonwoven web
with certain properties. For example, U.S. Pat. No. 5,244,482
issued to Hassenboehler, Jr. et al. on Sep. 14, 1993 discloses a
method for treating a nonwoven web wherein the nonwoven web is
heated at an elevated temperature and uniaxially drawn to
consolidate and stabilize the nonwoven web. Such nonwoven webs are
noted to exhibit an increased elasticity after processing. Such
elasticity increase is recognized as being caused by the new
"memory" instilled by the heating of the nonwoven web. For
applications desiring enhanced extensibility rather than
elasticity, such heating is therefore not desirable. Additionally,
such drawing and setting of the nonwoven web by heating at an
elevated temperature often causes fiber embrittlement and the
nonwoven web to exhibit increased gloss. For many applications
involving skin contact, e.g., such as in diaper coverstock, such
attributes are contrary to the desired cloth-like properties of
softness and nonplastic, (low gloss) appearance. Lastly, the
requirement of heating the nonwoven web to consolidate and
stabilize the web adds to the complexity and cost of the
process.
[0005] U.S. Pat. No. 4,981,747 issued to Morman on Jan. 1, 1991,
discloses a "reversibly necked" material. It is taught that the
unstabilized necked material must be held under high tension on the
re-wound roll until such time as the further heat setting step is
performed to stabilize the material. Such a material will again
suffer the deficits noted above with respect to preferred skin
contact applications, and will enhance the elastic properties of
the material rather than the extensible behavior of the
material.
[0006] U.S. Pat. No. 5,226,992 issued to Morman on Jul. 13, 1993,
discloses a method of producing a composite elastic necked-bonded
material. A tensioning force is applied to at least one neckable
material, such as a neckable nonwoven web, to neck or consolidate
the material. Instead of heating the consolidated nonwoven web,
this patent teaches superposing the tensioned consolidated nonwoven
web on an elastic material and joining the tensioned consolidated
nonwoven web to the elastic material while the tensioned
consolidated nonwoven web is in a tensioned condition. By joining
the tensioned consolidated nonwoven web to the elastic material
while still in a tensioned condition, the nonwoven web is
constrained to its necked dimension. Such a procedure does not
provide a means for producing a stabilized extensible web without
the attachment of the nonwoven web to an additional elastic
layer.
[0007] It is an object of the present invention to provide a
stabilized extensible necked nonwoven web, capable of being wound
into stable rollstock or festooned form, suitable for subsequent
conversion or combining operations.
[0008] It is also an object of the present invention to provide a
stabilized extensible necked nonwoven web, capable of very high
speed extension via mechanical straining means.
[0009] It is also an object of the present invention to provide a
post-processing method for producing a stabilized extensible necked
nonwoven web.
[0010] It is also an object of the present invention to provide a
post-processing method for producing a stabilized extensible necked
nonwoven web that does not require heating of the neckable material
to elevated temperatures, to enhance the extensible properties
rather than the elastic properties and to substantially preserve
the original properties of the neckable nonwoven web.
[0011] As used herein, the term "elastic", refers to any material
which, upon application of a biasing force, is stretchable, that
is, elongatable, to at least about 60 percent (i.e., to a
stretched, biased length which is at least about 160 percent of its
relaxed unbiased length), and which, will recover at least 55
percent of its elongation upon release of the stretching,
elongation force.
[0012] As used herein, the term "extensible" refers to any material
which, upon application of a biasing force, is stretchable, that
is, elongatable, to at least about 60 percent without suffering
catastrophic failure (i.e., to a stretched, biased length which is
at least about 160 percent of its relaxed unbiased length), but
does not recover more than 55 percent of its elongation upon
release of the stretching, elongation force.
[0013] As used herein, the term "highly extensible" refers to any
material which, upon application of a biasing force, is
stretchable, that is, elongatable, to at least about 100 percent
without suffering catastrophic failure (i.e., to a stretched,
biased length which is at least about 200 percent of its relaxed
unbiased length), but does not recover more than 55 percent of its
elongation upon release of the stretching, elongation force.
[0014] As used herein, the term "stabilized" refers to a material
of the present invention which is capable Of being stored in a
stable condition in any common or conventional web storage manner
without the need for further heating or the addition of or joinder
with other webs to stabilize the material. Such storage means would
include for example, low tension rolls or festooned material in
boxes.
[0015] As used herein, the term "nonwoven web", refers to a web
that has a structure of individual fibers or threads which are
interlaid, but not in any regular repeating manner. Nonwoven webs
have been, in the past, formed by a variety of processes such as,
for example, meltblowing processes, spunbonding process, and bonded
carded web processes.
[0016] As used herein, the term "necked material", refers to any
material which has been constricted in at least one dimension by
applying a tensioning force in a direction that is perpendicular to
the desired direction of neck-down.
[0017] As used herein, the term "neckable material", refers to any
material which can be necked.
[0018] As used herein, the term "percent neckdown", refers to the
ratio determined by measuring the difference between the un-necked
dimension and the stabilized necked dimensions of the neckable
material in the direction of necking, and then dividing that
difference by the un-necked dimension of the neckable material,
then multiplying by 100.
[0019] As used herein, the term "composite elastic material",
refers to a material comprising an elastic member joined to a
stabilized extensible necked material. The elastic member may be
joined to the stabilized extensible necked material at intermittent
points or may be continuously bonded thereto. The joining is
accomplished while the elastic member and the stabilized extensible
necked material are in juxtaposed configuration. The composite
elastic material is elastic in a direction generally parallel to
the direction of neckdown of the stabilized extensible necked
material and may be stretched in that direction to the breaking
point of the stabilized extensible necked material. A composite
elastic material may include more than two layers.
[0020] As used herein, the term "polymer", generally includes, but
is not limited to, homopolymers, copolymers, such as, for example,
block, graft, random, and alternating copolymers, terpolymers, etc.
and blends and modifications thereof. Furthermore, unless otherwise
specifically limited, the term "polymer" shall include all possible
molecular geometric configurations of the material. These
configurations include, but are not limited to, isotactic,
syndiotactic and random symmetries.
SUMMARY OF THE INVENTION
[0021] In accordance with the present invention there is provided a
method of producing a stabilized extensible necked material
comprising the steps of:
[0022] providing a neckable material;
[0023] applying a tensioning force to the neckable material to neck
the material; and
[0024] subjecting the necked material to mechanical stabilization
to provide a stabilized extensible necked material. The stabilized
extensible necked material is easily extended in a direction
parallel to the direction of necking. A preferred method for
mechanically stabilizing the necked material comprises subjecting
the necked material to incremental stretching in a direction
generally perpendicular to the necked direction.
[0025] The method may also comprise the additional step of winding
the stabilized extensible necked material onto a take-up roll or
festooning the stabilized extensible necked material into box.
[0026] The method may also comprise the additional step of joining
the stabilized extensible necked material to an elastic member to
form a composite elastic material.
[0027] If the material is stretchable it may be necked by
stretching in a direction generally perpendicular to the desired
direction of neck-down. The neckable material may be any material
that can be necked sufficiently at room temperature. Such neckable
materials include knitted and loosely woven fabrics, bonded carded
nonwoven webs, spunbonded nonwoven webs, or meltblown nonwoven
webs. The neckable material may also have multiple layers such as,
for example, multiple spunbonded layers and/or multiple meltblown
layers or film layers. The neckable material may be made of
polymers such as for example, polyolefins. Exemplary polyolefins
include polypropylene, polyethylene, ethylene copolymers, propylene
copolymers and blends thereof. The neckable material may be a
nonelastic material such as for example a nonelastic nonwoven
material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] While the specification concludes with claims particularly
pointing out and distinctly claiming the subject matter which is
regarded as forming the present invention, it is believed that the
invention will be better understood from the following description
which is taken in conjunction with the accompanying drawings in
which like designations are used to designate substantially
identical elements, and in which:
[0029] FIG. 1 is schematic illustration of an exemplary process for
forming a necked material of the present invention;
[0030] FIG. 2 is an enlarged perspective illustration of the
stabilizing roller arrangement;
[0031] FIG. 3 is a plan view of an exemplary neckable material
before tensioning and necking;
[0032] FIG. 4 is a plan view of an exemplary necked material;
[0033] FIG. 5 is a plan view of an exemplary composite elastic
material while partially stretched;
[0034] FIG. 6 is a schematic illustration of another exemplary
process for forming a necked material of the present invention;
[0035] FIG. 7 is a plan view of a spaced-apart pattern of
embossments which is not suitable for setting the necked
material;
[0036] FIG. 8 is a plan view of an embossment pattern of the
present invention which is suitable for setting the necked
material; and
[0037] FIG. 9 is a plan view of another embossment pattern of the
present invention which is suitable for setting the necked
material.
DETAILED DESCRIPTION OF THE INVENTION
[0038] Referring to FIG. 1 there is schematically illustrated at 20
a process for forming a stabilized extensible necked material of
the present invention.
[0039] According to the present invention, a neckable material 22
is unwound from a supply roll 23 and travels in the direction
indicated by the arrows associated therewith as the supply roll 23
rotates in the direction indicated by the arrows associated
therewith. The neckable material 22 passes through a nip 25 of the
S-roll arrangement 26 formed by the stack rollers 28 and 30.
[0040] The neckable material 22 may be formed by known nonwoven
extrusion processes, such as, for example, known meltblowing
processes or known spunbonding processes, and passed directly
through the nip 25 without first being stored on a supply roll.
[0041] The neckable material 22 passes through the nip 25 of the
S-roll arrangement 26 in a reverse-S path as indicated by the
rotation direction arrows associated with the stack rollers 28 and
30. From the S-roll arrangement 26 the neckable material 22 passes
through the nip 32 formed by the incremental stretching rollers 34
and 36 of the mechanical stabilization arrangement 38. Because the
peripheral linear speed of the rollers of the S-roll arrangement 26
is controlled to be less than the peripheral linear speed of the
rollers of the mechanical stabilization arrangement 38, the
neckable material 22 is tensioned between the S-roll arrangement 26
and the nip 32 of the incremental stretching rollers 34 and 36 of
the mechanical stabilization arrangement 38. By adjusting the
difference in the speeds of the rollers, the neckable material 22
is tensioned so that it necks a desired amount and is maintained in
such a tensioned, necked condition. The mechanical stabilization
arrangement 38 provides a stabilized necked material which may be
joined to other materials.
[0042] Other methods of tensioning the neckable material 22 may be
used such as, for example, tenter frames or other cross-machine
direction stretcher arrangements that expand the neckable material
22 in other directions such as, for example, the cross-machine
direction.
[0043] The neckable material 22 may be extensible, elastic, or
nonelastic nonwoven material. The neckable material 22 may be a
spunbonded web, a meltblown web, or a bonded carded web. If the
neckable material is a web of meltblown fibers, it may include
meltblown microfibers. The neckable material 22 may be made of
fiber forming polymers such as, for example, polyolefins. Exemplary
polyolefins include one or more of polypropylene, polyethylene,
ethylene copolymers, propylene copolymers, and butene
copolymers.
[0044] In one embodiment of the present invention, the neckable
material 22 may be a multilayer material having, for example, at
least one layer of a spunbonded web joined to at least one layer of
a meltblown web, a bonded carded web or other suitable material.
Alternatively, the neckable material 22 may be a single layer of
material such as, for example, a spunbonded web, a meltblown web,
or a bonded carded web.
[0045] The neckable material 22 may also be a composite material
made of a mixture of two or more different fibers or a mixture of
fibers and particles. Such mixtures may be formed by adding fibers
and/or particulates to the gas stream in which the meltblown fibers
are carried so that an intimate entangled commingling of meltblown
fibers and other materials, e.g., wood pulp, staple fibers and
particulates such as, for example, hydrocolloidal (hydrogel)
particles commonly referred to as superabsorbent materials, occurs
prior to collection of the meltblown fibers upon a collecting
device to form a coherent web of randomly dispersed meltblown
fibers and other materials.
[0046] The nonwoven web of fibers should be joined by bonding to
form a coherent web structure which is able to withstand necking.
Suitable bonding techniques include, but are not limited to,
chemical bonding, thermobonding, such as point calendering,
hydroentangling, and needling.
[0047] FIG. 2 is an enlarged perspective illustration of a
preferred embodiment of the mechanical stabilization arrangement 38
employing opposed pressure applicators having three-dimensional
surfaces which at least to a degree are complimentary to one
another. The mechanical stabilization arrangement 38 shown in FIG.
2 comprises incremental stretching rollers 34 and 36. The neckable
material 22 passes through the nip 32 formed by incremental
stretching rollers 34 and 36 as the incremental stretching rollers
rotate in the direction indicated by the arrows associated
therewith. Uppermost incremental stretching roller 34 comprises a
plurality of teeth 40 and corresponding grooves 41 which extend
about the entire circumference of roller 34. Lowermost incremental
stretching roller 36 comprises a plurality of teeth 42 and
corresponding grooves 43 which extend about the entire
circumference of roller 36. The teeth 40 on roller 34 intermesh
with or engage the grooves 43 on roller 36, while the teeth 42 on
roller 36 intermesh with or engage the grooves 41 on roller 34.
[0048] The teeth 40 and 42 on rollers 34 and 36, respectively,
extend in a direction substantially perpendicular to the travel
direction of the neckable web 22 or in a direction substantially
parallel to the width of the neckable material 22. That is, teeth
40 and 42 extend in a direction parallel to the cross-machine or CD
direction. The incremental stretching rollers 34 and 36
incrementally stretch the necked web in a direction generally
perpendicular to the necked direction thereby stabilizing the
necked material 22 such that it remains in its necked condition
after passing through the incremental stretching rollers 34 and 36
and the tension on the necked material is released. By stabilizing
the necked material, the necked material substantially maintains
its necked width without returning to its precursor width.
[0049] After being stabilized by passing through the incremental
stretching rollers 34 and 36, the stabilized necked material 22
includes a plurality of stabilizing embossments 44. Stabilizing
embossments 44 extend in a substantially linear direction parallel
to one another across the entire width of the stabilized necked
material 22. The stabilizing embossments 44 are shown to be
extending in a direction substantially parallel to the CD or
cross-machine direction. As seen in FIG. 2, each stabilizing
embossment extends across the stabilized necked material 22 from
one edge to the other edge. This is very important as this sets the
fibers across the entire width of the web thereby stabilizing the
web. If the stabilizing embossments 44 did not extend entirely
across the neckable material 22, the portion of the neckable
material that is not embossed would return to its precursor width.
For example, a spaced apart pattern of embossments such as shown in
FIG. 7, would not effectively set the material. The portions of the
material between the individual embossments would not be set, and
therefore, would allow the material to return to its precursor
width.
[0050] The incremental stretching rollers 34 and 36 may include any
number of teeth and grooves to provide the desired stabilization in
the nonwoven web. In addition, the teeth and grooves may be
nonlinear, such as for example, curved, sinusoidal, zig-zag, etc.
In addition, the teeth and grooves may extend in a direction other
than perpendicular to the travel direction of the neckable web. For
example, the teeth and grooves may extend at an angle to the CD
direction, but preferably not parallel to the MD or machine
direction, as this type of incremental stretching would tend to
expand the width of the web, thus defeating the purpose of the
necking operation.
[0051] Referring now to FIG. 1, after the neckable material 22
passes through the mechanical stabilization arrangement 38 it is
wound up on take-up roll 50. Stabilizing the neckable material in
its necked condition allows it to be wound up on a take-up roll
while in its necked condition and then later used for the desired
end use. Once the neckable material has been mechanically
stabilized or set, it is suitable for handling on high speed
conventional diaper converting equipment without the need for
special handling equipment.
[0052] The stabilized necked material is easily extended in a
direction parallel to the direction of necking. That is, the
stabilized necked material is easily extended in the cross-machine
direction. The stabilized extensible necked material is elongatable
upon application of a biasing force to at least about 60 percent
without suffering catastrophic failure, (i.e., to a stretched,
biased length which is at least about 160 percent of its relaxed
unbiased length). Preferably, the stabilized extensible necked
material is elongatable upon application of a biasing force to at
least about 100 percent without suffering catastrophic failure,
(i.e., to a stretched, biased length which is at least about 200
percent of its relaxed unbiased length). Because the stabilized
extensible necked material is extensible and not elastic, the
stabilized extensible necked material does not recover more than 55
percent of its elongation upon release of the stretching,
elongation force.
[0053] The stabilized extensible necked material is preferably
elongatable to at least about 60 percent and more preferably to at
least about 100 percent or more without suffering catastrophic
failure upon the application of a relatively low biasing force.
Being elongatable to at least about 60 percent and more preferably
to at least about 100 percent or more upon the application of a
relatively low biasing force makes the stabilized extensible necked
material particularly well suited for use in disposable absorbent
articles such as diapers, incontinence briefs, training pants,
feminine hygiene garments, and the like, as they are able to be
used in portions of the article where high extensibility can aid in
the article's fit to the body.
[0054] The stabilized extensible necked material is preferably
elongatable to at least about 60 percent and more preferably to at
least about 100 percent without suffering catastrophic failure upon
the application of a biasing force of less than about 100 grams,
more preferably upon the application of a biasing force of less
than about 200 grams, and most preferably upon the application of a
biasing force of less than about 300 grams.
[0055] Conventional drive means and other conventional devices
which may be utilized in conjunction with the apparatus of FIG. 1
are well known and, for purposes of clarity, have not been
illustrated in the schematic view of FIG. 1.
[0056] In addition to incremental stretching, there are other
suitable methods for mechanically stabilizing the necked material.
These methods include crimping, and/or creping rollers. Another
suitable method includes passing the necked material through the
nip of a pair of smooth rollers. The nip pressure and/or roller
engagements of such stabilizing rollers are set to provide the
desired degree of stabilization to the necked web.
[0057] FIG. 8 is a plan view of another suitable embossment pattern
for stabilizing the neckable material. The pattern includes a
plurality of linear embossments 210 extending continuously across
the entire width of the web 205 in a direction generally parallel
to the cross-machine direction. The pattern also includes a
plurality of linear embossments 212 extending continuously across
the entire width of the web 205 at an angle to the cross-machine
direction and at an angle to the embossments 210. The web 205 also
includes a plurality of linear embossments 214 extending
continuously across the entire width of the web 205 at an angle to
the cross-machine direction and at an angle to the embossments 210
and 212. The embossments 212 and 214 may extend at any angle to one
another and to the embossments 210.
[0058] FIG. 9 is a plan view of another embossment pattern for
stabilizing the neckable material. The pattern includes a plurality
of linear embossments 222 extending continuously across the entire
width of the web 220 at an angle to the cross-machine direction.
The web 220 also includes a plurality of linear embossments 224
extending continuously across the entire width of the web 220 at an
angle to the cross-machine direction and at an angle to the
embossments 222. The embossments 222 and 224 are preferably aligned
perpendicular to one another. However, other angles between the
linear embossments 222 and 224 may also be employed.
[0059] The embossment pattern of FIGS. 8 and 9, is provided by
feeding the necked material through a nip formed by a pair of
patterned compression rollers. Each roller comprises a series of
raised surfaces, similar to the teeth 40 and 42 on rollers 34 and
36, respectively. The raised surfaces on each of the rollers are
complimentary and engage one another and compress the necked
material providing the embossment pattern shown in FIGS. 8 and 9.
The compression provided by the patterned compression rollers sets
the individual fibers to stabilize the web in its necked
condition.
[0060] Alternatively, the patterned compression rollers may
comprise a pattern roller having a pattern of raised surfaces and
an anvil roller having a smooth surface. The raised surfaces on the
pattern roller compress the necked material against the anvil
roller to provide the embossment pattern shown in FIGS. 8 and
9.
[0061] The stabilized extensible necked material may later be
joined to an elastic member to form a composite elastic material.
Preferably, the stabilized extensible necked material is joined
with an elastic member while the elastic member is in a
substantially untensioned condition. The stabilized extensible
necked material and the elastic member may be joined to one another
either intermittently or substantially continuously along at least
a portion of their coextensive surfaces while the elastic member is
in either a tensioned or an untensioned condition. The stabilized
extensible necked material may be joined to an elastic member after
having been removed from a roll, such as take-up roll 50, or may be
joined to an elastic member after having been subjected to
mechanical stabilization.
[0062] The elastic member may be made from any suitable elastic
material. Generally, any suitable elastomeric fiber forming resins
or blends containing the same may be utilized for the nonwoven webs
of elastomeric fibers and any suitable elastomeric film forming
resins or blends containing the same may be utilized for the
elastomeric films of the invention. For example, the elastic member
may be an elastomeric film made from block copolymers having the
general formula A-B-A' where A and A' are each a thermoplastic
polymer endblock which contains a styrenic moiety such as a
poly(vinyl arene) and where B is an elastomeric polymer midblock
such as a conjugated diene or a lower alkene polymer. Other
exemplary elastomeric films which may be used to form the elastic
sheet include polyurethane elastomeric materials such as, for
example, those available under the trademark ESTANE from B.F.
Goodrich & Company, polyamide elastomeric materials such as,
for example, those available under the trademark PEBAX from the
Rilsan Company, and polyester elastomeric materials such as, for
example, those available under the trade designation Hytrel from E.
I. DuPont De Nemours & Company.
[0063] A polyolefin may also be blended with the elastomeric
polymer to improve the processability of the composition. The
polyolefin must be one which, when blended and subjected to an
appropriate combination of elevated pressure and elevated
temperature conditions, is extrudable, in blended form, with the
elastomeric polymer. Useful blending polyolefin materials include,
for example, polyethylene, polypropylene and polybutene, including
ethylene copolymers, polypropylene copolymers, and butene
copolymers.
[0064] The elastic member may also be a pressure sensitive
elastomeric adhesive sheet. For example, the elastic material
itself may be tacky or, alternatively, a compatible tackifying
resin may be added to the extrudable elastomeric compositions
described above to provide an elastomeric sheet that can act as a
pressure sensitive adhesive, e.g., to bond the elastomeric sheet to
a tensioned, necked nonelastic web. The elastic sheet may also be a
multilayer material that may include two or more individual
coherent webs or films. Additionally, the elastomeric sheet may be
a multilayer material in which one or more of the layers contain a
mixture of elastic and nonelastic fibers or particles.
[0065] Other suitable elastomeric materials for use as the elastic
member include "live" synthetic or natural rubber including heat
shrinkable elastomeric films, formed elastomeric scrim, elastomeric
foams, or the like. In an especially preferred embodiment, the
elastic member comprises an elastomeric scrim available from Conwed
Plastics.
[0066] The relation between the original dimensions of the neckable
material 22 to its dimensions after tensioning or necking
determines the approximate limits of stretch of the composite
elastic material. Because the neckable material is able to stretch
and return to its necked dimension in directions such as, for
example, the machine direction or cross-machine direction, the
composite elastic material will be stretchable in generally the
same direction as the neckable material 22.
[0067] For example, with reference to FIGS. 3, 4, and 5, if it is
desired to prepare a composite elastic material stretchable to a
150% elongation, a width of neckable material shown schematically
and not necessarily to scale in FIG. 3 having a width "X" such as,
for example, 250 cm, is tensioned so that it necks down to a width
"Y" of about 100 cm. The necked material shown in FIG. 4 is
mechanically stabilized to provide a stabilized extensible necked
material. The stabilized extensible necked material is then joined
to an elastic member having a width of approximately 100 cm and
which is at least stretchable to a width of 250 cm. The resulting
composite elastic material shown schematically and not necessarily
to scale in FIG. 5 has a width "Y" of about 100 cm and is
stretchable to at least the original 250 cm width "X" of the
neckable material for an elongation of about 150%. As can be seen
from the example, the elastic limit of the elastic member needs
only be as great as the minimum desired elastic limit of the
composite elastic material.
[0068] Referring now to FIG. 6, there is schematically illustrated
another process 100 for forming a necked material of the present
invention.
[0069] A neckable material 122 is unwound from a supply roll 123
and travels in the direction indicated by the arrows associated
therewith as the supply roll 123 rotates in the direction indicated
by the arrows associated therewith. The neckable material 122
passes through the nip 125 of the S-roll arrangement 126 formed by
the stack rollers 128 and 130.
[0070] The neckable material 122 may be formed by known nonwoven
extrusion processes, such as, for example, known meltblowing
processes or known spunbonding processes, and passed directly
through the nip 125 without first being stored on a supply
roll.
[0071] The neckable material 122 passes through the nip 125 of the
S-roll arrangement 126 in a reverse-S path as indicated by the
rotation direction arrows associated with the stack rollers 128 and
130. From the S-roll arrangement 126, the neckable material 122
passes through the pressure nip 145 formed by pressure roller
arrangement 140 comprised of pressure rollers 142 and 144. Because
the peripheral linear speed of the rollers of the S-roll
arrangement 126 is controlled to be less than the peripheral linear
speed of the rollers of the pressure roll arrangement 140, the
neckable material 122 is tensioned between the S-roll arrangement
126 and the pressure nip of the pressure roll arrangement 140. By
adjusting the difference in the speeds of the rollers, the neckable
material 122 is tensioned so that it necks a desired amount and is
maintained in such a tensioned, necked condition. From the pressure
roller arrangement 140 the necked material 122 passes through the
nip 151 formed by the mechanical stabilization arrangement 152
comprised of incremental stretching rollers 153 and 154. Because
the peripheral linear speed of the rollers of the pressure roll
arrangement 140 is controlled to be less than or equal to the
peripheral linear speed of the rollers of the mechanical
stabilization arrangement 152, the material is maintained in its
tensioned and/or necked condition between the pressure roll
arrangement 140 and the mechanical stabilization arrangement 152.
After leaving mechanical stabilization arrangement 152 the
stabilized necked material 122 is wound up on take-up roll 160.
[0072] Conventional drive means and other conventional devices
which may be utilized in conjunction with the apparatus of FIG. 6
are well known and, for purposes of clarity, have not been
illustrated in the schematic view of FIG. 6.
[0073] While particular embodiments of the present invention have
been illustrated and described, it would be obvious to those
skilled in the art that various other changes and modifications can
be made without departing from the spirit and scope of the
invention. It is therefore intended to cover in the appended claims
all such changes and modifications that are within the scope of
this invention.
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