U.S. patent application number 10/881064 was filed with the patent office on 2006-01-05 for efficient necked bonded laminates and methods of making same.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. Invention is credited to Michael T. Morman.
Application Number | 20060003656 10/881064 |
Document ID | / |
Family ID | 34976918 |
Filed Date | 2006-01-05 |
United States Patent
Application |
20060003656 |
Kind Code |
A1 |
Morman; Michael T. |
January 5, 2006 |
Efficient necked bonded laminates and methods of making same
Abstract
The present invention provides an elastic necked-bonded laminate
material or elastic neck stretched bonded laminate material
including at least one necked material joined to at least one
elastic sheet that has been stretched in the cross-machine
direction and allowed to relax prior to joining with the necked
material. The elastic sheet can be stretched prior to being joined
with the necked material or following the joining to the necked
material. Also disclosed is a method of producing a elastic
necked-bonded laminate material including the step of stretching
the elastic sheet in a macroscopic stretching apparatus, such as
between the nip of a series of spaced apart discs on two axles.
Inventors: |
Morman; Michael T.;
(Knoxville, TN) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
US
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
|
Family ID: |
34976918 |
Appl. No.: |
10/881064 |
Filed: |
June 30, 2004 |
Current U.S.
Class: |
442/327 |
Current CPC
Class: |
B32B 2555/02 20130101;
Y10T 442/60 20150401; A61F 13/4902 20130101; B32B 37/144
20130101 |
Class at
Publication: |
442/327 |
International
Class: |
D04H 1/00 20060101
D04H001/00 |
Claims
1. A method of producing an elastic necked-bonded laminate material
comprising: providing at least one neckable nonelastic material;
applying a tensioning force to the neckable nonelastic material to
neck said material; providing an elastic sheet; superposing the
necked nonelastic material onto said elastic sheet; joining said
necked nonelastic material and said elastic sheet at least at two
places to form a laminate material; and stretching said elastic
sheet in the cross-machine direction through the use of a
macroscopic stretching apparatus.
2. The method of claim 1 wherein said stretching of said elastic
sheet is performed prior to joining with said nonelastic
material.
3. The method of claim 1 wherein said stretching of said elastic
sheet is performed following joining of said elastic sheet with
said nonelastic material.
4. The method of claim 1 wherein said macroscopic stretching
apparatus is a macroscopic grooved roll arrangement.
5. The method of claim 1 wherein said macroscopic stretching
apparatus is a macroscopic disc on axle arrangement.
6. A method of producing an elastic necked-bonded laminate material
comprising: providing at least one neckable nonelastic material;
applying a tensioning force to the neckable nonelastic material to
neck said material; providing an elastic sheet; superposing the
necked nonelastic material onto said elastic sheet; joining said
necked nonelastic material and said elastic sheet at least at two
places to form a laminate material; and stretching said elastic
sheet in the cross-machine direction with the use of macroscopic
discs along axles.
7. The method of claim 6 wherein said stretching of said elastic
sheet is performed prior to joining to said nonelastic
material.
8. The method of claim 6, wherein said stretching of said elastic
sheet is performed following joining to said nonelastic
material.
9. The method of claim 6 wherein said elastic sheet is selected
from the group consisting of an elastic film, an elastic nonwoven
web, an elastic woven web, an elastic scrim or netting, and an
elastic foam.
10. The method of claim 6 wherein said neckable material is a
material selected from the group consisting of knitted fabrics,
loosely woven fabrics, and nonwoven webs.
11. The method of claim 6 wherein said neckable material is
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.
12. The method of claim 6 wherein said stretching step is
accomplished by passing said elastic sheet through a nip of
intermeshing discs along axles positioned in the cross-machine
direction.
13. The method of claim 12 wherein the discs along each axle of the
nip are of the same diameter.
14. The method of claim 12 wherein the discs on each axle are of
the same diameter and the diameters of discs between axles is
varied.
15. The method of claim 12 wherein the diameter of discs along the
same axle are varied.
16. The method of claim 12, wherein the discs include ball
bearings.
17. The method of claim 12, wherein the discs are non-circular in
shape.
18. The method of claim 12, wherein the discs are offset upon the
axle in that the core of the discs are not in the center of the
disc.
19. The method of claim 12 wherein the spacial distance between
discs along each axle is the same.
20. The method of claim 12 wherein the spacial distance between
discs along each axle is varied.
21. The method of claim 12 wherein during the step of stretching
said elastic material said elastic material is held at its
cross-machine direction edges so as to not move inward.
22. The method of claim 21, wherein said elastic material is held
at its cross-machine direction edges via the use of a belt
arrangement.
23. A necked nonwoven elastic laminate material produced by the
method of claim 1.
24. A personal care product made with the material produced by the
method of claim 1.
25. A necked nonwoven elastic laminate material produced by the
method of claim 6.
26. A personal care product comprising the necked nonwoven elastic
laminate of claim 23.
27. The personal care product of claim 26 comprising an ear
material comprising the necked nonwoven elastic laminate.
28. The personal care product of claim 26 comprising an outercover
material comprising the necked nonwoven elastic laminate.
29. The personal care product of claim 26 comprising a side panel
material comprising the necked nonwoven elastic laminate.
30. The method of claim 1 wherein said elastic layer is stretched
in the machine direction while bonding with said nonelastic necked
material.
31. The method of claim 6 wherein said elastic layer is stretched
in the machine direction while bonding with said nonelastic necked
material.
32. A macroscopic stretching apparatus for stretching an elastic
layer of a necked bonded laminate material comprising: a first
axle, macroscopic discs positioned about said first axle, a second
axle parallel and adjacent to said first axle, macroscopic discs
positioned about said second axle, and at least one of said axles
being adjustably moveable with respect to the other axle.
33. A necked bonded laminate material including machine direction
bands of prestretched and non prestretched zones wherein the
nonprestretched zones are at least 0.25 inch wide.
34. The necked bonded laminate material of claim 33 wherein said
bands are at least 0.5 inch wide.
35. The necked bonded laminate material of claim 33 wherein said
bands are at least 1 inch wide.
36. The necked bonded laminate material of claim 33 wherein said
machine direction bands demonstrate varying periodic degrees of
prestretching.
Description
FIELD OF INVENTION
[0001] The present invention relates to methods of making elastic
clothlike laminates, including laminates made from necked materials
and elastic layers. In particular, the present invention relates to
methods of making necked bonded laminates which can then be used at
least as personal care product construction materials, such as
bodyside facing liner material (or topsheets), outercovers, waist
elastic materials, side panel materials and ear materials. The
present invention also relates to apparatus that can be used in
such methods, as well as other methods of manufacture.
BACKGROUND OF THE INVENTION
[0002] Polymeric films and nonwoven webs may be manufactured into
personal care products and components of products so inexpensively
that the products could be viewed as disposable after only one or a
few uses. Such nonwoven webs may include bonded carded webs and
webs formed by nonwoven extrusion processes such as meltblowing
processes and spunbonding processes. Representatives of such
products include articles such as diapers, adult incontinence
devices, swimwear, feminine care products, and training pants.
Other such personal care disposable products include tissues,
wipes, mattress pads, veterinary products, mortuary products,
article covers and medical related protective products such as
garments worn in a medical setting, face masks, sterilization wraps
and hospital packaging materials.
[0003] Some of the challenges associated with products in these
groupings include the provision of an elastic material which is
resilient and flexible while still having a pleasing feel. One
specific problem is the provision of an elastic material which does
not feel plastic or rubbery, a characteristic common to most
elastic polymer materials.
[0004] It is generally known that the tactile properties of the
elastic materials can be improved by forming a laminate of the
elastic material with one or more nonelastic materials on the outer
surface(s) of the elastic material. For instance, in one such
laminate material, a nonelastic material is joined to an elastic
material while the elastic material is in a stretched condition so
that when the elastic material is relaxed, the nonelastic material
gathers between the locations where it is bonded to the elastic
material. The resulting elastic laminate material is stretchable to
the extent that the nonelastic material gathered between the bond
locations allows the elastic material to elongate. In the stretch
bonded laminate process, a just -formed (or pre-formed) elastic
material is stretched and then attached to the gatherable material.
The elastic is then allowed to retract gathering the gatherable
material and forming the stretch bonded laminate. Elastic materials
just formed from the melt inherently have elastic performance on a
"first time stretch" that is not as good (having higher immediate
set) as opposed to subsequent stretches. The "first time stretch"
is accomplished while forming the stretch bonded laminate material
so the elastic performance of the finished stretch bonded laminate
is high. For the purposes of this application, the term "first time
stretch" refers to the first stretch of an elastic layer following
formation. It could occur either during a manufacturing process, or
alternatively by a consumer in using a product. For example, in the
case of personal care products, a "first time stretch" may occur
when a consumer opens a personal care garment to insert a user's
legs or waist (such as in a diaper) and/or stretches a garment to
secure it about their person. An example of this type of stretch
bonded laminate material is disclosed, for example, by U.S. Pat.
No. 4,720,415 to Vander Wielen et al., and U.S. Pat. No. 5,385,775
to Wright and Publication No. WO 01/88245, each of which are hereby
incorporated by reference in its entirety. While stretch bonded
laminate materials are effective in providing high levels of
stretch and recovery, it is often not necessary to utilize such
high performance elastic materials throughout an entire personal
care product. It has been found that stretch bonded laminate
materials tend to be fairly costly to manufacture and their
inclusion in a product necessarily increases the cost of the end
product to the consumer. It would therefore be desirable to provide
efficient elastic materials, at a lower cost.
[0005] It is also known to laminate (or bond) a necked (neckable)
material to an elastic sheet to produce a neck bonded laminate.
This process involves an elastic member being bonded to a
non-elastic member while only the non-elastic member is extended in
one direction (usually the MD) and necked in the transverse
direction so as to reduce its dimension in the direction orthogonal
to the extension. Such is described in detail in U.S. Pat. Nos.
4,965,122, 4,981,747, 5,226,992, and 5,336,545 to Morman, each of
which is incorporated by reference herein in its entirety. While
such neck bonded laminates may be less costly to produce than
stretch bonded laminates, the production of such laminates is often
not efficient. In particular, it has been found that the use of the
non-elastic nonwoven materials on such elastic sheets drags on the
elastic sheets. Further, the bonding of the non-elastic members
(sheet(s)) to the elastic member (sheet(s)) is accomplished using a
process which does not take total advantage of the elastic sheet
properties. In forming a necked bonded laminate, the "first time
stretch" of the elastomeric layer doesn't occur, so essentially the
"first time stretch", which is done by the consumer, may not have
the desired elastic properties unless very expensive elastomers are
used.
[0006] It would be desirable to utilize a less costly material such
as a necked and bonded laminate that took greater advantage of the
elastic sheet material properties in the laminate. It would
therefore also be desirable to alter the neck bonded laminate
manufacturing process in order to more efficiently produce a higher
performance neck bonded laminate when used in an end product. The
term higher performance necked bonded laminate shall mean a
performance of the neck bonded laminate in a product that offers
lower permanent set upon stretching and lower force to extend upon
usage of a product by a consumer, as compared to current similarly
formulated neck bonded laminate materials in personal care
products.
[0007] It is also known to utilize intermeshing grooved rolls or
discs on axle apparatus for stretching nonwoven webs. For instance,
it is known to use grooved rolls generally to stretch a formed
elastic and non-elastic neck bonded laminate. See for example U.S.
Publication 20040121687. However, such grooved roll stretching
apparatus have posed problems from a manufacturing perspective, as
they often lead to equipment failure if the rolls are not properly
aligned, or alternatively to material failure if the roll speed and
alignment are not controlled. Such grooved rolls, if not properly
aligned (groove/peak and speed alignment) can be unduly harsh on
nonwoven materials. Also, to date, such apparatus have not been
used to benefit the elastic performance of elastic sheets
themselves, (making only such elastic sheets more efficient without
impacting the nonelastic sheet material) early in a manufacturing
processes. There is therefore a need for more efficient elastic low
cost laminates for use in personal care products and methods for
making such laminates. It is to such needs that the current
invention is directed.
Definitions
[0008] The term "elastic" is used herein to mean any material
which, upon application of a biasing force, is stretchable, that
is, elongatable, to a stretched, biased length which is at least
about 150 percent of its relaxed unbiased length, and which will
recover at least 50 percent of its elongation upon release of the
stretching, elongating force. A hypothetical example would be a one
(1) inch sample of a material which is elongatable to at least 1.50
inches and which, upon being elongated to 1.50 inches and released,
will recover to a length of not more than 1.25 inches. Many elastic
materials may be stretched by much more than 50 percent of their
relaxed length, for example, 80 percent or more, and many of these
will recover to substantially their original relaxed length, for
example, to within 105 percent of their original relaxed length,
upon release of the stretching force.
[0009] As used herein, the term "nonelastic" refers to any material
which does not fall within the definition of "elastic," above.
[0010] As used herein, the term "recover" refers to a contraction
(or retraction) of a stretched material upon termination of a
biasing force following stretching of the material by application
of the biasing force. For example, if a material having a relaxed,
unbiased length of one (1) inch is elongated 50 percent by
stretching to a length of one and one half (1.5) inches the
material would be elongated 50 percent (0.5 inch) and would have a
stretched length that is 150 percent of its relaxed length. If this
exemplary stretched material contracted, that is recovered to a
length of one and one tenth (1.1) inches after release of the
biasing and stretching force, the material would have recovered 80
percent (0.4 inch) of its one-half (0.5) inch elongation. Recovery
may be expressed as [(maximum stretch length-final sample
length)/(maximum stretch length-initial sample length)] times
100.
[0011] As used herein, the term "nonwoven web" means a web that has
a structure of individual fibers or threads which are interlaid,
but not in an identifiable, repeating manner. Nonwoven webs have
been, in the past, formed by a variety of processes such as, for
example, meltblowing processes, spunbonding processes and bonded
carded web processes. Laminates containing such web materials may
be formed and are considered a nonwoven material laminate.
[0012] As used herein, the term "microfibers" means small diameter
fibers having an average diameter not greater than about 100
microns, for example, having a diameter of from about 0.5 microns
to about 50 microns, more particularly, microfibers may have an
average diameter of from about 4 microns to about 40 microns.
[0013] As used herein, the term "meltblown fibers" means fibers
formed by extruding a molten thermoplastic material through a
plurality of fine, usually circular, die capillaries as molten
threads or filaments into a high velocity gas (e.g. air) stream
which attenuates the filaments of molten thermoplastic material to
reduce their diameter, which may be to microfiber diameter.
Thereafter, the meltblown fibers are carried by the high velocity
gas stream and are deposited on a collecting surface to form a web
of randomly dispersed meltblown fibers. Such a process is
disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, the
disclosure of which is hereby incorporated by reference.
[0014] As used herein, the terms "spunbonded fibers" and "spunbond
fibers" shall be used interchangeably and shall refer to small
diameter fibers which are formed by extruding a molten
thermoplastic material as filaments from a plurality of fine,
usually circular, capillaries of a spinnerette with the diameter of
the extruded filaments then being rapidly reduced as by, for
example, eductive drawing or other well-known spunbonding
mechanisms. The production of spunbonded nonwoven webs is
illustrated in patents such as, for example, in U.S. Pat. No.
4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner
et al., U.S. Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos.
3,338,992 and 3,341,394 to Kinney, U.S. Pat. No. 3,542,615 to Dobo
et al. The disclosures of these patents are hereby incorporated by
reference.
[0015] As used herein, the term "bonded carded webs" refers to webs
that are made from staple fibers which are usually purchased in
bales. The bales are placed in a fiberizing unit/picker which
separates the fibers. Next, the fibers are sent through a combining
or carding unit which further breaks apart and aligns the staple
fibers in the machine direction so as to form a machine
direction-oriented fibrous nonwoven web. Once the web has been
formed, it is then bonded by one or more of several bonding
methods. One bonding method is powder bonding wherein a powdered
adhesive is distributed throughout the web and then activated,
usually by heating the web and adhesive with hot air. Another
bonding method is pattern bonding wherein heated calender rolls or
ultrasonic bonding equipment is used to bond the fibers together,
usually in a localized bond pattern through the web and/or
alternatively the web may be bonded across its entire surface if so
desired. When using bicomponent staple fibers, through-air bonding
equipment is, for many applications, especially advantageous.
[0016] As used herein, the term "conjugate fibers" refers to fibers
which have been formed from at least two polymers extruded from
separate extruders but spun together to form one fiber. Conjugate
fibers are also sometimes referred to as multicomponent or
bicomponent fibers. The polymers are usually different from each
other though conjugate fibers may be monocomponent fibers. The
polymers are arranged in substantially constantly positioned
distinct zones across the cross-section of the conjugate fibers and
extend continuously along the length of the conjugate fibers. The
configuration of such conjugate fiber may be, for example, a
sheath/core arrangement wherein one polymer is surrounded by
another or may be a side by side arrangement, a pie arrangement or
an "islands-in-the-sea" arrangement. Conjugate fibers are taught in
U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No. 4,795,668
to Krueger et al., and U.S. Pat. No. 5,336,552 to Strack et al.
Conjugate fibers are also taught in U.S. Pat. No. 5,382,400 to Pike
et al., and may be used to produce crimp in the fibers by using the
differential rates of expansion and contraction of the two or more
polymers. For two component fibers, the polymers may be present in
varying desired ratios. The fibers may also have shapes such as
those described in U.S. Pat. No. 5,277,976 to Hogle et al., U.S.
Pat. No. 5,466,410 to Hills and U.S. Pat. Nos. 5,069,970 and
5,057,368 to Largman et al., which describe fibers with
unconventional shapes.
[0017] As used herein, the term "sheet" means a layer which may
either be a film or a nonwoven web.
[0018] As used herein, the term "necked material" refers to any
material which has been narrowed in at least one dimension by
application of a tensioning force in another direction
(dimension).
[0019] As used herein, the term "neckable material" means any
material which can be necked.
[0020] As used herein, the term "percent neckdown" refers to the
ratio determined by measuring the difference between the un-necked
dimension and the necked dimension of the neckable material and
then dividing that difference by the un-necked dimension of the
neckable material multiplied by a 100.
[0021] As used herein, the terms "elastic necked-bonded material"
or "neck-bonded laminate" shall be used interchangeably and refer
to a material having an elastic sheet joined to a necked material
at least at two places. The elastic sheet may be joined to the
necked material at intermittent points or may be completely bonded
thereto. The joining is accomplished while the elastic sheet and
the necked material are in juxtaposed configuration. The elastic
necked-bonded material is elastic in a direction generally parallel
to the direction of neckdown of the necked material and may be
stretched in that direction to the breaking point of the necked
material. An elastic necked-bonded material may include more than
two layers. For example, the elastic sheet may have necked material
joined to both of its sides so that a three-layer composite or
laminate elastic necked-bonded material is formed having a
structure of necked material/elastic sheet/necked material.
Additional elastic sheets and/or necked material layers may be
added. Yet other combinations of elastic sheets and necked
materials may be used.
[0022] 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
geometrical configurations of the material. These configurations
include, but are not limited to, isotactic, syndiotactic and random
symmetries.
[0023] "Neck bonding" refers to the process wherein an elastic
member is bonded to a non-elastic member (facing) while only the
non-elastic member (facing) is extended or necked so as to reduce
its dimension in the direction orthogonal to the extension. Such
materials generally have cross-machine direction stretch.
[0024] "Stretch bonding" refers to a process wherein an elastic
member is bonded to another member while only the elastic member is
extended, such as by at least about 25 percent of its relaxed
length. "Stretch bonded laminate" refers to a composite elastic
material made according to a stretch bonding process, i.e., the
layers are joined together when only the elastic layer is in an
extended condition so that upon relaxing the layers, the nonelastic
layer is gathered. Such laminates usually have machine directional
stretch properties and may be subsequently stretched to the extent
that the nonelastic material gathered between the bond locations
allows the elastic material to elongate.
[0025] "Neck-stretch bonding" generally refers to a process wherein
an elastic member is bonded to another member while the elastic
member is extended, such as by at least about 25 percent of its
relaxed length and the other layer is a necked, non-elastic layer.
"Neck-stretch bonded laminate" refers to a composite elastic
material made according to the neck-stretch bonding process, i.e.,
the layers are joined together when both layers are in an extended
condition and then allowed to relax. Such laminates usually have
multi or omni-directional stretch properties. Neck stretch bonded
laminates are described in U.S. Pat. Nos. 5,116,662 and 5,114,781
each incorporated by reference hereto in its entirety.
[0026] As used herein, the terms "machine direction" or MD means
the direction along the length of a fabric or film in the direction
in which it is produced. The terms "cross machine direction,"
"cross directional," or CD mean the direction across the width of
fabric or film, i.e. a direction generally perpendicular to the
MD.
[0027] The basis weight of nonwoven fabrics or films is usually
expressed in ounces of material per square yard (osy) or grams per
square meter (g/m.sup.2 or gsm) and the fiber diameters useful are
usually expressed in microns. (Note that to convert from osy to
gsm, multiply osy by 33.91). Film thicknesses may also be expressed
in microns or mil.
[0028] As used herein the term "set" refers to retained elongation
in a material sample following the elongation and recovery, i.e.
after the material has been stretched and allowed to relax.
[0029] As used herein the term "percent set" (Tension Set) is the
measure of the amount of the material stretched from its original
length after being cycled. The remaining strain after the removal
of the applied stress is measured as the percent set. The percent
set can be described as where the retraction curve of a cycle
crosses the elongation axis, and as further discussed below and is
represented by the following formula: Final .times. .times. length
- Initial .times. .times. length Stretched .times. .times. length -
Initial .times. .times. length .times. 100 ##EQU1##
[0030] The "hysteresis" is determined by first elongating a sample
to a given elongation (such as 50 or 100 percent) and determining
the energy required to elongate the sample to the given elongation,
and then allowing the sample to retract back to its original length
and determining the energy recovered during retraction. The
hysteresis value determining numbers would then be read for
instance at the 50 percent and 100 percent elongation, in either
the machine or the cross-machine directions. Hysteresis = Energy
.times. .times. Extension - Energy .times. .times. Retraction
Energy .times. .times. Extension .times. 100 ##EQU2##
[0031] A "pre-stretch" shall refer to a stretch of the elastic
layer which occurs prior to the first stretch of the material by a
consumer.
[0032] As used herein and in the claims, the term "comprising" is
inclusive or open-ended and does not exclude additional unrecited
elements, compositional components, or method steps. Accordingly,
such terms are intended to be synonymous with the words "has",
"have", "having", "includes", "including", and any derivatives of
these words.
SUMMARY OF THE INVENTION
[0033] A method for producing an elastic necked-bonded laminate
material includes the steps of providing at least one neckable
nonelastic material; applying a tensioning force to the neckable
nonelastic material to neck the material; providing an elastic
sheet; superposing the necked nonelastic material onto the elastic
sheet; joining the necked nonelastic material and the elastic sheet
at least at two places to form a laminate material; and stretching
the elastic sheet in the cross-machine direction through the use of
a macroscopic stretching apparatus.
[0034] In an alternative embodiment of the method, the stretching
of the elastic sheet is performed prior to joining with the
nonelastic material. In another alternative embodiment of the
method, the stretching of the elastic sheet is performed following
joining of the elastic sheet with the nonelastic material. In still
another alternative embodiment of the method, the macroscopic
stretching apparatus is a macroscopic grooved roll arrangement. In
still another alternative embodiment of the method, the macroscopic
stretching apparatus is a disc on axle arrangement.
[0035] In yet another alternative embodiment, a method of producing
an elastic necked-bonded laminate material includes the steps of
providing at least one neckable nonelastic material; applying a
tensioning force to the neckable nonelastic material to neck the
material; providing an elastic sheet; superposing the necked
nonelastic material onto the elastic sheet; and joining the necked
nonelastic material and the elastic sheet at least at two places to
form a laminate material; and stretching the elastic sheet in the
cross-machine direction with the use of macroscopic discs along
axles. In an alternative embodiment of this method, the stretching
of the elastic sheet is performed prior to joining to the
nonelastic material. In a further alternative embodiment of this
method, the stretching of the elastic sheet is performed following
joining to the nonelastic material. In still a further alternative
embodiment of this method, the elastic sheet is selected from the
group consisting of an elastic film, an elastic nonwoven web, an
elastic woven web, an elastic scrim or netting, and an elastic
foam. In still a further alternative embodiment of this method, the
neckable material is a material selected from the group consisting
of knitted fabrics, loosely woven fabrics, and nonwoven webs.
[0036] In still a further alternative embodiment of this method,
the neckable material is 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 the webs.
[0037] In still a further alternative embodiment of this method,
the stretching step is accomplished by passing the elastic sheet
through a nip of intermeshing discs along axles positioned in the
cross-machine direction. In yet a further alternative embodiment of
this method, the discs along each axle of the nip are of the same
diameter. In yet still a further alternative embodiment of this
method, the discs on each axle are of the same diameter and the
diameters of discs between axles is varied. In yet still a further
alternative embodiment of this method, the diameter of discs along
the same axle are varied. In yet still a further alternative
embodiment of this method, the discs include ball bearings for free
independent rotation about the axles. In yet still a further
alternative embodiment of this method, the discs are non-circular
in shape. In yet still a further alternative embodiment of this
method, the discs are offset upon the axle in that the core of the
discs are not in the center of the disc. In yet still a further
alternative embodiment of this method, the spacial distance between
discs along each axle is the same. In yet still a further
alternative embodiment of this method, the spacial distance between
discs along each axle is varied. In yet still a further alternative
embodiment of this method, during the step of stretching the
elastic sheet material the elastic material is held at its
cross-machine direction edges so as to not move inward. In yet
still a further alternative embodiment of this method, the elastic
material is held at its cross-machine direction edges via the use
of a belt arrangement. In yet still a further alternative
embodiment of this method, the elastic layer is stretched in the
machine direction while bonding with the nonelastic necked
material.
[0038] A macroscopic disc stretching apparatus for stretching an
elastic layer of a necked bonded laminate material includes a first
axle, macroscopic discs positioned about the first axle, a second
axle parallel and adjacent to the first axle, macroscopic discs
positioned about the second axle, and at least one of the axles
being adjustably moveable with respect to the other axle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] FIG. 1 is a schematic representation of an exemplary process
for forming an efficient elastic necked-bonded material in
accordance with the invention.
[0040] FIG. 2A is a schematic view of a portion of the schematic
process of FIG. 1, showing one embodiment of the portion of the
process, showing a macroscopic grooved roll arrangement.
[0041] FIG. 2B is a cross-sectional view of a portion of
macroscopic grooved rolls from FIG. 2A.
[0042] FIG. 3 is a perspective view of an alternative portion of
the schematic process of FIG. 1, showing a macroscopic disc on axle
arrangement for stretching the elastic layer.
[0043] FIG. 3A is a top view of a noncircular macroscopic disc as
may be used in the process of FIG. 1.
[0044] FIG. 3B is a perspective view of a macroscopic disc as may
be used in the process of FIG. 1 (including ball bearings for free
movement about a non-rotating axle).
[0045] FIG. 3C is a top view of a circular macroscopic disc with a
non centered core.
[0046] FIG. 4 is a front view (in the MD direction) of a
macroscopic disc on axle arrangement.
[0047] FIG. 5 is a front view (in the MD direction) of an
alternative embodiment of a macroscopic disc on axle
arrangement.
[0048] FIG. 6 is a side schematic view of a macroscopic disc on
axle arrangement showing an alternative embodiment with a material
edge hold-down mechanism.
[0049] FIG. 7 is an illustration of an exemplary personal care
product utilizing material made in accordance with the
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0050] Increased elastic performance of an elastic necked-bonded
laminate material can be achieved by stretching the elastic sheet
component of the laminate either prior to lamination with a
non-elastic necked material, or alternatively, following lamination
to a non-elastic necked material. Such elastic sheet component is
given a one-time stretch by a macroscopic stretching apparatus in
the cross-machine direction (for instance, a pre-stretch prior to
usage in a product) to improve the efficiency of the elastic
component when in actual use by the consumer. Such one-time
pre-stretch may be to between about 10 and 1000 percent of the
initial width of the elastic sheet component. Such one-time
pre-stretch may be a partial material stretch or a total material
stretch (in the CD). Such material should then be allowed to either
partially or totally recover prior to lamination to a necked
non-elastic component. In an alternative embodiment, such one-time
pre-stretch may be to between about 20 and 700 percent of its
initial width and then allowed to either partially or totally
recover prior to lamination to a necked non-elastic component. In
still a further alternative embodiment, such one-time pre-stretch
may be to between about 50 and 500 percent of its initial width and
then allowed to either partially or totally recover prior to
lamination to a necked non-elastic component.
[0051] By giving an elastic material a one time pre-stretch, the
process removes the poor or less efficient "first" stretch out of
the process. Such pre-stretch is separate and apart from any
stretching that may occur in the initial formation of the film or
elastic layer, such as stretching that may occur as a result of a
machine direction orienter.
[0052] Also, by giving an elastic material a one time pre-stretch
in the direction of consumer use (CD), before it has been laminated
to a necked nonelastic material, such pre-stretch affects only the
properties of the elastic material and not the nonelastic material.
If one were to stretch both the elastic material and the nonelastic
material, it would be possible to affect the performance and
properties of the nonelastic material. For example, such
prestretching would soften the nonelastic material, but could also
cause fuzziness or fraying of the nonelastic material, which would
be unacceptable for certain medical applications (where linting is
discouraged). If it is desired to stretch both the nonwoven and the
elastic layer, in one alternative embodiment the elastic layer is
pre-stretched and the nonwoven is separately necked and
pre-stretched.
[0053] If it is desired that materials ultimately stretch a certain
percentage in use, the material could be essentially prestretched,
such that it delivers the necessary elongation during use. Upon
subsequent stretching, products employing the elastic necked
material would then satisfy this objective. Such prestretching step
acts to remove the first level of immediate set that is produced in
the elastic material under normal usage. Instead of the ultimate
consumer having to encounter the immediate set, and consequent loss
of comfort (such as looseness of product), this immediate set is
eliminated or reduced in processing, such that the consumer never
encounters it, or encounters it to a lesser degree in actual
use.
[0054] In a further alternative embodiment of the invention, such
prestretching occurs as part of a neck stretch bonded laminate
process. In such a fashion, an efficient neck bonded laminate is
produced that also includes machine direction stretch
capabilities.
[0055] In still another alternative embodiment, such prestretching
is imparted to the elastic sheet material either prior to
lamination or following lamination (if following lamination, then
to the entire laminate material) by a macroscopic stretching
apparatus.
[0056] For the purposes of this application, the term "macroscopic
stretching apparatus", shall refer to either a set of intermeshing
grooved rolls or intermeshing discs on adjacent parallel axles. The
distances between adjacent grooves or discs are clearly visible
without the use of image enhancement/magnification lenses, because
the macroscopic discs or grooves are of appreciable size/scale. In
macroscopic grooved rolls the spaces between intermeshing peaks or
raised areas on the grooved rolls is in one embodiment greater than
about 0.5 inches. In one embodiment, the distance is greater than
about 1 inch. In still another alternative embodiment, the distance
is greater than about 2 inches. In still another alternative
embodiment, the distance is between about 0.5 inch to 2 inches.
These distances are shown in FIG. 2B as 57, from the center of
adjacent peaks on the grooved roll. In another alternative
embodiment, the depth of a groove, from top of peak to bottom of
adjacent valley (59 on FIG. 2B) is greater than about 0.5 inches.
In an alternative embodiment the depth is greater than about one
inch. In still a further alternative embodiment, the depth is
greater than about 4 inches. In still another alternative
embodiment, the depth is greater than about 12 inches. In still a
further alternative embodiment, the depth is between about 0.5 and
12 inches. In still another alternative embodiment, the depth of
engagement (distance of penetration of peak into valley, and
reflected as "Z" on FIG. 2B) is greater than about 0.5 inch. In
still another alternative embodiment, the depth of engagement is
greater than about one inch. In still another alternative
embodiment, the depth of engagement is greater than about four
inches. In still another alternative embodiment, the depth of
engagement is greater than about eight inches. In yet another
alternative embodiment, the depth of engagement is between about
0.5 and 8 inches.
[0057] For a macroscopic disc on axle arrangement, the diameter of
such macroscopic discs is desirably greater than about 1 inch. In
an alternative embodiment the diameter of the macroscopic disc is
greater than about 2 inches. In still another alternative
embodiment the diameter of the macroscopic disc is greater than
about 4 inches. In still another alternative embodiment, the
diameter of the macroscopic disc is greater than about 12 inches.
In still a further alternative embodiment, the diameter of such
discs is between about 1 inch and 12 inches. The diameter dimension
of such disc is shown in FIG. 4 as C.
[0058] In one embodiment, the macroscopic disc has parallel side
edges. In one desirable embodiment, such macroscopic disc has a
thickness of greater than 0.25 inch. In another alternative
embodiment, such macroscopic disc has a thickness of greater than
about 0.5 inch. In still another alternative embodiment, such
macroscopic disc has a thickness of greater than about 1 inch. In
still a further alternative embodiment, the disc has a thickness of
between about 0.25 inch and 1 inch. The thickness dimension of such
disc is shown in FIG. 4 as D.
[0059] In still another alternative embodiment, the distance from
the centerline of one disc to the centerline of an adjacent engaged
(intermeshed) disc (on two different axle as shown as F in FIG. 4)
is desirably greater than about 0.5 inch. In an alternative
embodiment, the distance is greater than about an inch. In still
another alternative embodiment, the distance is greater than about
2 inches. In still another alternative embodiment, the distance is
between about 0.5 inch and 2 inch.
[0060] In still another alternative embodiment, the level of
engagement of discs from two axles (intermeshing, shown as E on
FIG. 4) is greater than about an inch. In an alternative
embodiment, the level of engagement is greater than about 2 inches.
In still another alternative embodiment, the level of engagement is
greater than about 4 inches. In still a further alternative
embodiment, the level of engagement is greater than about 12
inches. In yet another alternative embodiment, the level of
engagement is between about 1 and 12 inches.
[0061] In still another alternative embodiment, the distance from
the centerline of adjacent discs along the same axle (shown as G on
FIG. 4) is greater than about one inch. In an alternative
embodiment, the distance is greater than about 2 inches. In an
alternative embodiment, the distance is greater than about 4
inches. In an alternative embodiment, the distance is between about
1 and 4 inches.
[0062] For the purposes of this application, the term "microscopic"
shall refer to grooved rolls or discs that do not fall within the
definitions of macroscopic above.
[0063] In one embodiment, such neckable material is necked between
about 10 and 80 percent. In an alternative embodiment, such
neckable material is necked between about 20 and 70 percent
(percent neckdown).
[0064] Referring to FIG. 1 of the drawings there is schematically
illustrated at 10 a process for forming an efficient elastic
necked-bonded material (laminate). According to the present
invention, a neckable material 12 is unwound from a supply roll 14
and travels in the direction indicated by the arrow associated
therewith as the supply roll 14 rotates in the direction of the
arrows associated therewith. The neckable material 12 passes
through a nip 16 of the drive roller arrangement 18 formed by the
drive rollers 20 and 22. The neckable material 12 may be formed by
known nonwoven extrusion processes, such as, for example, known
meltblowing processes, spunbonding or bonded carded web processes,
and passed directly through the nip 16 without first being stored
on a supply roll.
[0065] An elastic sheet 32 is unwound from a supply roll 34 and
travels in the direction indicated by the arrow associated
therewith as the supply roll 34 rotates. It should be recognized
that the elastic sheet material (which forms the elastic component
of the laminate) may be made online or provided from a supply roll
as illustrated. The elastic sheet is either stretched in the CD at
a nip of a macroscopic stretching apparatus 25 prior to being
brought into contact with the non-elastic necked material, and/or
following bonding at a post bonding macroscopic stretching
apparatus 29. If the stretching occurs prior to lamination, the
stretched material is allowed to partially or totally retract
(relax or recover) prior to being brought in contact with the
non-elastic necked sheet. If the elastic only partially retracts,
subsequent retraction will gather the necked material in the CD,
producing a combined neck bonded laminate/stretch bonded laminate
with very high CD stretch. The elastic sheet material is stretched
in the cross-machine direction by the macroscopic stretching
apparatus, no matter which alternative stretching arrangement is
utilized.
[0066] In either case, the elastic sheet passes through the nip 24
of the bonder roller arrangement 26 formed by the bonder rollers 28
and 30. The elastic sheet 32 may be formed by extrusion processes
such as, for example, meltblowing processes, scrim forming
processes or film extrusion processes, or alternatively foam
forming processes, and passed directly through the nip 24 without
first being stored on a supply roll.
[0067] In one embodiment, the neckable material 12 passes through
the nip 16 of the S-roll arrangement 18 in a reverse-S path as
indicated by the rotation direction arrows associated with the
stack rollers 20 and 22. From the S-roll arrangement 18, the
neckable material 12 passes through the pressure nip 24 formed by a
bonder roller arrangement 26. Because the peripheral linear speed
of the rollers of the S-roll arrangement 18 is controlled to be
less than the peripheral linear speed of the rollers of the bonder
roller arrangement 26, the neckable material 12 is tensioned
between the S-roll arrangement 18 and the pressure nip of the
bonder roll arrangement 26. By adjusting the difference in the
speeds of the rollers, the neckable material 12 is tensioned so
that it necks a desired amount and is maintained in such tensioned,
necked condition while the elastic sheet 32 is joined to the necked
material 12 during their passage through the bonder roller
arrangement 26 to form a composite elastic necked-bonded laminate
40. Although not shown, the necking could occur in stages at
various other positions in the process. For instance, the supply
roll 14 could be slowed to create necking on the material prior to
entering the reverse S-roll arrangement.
[0068] Other methods of tensioning the neckable material 12 may be
used such as, for example, tenter frames or other cross-machine
direction stretcher arrangements that expand the neckable material
12 in other directions such as, for example, the cross-machine
direction so that the material shortens in the MD. After bonding to
the elastic sheet 32, the resulting elastic necked-bonded material
40 will be elastic in a direction generally parallel to the
direction of necking, i.e., in the machine direction.
[0069] The neckable material 12 may be a nonwoven material such as,
for example, a spunbonded web, meltblown web or bonded carded web,
or alternatively a woven or knit material. If the neckable material
is a web of meltblown fibers, it may include meltblown microfibers.
The neckable material 12 may be made of fiber forming polymers such
as, for example, polyolefins, polyesters, as well as nylons.
Exemplary polyolefins include one or more of polypropylene,
polyethylene, ethylene copolymers, propylene copolymers, butene
copolymers and blends of such polymers.
[0070] In one embodiment of the present invention, the neckable
material 12 is a multilayer material having, for example, at least
one layer of spunbonded web joined to at least one layer of
meltblown web, bonded carded web or other suitable material. For
example, neckable material 12 may be a multilayer
spunbond/meltblown/spunbond material having a first layer of
spunbonded polypropylene having a basis weight from about 0.2 to
about 8 ounces per square yard (osy), a layer of meltblown
polypropylene having a basis weight from about 0.2 to about 4 osy,
and a second layer of spunbonded polypropylene having a basis
weight of about 0.2 to about 8 osy. Alternatively, the neckable
material 12 may be a single layer of material such as, for example,
a spunbonded web having a basis weight of from about 0.2 to about
10 osy or a meltblown web having a basis weight of from about 0.2
to about 8 osy.
[0071] The neckable material 12 may also be a composite material
made of a mixture of two or more different fibers of different
composition or a mixture of fibers and particulates. Such mixtures
may be formed by adding fibers and/or particulates to the gas
stream in which 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, hydrocolloid (hydrogel) particulates commonly referred to
as superabsorbant 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 such as
disclosed in U.S. Pat. No. 4,100,324, the disclosure of which is
hereby incorporated by reference (coform). The neckable material
may also include bicomponent fibers or conjugate fibers as
well.
[0072] If the neckable material 12 is a nonwoven web of fibers, the
fibers should be joined by interfiber bonding to form a coherent
web structure which is able to withstand necking. Interfiber
bonding may be produced by entanglement between individual
meltblown fibers. The fiber entangling is inherent in the meltblown
process but may be generated or increased by processes such as, for
example, hydraulic entangling or needlepunching. Alternatively
and/or additionally a bonding agent may be used to increase the
desired bonding.
[0073] The elastic sheet 32 may be made from any material which may
be manufactured in sheet form. Generally, any suitable elastomeric
fiber forming resins or blends containing the same may be utilized
for the nonwoven webs of elastomeric fibers of the invention and
any suitable elastomeric film forming resins or blends containing
the same may be utilized for the elastomeric films of the
invention. The elastic sheet may also be a scrim-like or netting
material, or an elastic foam.
[0074] For example, the elastic sheet 12 may be made from styrenic
block copolymers available from the Kraton Polymers of Houston,
Tex. under the designation KRATON G. Other such styrenic block
copolymers are available from Septon Company of America, Dexco
Polymers, and Dynasol of Spain. Still other exemplary elastomeric
materials which may be used to form the elastic sheet 32 include
polyurethane elastomeric materials such as, for example, those
available under the trademark ESTANE from Noveon of Cleveland,
Ohio, polyamide elastomeric materials such as, for example, those
available under the designation PEBAX from AtoFina Chemicals Inc.
of Philadelphia, Pa., and polyester elastomeric materials such as,
for example, those available under the trade designation Hytrel
from E. I. DuPont De Nemours & Company. Formation of elastic
sheets from polyester elastic materials is disclosed in, for
example, U.S. Pat. No. 4,741,949 to Morman et al., hereby
incorporated by reference. Additionally, less elastic materials may
be used as the elastic component, such as single site catalyzed
polyolefins. Such single site catalyzed polyolefins include
metallocene-catalyzed polyolefins and constrained geometry
polyolefins, available from either ExxonMobil or Dow Chemical. The
one time pre-stretch of these less elastic materials can improve
their performance in use relative to more costly higher performance
elastomer materials without the one time pre-stretching step.
[0075] A polyolefin may also be blended with the elastomeric
polymer to improve the processability of the composition. The
polyolefin must be one which, when so 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, propylene copolymers and butene copolymers.
Two or more of the polyolefins may be utilized. Extrudable blends
of elastomeric polymers and polyolefins are disclosed in, for
example., U.S. Pat. No. 4,663,220 to Wisneski et al., hereby
incorporated by reference.
[0076] The elastic sheet 32 may also be a pressure sensitive
elastomer 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 the
tensioned, necked nonelastic web. In regard to the tackifying
resins and tackified extrudable elastomeric compositions, note the
resins and compositions as described in U.S. Pat. No. 4,789,699 of
J. S. Keiffer and T. J. Wisneski, the disclosure of which is hereby
incorporated by reference.
[0077] Any tackifier resin can be used which is compatible with the
elastomeric polymer and can withstand the high processing (e.g.,
extrusion) temperatures. If blending materials such as, for
example, polyolefins or extending oils are used, the tackifier
resin should also be compatible with those blending materials.
Generally, hydrogenated hydrocarbon resins are preferred tackifying
resins, because of their better temperature stability. Other
tackifying resins which are compatible with the other components of
the composition and can withstand the high processing temperatures,
can also be used.
[0078] A pressure sensitive elastomer adhesive may include, for
example, from about 40 to about 80 percent by weight elastomeric
polymer, from about 5 to about 40 percent polyolefin and from about
5 to about 40 percent resin tackifier.
[0079] The elastic sheet 32 may also be a multilayer material in
that it may include two or more individual coherent webs or films
or combinations of such. Additionally, the elastic sheet 12 may be
a multilayer material in which one or more of the layers contain a
mixture of elastic and nonelastic fibers or particulates. For an
example of the latter type of elastic web, reference is made to
U.S. Pat. No. 4,209,563, incorporated herein by reference, in which
elastomeric and non-elastomeric fibers are commingled to form a
single coherent web of randomly dispersed fibers. Another example
of such a composite web would be one made by a technique such as
disclosed in U.S. Pat. No. 4,100,324 also incorporated herein by
reference. That patent discloses a nonwoven material which includes
a mixture of meltblown thermoplastic fibers and other materials.
The fibers and other materials are combined in the gas stream in
which the meltblown fibers are borne so that an intimate entangled
commingling of meltblown fibers and other materials, e.g., wood
pulp, staple fibers or particulates such as, for example,
hydrocolloid (hydrogel) particulates commonly referred to as super-
absorbents occurs prior to collection of the fibers upon a
collecting device to form a coherent web of randomly dispersed
fibers. The elastic sheet 32 may also be further processed such as
by slitting or aperturing stations.
[0080] The bonder roller arrangement 26 may be a smooth calender
roller 28 and a smooth anvil roller 30 or may include one or both
patterned calender roller(s), such as, for example, a pin embossing
roller arranged with a smooth anvil roller. One or both of the
calender roller and the smooth anvil roller may be heated and the
pressure between these two rollers may be adjusted by well-known
means to provide the desired temperature, if any, and bonding
pressure to join the necked material 12 to the elastic sheet 32
forming a composite elastic necked-bonded material 40. Such
material may then be rolled for storage upon a winding roll or
passed directly to another processing station for further
modifications.
[0081] The necked material and the elastic sheet may be completely
bonded together and still provide a composite elastic necked-bonded
material with good stretch properties. That is, a composite elastic
material may be formed by joining a necked material to an elastic
sheet utilizing bonding surfaces such as, for example, smooth
rollers or platens to provide a high bond surface area. A composite
elastic necked-bonded material 40 may also be formed utilizing a
bonding pattern.
[0082] Necked materials may be joined to the elastic sheet 32 at
least at two places by any suitable means such as, for example,
thermal bonding or ultrasonic welding which softens at least
portions of at least one of the materials, usually the elastic
sheet because the elastomeric materials used for forming the
elastic sheet 32 have a lower softening point than the components
of the necked material 12. Joining may be produced by applying heat
and/or pressure to the overlaid elastic sheet 32 and the necked
material 12 by heating these portions (or the overlaid layer) to at
least the softening temperature of the material with the lowest
softening temperature to form a reasonably strong and permanent
bond between the re-solidified softened portions of the elastic
sheet 32 and the necked material 12. Additionally, such bonding
arrangement may utilize an adhesive bonding arrangement as long as
the adhesive does not significantly impact the elastic performance
of the laminate. Additionally, such bonding arrangement may utilize
an entangling process. Elastic sheets can be used having basis
weights less than 0.5 osy (ounces per square yard), for example,
from about 0.1 to about 0.4 osy, or alternatively between about
0.25 to about 0.4 osy. Such extremely low basis weight sheets are
useful for economic reasons, particularly for use in disposable
products. Additionally, elastic sheets having higher basis weights
such as, for example, from about 0.5 to about 10 osy may also be
used.
[0083] With regard to thermal bonding, one skilled in the art will
appreciate that the temperature to which the materials, or at least
the bond sites thereof, are heated for heat-bonding will depend not
only on the temperature of the heated roll(s) or other heat sources
but on the residence time of the materials on the heated surfaces,
the basis weights of the materials and their specific heats and
thermal conductivities. However, for a given combination of
materials, and in view of the herein contained disclosure, the
processing conditions necessary to achieve satisfactory bonding can
be readily determined by one of skill in the art. 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.
[0084] With specific reference to the macroscopic stretching
apparatus shown schematically at either 25 or 29, a variety of
apparatus may be used to impart a one time pre-stretch to the
elastic sheet of the laminate. For example, FIG. 2A is a schematic
view of a portion (either at 25 or 29) of the schematic process of
FIG. 1, showing one embodiment of the prestretching portion of the
process. Specifically, a macroscopic grooved roll arrangement is
illustrated. In such embodiment a large diameter roll system 50 may
be utilized, which employs one large diameter roll 51 (such as for
example of approximately 6 feet in diameter) with machine direction
oriented valleys going deeply into the roll. The peaks 55 and
valleys (grooves) 53 run in the machine direction across the cross
direction of the roll (from side to side). These can be seen in the
cross-sectional view of FIG. 2B showing a machine direction view of
the rolls. Either a single intermeshing grooved roll, or a series
of satellite rolls 52, 54, and 56 could also be employed with peaks
that fit within the valleys of the larger diameter roll. The
satellite rolls could be adjustable such that their depth within
the grooves/valleys of the larger roll could be changed. For
example the rolls may be independently controlled with respect to
each other, such that their speed of rotation and distance from
each other may be independently adjustable. In this fashion, the
first satellite roll could push the elastic material in (either by
itself if positioned at 25, or with the necked nonelastic material,
if positioned at 29), for example 4 inches, while the second
satellite roll could push the material in, for example 8 inches and
so on, until the material received the desired amount of stretch.
The satellite rolls could be adjusted such that if less stretch is
desired, the first could be pushed into the valleys of the bigger
roll for example by 2 inches. The satellite roll system offers the
elastic material multiple gentle stretches with relaxation between
each stretch, instead of one large stretch extension with standard
grooved rolls.
[0085] It is in one embodiment desirable that the macroscopic
prestretching apparatus stretch the elastic sheet material (either
prior to lamination to the nonelastic sheet or following
lamination) an amount in the CD direction of greater than about 20
percent of the initial width, alternatively greater than about 50
percent, still alternatively, greater than about 100 percent, still
alternatively, greater than about 200 percent, and still further
alternatively, greater than about 300 percent. In a further
alternative embodiment such elastic sheet is stretched in the CD in
an amount of between about 20 and 300 percent.
[0086] In an alternative embodiment, following this roll apparatus,
an identical roll apparatus shifted one half cycle to the left or
right (not shown) could stretch the material that was not stretched
in the first apparatus. This would produce a uniformly stretched
material across the width of the material. That is, there are no
unstretched bands of material where the material contacted the
prestretching macroscopic grooves or discs. The material could be
pinched on the edges of the bigger roll by a belt 61 in a groove
such that the material could not slide in the CD, but would have
stretch.
[0087] In still another alternative embodiment, only part of the
elastic sheet material could be prestretched, so as to incur easy
stretch in the pre-stretched part, while the remainder of the
material would only be stretched with a higher force. Furthermore,
some area on the elastic sheet material could have machine
direction stretch, while other areas could have cross-directional
stretch.
[0088] As can be seen in FIG. 3, a perspective view of an
alternative portion of the schematic process of FIG. 1 shows a
macroscopic "disc on axle" apparatus arrangement for use in
stretching the elastic sheet either prior to or following
lamination with the nonelastic necked material. While prestretching
the elastic material of neck bonded laminates using grooved rolls
offers benefits, it also raises apparatus difficulties. When using
grooved rolls, each CD stretch profile and stretch amount requires
a new set of rolls. Damage done to any portion of a roll requires a
new roll to be made.
[0089] As an alternative, a macroscopic disc arrangement can be
used such that the material is stretched between
intermeshing/engaged macroscopic discs that are positioned along
parallel and adjacent axle shafts. As previously stated, in one
embodiment, the discs are at least 1 inch in diameter and may range
in size to about 12 inches in diameter or greater. Desirably such
discs are manufactured from rigid material (as with the grooved
rolls) such as metal, or molded resins or rubbers. The disc design
and set up minimizes material contact with metal surfaces and
especially sharp metal edges that are encountered with microscopic
grooved rolls. It is therefore contemplated that the discs will
include rounded edges to further minimize contacting the material
with harsh sharp edging. It is also contemplated that the
individual discs adjustably slide on the axle shafts into position
such that spaces between the discs may be readily changeable.
However, it is also contemplated that "spacers" may be used to
maintain separation between the discs, if the discs do not
themselves include other known axle locking mechanisms. Such discs
may either be freely rotatable about the axles or held fast to the
axles (in which case the axles would be rotatable). Such spacers
may include ball bearings to provide for free movement of adjacent
discs. Similarly, such discs may likewise include ball bearings
around their core (hole for receiving the axle shaft) to provide
for free independent movement about the axles. In such a fashion,
the discs can move at different revolutions per minute to
accommodate their differing diameters. In a further alternative
embodiment, such discs are held in place and the axle is operated
to move, rather than the discs freely moving about the axle. Still
in a further alternative embodiment, one or more shafts are motor
driven while others are not.
[0090] Using discs of varying diameters (which is one embodiment
contemplated) necessitates using individual free rotating discs as
there is the same circumferential surface speed between discs
necessitating different revolutions per minute (RPMs). Such a
feature cannot be accomplished with grooved rolls.
[0091] At least two axle shafts with individual discs can engage
(intermesh) such that the edges of such discs overlap (that is pass
alongside or between discs on the other axle), during running of
material through a nip formed by the discs. Desirably, in one
embodiment, such discs are capable of being independently driven
and adjusted toward or away from each other, (as shown as A and B
in FIG. 3) as with the previously described grooved roll
arrangement.
[0092] As can be seen in FIG. 3, the disc and axle arrangement 66
includes central shafts 67, 68, about which are positioned discs
69, 70. In one embodiment the discs are of equal diameters along
each axle, and between all intermeshing axles (not shown). In a
second embodiment, the discs are of the same diameter 74, 75 about
one axle, and of different diameters between intermeshing discs (as
shown, where one diameter 74 is larger than the other 75). As with
the previously described satellite grooved roll arrangement, the
disc on axle arrangement may include any number of satellite axles
and discs that can engage to different disc depths with
progressively more material stretching as material passes around
the central largest axle. Alternatively, each of the satellite
shafts may include discs at nonoverlapping portions about the
central shaft, such that different portions of the material to be
stretched would be stretched by different satellite disc and axle
components around the central disc and axle shaft. Alternatively,
such axle disc arrangement may include only two shafts (as
shown).
[0093] The disc and axle arrangement are positioned in the process
such that the disc outer edges 71 and 72 are aligned with the
machine direction. As previously stated with respect to the grooved
roll apparatus, one or more of the axles may be capable of movement
A, B with respect to each other to provide for varying degrees of
intermeshing. Spacers 73 may be used to separate the discs, or the
discs may be held in place by other known mechanisms.
[0094] It should be noted that necked material normally has a CD
basis weight and elastic property profile. Using discs to stretch
one area of a material greater than another can be used to either
amplify the profile to obtain a material with a very high CD
stretch on the edges (as would be desired in a diaper outer cover
or liner, or other personal care product) or flatten the profile
(as would be desired when making wide material which will be
eventually slit and consistent slits are desired).
[0095] By using CD movable discs along an axle (that is discs with
their thin outer edge 71, 72 facing in the machine direction but
stored along an axle from one CD end to the other, such that
stretching occurs in the CD direction), multiple widths of material
and multiple stretch profiles can be placed in a neck bonded
laminate by simply changing the individual discs used (diameter and
thickness of the discs), the location of the discs, whether the
discs are centered (equidistant) from counterpart adjacent discs
when in an intermeshed (or engaged) position, and the amount of
intermeshing (engagement).
[0096] Unlike grooved roll apparatus, discs are relatively easy to
maintain, and should they be damaged, can be easily removed and
replaced. Additionally, the outer edge shape of discs can be of
non-circular configuration, such as oval or elliptical in shape.
Such an elliptical disc is shown in FIG. 3A having a circular core
for receiving an axle. The CD elastic properties of the sheet could
be altered in this fashion along the MD of the material.
Essentially a pattern of greater stretch followed by less stretch
could be achieved along the MD of the material, depending on the
outer circumference shape of the disc. The material would
demonstrate different CD stretch properties along the MD. Obviously
the core would have to be circular, unless the disc was held
unmoveably to the support shaft. The elliptical shaped disc is
shown in FIG. 3A, having an outer circumference edge 71A. The core
of the disc 73A is circular in shape, while the outer circumference
edge is shaped as an ellipse. The edge to edge diameter distances
75A varies depending on which location on the edge one starts with.
Further the disc contains distinct wide and narrow areas 74A. This
will produce machine direction bands in the material that
demonstrate varying periodic degrees of prestretching. As can be
seen in FIG. 3B, the discs 69, may include ball bearings 170, for
easy rotation about the axle shafts, if free rotation is desired.
In a further alternative embodiment, as seen in FIG. 3C, the disc
may be circular or some other noncircular shape, and include a core
opening that is off center. Such a disc would also provide for high
and low stretch effects on materials. In still a further
alternative embodiment, the thickness of discs can be varied along
an axle or between axles to provide for varying stretch effects on
materials.
[0097] FIG. 4 illustrates a front view of an intermeshing disc on
axle arrangement 76 showing the discs 78, 81 in an engaged
position, and the elastic sheet material 96 passing through the nip
of the discs towards the viewer in the MD. The intermeshing disc on
axle arrangement includes two parallel axles 77, 90. The discs
shown include discs of equal diameter 82, 86, having equal spacing
between discs 83, 84, 79, 80. The Figure also shows equal spacing
between discs but discs of different diameters, 80,85. Further, the
figure also shows, discs having unequal spacing, but of equal
diameter 87, 88, and 89. Spacers are shown between the discs on one
axle 77.
[0098] FIG. 5 is a front view of an alternative embodiment of a
disc on axle arrangement of FIG. 4. The discs are shown in a
disengaged orientation. The axles 90 and 91 are moved apart, such
that the discs 92, 93 do not intermesh as in FIG. 4. The Figure
illustrates equal spacing between discs 94 and would-be
intermeshing discs 95.
[0099] In an alternative embodiment (as seen in FIG. 6) of the disc
on axle arrangement 100, a "V" belt 107 is included on the sides of
the material so as to maintain the sides of the material 106 from
sliding off the edge of disc 101 toward disc 102. Belt rolls 103
guide a belt to the sides of the material 106 as the material
passes in the MD 109. Carrier rolls 105 help support the elastic
material as it moves in the machine direction to the next
processing station. In such an embodiment, the edges of the
material are held so that they do not get pulled inward. Two belts
are utilized, one on each side of the disc arrangement.
[0100] Prestretching an elastic material decreases the immediate
percent set in the CD and the force required to stretch the
material to the pre-stretch width (following retraction) on
subsequent stretches up to the pre-stretched length. In other
words, after being prestretched, the material retains its shape
after subsequent stretching. In manufacturing of a product
incorporating the material, the material should be first
prestretched and then cut to its desired shape before insertion
into the product. Prestretching also decreases the hysteresis in
the CD on subsequent stretches. The step of prestretching a
material prior to incorporating such material into a product allows
for greater retraction in the product, as opposed to incorporation
of the unstretched material into a final product. Essentially, by
prestretching an elastic component of a necked bonded laminate, and
in particular with a macroscopic stretching apparatus, a more
efficient better performing elastic product is received by a
consumer of such product. The consumer does not experience the
first high resistance to stretch and immediate set upon initial
stretch use of the material. Immediate set can translate directly
into extension with less recovery, giving the impression of a
loosening of the elastic components in a product and a reduction in
product comfort and fit. Such prestretching is particularly
effective for lower cost, lower performance elastomers.
[0101] In addition to the elastic material attributes (whether such
has been made more efficient utilizing one of the previously
described prestretching apparatus), the relation between the
original dimensions of the neckable material 12 to its dimensions
after tensioning also determines the approximate limits of stretch
of the elastic necked-bonded material. Because the neckable
material 12 is able to stretch and return to its prenecked
dimensions in directions such as, for example the machine direction
or the cross-machine direction, the composite elastic necked-bonded
material will be stretchable in generally the same direction as the
neckable material 12.
[0102] For example, if it is desired to prepare an elastic
necked-bonded material stretchable to a 150% elongation, a first
width of neckable material such as, for example, 250 cm, is
tensioned so that it necks down to a second width of about 100 cm.
The necked material is then joined to an elastic sheet having a
width of approximately 100 cm and which is at least stretchable to
a width of 250 cm. The resulting elastic necked-bonded material has
a width of about 100 cm and is stretchable to at least the original
250 cm width of the neckable material for an elongation of about
150%. As can be seen from the example, the elastic limit of the
elastic sheet needs only to be as great as the minimum desired
elastic limit of the composite elastic necked-bonded material. If
an elastic material is prestretched either prior to lamination with
a nonelastic necked material, or following lamination as described,
the consumer's stretch to the elastic limit (in the first instance)
in use, encounters less resistance and suffers less set. For
example, if the above material was prestretched 150% to its
original 250 cm, it may retract back to about 150 cm for a percent
set of 33%. Following stretches to between about 150 and 250 cm
would be followed by a retraction back to approximately 150 cm.
That is, there is little if any additional permenant set if the
material encounters similar or less degrees of stretching. Thus,
giving the material a one time first pre-stretch before the
consumer uses the material, improves the performance of the
material within a product.
[0103] The apparatus and method described above can be used to
produce a material with bands of improved prestretched elastic
performance material and bands of non-treated (non stretched)
elastic performance material. The improved elastic performance
material is produced between the disc or groove contact points
where the material is stretched in the CD. The nontreated material
is produced by having the surfaces that the material contacts on
the discs or rolls, ie, the outer circumferential surfaces, being a
high frictional surface so the material can not slide in the CD and
remains unstretched. As the material is run in the MD, it is
stretched in the CD from the MD oriented grooves or discs.
[0104] The resulting material can be characterized by stretching
about 0.25 inch lengths of the material in the CD, ie, an 0.25 inch
length in a known tensile tester. The prestretched and non
prestretched bands will be readily apparent. In one embodiment, the
nontreated (nonstretched) bands should be less than 2 inches, or
alternatively less than 1 inch wide to ensure pieces of the
material cut for product use contain at least some prestretched
material. By varying the width and number of bands of nonstretched
material, material can be produced which is essentually non
stretched all the way to essentually totally prestretched.
[0105] With reference to FIG. 7, a personal care disposable
absorbent product is illustrated which incorporates material made
in accordance with the inventive method and the apparatus. In
particular, a disposable diaper 130 generally defines a front waist
section 132, a rear waist section 134, and an intermediate section
136 which interconnects the front and rear waist sections. The
front and rear waist sections 132 and 134 include the general
portions of the diaper which are constructed to extend
substantially over the wearer's front and rear abdominal regions,
respectively, during use. The intermediate section 136 of the
diaper includes the general portion of the diaper that is
constructed to extend through the wearer's crotch region between
the legs. Thus, the intermediate section 136 is an area where
repeated liquid surges typically occur in the diaper.
[0106] The diaper 130 includes, without limitation, an outer cover,
or backsheet 138, a liquid permeable bodyside liner, or topsheet,
140 positioned in facing relation with the backsheet 138, and an
absorbent core body, or liquid retention structure, 154, such as an
absorbent pad, which is located between the backsheet 138 and the
topsheet 140. The backsheet 138 defines a length, or longitudinal
direction 150, and a width, or lateral direction 152 which, in the
illustrated embodiment, coincide with the length and width of the
diaper 130. The liquid retention structure 154 generally has a
length and width that are less than the length and width of the
backsheet 138, respectively. Thus, marginal portions of the diaper
130, such as marginal sections of the backsheet 138, may extend
past the terminal edges of the liquid retention structure 154. In
the illustrated embodiments, for example, the backsheet 138 extends
outwardly beyond the terminal marginal edges of the liquid
retention structure 154 to form side margins and end margins of the
diaper 130. The topsheet 140 is generally coextensive with the
backsheet 138 but may optionally cover an area which is larger or
smaller than the area of the backsheet 138, as desired. The
outercover can be manufactured from material produced in accordance
with the described methods.
[0107] To provide improved fit and to help reduce leakage of body
exudates from the diaper 130, the diaper side margins and end
margins may be elasticized with suitable elastic members, as
further explained below. For example, as representatively
illustrated in FIG. 7, the diaper 130 may include leg elastics 156
which are constructed to operably tension the side margins of the
diaper 130 to provide elasticized leg bands which can closely fit
around the legs of the wearer to reduce leakage and provide
improved comfort and appearance. Waist elastics 158 are employed to
elasticize the end margins of the diaper 130 to provide elasticized
waistbands. The waist elastics 158 are configured to provide a
resilient, comfortably close fit around the waist of the wearer.
The laminates of the inventive methods are suitable for use as the
liner if porous or apertured, the backsheet, the leg elastics 156
and the waist elastics 158.
[0108] As is known, fastening means, such as hook and loop
fasteners, may be employed to secure the diaper 130 on a wearer.
Alternatively, other fastening means, such as buttons, pins, snaps,
adhesive tape fasteners, cohesives, fabric-and-loop fasteners, or
the like, may be employed. In the illustrated embodiment, the
diaper 130 includes a pair of side panels 160 (or ears) to which
the fasteners 162, indicated as the hook portion of a hook and loop
fastener, are attached. Generally, the side panels 160 are attached
to the side edges of the diaper 130 in one of the waist sections
132, 134 and extend laterally outward therefrom. The side panels
160 may be elasticized or otherwise rendered elastomeric by use of
laminate made by the inventive methods. For example, the side
panels 160, or indeed, any precursor webs of the garment, may be an
elastomeric material such as a neck-bonded laminate made in
accordance with the inventive method or neck stretch bonded
laminate. Examples of absorbent articles that include elasticized
side panels and selectively configured fastener tabs are described
in PCT Patent Application No. WO 95/16425 to Roessler; U.S. Pat.
No. 5,399,219 to Roessler et al.; U.S. Pat. No. 5,540,796 to Fries;
and U.S. Pat. No. 5,595,618 to Fries each of which is hereby
incorporated by reference in its entirety.
[0109] The diaper 130 may also include a surge management layer
142, located between the topsheet 140 and the liquid retention
structure, to rapidly accept fluid exudates and distribute the
fluid exudates to the liquid retention structure 154 within the
diaper 130. The diaper 130 may further include a ventilation layer
(not illustrated), also called a spacer, or spacer layer, located
between the liquid retention structure 154 and the backsheet 138,
to insulate the backsheet 138 from the liquid retention structure
154 to reduce the dampness of the garment at the exterior surface
of a breathable outer cover, or backsheet, 138. Examples of
suitable surge management layers 142 are described in U.S. Pat. No.
5,486,166 to Bishop and U.S. Pat. No. 5,490,846 to Ellis.
[0110] As representatively illustrated in FIG. 7, the disposable
diaper 130 may also include a pair of containment flaps 164 which
are configured to provide a barrier to the lateral flow of body
exudates. The containment flaps 164 may be located along the
laterally opposed side edges of the diaper 130 adjacent the side
edges of the liquid retention structure 154. Each containment flap
164 typically defines an unattached edge which is configured to
maintain an upright, perpendicular configuration in at least the
intermediate section 136 of the diaper 130, to form a seal against
the wearer's body. The containment flaps 164 may extend
longitudinally along the entire length of the liquid retention
structure 154 or may only extend partially along the length of the
liquid retention structure. When the containment flaps 164 are
shorter in length than the liquid retention structure 154, the
containment flaps 164 can be selectively positioned anywhere along
the side edges of the diaper 130 in the intermediate section 136.
Such containment flaps 164 are generally well known to those
skilled in the art. For example, suitable constructions and
arrangements for containment flaps 164 are described in U.S. Pat.
No. 4,704,116 to K. Enloe, incorporated by reference herein in its
entirety. Such containment flaps may likewise be made from material
produced according to the inventive methods.
[0111] The diaper 130 may be of various suitable shapes. For
example, the diaper may have an overall rectangular shape, T-shape
or an approximately hour-glass shape. In the shown embodiment, the
diaper 130 has a generally I-shape. Other suitable components which
may be incorporated on absorbent articles of the present invention
may include waist flaps and the like which are generally known to
those skilled in the art. Examples of diaper configurations
suitable for use in connection with the instant invention which may
include other components suitable for use on diapers are described
in U.S. Pat. No. 4,798,603 to Meyer et al.; U.S. Pat. No. 5,176,668
to Bernardin; U.S. Pat. No. 5,176,672 to Bruemmer et al.; U.S. Pat.
No. 5,192,606 to Proxmire et al. and U.S. Pat. No. 5,509,915 to
Hanson et al. each of which is hereby incorporated by reference
herein in its entirety.
[0112] The various components of the diaper 130 are assembled
together employing various types of suitable attachment means, such
as adhesive, ultrasonic bonds, thermal bonds or combinations
thereof. In the shown embodiment, for example, the topsheet 140 and
backsheet 138 may be assembled to each other and to the liquid
retention structure 154 with lines of adhesive, such as a hot melt,
pressure-sensitive adhesive. Similarly, other diaper components,
such as the elastic members 156 and 158, fastening members 162, and
surge layer 142 may be assembled into the article by employing the
above-identified attachment mechanisms.
[0113] In a further alternative embodiment, such inventive
materials may be particularly useful as an ear attachment (as
previously described) for a diaper or other personal care
product.
[0114] Although various embodiments of the invention have been
described using specific terms, devices, and methods, such
description is for illustrative purposes only. The words are words
of description rather than of limitation. It is to be understood
that changes and variations may be made by those of ordinary skill
in the art without departing from the spirit or scope of the
present invention, which is set forth in the following claims. In
addition, it should be understood that aspects of the various
embodiments may be interchanged both in whole or in part.
Therefore, the spirit and scope of the appended claims should not
be limited to the description of the preferred versions contained
therein.
* * * * *