U.S. patent application number 11/021043 was filed with the patent office on 2006-06-29 for absorbent structure with aggregate clusters.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. Invention is credited to Michael John Faulks, David Arthur Fell, Jeffrey Mark La Fortune, Shannon Kathleen Melius, Michael Barth Venturino.
Application Number | 20060141891 11/021043 |
Document ID | / |
Family ID | 36182411 |
Filed Date | 2006-06-29 |
United States Patent
Application |
20060141891 |
Kind Code |
A1 |
Melius; Shannon Kathleen ;
et al. |
June 29, 2006 |
Absorbent structure with aggregate clusters
Abstract
An absorbent structure has a macro absorbent structure with a
plurality of aggregate clusters intermixed therein. The aggregate
clusters have a periphery, an interior, and thermoplastic binder
fibers. The thermoplastic binder fibers have thermoplastic binder
fiber ends. The thermoplastic binder fiber ends are located at the
periphery of the aggregate clusters. The interior of the aggregate
clusters are substantially free of thermoplastic binder fiber ends.
The macro absorbent structure and the aggregate clusters may also
include thermoplastic binder fibers, staple fibers, superabsorbent
particles and the like. A method of making absorbent structures
includes a first absorbent structure, dividing the first absorbent
structure to create aggregate clusters, providing a stream of the
aggregate clusters, providing polymeric fibers, merging the
aggregate cluster stream and polymeric fiber stream into a single
product stream, and making a second absorbent structure. The method
may further include staple fibers, superabsorbent particles, and
the like.
Inventors: |
Melius; Shannon Kathleen;
(Appleton, WI) ; La Fortune; Jeffrey Mark;
(Neenah, WI) ; Faulks; Michael John; (Neenah,
WI) ; Fell; David Arthur; (Neenah, WI) ;
Venturino; Michael Barth; (Appleton, WI) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
US
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
|
Family ID: |
36182411 |
Appl. No.: |
11/021043 |
Filed: |
December 23, 2004 |
Current U.S.
Class: |
442/416 ;
442/415; 442/417 |
Current CPC
Class: |
A61F 13/532 20130101;
A61F 13/15642 20130101; Y10T 442/697 20150401; Y10T 442/698
20150401; Y10T 442/699 20150401; A61F 13/15634 20130101 |
Class at
Publication: |
442/416 ;
442/415; 442/417 |
International
Class: |
D04H 5/00 20060101
D04H005/00 |
Claims
1. An absorbent structure comprising a macro absorbent structure,
the macro absorbent structure comprising a plurality of aggregate
clusters intermixed within the macro absorbent structure, the
aggregate clusters having a periphery and an interior and
comprising thermoplastic binder fibers having thermoplastic binder
fiber ends, the thermoplastic binder fiber ends being located at
the periphery of the aggregate clusters, and the interior of the
aggregate clusters being substantially free of thermoplastic binder
fiber ends.
2. The absorbent structure of claim 1 wherein the macro absorbent
structure further comprises long thermoplastic binder fibers and
superabsorbent particles constrained within the thermoplastic
binder fibers.
3. The absorbent structure of claim 2 wherein the aggregate
clusters further comprise superabsorbent particles constrained
within the thermoplastic binder fibers within the aggregate
clusters.
4. The absorbent structure of claim 3 wherein the aggregate
clusters further comprise staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters.
5. The absorbent structure of claim 2 wherein the aggregate
clusters further comprise staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters.
6. The absorbent structure of claim 1 wherein the macro absorbent
structure further comprises long thermoplastic binder fibers and
staple fibers constrained within the long thermoplastic binder
fibers.
7. The absorbent structure of claim 6 wherein the aggregate
clusters further comprise superabsorbent particles constrained
within the thermoplastic binder fibers within the aggregate
clusters.
8. The absorbent structure of claim 7 wherein the aggregate
clusters further comprise staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters.
9. The absorbent structure of claim 6 wherein the aggregate
clusters further comprise staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters.
10. The absorbent structure of claim 1 wherein the macro absorbent
structure further comprises long thermoplastic binder fibers,
superabsorbent particles constrained within the long thermoplastic
binder fibers, and staple fibers constrained within the long
thermoplastic binder fibers.
11. The absorbent structure of claim 10 wherein the aggregate
clusters further comprise superabsorbent particles constrained
within the thermoplastic binder fibers within the aggregate
clusters.
12. The absorbent structure of claim 11 wherein the aggregate
clusters further comprise staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters.
13. The absorbent structure of claim 10 wherein the aggregate
clusters further comprise staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters.
14. The absorbent structure of claim I wherein the macro absorbent
structure further comprises staple fibers and superabsorbent
particles intermixed with the staple fibers.
15. The absorbent structure of claim 1 wherein the macro absorbent
structure further comprises long thermoplastic binder fibers and
the aggregate clusters are constrained within the long
thermoplastic binder fibers.
16. A stabilized absorbent structure comprising, a. 5 to 50 wt %
meltblown elastomeric polyolefin binder fibers having an average
fiber length greater than 1 cm; b. 1 to 50 wt % cellulose fibers
constrained within the elastomeric polyolefin binder fibers; c. 30
to 90 wt % superabsorbent particles constrained or entrapped within
the polyolefin binder fibers; and d. 1 to 50 wt % aggregate
clusters each having a periphery and interior, the aggregate
clusters comprising meltblown polyolefin binder fibers having
meltblown polyolefin binder fiber ends, cellulose fibers
constrained within the polyolefin binder fibers within the
aggregate clusters, superabsorbent particles constrained or
entrapped within the polyolefin binder fibers within the aggregate
clusters, wherein the meltblown polyolefin binder fiber ends are
located at the periphery of the aggregate clusters and the
interiors of the aggregate clusters are substantially free of
meltblown polyolefin binder fiber ends.
17. A method of making a stabilized absorbent structure comprising;
a. providing a first absorbent structure comprising long
thermoplastic binder fibers; b. dividing the first absorbent
structure to create aggregate clusters; c. providing a stream of
the aggregate clusters; d. providing a stream of extruded molten
polymeric fibers; e. merging the aggregate cluster stream and
polymeric fiber stream into a single product stream; and f.
collecting the single product stream on a forming surface to make a
second absorbent structure.
18. The method of claim 17 further comprising, merging a stream of
superabsorbent particles in the aggregate cluster stream, the
polymeric fiber stream, or the single product stream.
19. The method of claim 17 further comprising, merging a stream of
wood pulp fibers in the aggregate cluster stream, the polymeric
fiber stream, or the single product stream.
20. A disposable absorbent article produced by the method of claim
17.
Description
BACKGROUND OF THE INVENTION
[0001] Disposable absorbent articles are used for a variety of
applications including disposable diapers, training pants,
disposable swim pants, adult incontinence garments, feminine
hygiene products, wound dressings, nursing pads, bed pads, wipes,
bibs, wound dressings, surgical capes or drapes, and the like. Such
disposable absorbent products are generally suited to absorb many
substances such as water and body exudates such as urine, menses,
blood, and the like.
[0002] Some disposable absorbent articles are formed from densified
cellulose intermixed with superabsorbent particles. Others are
formed from high integrity absorbent structures containing high
concentrations of superabsorbent particles entangled or otherwise
commingled with long thermoplastic fibers and/or cellulosic fibers
to improve fit, comfort, and/or performance. In general, the
absorbent structures may be mechanically constrained or limited,
particularly the high integrity structures, in such a way that the
absorbent structure is not able to fully expand in the presence of
liquids. Additionally, the high integrity absorbent structures may
be expensive due to the addition of thermoplastic fibers.
[0003] Therefore, there exists a need for absorbent structures,
including high integrity absorbent structures, that can expand more
fully in the presence of liquids and are more cost effective to
manufacture.
SUMMARY OF THE INVENTION
[0004] In response to the discussed needs, the present invention
provides absorbent structures with aggregate clusters and methods
of making absorbent structures with aggregate clusters.
[0005] In various embodiments, an absorbent structure includes a
macro absorbent structure. The macro absorbent structure includes a
plurality of aggregate clusters intermixed within the macro
absorbent structure. The aggregate clusters have a periphery and an
interior and include thermoplastic binder fibers having
thermoplastic binder fiber ends. The thermoplastic binder fiber
ends are located at the periphery of the aggregate clusters.
[0006] The interiors of the aggregate clusters are substantially
free of thermoplastic binder fiber ends. The macro absorbent
structure includes long thermoplastic binder fibers and
superabsorbent particles constrained within the long thermoplastic
binder fibers. In these embodiments, the aggregate clusters may
include superabsorbent particles constrained within the
thermoplastic binder fibers within the aggregate clusters, staple
fibers constrained within the thermoplastic binder fibers within
the aggregate clusters, or both superabsorbent particles and staple
fibers constrained within the thermoplastic binder fibers within
the aggregate clusters.
[0007] In various other embodiments, an absorbent structure
includes a macro absorbent structure. The macro absorbent structure
includes a plurality of aggregate clusters intermixed within the
macro absorbent structure. The aggregate clusters have a periphery
and an interior and include thermoplastic binder fibers have
thermoplastic binder fiber ends. The thermoplastic binder fiber
ends are located at the periphery of the aggregate clusters. The
interiors of the aggregate clusters are substantially free of
thermoplastic binder fiber ends. The macro absorbent structure
includes long thermoplastic binder fibers and staple fibers
constrained within the long thermoplastic binder fibers. In these
embodiments, the aggregate clusters may include superabsorbent
particles constrained within the thermoplastic binder fibers within
the aggregate clusters, staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters, or both
superabsorbent particles and staple fibers constrained within the
thermoplastic binder fibers within the aggregate clusters.
[0008] In yet other embodiments, an absorbent structure includes a
macro absorbent structure. The macro absorbent structure includes a
plurality of aggregate clusters intermixed within the macro
absorbent structure. The aggregate clusters have a periphery and an
interior and include thermoplastic binder fibers having
thermoplastic binder fiber ends. The thermoplastic binder fiber
ends are located at the periphery of the aggregate clusters. The
interiors of the aggregate clusters are substantially free of
thermoplastic binder fiber ends. The macro absorbent structure
includes long thermoplastic binder fibers, superabsorbent particles
constrained within the long thermoplastic binder fibers, and staple
fibers constrained within the long thermoplastic binder fiber. In
these embodiments, the aggregate clusters may include
superabsorbent particles constrained within the thermoplastic
binder fibers within the aggregate clusters, staple fibers
constrained within the thermoplastic binder fibers within the
aggregate clusters, or both superabsorbent particles and staple
fibers constrained within the thermoplastic binder fibers within
the aggregate clusters.
[0009] In yet other embodiments, an absorbent structure includes a
macro absorbent structure. The macro absorbent structure includes a
plurality of aggregate clusters intermixed within the macro
absorbent structure. The aggregate clusters have a periphery and an
interior and include thermoplastic binder fibers having
thermoplastic binder fiber ends. The thermoplastic binder fiber
ends are located at the periphery of the aggregate clusters. The
interiors of the aggregate clusters are substantially free of
thermoplastic binder fiber ends. The macro absorbent structure
includes staple fibers and superabsorbent particles intermixed with
the staple fibers. In these embodiments, the aggregate clusters may
include superabsorbent particles constrained within the
thermoplastic binder fibers within the aggregate clusters, staple
fibers constrained within the thermoplastic binder fibers within
the aggregate clusters, or both superabsorbent particles and staple
fibers constrained within the thermoplastic binder fibers within
the aggregate clusters.
[0010] In various embodiments, the aggregate clusters may have a
greatest dimension of 0.5 mm to 20 mm and/or a weight percent of 20
to 50 percent. In various embodiments, the long thermoplastic
binder fibers are elastic.
[0011] In one embodiment, a stabilized absorbent structure includes
5 to 50 weight percent meltblown polyolefin binder fibers having an
average fiber length greater than 1 cm. The stabilized absorbent
structure also has 1 to 50 weight percent cellulose fibers
constrained within the polyolefin binder fibers. The stabilized
absorbent structure also has 30 to 90 weight percent superabsorbent
particles constrained within the polyolefin binder fibers. The
stabilized absorbent structure also has 1 to 50 weight percent
aggregate clusters. Each aggregate cluster has a periphery and an
interior. The aggregate clusters include meltblown polyolefin
binder fibers having meltblown polyolefin binder fiber ends. The
aggregate clusters further include cellulose fibers constrained
within the polyolefin binder fibers within the aggregate clusters.
The aggregate clusters further include superabsorbent particles
constrained in the polyolefin binder fibers within the aggregate
clusters. The meltblown polyolefin binder fiber ends are located at
the periphery of the aggregate clusters. The interiors of the
aggregate clusters are substantially free of meltblown polyolefin
binder fiber ends.
[0012] In another aspect, the present invention provides a method
of making a stabilized absorbent structure. The method includes
providing a first absorbent structure. The first absorbent
structure includes long thermoplastic binder fibers. The method
further includes dividing the first absorbent structure into
aggregate clusters. The aggregate clusters are provided as a stream
of aggregate clusters. The method includes providing a stream of
extruded molten thermoplastic polymeric fibers. The aggregate
clusters stream and the polymeric fiber stream are merged into a
single product stream. The single product stream is collected on a
forming surface to make a second stabilized absorbent structure
including aggregate clusters. In various embodiments, the second
stabilized absorbent structure including aggregate clusters may be
used to produce a disposable absorbent article.
[0013] In various embodiments, the process further includes merging
a stream of superabsorbent particles into the aggregate clusters
stream, the polymeric fiber stream, or the single product
stream.
[0014] In various embodiments, the process further includes merging
a stream of wood pulp fibers into the aggregate cluster stream, the
polymeric fiber stream, or the single product stream.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 representatively illustrates a perspective view of an
exemplary absorbent article according to the present invention;
[0016] FIG. 2A representatively illustrates a cross-sectional view
of a first alternative embodiment of the absorbent article of FIG.
1 taken along the line 2-2;
[0017] FIG. 2B representatively illustrates a cross-sectional view
of a second alternative embodiment of the absorbent article of FIG.
1 taken along the line 2-2;
[0018] FIG. 3A is a light photomicrograph image of an exemplary
macro absorbent structure containing aggregate clusters according
to the present invention;
[0019] FIG. 3B is a Scanning Electron Micrograph image of a portion
of the exemplary macro absorbent structure of FIG. 3A;
[0020] FIG. 4 is a Scanning Electron Micrograph image of an
exemplary aggregate cluster according to the present invention;
[0021] FIG. 4A is a Scanning Electron Micrograph image of a cut
thermoplastic binder fiber end;
[0022] FIG. 5 is a Scanning Electron Micrograph image of an
exemplary aggregate cluster according to the present invention;
[0023] FIG. 6A representatively illustrates an embodiment of an
aggregate cluster according to the present invention;
[0024] FIG. 6B representatively illustrates another embodiment of
an aggregate cluster according to the present invention;
[0025] FIG. 6C representatively illustrates a further embodiment of
an aggregate cluster according to the present invention; and
[0026] FIG. 7 is a partially schematic side elevation, partially in
section, of a method and apparatus for producing the absorbent
structure of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0027] In one aspect, the absorbent structures according to the
present invention are suited to absorb many liquids, such as water,
saline, and synthetic urine, and body liquids such as urine,
menses, and blood, and are suited for use in disposable absorbent
products such as diapers, adult and youth incontinent garments and
pads, and bed pads; in catamenial devices such as sanitary napkins,
interlabial pads, and tampons; and in other disposable absorbent
products such as wipes, bibs, wound dressings, and surgical capes
or drapes. For purposes of illustration, the absorbent structure of
the present invention will be described as used in a disposable
diaper. However, those skilled in the art will appreciate the many
other uses available for this structure.
[0028] The absorbent structure of the present invention generally
includes a macro structure and a micro structure. The micro
structure comprises a plurality of aggregate clusters that form a
component of the macro structure. The macro structure includes the
aggregate clusters and may further include one or more of the
following: staple fibers, long thermoplastic fibers, superabsorbent
materials, and the like.
[0029] As used herein, the term "fiber" or "fibrous" is meant to
refer to a particulate material wherein the length to diameter
ratio of such particulate material is greater than about 10.
Conversely, a "nonfiber" or "nonfibrous" material is meant to refer
to a particulate material wherein the length to diameter ratio of
such particulate material is about 10 or less.
[0030] As used herein, the term "virgin" refers to materials or
fibers that are being introduced to the manufacturing process for
the first time. The term "virgin" excludes fibers or materials that
are "reclaimed" or "recycled". As used herein, the terms "reclaim"
or "recycle" refer to fibers, particles, aggregates, or materials
that have previously been introduced to a manufacturing process,
have been segregated because of defect or other reason, and have
been reintroduced to the manufacturing process and/or a second
manufacturing process. The recycled materials may be subjected to
additional processing prior to reintroduction to the manufacturing
process or the recycled material may be added to the manufacturing
process in the condition in which it was removed.
[0031] As used herein, the term "wettable" refers to a fiber which
exhibits a liquid (such as water, synthetic urine, or a 0.9 weight
percent aqueous saline solution) in air contact angle of less than
90.degree.. As used herein, the contact angle may be determined,
for example, as set forth by Robert J. Good and Robert J.
Stromberg, Ed., in "Surface and Colloid Science--Experimental
Methods", Vol. 11, (Plenum Press, 1979). Suitably, a wettable fiber
refers to a fiber which exhibits a 0.9 weight percent aqueous
saline solution in air contact angle of less than 90.degree. at a
temperature between about 0.degree. C. and about 100.degree. C. and
suitably at ambient conditions, such as about 23.degree. C.
[0032] As used herein, the term "staple fiber" is meant to refer to
a natural fiber or a length cut from, for example, a manufactured
filament. Such staple fibers are intended to act in the absorbent
structure of the present invention as a temporary reservoir for
liquid and also as a conduit for liquid distribution.
[0033] Suitably, the staple fibers used in the absorbent structures
herein may range in length from about 0.5 millimeters (mm) to about
20 mm, and more suitably from about 1 mm to about 15 mm. In some
embodiments, the staple fibers may be from 3 mm to 6 mm in length.
In some embodiments, the staple fibers may be 1 to 2 mm. Staple
fibers of these size characteristics help to impart desirable bulk,
liquid acquisition, liquid distribution and strength
characteristics, and/or desirable flexibility and resilience
properties to the absorbent structures of this invention.
[0034] A wide variety of staple fiber materials can be employed in
the absorbent structures described herein. Staple fibers useful in
the present invention may be formed from natural or thermoplastic
materials and may include cellulosic fibers such as wood pulp
fibers and modified cellulose fibers, textile fibers such as cotton
or rayon, and substantially nonabsorbent thermoplastic polymeric
fibers.
[0035] For reasons of availability and cost, cellulosic fibers will
frequently be preferred for use as the staple fiber component of
the absorbent structures of this invention, for example wood pulp
fibers. However, other cellulosic fiber materials, such as cotton
fibers, may also be used as the staple fiber.
[0036] Another preferred type of staple fiber useful herein
comprises substantially nonabsorbent, crimped thermoplastic
polymeric fibers. The individual fibers of this type are in and of
themselves substantially nonabsorbent. Thus, such fibers should be
prepared from a thermoplastic polymer material which does not
substantially swell or gel in the presence of liquids, such as
urine or menses, typically encountered in disposable absorbent
products. Suitable polymeric materials which may be used to prepare
the staple fibers include polyesters, polyolefins, polyacrylics,
polyamides, and polystyrenes. In some embodiments, the staple
fibers are made of polyethylene, polypropylene, or polyethylene
terephthalate.
[0037] The staple fibers used herein may also be crimped such that
the resulting absorbent structure has the desired resilience and
resistance to bunching during use in absorbent products. Crimped
staple fibers are those which have a continuous wavy, curvy or
jagged character along their length. Fiber crimping of this sort is
described more fully in U.S. Pat. No. 4,118,531 issued Oct. 3, 1978
to Hauser, the entirety of which is incorporated herein by
reference where not inconsistent.
[0038] Suitable wettable fibers may be formed from intrinsically
wettable fibers or may be formed from intrinsically hydrophobic
fibers having a surface treatment thereon which renders the fiber
hydrophilic. When surface treated fibers are employed, the surface
treatment is desirably nonfugitive. That is, the surface treatment
desirably does not wash off the surface of the fiber with the first
liquid insult or contact. For the purposes of this application, a
surface treatment on a generally hydrophobic polymer will be
considered to be nonfugitive when a majority of the fibers
demonstrate a liquid in air contact angle of less than 90.degree.
for three consecutive contact angle measurements, with drying
between each measurement. In other words, the same fiber is
subjected to three separate contact angle determinations and, if
all three of the contact angle determinations indicate a contact
angle of liquid in air of less than 90.degree., the surface
treatment on the fiber will be considered to be nonfugitive. If the
surface treatment is fugitive, the surface treatment will tend to
wash off of the fiber during the first contact angle measurement,
thus, exposing the hydrophobic surface of the underlying fiber and
will demonstrate subsequent contact angle measurements greater than
90.degree..
[0039] The wettable staple fibers are desirably present in an
elastomeric absorbent structure of the present invention in an
amount from 0 to about 80 weight percent, suitably from about 1 to
about 50 weight percent, and more suitably from about 10 to about
40 weight percent wettable staple fiber. "Weight percent (wt %)" is
based on the total weight of the materials present. For example, a
60 gram mixture consisting of 10 grams substance X, 20 grams
substance Y, and 30 grams substance Z, would have 16.7 wt % X, 33.3
wt % Y, and 50 wt % Z.
[0040] It has been found that by including a thermoplastic binder
fiber in an absorbent structure, the properties of the absorbent
structure may be substantially improved, particularly as compared
to an otherwise essentially identical absorbent structure not
comprising a thermoplastic binder fiber. As used herein, the term
"thermoplastic binder fiber" is meant to describe a material that
softens when exposed to heat and which substantially returns to its
original condition when cooled to room temperature. The
thermoplastic binder fiber, when in the softened state, conforms
around, entangles, constrains, or entraps those fibers or particles
proximate the thermoplastic binder fiber to stabilize the absorbent
structure.
[0041] As used herein, the term "constrain" refers to staple fibers
and/or aggregate clusters and/or superabsorbent particles that are
substantially immobilized, such that the staple fibers and/or
aggregate clusters and/or superabsorbent particles, and/or other
components are not free to substantially move or migrate within or
without the web structure. Such constraining may be, for example,
by autogeneous bonding, thermal deformation, entrapment, or by the
entanglement of the thermoplastic fibers of the web structure. The
thermoplastic binder fibers may be elastic or non-elastic.
[0042] The thermoplastic binder fibers may be long or short. As
used herein, the term "long" means fibers that are greater than 6
mm. In some embodiments, the long fibers may be greater than 1
centimeter (cm), greater than 2.5 cm, greater than 50 cm, or
greater than 100 cm in length. In some embodiments, the long
thermoplastic binder fibers may be substantially continuous
filaments or fibers. As used herein, the terms "substantially
continuous" or "substantially continuously formed" refers to
filaments or fibers prepared by extrusion from a spinnerette,
including without limitation spunbonded and meltblown fibers, which
are not cut from their original length prior to being formed into a
nonwoven web or fabric. Substantially continuous filaments or
fibers may have lengths ranging from greater than about 15 cm to
more than one meter; and up to lengths greater than the length of
the nonwoven web or fabric being formed. The definition of
"substantially continuous filaments or fibers" includes those
fibers which are not cut prior to being formed into a nonwoven web
or fabric, but which are cut after the nonwoven web, article, or
fabric are formed, such as when the absorbent article is cut into
individual product units or divided into aggregate clusters. As
used herein, the term "short" generally means less than about 6
mm.
[0043] As used herein, the terms "elastic" and "elastomeric" are
used interchangeably to mean a material that is generally capable
of recovering its shape after deformation when the deforming force
is removed. Specifically, as used herein, elastic or elastomeric is
meant to be that property of any material which, upon application
of a biasing force, permits that material to be stretchable to a
stretched, biased length, which is at least about 125 percent, that
is about 1.25 times, its relaxed, unbiased length, and that will
cause the material to recover at least 40 percent of its elongation
upon release of the stretching, elongating force. A hypothetical
example which would satisfy this definition of an elastomeric
material would be a 10 centimeter sample of a material which is
elongatable to at least 12.5 centimeters and which, upon being
elongated to 12.5 centimeters and released, will recover to a
length of not more than 11.5 centimeters. Many elastic materials
may be stretched by much more than 25 percent of their relaxed
length, and many of these will recover to substantially their
original relaxed length upon release of the stretching, elongating
force. This latter class of materials is generally beneficial for
purposes of the present invention.
[0044] The term "recover" relates to a contraction 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 10 centimeters
were elongated 50 percent by stretching to a length of 15
centimeters, the material would have been elongated 50 percent 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 11 centimeters after release of the
biasing and stretching force, the material would have recovered 80
percent (4 centimeters) of its elongation.
[0045] Materials suitable for use in preparing thermoplastic
elastomeric binder fibers include diblock, triblock, or multiblock
elastomeric copolymers such as olefinic copolymers such as
styrene-isoprene-styrene, styrene-butadiene-styrene,
styrene-ethylene/butylene-styrene, or
styrene-ethylene/propylene-styrene, such as those available from
the Shell Chemical Company, under the trade designation KRATON
elastomeric resin; polyurethanes, such as those available from
Invista Corporation with offices in Wichita, Kans., U.S.A. under
the trade name LYCRA; polyamides, such as polyether block amides
available from Ato Chemical Company, under the trade name PEBAX
polyether block amide; polyesters, such as those available from E.
I. Du Pont de Nemours Co., under the trade name HYTREL polyester;
or low molecular weight metallocene polyolefins, such as those
available from ExxonMobil Chemical Company, having offices in
Houston, Tex., U.S.A. under the trade name VISTAMAXX.
[0046] A number of block copolymers can be used to prepare the
thermoplastic elastomeric binder fibers useful in this invention.
Such block copolymers generally comprise an elastomeric midblock
portion and a thermoplastic endblock portion. Suitable block
copolymers and methods for synthesizing them are described in U.S.
Pat. No. 5,645,542 issued Jul. 8, 1997 to Anjur et al. and U.S.
Pat. No. 6,362,389 issued Mar. 26, 2002 to McDowall et al., the
entireties of both are incorporated herein by reference where not
contradictory.
[0047] Materials suitable for use in preparing non-elastic
thermoplastic binder fibers include polyolefins such as
polypropylene and polyethylene, polyamides, and polyesters such as
polyethylene tetraphthalate. Other suitable thermoplastic polymers
are described in U.S. Pat. No. 4,100,324 issued Jul. 11, 1978 to
Anderson et al., the entirety of which is incorporated by reference
where not contradictory.
[0048] The thermoplastic binder fiber may generally be formed from
any thermoplastic composition capable of extrusion into fibers. A
suitable thermoplastic binder fiber for the present invention
comprises meltblown fibers. Such meltblown fibers are typically
very fine fibers prepared by extruding liquefied, or melted,
fiber-forming copolymer through orifices in a die into a high
velocity gaseous stream. The fibers are attenuated by the gaseous
stream and are subsequently solidified. For example, the resulting
stream of solidified thermoplastic fibers can be collected as an
entangled coherent fibrous mass on a screen disposed in the gaseous
stream. Such an entangled fibrous mass is characterized by extreme
entanglement of the fibers which results in a stabilized absorbent
structure. This entanglement provides coherency and strength to the
resulting web structure. For example, the dry strength of such a
structure can be 6 Newtons per 50 mm or more and the wet strength
can be 2 Newtons per 50 mm or more as measured by the tensile
strength test disclosed in example 4 of U.S. publication
2004/0122394A1 to Fell et al. published Jun. 24, 2004, the entirety
of which is incorporated herein by reference where not
contradictory.
[0049] Such entanglement also adapts the web structure to constrain
or entrap the wettable staple fiber, the aggregate clusters, the
superabsorbent particles, or other components within the absorbent
structure either during or after formation of the web structure.
The thermoplastic fibers are generally entangled sufficiently that
it is difficult if not impossible to remove one complete fiber from
the mass of fibers or to trace one fiber from beginning to end.
[0050] The thermoplastic binder fiber used herein may be circular
in cross section but may also have other cross-sectional geometries
such as elliptical, rectangular, triangular, irregular or
multi-lobal. The thermoplastic binder fiber is suitably wettable.
The thermoplastic binder fiber may be made wettable by first
preparing the thermoplastic binder fiber and then subsequently
applying a hydrophilizing surface treatment to the fiber.
[0051] Alternatively, the thermoplastic binder fibers may be made
wettable by adding a hydrophilic ingredient to the polymer prior to
spinning. In general, any polymeric component capable of being
polymerized with the thermoplastic component, capable of
hydrophilizing the resultant copolymeric material to render it
wettable, wherein the hydrophilizing component does not
substantially affect the properties of the prepared fiber, is
suitable for use in the present invention. Hydrophilizing polymeric
components suitable for use in the present invention include,
without limitation, polyethylene oxide or polyvinyl alcohol, as
well as a wide variety of commercial hydrophilic surfactants.
[0052] The thermoplastic binder fibers are therefore desirably
present in an absorbent structure of the present invention in an
amount from about 1 to about 80 weight percent, from about 10 to
about 50 weight percent, and from about 15 to about 30 weight
percent, with all weight percents based on the total weight of the
absorbent structure. The thermoplastic binder fibers are generally
greater than about 1 cm in length, greater than about 10 cm in
length, greater than about 50 cm, or may be substantially
continuous. The thermoplastic binder fibers may be less than about
100 microns in average diameter, may be less than about 50 microns
in average diameter, and may be less than about 30 microns in
average diameter.
[0053] In various embodiments, the absorbent structure may include
superabsorbent material, such as a hydrogel-forming polymeric
material. The introduction of hydrogel-forming polymeric material
into such an absorbent structure generally allows for the use of
less wettable staple fiber, since the hydrogel-forming polymeric
material generally has a higher liquid absorption capacity on a
gram per gram basis than the wettable staple fiber. Moreover, such
hydrogel-forming polymeric material is generally less pressure
sensitive than wettable staple fiber. Thus, the use of the
hydrogel-forming polymeric material generally allows for the
production and use of a smaller, thinner disposable absorbent
product. As such, the absorbent structure of the present invention
may also optionally include a hydrogel-forming polymeric material
either in the macro structure, micro structure, or both.
[0054] As used herein, "hydrogel-forming polymeric material" is
meant to refer to a high absorbency material commonly referred to
as a superabsorbent material. Such high absorbency materials are
generally capable of absorbing an amount of a liquid, such as
synthetic urine, a 0.9 weight percent aqueous saline solution, or
bodily fluids, such as menses, urine, or blood, at least about 10,
suitably about 20, and up to about 100 times the weight of the
superabsorbent material at the conditions under which the
superabsorbent material is being used. Typical conditions include,
for example, a temperature of between about 0.degree. C. to about
100.degree. C. and suitably ambient conditions, such as about
23.degree. C. and about 30 to about 60 percent relative humidity.
Upon absorption of the liquid, the superabsorbent material
typically swells and forms a hydrogel.
[0055] The hydrogel-forming polymeric material may be formed from
an organic hydrogel material which may include natural materials,
such as agar, pectin, and guar gum, as well as polyacrylate
hydrogel polymers. Suitable hydrogels are taught in U.S. Pat. No.
5,645,542 issued Jul. 8, 1997 to Anjur et al., the entirety of
which is incorporated herein by reference where not contradictory.
Additionally, suitable hydrogel-forming materials are commercially
available as FAVOR SXM-880 supplied by Degussa Superabsorbers with
offices in Greensboro, N.C., U.S.A. and HYSORB 8800AD supplied by
BASF with offices in Charlotte, N.C., U.S.A.
[0056] Suitably, the hydrogel-forming polymeric material is in the
form of particles which, in the unswollen state, have maximum
cross-sectional diameters within the range of from about 50
micrometers to about 1000 micrometers, preferably within the range
of from about 100 micrometers to about 800 micrometers, as
determined by sieve analysis according to American Society for
Testing and Materials (ASTM) test method D-1921. It is to be
understood that the particles of hydrogel-forming polymeric
material falling within the ranges described above may comprise
solid particles, porous particles, or may be agglomerated particles
comprising many smaller particles agglomerated into particles
falling within the described size ranges.
[0057] The hydrogel-forming polymeric material may additionally or
alternatively comprise "coated" superabsorbent as taught in U.S.
Pat. No. 6,387,749 issued May 14, 2002 to Reeves et al., the
entirely of which is incorporated herein in its entirety where not
contradictory.
[0058] The hydrogel-forming polymeric material is beneficially
present in an absorbent structure in an amount of from about 0 to
90 weight percent, suitably in an amount of from about 20 to about
85 weight percent, and more suitably of from about 30 to about 80
weight percent, based on the total weight of the absorbent
structure.
[0059] It has been found that by including aggregate clusters in an
absorbent structure, the properties of the absorbent structure may
be maintained or improved but at a lower overall manufacturing cost
as compared to an otherwise essentially identical absorbent
structure not comprising aggregate clusters. Although suitable for
a wide range of absorbent articles, the absorbent structure of the
present invention will be described, for purposes of illustration,
in conjunction with a disposable diaper.
[0060] Referring to FIG. 1, a disposable diaper is shown generally
at 26. The diaper 26 has a topsheet 28, a backsheet 30, and an
absorbent structure 10 disposed between the topsheet 28 and the
backsheet 30. FIGS. 2A and 2B are cross sectional views of two
alternative examples of the disposable diaper of FIG. 1 taken along
line 2-2. The disposable diaper 26 of FIG. 2A illustrates a macro
absorbent structure 10 comprising long or substantially continuous
thermoplastic binder fibers 12, staple fibers 14, superabsorbent
particles 16, and aggregate clusters 18. In various embodiments,
the macro absorbent structure may comprise long thermoplastic
binder fibers, superabsorbent particles, and aggregate clusters,
but no staple fibers outside the aggregate clusters. In various
embodiments, the macro absorbent structure may include long or
substantially continuous thermoplastic binder fibers, staple
fibers, aggregate clusters, but no superabsorbent particles outside
the aggregate clusters. In various embodiments, the macro absorbent
structure may include long or substantially continuous
thermoplastic binder fibers and aggregate clusters, but no
superabsorbent particles, or staple fibers outside of the aggregate
clusters.
[0061] The disposable diaper 26 of FIG. 2B illustrates an
alternative exemplary macro absorbent structure 10 comprising
staple fibers 14, superabsorbent particles 16, and aggregate
clusters 18. In various embodiments, the macro absorbent structure
may comprise only staple fibers and aggregate clusters in the macro
absorbent structure.
[0062] As used herein, the term "aggregate clusters" refers to
structures that are the collection of units into a mass; that are
generally less than 2 cm in the greatest dimension; that form
discrete parts of the macro absorbent structure; that have a
periphery and an interior; that are held together by thermoplastic
binder fibers having thermoplastic binder fiber ends at the
periphery while the interior of the aggregate cluster is
substantially free of thermoplastic binder fiber ends; that include
superabsorbent particles, staple fibers, or both constrained within
the thermoplastic binder fibers; and that require no additional
bonding, cross-link polymerization, adhesive, or associating agent
to maintain the structure.
[0063] In various embodiments, the aggregate clusters may
additionally include cross-link polymerization, adhesive,
associating agent, or the like, but such additional element is not
required to maintain the physical structure of the aggregate
clusters.
[0064] As used herein, the terms "end" or "ends" refer to the
extreme or distal part lengthwise of a fiber. A fiber may have a
natural end such as found in cellulose fibers, cotton fibers, and
the like, or a fiber may have an end that is mechanically formed,
for example, by cutting, crushing, breaking, pinching, nipping, and
the like.
[0065] As used herein, the term "periphery" refers to the external
boundary or surface of a body, such as an aggregate cluster. As
used herein, the term "interior" refers to the volume defined by
the periphery.
[0066] As used herein, the term "substantially free of ends" means
having 5 or less thermoplastic binder fiber ends visible within the
interior of the aggregate cluster. One way of determining whether
the thermoplastic binder fibers in the interior of an aggregate
cluster are substantially free of ends is to use a scanning
electron microscope (SEM) or equivalent instrument. A suitable SEM
is a model JSM-840 available from JEOL USA Inc. having offices in
Peabody, Mass., USA.
[0067] FIG. 3A is a light photomicrograph produced using a NIKON
brand digital camera model 8700. The image uses light transmitted
through a portion of a macro absorbent structure, shown generally
at 10. The image is produced at 4.times. magnification. The darker
areas are aggregate clusters and are indicated generally by arrows.
Two of the aggregate clusters are identified as 1 and 2.
[0068] FIG. 3B is an image from a SEM of a portion of the macro
absorbent structure of FIG. 3A. The aggregate clusters 1 and 2
located in the macro absorbent structure 10 are generally outlined
in dash line, for purposes of illustration.
[0069] FIG. 4 is an image from an SEM of one exemplary aggregate
cluster according to the present invention shown generally at 18.
The aggregate cluster 18 has a periphery 62 and an interior. The
aggregate cluster 18 was manually removed from the absorbent
structure containing the aggregate cluster 18 for inspection in
such a way so as to minimize any disruption to the aggregate
cluster structure. The periphery 62 can be examined at various
magnifications to see the thermoplastic binder fiber ends 60. For
example, at 150.times. magnification, a thermoplastic binder fiber
end 60 can be seen in FIG. 4A.
[0070] FIG. 5 is a SEM image of one exemplary aggregate cluster
shown generally at 18 according to the present invention that has
been manipulated with a small probe to expose the interior 64. The
interior 64 can be examined at various magnifications to confirm
that the interior 64 is substantially free of thermoplastic binder
fiber ends.
[0071] As an alternative to SEM imaging, a three dimensional
visualization and measurement technique such as micro computerized
tomography may be used to non-destructively view the structure. A
suitable apparatus is a SkyScan-1072 available from SkyScan having
offices in Aartselaar, Belgium. Suitable software is Voxblast.TM.
3D Visualization and Measurement software available from VayTek,
Inc. having offices in Fairfield, Iowa, U.S.A.
[0072] Exemplary aggregate clusters 18, according to the present
invention, are representatively illustrated in FIGS. 6A, 6B, and
6C. Referring to FIG. 6A, one or more thermoplastic binder fibers
20 may constrain or entrap one or more staple fibers 22 and one or
more superabsorbent particles 24 to form an aggregate cluster 18.
The aggregate clusters 18 have a periphery 62, generally depicted
for purposes of illustration with dashed lines, and an interior 64.
The thermoplastic binder fibers 20 have thermoplastic binder fiber
ends 60 that are formed when the aggregate clusters 18 are divided
from a stabilized absorbent structure. The thermoplastic binder
fiber ends 60 are located at the periphery 62 of the aggregate
clusters 18, whereas the interior 64 of the aggregate clusters 18
is substantially free of thermoplastic binder fiber ends 60. In
contrast, the staple fibers 22 may also be cut, fractured, or
broken during the formation of the aggregate clusters 18 thus
creating staple fiber ends 66, but the interior 64 of the aggregate
clusters 18 will generally include many staple fiber ends 66 unlike
the thermoplastic binder fiber ends 60.
[0073] FIG. 6B representatively illustrates an alternative example
of an aggregate cluster 18. In FIG. 6B, the aggregate cluster 18
includes thermoplastic binder fibers 20 and staple fibers 22
constrained or entrapped within the thermoplastic binder fibers 20.
The thermoplastic binder fibers 20 have thermoplastic binder fiber
ends 60 at the periphery 62 of the aggregate clusters 18. The
interior 64 of the aggregate clusters 18 is substantially free of
thermoplastic binder fiber ends 60. The staple fibers 22 have
staple fiber ends 66 both at the periphery 62 and within the
interior 64 of the aggregate clusters 18.
[0074] FIG. 6C representatively illustrates an alternative example
of an aggregate cluster 18. In FIG. 6C, the aggregate cluster 18
includes thermoplastic binder fibers 20 and superabsorbent
particles 24 constrained or entrapped within the thermoplastic
binder fibers 20. The thermoplastic binder fibers 20 have
thermoplastic binder fiber ends 60 at the periphery 62 of the
aggregate clusters 18. The interior 64 of the aggregate clusters 18
is substantially free of thermoplastic binder fiber ends 60. The
superabsorbent particles 24 may be at least partially located at
the periphery 62 of the aggregate cluster 18, within the interior
64 of the aggregate cluster 18, or both.
[0075] Typically, the aggregate clusters are formed by dividing a
stabilized absorbent structure comprising substantially continuous
thermoplastic binder fibers into discrete units of various sizes.
Dividing the stabilized absorbent structure can be accomplished by
pulverizing, grinding, chopping, micerating, shocking, shredding or
otherwise breaking apart the stabilized absorbent composite. The
stabilized absorbent composite used to produce the aggregate
clusters may be stabilized absorbent composites produced
specifically for the purpose of creating aggregate clusters or may
be waste material, trim material, or reclaimed product.
[0076] Once produced, the aggregate clusters are then introduced
into an absorbent manufacturing process along with virgin materials
to form macro absorbent structures of absorbent articles. The
aggregate clusters described herein retain a similar structure to
the macro composite structure, from which the aggregate clusters
are formed, due to the inherently high integrity of the source
absorbent material. The high integrity of the source absorbent
material is due, at least in part, to the long or substantially
continuously formed thermoplastic binder fibers constraining,
entrapping, or entangling the other components. It is believed that
the aggregate clusters retain most of the fluid handling
performance of the original absorbent material from which they are
divided. While not wishing to be bound by any single theory, it is
believed that the aggregate clusters create discontinuities in the
otherwise continuous fibrous structures of various macro absorbent
structures, and stabilized absorbent structures in particular,
which may improve the absorbent capacity of the entire absorbent
assembly because of the increased interstitial space created by the
aggregate clusters. This interstitial space may result in less
restrictive swelling of the superabsorbent material outside and
surrounding the aggregate clusters. In other words, the
superabsorbent material, which may otherwise have been hindered by
the macro absorbent structure, may now be able to move and expand
into areas opened by the aggregate clusters. In addition, the use
of aggregate clusters in absorbent structures can reduce costs when
using reclaimed product or trim waste generated in the production
of stabilized absorbent composites as the source material.
[0077] The aggregate clusters may be divided into discrete units of
various sizes. In various embodiments, the aggregate clusters may
have a greatest dimension of less than 20 mm, less than 10 mm, or
less than 5 mm. In some embodiments, the aggregate clusters may
have a greatest dimension of 0.5 mm to 5 mm.
[0078] The absorbent structure may be in the form of a single,
integrally formed layer or of a composite comprising multiple
layers. If the absorbent structure comprises multiple layers, the
layers are preferably in liquid communication with one another,
such that, a liquid present in one layer can flow or be transported
to the other layers. For example, the layers may be separated by
cellulosic tissue wrap sheets such as those known to those skilled
in the art.
[0079] The absorbent structure of the present invention may also be
used or combined with other absorbent structures, with the
absorbent structure of the present invention being used as a
separate layer or as an individual zone or area within a larger,
composite absorbent structure. The absorbent structure of the
present invention may be combined with other absorbent structures
by methods well known to those skilled in the art, such as by using
adhesives or simply by layering the different structures together
and holding together the composite structures with, for example, a
tissue wrap sheet.
[0080] The hydrogel-forming polymeric material may be distributed
in the individual layers in a generally uniform manner or may be
present in the fibrous layers as a layer or other nonuniform
distribution. Likewise, the aggregate clusters may be distributed
in the individual layers in a general uniform manner or may be
present in the fibrous layers as a layer or other nonuniform
distribution.
[0081] The absorbent structures of the present invention suitably
have a basis weight of about 50 grams per square meter (g/sm) to
about 2000 g/sm, or about 200 g/sm to about 1500 g/sm, or about 300
g/sm to about 1000 g/sm depending on the end use. A pantiliner, for
example, would require a lower basis weight (about 100 g/sm) than a
diaper (about 700 g/sm).
[0082] The absorbent structures of the present invention suitably
have a density of about 0.03 gram per cubic centimeter (g/cc) to
about 0.5 g/cc, or about 0.05 g/cc to about 0.45 g/cc, or about
0.08 g/cc to about 0.4 g/cc. In specific embodiments, the density
may be 0.12 g/cc to 0.32 g/cc.
[0083] In some embodiments, the macro absorbent structure may
include long or substantially continuously formed thermoplastic
binder fibers, wettable staple fibers, superabsorbent particles, a
plurality of aggregate clusters, or combinations thereof. The
aggregate clusters may include thermoplastic binder fibers, staple
fibers, superabsorbent particles, and combinations thereof. The
thermoplastic binder fibers, within the aggregate clusters, may
have thermoplastic binder fiber ends located at the periphery of
the aggregate clusters, but the interior of the aggregate clusters
may be substantially free of thermoplastic binder fiber ends. In
various embodiments, the wettable staple fibers of the macro
absorbent structure and/or the aggregate clusters may be selected
from the group consisting of cellulose fibers, textile fibers, and
thermoplastic polymeric fibers. In certain embodiments, the
wettable staple fibers of the macro absorbent structure and/or the
aggregate clusters may be wood pulp fiber.
[0084] In one embodiment, the macro absorbent structure may include
5 to 50 wt % meltblown polyolefin binder fibers having an average
fiber length greater than 1 cm. The macro absorbent structure may
further include 0 to 50 wt % cellulose fibers constrained or
entrapped within the polyolefin binder fibers. The macro absorbent
structure may further include 30 to 90 wt % superabsorbent
particles constrained or entrapped within the polyolefin binder
fibers. The macro absorbent structure may further include 1 to 50
wt % aggregate clusters. The aggregate clusters may include
meltblown polyolefin binder fibers having meltblown binder fiber
ends located at the periphery of the aggregate clusters, but the
interior of the aggregate clusters may be substantially free of
meltblown binder fiber ends. In other embodiments, the aggregate
clusters may include meltblown polyolefin binder fibers having a
fiber length greater than 5 mm.
[0085] The fiber length can be determined by well known optical
imaging techniques including Scanning Electron Micrography or other
methods. This may be applied to the macro absorbent structure or
the aggregate cluster. Inspection of the inside of the aggregate
clusters may require disruption of the structure by manipulating
the aggregate cluster with a small probe. Alternatively, a three
dimensional visualization and measurement technique such as micro
computerized tomography may be used to non-destructively view the
structure, as discussed previously.
[0086] In one embodiment, the macro absorbent structure may include
5 to 50 wt % meltblown polyolefin binder fibers having an average
fiber length greater than 1 cm. The macro absorbent structure may
further include 0 to 50 wt % cellulose fibers constrained or
entrapped within the polyolefin binder fibers. The macro absorbent
structure may further include 30 to 90 wt % superabsorbent
particles constrained or entrapped within the polyolefin binder
fibers. The macro absorbent structure may further include 1 to 50
wt % aggregate clusters. The aggregate clusters may include
continuously formed meltblown polyolefin binder fibers. The
aggregate clusters may be created by dividing a stabilized
absorbent structure formed, in part, by continuous meltblown binder
fibers. The process of dividing the stabilized absorbent material,
the source absorbent material, results in polyolefin binder fiber
ends being located at the periphery of the aggregate clusters.
[0087] In various embodiments, the aggregate clusters may also
include cellulose fibers constrained or entrapped within the long
meltblown polyolefin binder fibers within the aggregate clusters.
The aggregate clusters may further include superabsorbent particles
constrained or entrapped within the meltblown polyolefin binder
fibers within the aggregate clusters.
[0088] In another embodiment, the macro absorbent structure may
include 10 to 40 wt % meltblown polyolefin binder fibers having an
average fiber length greater than 1 cm. The macro absorbent
structure may further include 40 to 80 wt % cellulose fibers
constrained or entrapped within the polyolefin binder fibers. The
macro absorbent structure may further include 0 to 20 wt %
superabsorbent particles constrained or entrapped within the
polyolefin binder fibers. The macro absorbent structure may further
include 1 to 50 wt % aggregate clusters. The aggregate clusters may
include meltblown polyolefin binder fibers having a fiber length
greater than 1 cm or greater than 5 mm. The meltblown polyolefin
binder fibers of the aggregate clusters may have meltblown
polyolefin binder fiber ends located at the periphery of the
aggregate clusters. The interiors of the aggregate clusters being
substantially free of meltblown polyolefin binder fiber ends. The
aggregate clusters may also include cellulose fibers constrained or
entrapped within the polyolefin binder fibers within the aggregate
clusters. The aggregate clusters may further include superabsorbent
particles constrained or entrapped within the polyolefin binder
fibers within the aggregate clusters.
[0089] In another embodiment, the macro absorbent structure may
include short thermoplastic binder fibers, wettable staple fibers,
superabsorbent particles, and a plurality of aggregate clusters.
The aggregate clusters may include thermoplastic binder fibers
constraining or entrapping wettable staple fibers and
superabsorbent particles. The thermoplastic binder fibers, within
the aggregate clusters, have thermoplastic binder fiber ends
located at the periphery of the aggregate clusters, whereas the
interior of the aggregate clusters is substantially free of
thermoplastic binder fiber ends.
[0090] In another embodiment, the macro absorbent structure may
include wettable staple fibers, superabsorbent particles, and a
plurality of aggregate clusters. The aggregate clusters may include
thermoplastic binder fibers constraining or entrapping cellulose
fibers and superabsorbent particles. The thermoplastic binder
fibers, within the aggregate clusters, have thermoplastic binder
fiber ends located at the periphery of the aggregate clusters,
whereas the interior of the aggregate clusters is substantially
free of thermoplastic binder fiber ends.
[0091] In another embodiment, the macro absorbent structure may
include long or substantially continuous thermoplastic binder
fibers, wettable staple fibers, superabsorbent particles, and a
plurality of aggregate clusters. The aggregate clusters may include
thermoplastic binder fibers and wettable staple fibers constrained
or entrapped in the thermoplastic binder fibers. The thermoplastic
binder fibers, within the aggregate clusters, have thermoplastic
binder fiber ends located at the periphery of the aggregate
clusters, whereas the interior of the aggregate clusters is
substantially free of thermoplastic binder fiber ends.
[0092] In another embodiment, the macro absorbent structure may
include substantially continuous thermoplastic binder fibers
constraining or entrapping wettable staple fibers, superabsorbent
particles, and a plurality of aggregate clusters. The aggregate
clusters may include thermoplastic binder fibers and superabsorbent
particles constrained or entrapped within the thermoplastic binder
fibers. The thermoplastic binder fibers, within the aggregate
clusters, have thermoplastic binder fiber ends located at the
periphery of the aggregate clusters, whereas the interior of the
aggregate clusters is substantially free of thermoplastic binder
fiber ends.
[0093] In another embodiment, the macro absorbent structure may
include wettable staple fibers, superabsorbent particles, and a
plurality of aggregate clusters. The aggregate clusters may include
thermoplastic binder fibers and wettable staple fibers constrained
or entrapped within the thermoplastic binder fibers. The
thermoplastic binder fibers, of the aggregate clusters, have
thermoplastic binder fiber ends located at the periphery of the
aggregate clusters but the interior of the aggregate clusters is
substantially free of thermoplastic binder fiber ends.
[0094] In another embodiment, the macro absorbent structure may
include short thermoplastic binder fibers, wettable staple fibers,
superabsorbent particles, and a plurality of aggregate clusters.
The aggregate clusters may include thermoplastic binder fibers and
cellulose fibers constrained or entrapped within the thermoplastic
binder fibers. The thermoplastic binder fibers, within the
aggregate clusters, have thermoplastic binder fiber ends located at
the periphery of the aggregate clusters but the interior of the
aggregate clusters is substantially free of thermoplastic binder
fiber ends.
[0095] In another embodiment, the macro absorbent structure may
include wettable staple fibers, superabsorbent particles, and a
plurality of aggregate clusters. The aggregate clusters may include
thermoplastic binder fibers and superabsorbent particles
constrained or entrapped within the thermoplastic binder fibers.
The thermoplastic binder fibers, within the aggregate clusters,
have thermoplastic binder fiber ends located at the periphery of
the aggregate clusters but the interior of the aggregate clusters
is substantially free of thermoplastic binder fiber ends.
[0096] In another embodiment, the macro absorbent structure may
include short thermoplastic binder fibers, wettable staple fibers,
superabsorbent particles, and a plurality of aggregate clusters.
The aggregate clusters may include thermoplastic binder fibers and
superabsorbent particles constrained or entrapped within the
thermoplastic binder fibers. The thermoplastic binder fibers,
within the aggregate clusters, have thermoplastic binder fiber ends
located at the periphery of the aggregate clusters but the interior
of the aggregate clusters being substantially free of thermoplastic
binder fiber ends.
[0097] In another embodiment, the macro absorbent structure may
include substantially continuous thermoplastic binder fibers,
superabsorbent particles, and a plurality of aggregate clusters.
The aggregate clusters may include thermoplastic binder fibers and
superabsorbent particles constrained or entrapped within the
thermoplastic binder fibers. The thermoplastic binder fibers,
within the aggregate clusters, have thermoplastic binder fiber ends
located at the periphery of the aggregate clusters, whereas the
interior of the aggregate clusters is substantially free of
thermoplastic binder fiber ends.
[0098] In another embodiment, the macro absorbent structure may
include substantially continuous thermoplastic binder fibers,
wettable staple fibers, and a plurality of aggregate clusters. The
aggregate clusters may include thermoplastic binder fibers and
wettable staple fibers constrained or entrapped within the
thermoplastic binder fibers. The thermoplastic binder fibers, of
the aggregate clusters, have thermoplastic binder fiber ends
located at the periphery of the aggregate clusters but the interior
of the aggregate clusters is substantially free of thermoplastic
binder fiber ends.
[0099] In another embodiment; the macro absorbent structure may
include substantially continuous thermoplastic binder fibers and a
plurality of aggregate clusters. The aggregate clusters may include
thermoplastic binder fibers and wettable staple fibers constrained
or entrapped within the thermoplastic binder fibers. The
thermoplastic binder fibers, of the aggregate clusters, have
thermoplastic binder fiber ends located at the periphery of the
aggregate clusters but the interior of the aggregate clusters is
substantially free of thermoplastic binder fiber ends.
[0100] In another embodiment, the macro absorbent structure may
include substantially continuous thermoplastic binder fibers and a
plurality of aggregate clusters. The aggregate clusters may include
thermoplastic binder fibers and superabsorbent particles
constrained or entrapped within the thermoplastic binder fibers.
The thermoplastic binder fibers, of the aggregate clusters, have
thermoplastic binder fiber ends located at the periphery of the
aggregate clusters but the interior of the aggregate clusters is
substantially free of thermoplastic binder fiber ends.
[0101] In another embodiment, the macro absorbent structure may
include substantially continuous thermoplastic binder fibers and a
plurality of aggregate clusters. The aggregate clusters may include
thermoplastic binder fibers, wettable staple fibers constrained or
entrapped within the thermoplastic binder fibers, and
superabsorbent particles constrained or entrapped within the
thermoplastic binder fibers. The thermoplastic binder fibers, of
the aggregate clusters, have thermoplastic binder fiber ends
located at the periphery of the aggregate clusters but the interior
of the aggregate clusters is substantially free of thermoplastic
binder fiber ends.
[0102] In another embodiment, the macro absorbent structure
includes short thermoplastic binder fibers, wettable staple fibers,
and a plurality of aggregate clusters. The aggregate clusters
include thermoplastic binder fibers. The aggregate clusters further
include superabsorbent particles constrained or entrapped within
the thermoplastic binder fibers, staple fibers constrained or
entrapped within the thermoplastic binder fibers, or both. The
thermoplastic binder fibers, within the aggregate clusters, have
thermoplastic binder fiber ends located at the periphery of the
aggregate clusters but the interior of the aggregate clusters being
substantially free of thermoplastic binder fiber ends.
[0103] In another embodiment, the macro absorbent structure
includes short thermoplastic binder fibers, superabsorbent
particles, and a plurality of aggregate clusters. The aggregate
clusters include thermoplastic binder fibers. The aggregate
clusters further include superabsorbent particles constrained or
entrapped within the thermoplastic binder fibers, staple fibers
constrained or entrapped within the thermoplastic binder fibers, or
both. The thermoplastic binder fibers, within the aggregate
clusters, have thermoplastic binder fiber ends located at the
periphery of the aggregate clusters but the interior of the
aggregate clusters being substantially free of thermoplastic binder
fiber ends.
[0104] In another embodiment, the macro absorbent structure
includes short thermoplastic binder fibers and a plurality of
aggregate clusters. The aggregate clusters include thermoplastic
binder fibers. The aggregate clusters further include
superabsorbent particles constrained or entrapped within the
thermoplastic binder fibers, staple fibers constrained or entrapped
within the thermoplastic binder fibers, or both. The thermoplastic
binder fibers, within the aggregate clusters, have thermoplastic
binder fiber ends located at the periphery of the aggregate
clusters but the interior of the aggregate clusters being
substantially free of thermoplastic binder fiber ends.
[0105] In another embodiment, the macro absorbent structure may
include wettable staple fibers and a plurality of aggregate
clusters. The aggregate clusters include thermoplastic binder
fibers. The aggregate clusters further include superabsorbent
particles constrained or entrapped within the thermoplastic binder
fibers, staple fibers constrained or entrapped within the
thermoplastic binder fibers, or both. The thermoplastic binder
fibers, within the aggregate clusters, have thermoplastic binder
fiber ends located at the periphery of the aggregate clusters but
the interior of the aggregate clusters being substantially free of
thermoplastic binder fiber ends.
[0106] In embodiments that include substantially continuous
thermoplastic binder fibers in the macro absorbent structure and
thermoplastic binder fibers in the aggregate clusters, the
substantially continuous thermoplastic binder fibers of the macro
absorbent structure, may be essentially the same composition as the
thermoplastic binder fibers of the aggregate clusters.
Additionally, in embodiments that include staple fibers in the
macro absorbent structure and the aggregate clusters, the staple
fiber of the macro absorbent structure, may have essentially the
same composition as the staple fibers of the aggregate clusters.
Likewise, in embodiments that include superabsorbent particles in
the macro absorbent structure and the aggregate clusters, the
superabsorbent particles of the macro absorbent structure, may have
essentially the same composition as the superabsorbent particles of
the aggregate clusters.
[0107] In embodiments that include substantially continuous
thermoplastic binder fibers in the macro absorbent structure and
thermoplastic binder fibers in the aggregate clusters, the
substantially continuous thermoplastic binder fibers of the macro
absorbent structure may have a different composition than the
thermoplastic binder fibers of the aggregate clusters.
Additionally, in embodiments that include staple fibers in the
macro absorbent structure and the aggregate clusters, the staple
fibers of the macro absorbent structure, may have a different
composition than the staple fibers of the aggregate clusters.
Likewise, in embodiments that include superabsorbent particles in
the macro absorbent structure and the aggregate clusters, the
superabsorbent particles of the macro absorbent structure, may have
a different composition than the superabsorbent particles of the
aggregate clusters. In some embodiments, the macro absorbent
structure and/or the aggregate clusters may have one or more
additional types of staple fibers.
[0108] The absorbent structure of the present invention can include
other components not adversely affecting the desired absorbent of
the absorbent structure. Exemplary materials which could be used as
additional components would include, without limitation, pigments,
antioxidants, stabilizers, surfactants, waxes, flow promoters,
particulates, binder fibers, and materials added to enhance
processability, liquid handling and mechanical properties or
visual/tactile appearance of the absorbent of the components,
and/or the various components.
[0109] Referring again to FIG. 1, a disposable diaper 26 is
illustrated according to one embodiment of the present invention.
Disposable diaper 26 includes a backsheet 30, a topsheet 28, and an
absorbent structure 10, located between the backsheet 30 and the
topsheet 28. Absorbent structure 10 is an absorbent structure
according to the present invention.
[0110] Those skilled in the art will recognize various materials
suitable for use as the topsheet and backsheet. Exemplary of
materials suitable for use as the topsheet are liquid-permeable
materials, such as spunbonded polypropylene or polyethylene having
a basis weight of from about 15 to about 25 grams per square meter.
Exemplary of materials suitable for use as the backsheet are
liquid-impervious materials, such as polyolefin films, as well as
vapor-pervious materials, such as microporous polyolefin films.
Also laminates including cloth-like nonwovens are well known in the
art and are suitable for use herein as a backsheet.
[0111] Those skilled in the art will also recognize that additional
components may optionally be added depending upon the intended use
of the diaper. For example, the diaper may include containment
flaps, leg elastics, waist elastics, fasteners, lotions and
treatments, surge management layers, tissue layers, spacer layers,
fit panels, and the like. These components and others are described
in U.S. Pat. No. 6,682,512 issued Jan. 27, 2004 to Uitenbroek et
al., the entirety of which is incorporated herein by reference
where not contradictory.
[0112] In another aspect, the present invention concerns a method
of making an absorbent structure with aggregate clusters and one or
more: wettable staple fibers, thermoplastic fibers, superabsorbent
particles, and the like. The absorbent structure is in the form of
a fibrous matrix. The fibrous matrix may be formed by air-laying
fibers, through a spunbond or meltblown process, a carding process,
a wet-laid process, or through essentially any other means, known
to those skilled in the art, for forming a fibrous matrix.
[0113] Methods of incorporating the wettable staple fiber and/or a
hydrogel-forming polymeric material into the fibrous matrix are
known to those skilled in the art. Suitable methods include
incorporating the wettable staple fiber and/or a hydrogel-forming
polymeric material into the matrix during formation of the matrix,
such as by air laying the fibers of the fibrous matrix and the
wettable staple fiber and/or a hydrogel-forming polymeric material
at the same time or wet-laying the fibers of the fibrous matrix and
the wettable staple fiber and/or a hydrogel-forming polymeric
material at the same time. Alternatively, it is possible to apply
the wettable staple fiber and/or a hydrogel-forming polymeric
material to the fibrous matrix after formation of the fibrous
matrix. Other methods include sandwiching the hydrogel-forming
polymeric material between two sheets of material, at least one of
which is fibrous and liquid permeable. The hydrogel-forming
polymeric material may be generally uniformly located between the
two sheets of material or may be located in discrete pockets formed
by the two sheets. It is preferable that the wettable staple fiber
be generally uniformly distributed within the fibrous matrix.
However, the wettable staple fiber may be non-uniformly distributed
to achieve the desired liquid absorptive properties.
[0114] One method of making a stabilized absorbent structure
comprises providing a stream containing substantially continuously
extruded molten polymeric binder fibers, such as polyolefin;
providing a stream containing individualized staple fibers, such as
wood pulp fibers; and providing a stream containing a plurality of
aggregate clusters. One or more of the streams may be merged into a
single product stream prior to collecting the contents of the
streams on a forming surface to create a stabilized absorbent
structure. In various embodiments, the method may include a carrier
sheet onto which the product streams are collected. In various
embodiments, the stabilized absorbent structure made by this
process may include an intimate mixture of the wood pulp fibers and
the aggregate clusters integrated by physical entrapment and
mechanical entanglement within the substantially continuous
polymeric binder fibers. In various embodiments, the method may
further include a stream comprising superabsorbent particles. In
particular embodiments, the superabsorbent stream and the pulp
fiber stream are combined into a single stream prior to combining
with the stream containing the substantially continuous extruded
molten polymeric binder fiber.
[0115] The stream containing aggregate clusters can be introduced
into the absorbent manufacturing process, in several locations, via
pneumatic conveying. Locations that are under a vacuum (negative
pressure) are preferred for proper blending.
[0116] Referring to FIG. 7, one method of introducing a plurality
of aggregate clusters includes pneumatically conveying the
aggregate clusters 18 to a fiberizer 32 generally at an entry
location 34. The fiberizer 32 is a commercially available device
that separates the individual staple fibers 14 from a source sheet
36, such as a cellulose pulp sheet. Fiberizers are available from
Paper Converting Machine Company located in Green Bay Wis., U.S.A.;
Curt G. Joa Inc. a company having an office in Sheboygan Falls
Wis., U.S.A.; and Kamas Industries AB a company having an office in
Vellinge Sweden among others.
[0117] One advantage of introducing the aggregate clusters 18
stream into the fiberizer 32 at entry location 34 is the uniform
mixing of the aggregate clusters 18 with the virgin staple fibers
14. This method of introduction may also provide uniform basis
weight and low weight variability in the absorbent structure 10.
Adding the aggregate clusters 18 to the fiberizer 32 imposes
significant fiberizer impact energy upon the superabsorbent within
the aggregate clusters 18. As a result, it is possible with this
configuration that some degradation of the superabsorbent's fluid
handling properties may occur.
[0118] Alternatively, the aggregate clusters 18 can be introduced
into the forming process after the fiberizer discharge; in a
conduit duct 38 that connects the fiberizer 32 to a forming surface
40, illustrated at entry location 44. Examples of such conduit
ducts include forming chambers, usually constructed of
polycarbonate, or ductwork of the galvanized spiral, or seamless
variety.
[0119] Most forming systems utilize a fan 42 or other device to
create motive energy for transporting the staple fibers 14 to a
forming surface 40. Some forming systems locate this motive energy
device on the side of the forming surface 40 opposite the fiberizer
32. Other forming systems locate this motive energy device between
the fiberizer 32 and the forming surface 40. For those instances,
the vacuum created by the motive energy device (suction side) is a
preferred location for introduction of the aggregate clusters 18 to
the manufacturing process. The vacuum helps integrate the flow of
aggregate clusters 18, while the motive energy device helps blend
the aggregate clusters 18 with the virgin staple fibers 14.
Examples of motive energy devices include fans, blowers, and
venturi eductors, available from New York Blower Company, having
offices in LaPorte Id., U.S.A. and Fox Valve, a company having
offices in Dover N.J., U.S.A.
[0120] Forming systems that pneumatically convey superabsorbent
particles 16 to the forming process offer another alternative
location for introducing aggregate clusters 18 to the process. A
venturi eductor 50 may be used to impart a vacuum to draw
superabsorbent 16 into a delivery pipe 46. This vacuum source
provides an opportunity to introduce the aggregate clusters 18 into
the superabsorbent delivery system at entry location 48. The
venturi eductor vacuum helps to integrate the flow of the
pneumatically conveyed aggregate clusters 18, while the venturi
eductor 50 helps blend the aggregate clusters 18 with the virgin
superabsorbent 16.
[0121] In general, to minimize any degradation of the fluid
handling properties of the superabsorbent 24 within the aggregate
clusters 18, the pneumatic conveying velocity of the aggregate
clusters 18 to the forming process should be kept to a minimum. To
prevent the aggregate clusters 18 from settling out of the air
stream (salutation) a velocity above 3,500 ft/min should be
maintained. Therefore, it is suitable to pneumatically convey the
aggregate clusters 18 at a velocity of 3,000 to 6,000 ft/min (914.4
m/min to 1,828.8 m/min), 3,000 to 5,000 ft/min (914.4 m/min to
1,524 m/min), or 3,500 to 4,000 ft/min (1,066.8 m/min to 1,219.2
m/min). A suitable method and apparatus for delivering particulate
material to an air stream is taught in U.S. Pat. No. 6,461,086,
issued Oct. 8, 2002 to Milanowski et al., the entirety of which is
incorporated herein by reference where not contradictory.
[0122] In another aspect, the present invention involves a method
of making an absorbent structure comprising the production of a
plurality of first absorbent articles on a first production line.
The first absorbent articles have macro structures including
substantially continuous thermoplastic binder fibers. The macro
absorbent structures may further include superabsorbent particles,
staple fibers, aggregate clusters or combinations thereof,
constrained or entrapped within the substantially continuous
thermoplastic binder fibers of the macro absorbent structure.
[0123] The first absorbent articles from the first production line
may then be pulverized, ground, chopped, micerated, shocked, or
otherwise worked or divided to produce aggregate clusters having a
periphery and an interior. The aggregate clusters include
thermoplastic binder fibers and may include superabsorbent
particles, staple fibers, or both constrained or entrapped within
the thermoplastic binder fibers within the aggregate clusters. The
thermoplastic binder fibers within the aggregate clusters have
thermoplastic binder fiber ends located at the periphery of the
aggregate clusters but the interior of the aggregate clusters is
substantially free of thermoplastic binder fiber ends.
[0124] The aggregate clusters are then combined with virgin
materials on a second production line to produce at least one
second absorbent article. The second absorbent article may further
include, but is not limited to: thermoplastic fibers, long fibers,
staple fibers, superabsorbent particles, and combinations
thereof.
[0125] In various embodiments, the second production line may be
the same as the first production line. As such, at least a portion
of the first absorbent articles may be worked to form aggregate
clusters and the aggregate clusters may be reintroduced into the
same process to produce more of the first absorbent articles
further including aggregate clusters. In other embodiments, the
second production line may produce absorbent articles by means of
air forming, wet laying, or other absorbent article forming
processes known to those of skill in the art.
[0126] It will be appreciated that details of the absorbent cores
of the invention, given for purposes of illustration, are not to be
construed as limiting the scope of this invention.
[0127] Those skilled in the art will readily appreciate that many
modifications are possible in the exemplary aspects without
materially departing from the novel teachings and advantages of
this invention. Accordingly, all such modifications are intended to
be included within the scope of this invention, which is defined in
the following claims and all equivalents thereto. Further, it is
recognized that many aspects may be conceived that do not achieve
all of the advantages of some aspects, particularly of the
preferred aspects., yet the absence of a particular advantage
should not be construed to necessarily mean that such an aspect is
outside the scope of the present invention.
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