Note: Descriptions are shown in the official language in which they were submitted.
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BETTER FITTING DIAPER OR PANT WITH ABSORBENT PARTICULATE
POLYMER MATERIAL AND PREFORMED CROTCH
FIELD OF THE INVENTION
The invention generally relates to an absorbent article, and more particularly
to a
disposable absorbent garment with absorbent particulate polymer material and
preformed crotch.
BACKGROUND OF THE INVENTION
Absorbent articles, such as disposable diapers, training pants, and adult
incontinence
undergarments, absorb and contain body exudates. They also are intended to
prevent body
exudates from soiling, wetting, or otherwise contaminating clothing or other
articles, such as
bedding, that come in contact with the wearer. A disposable absorbent article,
such as a
disposable diaper, may be worn for several hours in a dry state or in a urine
loaded state.
Accordingly, efforts have been made toward improving the fit and comfort of
the absorbent
article to the wearer, both when the article is dry and when the article is
fully or partially loaded
with liquid exudate, while maintaining or enhancing the absorbing and
containing functions of
the article.
Some absorbent articles, like diapers, contain an absorbent polymer material
(also
known as super absorbent polymer), such as an absorbent particulate polymer
material.
Absorbent particulate polymer material absorbs liquid and swells and may be
more effective
when disposed in an absorbent article in a certain pattern or arrangement
intended for optimal
absorbency, fit, and/or comfort. Thus, it may be desirable for absorbent
particulate polymer
material to remain in its intended location in an absorbent article and
absorbent particulate
polymer material, therefore, is desirably immobilized in the absorbent article
such that the
absorbent particulate polymer material remains immobilized when the absorbent
article is dry
and when it is wet.
In addition to being absorbent, absorbent articles, such as diapers, desirably
may be thin
and flexible, for ease and comfort in use and for more convenient and neat
packaging and
storage. Absorbent articles, which may often be used in large quantities, may
also desirably be
inexpensive. Some technologies of immobilizing absorbent particulate polymer
material in an
absorbent article add bulk to the absorbent article and thereby increase
thickness, reduce
flexibility, and/or increase cost of the absorbent article. Other technologies
for immobilizing
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absorbent particulate polymer material in an absorbent article may not be as
effective in
maintaining immobilization when the absorbent article is in a wet state as
when in a dry state.
Accordingly, there remains a need for a thin, flexible, and/or inexpensive
absorbent article
containing absorbent particulate polymer material with enhanced immobilization
of the
absorbent particulate polymer material in the article in dry and wet states.
It would be
furthermore desirable to meet this need without reducing, or even while
enhancing, effective
retention of the free liquid exudate before and during absorption by the
absorbent core.
SUMMARY OF THE INVENTION
Embodiments of the invention can address one or more technical problems
described
above and can provide a disposable absorbent garment with absorbent
particulate polymer
material and preformed crotch. In one embodiment, a disposable absorbent
article is provided.
The article can include an absorbent core with a chassis that can include a
topsheet and a
backsheet, with the absorbent core located between the topsheet and the
backsheet. The chassis
may include an absorbent core which includes an absorbent particulate polymer
material, the
absorbent core being located between the topsheet and the backsheet, and
wherein the absorbent
core includes at least one strip extending through a portion of a crotch
region of the article. The
article can also include at least one longitudinally oriented crease passing
through a portion of
the crotch region, wherein a concave shape is formed within the article.
Methods for making the article are also provided.
Other features and advantages of the invention may be apparent from reading
the
following detailed description, drawings, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a plan view of a diaper in accordance with an embodiment of the
invention.
Fig. 2 is a cross sectional view of the diaper shown in Fig. 1 taken along the
sectional
line 2-2 of Fig. 1.
Fig. 3 is an overhead view of an absorbent core layer in accordance with an
embodiment
of the invention.
Fig. 4 is a cross sectional view of an absorbent core layer shown in Fig. 3
taken along the
sectional line 4-4 of Fig. 3.
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Fig. 5 is an overhead view of another absorbent core layer in accordance with
an
embodiment of the invention.
Fig. 6 is a schematic illustration of a process for making an absorbent core
in accordance
with an embodiment of the invention.
Fig. 7 is a partial sectional view of an apparatus for making an absorbent
core in
accordance with an embodiment of the invention.
Fig. 8 is a perspective view of the printing roll illustrated in Fig. 7.
Fig. 9 is a partial sectional view of the printing roll illustrated in Fig. 8
showing an
absorbent particulate polymer material reservoir.
Fig. 10 is a perspective view of the supporting roll illustrated in Fig. 8.
Fig. 11 is a schematic illustration of a process for making a diaper with an
absorbent core
in accordance with an embodiment of the invention
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
As summarized above, embodiments of the invention may encompass an absorbent
article, such as a diaper, having an absorbent core and a preformed crotch.
The combination of
an absorbent core and preformed crotch advantageously may provide the
disposable absorbent
article with improved compressibility, flexibility, and conformity to a
wearer's body for greater
comfort without increasing the likelihood of leakage from the disposable
absorbent article.
Section A below describes terms for assisting the reader in understanding
features of the
invention, but not introducing limitations in the terms inconsistent with the
context with which
they are used in the specification. Section B is a detailed description for
absorbent articles made
in accordance with embodiments of this invention. Section C describes methods
of
manufacturing absorbent cores and absorbent articles in accordance with
embodiments of this
invention.
A. Terms
"Absorbent article" refers to devices that absorb and contain body exudates,
and, more
specifically, refers to devices that are placed against or in proximity to the
body of the wearer to
absorb and contain the various exudates discharged from the body. Absorbent
articles may
include diapers, training pants, adult incontinence undergarments, feminine
hygiene products,
breast pads, care mats, bibs, wound dressing products, and the like. As used
herein, the term
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"body fluids" or "body exudates" includes, but is not limited to, urine,
blood, vaginal discharges,
breast milk, sweat and fecal matter.
"Absorbent core" means a structure typically disposed between a topsheet and
backsheet
of an absorbent article for absorbing and containing liquid received by the
absorbent article and
may comprise one or more substrates, absorbent polymer material disposed on
the one or more
substrates, and a thermoplastic composition on the absorbent particulate
polymer material and at
least a portion of the one or more substrates for immobilizing the absorbent
particulate polymer
material on the one or more substrates. In a multilayer absorbent core, the
absorbent core may
also include a cover layer. The one or more substrates and the cover layer may
comprise a
nonwoven. Further, the absorbent core is substantially cellulose free. The
absorbent core does
not include an acquisition system, a topsheet, or a backsheet of the absorbent
article. In a certain
embodiment, the absorbent core would consist essentially of the one or more
substrates, the
absorbent polymer material, the thermoplastic composition, and optionally the
cover layer.
"Absorbent polymer material," "absorbent gelling material," "AGM,"
"superabsorbent,"
and "superabsorbent material" are used herein interchangeably and refer to
cross linked
polymeric materials that can absorb at least 5 times their weight of an
aqueous 0.9% saline
solution as measured using the Centrifuge Retention Capacity test (Edana 441.2-
01).
"Absorbent particulate polymer material" is used herein to refer to an
absorbent polymer
material which is in particulate form so as to be flowable in the dry state.
"Airfelt" is used herein to refer to comminuted wood pulp, which is a form of
cellulosic
fiber.
"Compressed" or "compression" is used to describe moving fibers or components
of a
material relatively closer together.
"Comprise," "comprising," and "comprises" are open ended terms, each specifies
the
presence of what follows, e.g., a component, but does not preclude the
presence of other
features, e.g., elements, steps, components known in the art, or disclosed
herein.
"Concave" is used herein to describe a curved surface which bends, narrows, or
otherwise slopes slightly inward. Examples of suitable concave shapes can be,
but are not
limited to, a V-shape, a U- shape, and any other similar shape that bends,
narrows, or slopes
slightly inward.
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"Consisting essentially of' is used herein to limit the scope of subject
matter, such as that
in a claim, to the specified materials or steps and those that do not
materially affect the basic and
novel characteristics of the subject matter.
"Disposable" is used in its ordinary sense to mean an article that is disposed
or discarded
after a limited number of usage events over varying lengths of time, for
example, less than about
20 events, less than about 10 events, less than about 5 events, or less than
about 2 events.
"Diaper" refers to an absorbent article generally worn by infants and
incontinent persons
about the lower torso so as to encircle the waist and legs of the wearer and
that is specifically
adapted to receive and contain urinary and fecal waste. As used herein, term
"diaper" also
includes "pants" which is defined below.
"Elastic", "elastically extensible", and "elasticized" refer herein to the
property of a
material and/or an element of a diaper or other disposable absorbent article
whereby the material
and/or the element can be elongated to at least 150% of its original
unstretched length without
rupture or catastrophic failure upon the application of tensioning force and
will substantially
return to its original length or near its original length after the tension is
released.
"Fiber" and "filament" are used interchangeably.
A "nonwoven" is a manufactured sheet, web or batt of directionally or randomly
orientated fibers, bonded by friction, and/or cohesion and/or adhesion,
excluding paper and
products which are woven, knitted, tufted, stitch-bonded incorporating binding
yarns or
filaments, or felted by wet-milling, whether or not additionally needled. The
fibers may be of
natural or man-made origin and may be staple or continuous filaments or be
formed in situ.
Commercially available fibers have diameters ranging from less than about
0.001 mm to more
than about 0.2 mm and they come in several different forms: short fibers
(known as staple, or
chopped), continuous single fibers (filaments or monofilaments), untwisted
bundles of
continuous filaments (tow), and twisted bundles of continuous filaments
(yarn). Nonwoven
fabrics can be formed by many processes such as meltblowing, spunbonding,
solvent spinning,
electrospinning, and carding. The basis weight of nonwoven fabrics is usually
expressed in
grams per square meter (gsm).
"Pant" or "training pant", as used herein, refer to disposable garments having
a waist
opening and leg openings designed for infant or adult wearers. A pant may be
placed in position
on the wearer by inserting the wearer's legs into the leg openings and sliding
the pant into
position about a wearer's lower torso. A pant may be preformed by any suitable
technique
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including, but not limited to, joining together portions of the article using
refastenable and/or
non-refastenable bonds (e.g., seam, weld, adhesive, cohesive bond, fastener,
etc.). A pant may
be preformed anywhere along the circumference of the article (e.g., side
fastened, front waist
fastened). While the terms "pant" or "pants" are used herein, pants are also
commonly referred
to as "closed diapers," "prefastened diapers," "pull-on diapers," "training
pants," and "diaper-
pants". Suitable pants are disclosed in U.S. Patent No. 5,246,433, issued to
Hasse, et al. on
September 21, 1993; U.S. Patent No. 5,569,234, issued to Buell et al. on
October 29, 1996; U.S.
Patent No. 6,120,487, issued to Ashton on September 19, 2000; U.S. Patent No.
6,120,489,
issued to Johnson et al. on September 19, 2000; U.S. Patent No. 4,940,464,
issued to Van
Gompel et al. on July 10, 1990; U.S. Patent No. 5,092,861, issued to Nomura et
al. on March 3,
1992; U.S. Patent Publication No. 2003/0233082 Al, entitled "Highly Flexible
And Low
Deformation Fastening Device", filed on June 13, 2002; U.S. Patent No.
5,897,545, issued to
Kline et al. on April 27, 1999; U.S. Patent No. 5,957,908, issued to Kline et
al on September 28,
1999.
"Substantially cellulose free" is used herein to describe an article, such as
an absorbent
core, that contains less than 10% by weight cellulosic fibers, less than 5%
cellulosic fibers, less
than 1% cellulosic fibers, no cellulosic fibers, or no more than an immaterial
amount of
cellulosic fibers. An immaterial amount of cellulosic material would not
materially affect the
thinness, flexibility, or absorbency of an absorbent core.
"Thermoplastic adhesive material" as used herein is understood to comprise a
polymer
composition from which fibers are formed and applied to the superabsorbent
material with the
intent to immobilize the superabsorbent material in both the dry and wet
state. The
thermoplastic adhesive material of the present invention forms a fibrous
network over the
superabsorbent material.
"Thickness" and "caliper" are used herein interchangeably. B. Absorbent
Articles
Fig. 1 is a plan view of a diaper 10 according to a certain embodiment of the
invention.
The diaper 10 is shown in its flat out, uncontracted state (i.e., without
elastic induced
contraction) and portions of the diaper 10 are cut away to more clearly show
the underlying
structure of the diaper 10. A portion of the diaper 10 that contacts a wearer
is facing the viewer
in Fig. 1. The diaper 10 generally may comprise a chassis 12 and an absorbent
core 14 disposed
in the chassis. The absorbent core 14 may include one or more strips 15. The
strip 15 may be a
discontinuity in a homogeneous member produced by cutting, adhering, shearing,
leaving a gap,
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perforation, compressing, or any other method of creating a discontinuity. In
a certain
embodiment, the absorbent core 14 may include one or more compressed strips
15. The
compressed strip 15 can be provided by way of mechanical or pressurized
compression of a
selected portion of the absorbent core 14.
As shown in Figs. 3 and 4, the absorbent core 14 can include at least one
compressed
strip 15 generally positioned in a central portion of the core 14. The
compressed strip 15 shown
is generally aligned parallel with and along the transverse axis 100 of the
absorbent core 14. As
shown in Fig. 4, which is a sectional view taken along sectional line 4-4 in
Fig. 3, the
compressed strip 15 is a slightly compressed portion of the absorbent core 14
relative to the
other, non-compressed material comprising the absorbent core 14. In other
certain
embodiments, a compressed strip can be offset from the transverse axis 100
and/or may be
segmented into multiple parts. The compressed strip 15 shown can be made, for
example, by
nip rolls. In certain other embodiments, for example in FIG. 5, an absorbent
core 14 can include
more than one compressed strip, for instance, two compressed strips 102 and
104 generally
aligned parallel with and along the transverse axis 100 of the absorbent core
14.
The chassis 12 of the diaper 10 in Fig. 1 may comprise the main body of the
diaper 10.
The chassis 12 may comprise an outer covering 16 including a topsheet 18,
which may be liquid
pervious, and/or a backsheet 20, which may be liquid impervious. The absorbent
core 14 may
be encased between the topsheet 18 and the backsheet 20. The chassis 12 may
also include side
panels 22, elasticized leg cuffs 24, and an elastic waist feature 26.
The leg cuffs 24 and the elastic waist feature 26 may each typically comprise
elastic
members 28. One end portion of the diaper 10 may be configured as a first
waist region 30 of
the diaper 10. An opposite end portion of the diaper 10 may be configured as a
second waist
region 32 of the diaper 10. An intermediate portion of the diaper 10 may be
configured as a
crotch region 34, which extends longitudinally between the first and second
waist regions 30 and
32. The waist regions 30 and 32 may include elastic elements such that they
gather about the
waist of the wearer to provide improved fit and containment (elastic waist
feature 26). The
crotch region 34 is that portion of the diaper 10 which, when the diaper 10 is
worn, is generally
positioned between the wearer's legs.
The diaper 10 is depicted in Fig. 1 with its longitudinal axis 36 and its
transverse axis 38.
The periphery 40 of the diaper 10 is defined by the outer edges of the diaper
10 in which the
longitudinal edges 42 run generally parallel to the longitudinal axis 36 of
the diaper 10 and the
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end edges 44 run between the longitudinal edges 42 generally parallel to the
transverse axis 38
of the diaper 10. The chassis 12 may also comprise a fastening system, which
may include at
least one fastening member 46 and at least one stored landing zone 48.
In certain embodiments, an absorbent core 14 can include a compressed strip 15
oriented
substantially parallel with the longitudinal axis 36 of the absorbent core 14.
The length of the
compressed strip 15 can, for example, generally extend within or through the
crotch region 34 of
the absorbent core 14, and substantially between end edges 44 of the diaper
10. In certain
embodiments, for example shown in Fig. 5, multiple compressed strips 102, 104
can be oriented
substantially parallel with the longitudinal axis 36 of the absorbent core 14.
The lengths of
multiple compressed strips 102, 104 can, for example, generally extend within
or through the
central region of the absorbent core 14, and substantially between end edges
44 of the diaper 10.
Each of the multiple compressed strips 102, 104 could have similar or
different lengths. In any
embodiment, a compressed strip 15 can be provided in the absorbent core 14 by
way of
mechanical or pressurized compression of a selected portion of the absorbent
core 14.
The diaper 10 shown in Fig. 1 can also include one or more creases 49 oriented
substantially parallel with the longitudinal axis 36 and extending
substantially between the end
edges 44. In certain embodiments, one or more creases can extend in directions
generally along
the longitudinal axis 36, or may extend partially between the end edges 44. In
certain other
embodiments, one or more creases can include multiple creases oriented
substantially parallel
with the longitudinal axis 36 and extending substantially between the end
edges 44. In other
certain embodiments, one or more creases can be slightly offset from the
transverse axis 100
and/or each crease may be segmented into multiple parts. As shown in the
embodiment of Fig.
1, the crease 49 can extend substantially through the compressed strip 15. In
certain
embodiments, a crease 49 can extend substantially through multiple compressed
strips, or in
some certain embodiments, a crease may extend adjacent to multiple compressed
strips.
For certain embodiments when the absorbent core 14 may be relatively
incompressible,
such as an airfelt free core, i.e. with little or no wood pulp or cellulosic
material, a crease 49 can
include an auxiliary adhesive which is not illustrated in the figures. The
auxiliary adhesive may
be deposited in the crease 49 when the diaper 10 is folded or compressed along
the crease 49.
The auxiliary glue may aid in maintaining the relative shape of the crease 49
in the diaper 10.
An auxiliary adhesive can include, but is not limited to, sprayable hot melt
adhesives, such as
H.B. Fuller Co. (St. Paul, MN) Product No. HL-1620-B.
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The diaper 10 may also include such other features as are known in the art
including
front and rear ear panels, waist cap features, elastics and the like to
provide better fit,
containment and aesthetic characteristics. Such additional features are well
known in the art and
are e.g., described in U.S. Pat. No. 3,860,003 and U.S. Pat. No. 5,151,092.
In order to keep the diaper 10 in place about the wearer, at least a portion
of the first
waist region 30 may be attached by the fastening member 46 to at least a
portion of the second
waist region 32 to form leg opening(s) and an article waist. When fastened,
the fastening system
carries a tensile load around the article waist. The fastening system may
allow an article user to
hold one element of the fastening system, such as the fastening member 46, and
connect the first
waist region 30 to the second waist region 32 in at least two places. This may
be achieved
through manipulation of bond strengths between the fastening device elements.
According to certain embodiments, the diaper 10 may be provided with a re-
closable
fastening system or may alternatively be provided in the form of a pant-type
diaper. When the
absorbent article is a diaper, it may comprise a re-closable fastening system
joined to the chassis
for securing the diaper to a wearer. When the absorbent article is a pant-type
diaper, the article
may comprise at least two side panels joined to the chassis and to each other
to form a pant. The
fastening system and any component thereof may include any material suitable
for such a use,
including but not limited to plastics, films, foams, nonwoven, woven, paper,
laminates, fiber
reinforced plastics and the like, or combinations thereof. In certain
embodiments, the materials
making up the fastening device may be flexible. The flexibility may allow the
fastening system
to conform to the shape of the body and thus, reduce the likelihood that the
fastening system will
irritate or injure the wearer's skin.
For unitary absorbent articles, the chassis 12 and absorbent core 14 may form
the main
structure of the diaper 10 with other features added to form the composite
diaper structure.
While the topsheet 18, the backsheet 20, and the absorbent core 14 may be
assembled in a
variety of well-known configurations, exemplary diaper configurations are
described generally
in U.S. Pat. No. 5,554,145 entitled "Absorbent Article With Multiple Zone
Structural Elastic-
Like Film Web Extensible Waist Feature" issued to Roe et al. on Sep. 10, 1996;
U.S. Pat. No.
5,569,234 entitled "Disposable Pull-On Pant" issued to Buell et al. on Oct.
29, 1996; and U.S.
Pat. No. 6,004,306 entitled "Absorbent Article With Multi-Directional
Extensible Side Panels"
issued to Robles et al. on Dec. 21, 1999.
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The topsheet 18 in Fig. 1 may be fully or partially elasticized or may be
foreshortened to
provide a void space between the topsheet 18 and the absorbent core 14.
Exemplary structures
including elasticized or foreshortened topsheets are described in more detail
in U.S. Pat. No.
5,037,416 entitled "Disposable Absorbent Article Having Elastically Extensible
Topsheet"
issued to Allen et al. on Aug. 6, 1991; and U.S. Pat. No. 5,269,775 entitled
"Trisection
Topsheets for Disposable Absorbent Articles and Disposable Absorbent Articles
Having Such
Trisection Topsheets" issued to Freeland et al. on Dec. 14, 1993.
The backsheet 26 may be joined with the topsheet 18. The backsheet 20 may
prevent the
exudates absorbed by the absorbent core 14 and contained within the diaper 10
from soiling
other external articles that may contact the diaper 10, such as bed sheets and
undergarments. In
certain embodiments, the backsheet 26 may be substantially impervious to
liquids (e.g., urine)
and comprise a laminate of a nonwoven and a thin plastic film such as a
thermoplastic film
having a thickness of about 0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils).
Suitable
backsheet films include those manufactured by Tredegar Industries Inc. of
Terre Haute, Ind. and
sold under the trade names X15306, X10962, and X10964. Other suitable
backsheet materials
may include breathable materials that permit vapors to escape from the diaper
10 while still
preventing exudates from passing through the backsheet 10. Exemplary
breathable materials
may include materials such as woven webs, nonwoven webs, composite materials
such as film-
coated nonwoven webs, and microporous films such as manufactured by Mitsui
Toatsu Co., of
Japan under the designation ESPOIR NO and by EXXON Chemical Co., of Bay City,
Tex.,
under the designation EXXAIRE. Suitable breathable composite materials
comprising polymer
blends are available from Clopay Corporation, Cincinnati, Ohio under the name
HYTREL blend
P18-3097. Such breathable composite materials are described in greater detail
in PCT
Application No. WO 95/16746, published on Jun. 22, 1995 in the name of E.I.
DuPont. Other
breathable backsheets including nonwoven webs and apertured formed films are
described in
U.S. Pat. No. 5,571,096 issued to Dobrin et al. on Nov. 5, 1996.
In certain embodiments, the backsheet of the present invention may have a
water vapor
transmission rate (WVTR) of greater than about 2000 g/24h/m2, greater than
about 3000
g/24h/m2, greater than about 5000 g/24h/m2, greater than about 6000 g/24h/m2,
greater than
about 7000 g/24h/m2, greater than about 8000 g/24h/m2, greater than about 9000
g/24h/m2,
greater than about 10000 g/24h/m2, greater than about 11000 g/24h/m2, greater
than about 12000
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g/24h/m2, greater than about 15000 g/24h/m2, measured according to WSP 70.5
(08) at 37.8 C
and 60% Relative Humidity.
Fig. 2 shows a cross section of Fig. 1 taken along the sectional line 2-2 of
Fig. 1.
Starting from the wearer facing side 56, the diaper 10 may comprise the
topsheet 18, the
components of the absorbent core 14, and the backsheet 20. As shown in Figs. 1
and 2, the
diaper 10 can include at least one compressed strip 15 aligned with a crease
49, which together
can cooperate to facilitate formation of a concave shape 58 in the diaper 10.
The concave shape
is also known as a "preformed concave shape" or "preformed shaped" since the
concave shape is
formed in the diaper 10 prior to use of the diaper 10 by a wearer. The concave
shape 58 can
have the shape of a slight trough oriented generally in the crotch region 34
of the diaper 10. In
certain embodiments, a diaper with a preformed concave shape can relatively
increase bucket
volume over conventional diapers. This aspect may be attributed to the concave
shape 58 which
can generally receive fluids or liquid exudates within the cavity of the
concave shape 58.
Furthermore, a diaper with a concave shape can have improved fit between a
wearer's legs. This
aspect may be attributed to the concave shape 58 which generally conforms with
the shape of a
wearer's body, and thus reduces the relative amount of the diaper 10 which may
not conform
with the wearer's body.
In certain embodiments, a concave shape can be a concave V-shape. In other
certain
embodiments, a concave shape can be a concave U-shape. In certain other
embodiments, a
concave shape can be a surface that bends, narrows, or slopes slightly inward.
According to a certain embodiment, diaper 10 may also comprise an acquisition
system
50 disposed between the liquid permeable topsheet 18 and a wearer facing side
of the absorbent
core 14. The acquisition system shown in Fig. 1 can include an upper
acquisition layer 52 and a
lower acquisition layer 54. The acquisition system 50 may, for example,
comprise chemically
cross-linked cellulosic fibers. Such cross-linked cellulosic fibers may have
desirable absorbency
properties. Exemplary chemically cross-linked cellulosic fibers are disclosed
in US Patent No.
5,137,537. In certain embodiments, the chemically cross-linked cellulosic
fibers are cross-
linked with between about 0.5 mole % and about 10.0 mole % of a C2 to C9
polycarboxylic
cross-linking agent or between about 1.5 mole % and about 6.0 mole % of a C2
to C9
polycarboxylic cross-linking agent based on glucose unit. Citric acid is an
exemplary cross-
linking agent. In other embodiments, polyacrylic acids may be used. Further,
according to
certain embodiments, the cross-linked cellulosic fibers have a water retention
value of about 25
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to about 60, or about 28 to about 50, or about 30 to about 45. A method for
determining water
retention value is disclosed in US Patent No. 5,137,537. According to certain
embodiments, the
cross-linked cellulosic fibers may be crimped, twisted, or curled, or a
combination thereof
including crimped, twisted, and curled.
In a certain embodiment, the acquisition system 50 may comprise a non-woven,
which
may be hydrophilic. Further, according to a certain embodiment, the
acquisition system 50 may
comprise the chemically cross-linked cellulosic fibers, which may or may not
form part of a
nonwoven material. According to another embodiment, the acquisition system 50
may comprise
a combination of nonwovens, at least one nonwoven without the cross-linked
cellulosic fibers
and at least one nonwoven with chemically cross-linked cellulosic fibers.
Further, according to
an embodiment, the acquisition system 50 may comprise the chemically cross-
linked cellulosic
fibers mixed with other fibers such as natural or synthetic polymeric fibers.
According to other
embodiments, such other natural or synthetic polymeric fibers may include high
surface area
fibers, thermoplastic binding fibers, polyethylene fibers, polypropylene
fibers, PET fibers, rayon
fibers, lyocell fibers, and mixtures thereof.
According to a certain embodiment, the acquisition system 50 desirably has a
high fluid
uptake capability. Fluid uptake is measured in grams of absorbed fluid per
gram of absorbent
material and is expressed by the value of "maximum uptake." A high fluid
uptake corresponds
therefore to a high capacity of the material and is beneficial, because it
ensures the complete
acquisition of fluids to be absorbed by an acquisition material.
A relevant attribute of the acquisition system 50 is its Median Desorption
Pressure,
MDP. The MDP is a measure of the capillary pressure that is required to
dewater the lower
acquisition layer 54 to about 50% of its capacity at 0 cm capillary suction
height under an
applied mechanical pressure of 0.3psi. Generally, a relatively lower MDP may
be useful. The
methods for determining MDP and maximum uptake are disclosed in U.S. Patent
Application
11/600,691 (Flohr et al.).
Suitable non-woven materials for the acquisition system 50 can include, but
are not
limited to SMS material, comprising a spunbonded, a melt-blown and a further
spunbonded
layer. In certain embodiments, permanently hydrophilic non-wovens, and in
particular,
nonwovens with durably hydrophilic coatings are desirable. Another suitable
embodiment
comprises a SMMS-structure. In certain embodiments, the non-wovens are porous.
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In certain embodiments, suitable non-woven materials may include, but are not
limited to
synthetic fibers, such as PE, PET, and PP. As polymers used for nonwoven
production may be
inherently hydrophobic, they may be coated with hydrophilic coatings. One way
to produce
nonwovens with durably hydrophilic coatings, is via applying a hydrophilic
monomer and a
radical polymerization initiator onto the nonwoven, and conducting a
polymerization activated
via UV light resulting in monomer chemically bound to the surface of the
nonwoven as
described in co-pending U.S. Patent Publication No. 2005/0159720. Another way
to produce
nonwovens with durably hydrophilic coatings is to coat the nonwoven with
hydrophilic
nanoparticles as described in co-pending applications U.S. Patent No.
7,112,621 to Rohrbaugh et
al. and in PCT Application Publication WO 02/064877.
Typically, nanoparticles have a largest dimension of below 750 nm.
Nanoparticles with
sizes ranging from 2 to 750 nm may be economically produced. An advantage of
nanoparticles
is that many of them can be easily dispersed in water solution to enable
coating application onto
the nonwoven, they typically form transparent coatings, and the coatings
applied from water
solutions are typically sufficiently durable to exposure to water.
Nanoparticles can be organic or
inorganic, synthetic or natural. Inorganic nanoparticles generally exist as
oxides, silicates,
and/or, carbonates. Typical examples of suitable nanoparticles are layered
clay minerals (e.g.,
LAPONITETM from Southern Clay Products, Inc. (USA), and Boehmite alumina
(e.g., Disperal
P2TM from North American Sasol. Inc.). According to a certain embodiment, a
suitable
nanoparticle coated non-woven is that disclosed in the co-pending patent
application Ser. No.
10/758,066 entitled "Disposable absorbent article comprising a durable
hydrophilic core wrap"
to Ekaterina Anatolyevna Ponomarenko and Mattias NMN Schmidt.
Further useful non-wovens are described in U.S. Pat. No. 6,645,569 to Cramer
et al.,
U.S. Patent No. 6,863,933 to Cramer et al., U.S. Patent No. 7,112,621 to
Rohrbaugh et al., and
co-pending patent applications 10/338,603 to Cramer et al. and 10/338,610 to
Cramer et al.
In some cases, the nonwoven surface can be pre-treated with high energy
treatment
(corona, plasma) prior to application of nanoparticle coatings. High energy
pre-treatment
typically temporarily increases the surface energy of a low surface energy
surface (such as PP)
and thus enables better wetting of a nonwoven by the nanoparticle dispersion
in water.
Notably, permanently hydrophilic non-wovens are also useful in other parts of
an
absorbent article. For example, topsheets and absorbent core layers comprising
permanently
hydrophilic non-wovens as described above have been found to work well.
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In certain embodiments, the absorbent core 14 may further comprise any
absorbent
material that is generally compressible, conformable, non-irritating to the
wearer's skin, and
capable of absorbing and retaining liquids such as urine and other certain
body exudates. In
such embodiments, the absorbent core 14 may comprise a wide variety of liquid-
absorbent
materials commonly used in disposable diapers and other absorbent articles
such as comminuted
wood pulp, which is generally referred to as airfelt, creped cellulose
wadding, melt blown
polymers, including co-form, chemically stiffened, modified or cross-linked
cellulosic fibers,
tissue, including tissue wraps and tissue laminates, absorbent foams,
absorbent sponges, or any
other known absorbent material or combinations of materials. The absorbent
core 14 may
further comprise minor amounts (typically less than about 10%) of materials,
such as adhesives,
waxes, oils and the like.
Exemplary absorbent structures for use as the absorbent assemblies are
described in U.S.
Pat. No. 4,610,678 (Weisman et al.); U.S. Pat. No. 4,834,735 (Alemany et al.);
U.S. Pat. No.
4,888,231 (Angstadt); U.S. Pat. No. 5,260,345 (DesMarais et al.); U.S. Pat.
No. 5,387,207 (Dyer
et al.); U.S. Pat. No. 5,397,316 (LaVon et al.); and U.S. Pat. No. 5,625,222
(DesMarais et al.).
C. Methods For Making Absorbent Articles
A printing system 130 for making an absorbent core 14 for a diaper 10 in
accordance
with an embodiment of the invention is illustrated in Fig. 6. The printing
system 130 may
generally comprise a first printing unit 132 for forming a first absorbent
layer 60 of the
absorbent core 14 and a second printing unit 134 for forming a second
absorbent layer 62 of the
absorbent core 14.
The first printing unit 132 may comprise a first auxiliary adhesive applicator
136 for
applying an auxiliary adhesive to a substrate 64, which may be a nonwoven web,
a first rotatable
support roll 140 for receiving the substrate 64, a hopper 142 for holding
absorbent particulate
polymer material 66, a printing roll 144 for transferring the absorbent
particulate polymer
material 66 to the substrate 64, and a thermoplastic adhesive material
applicator 146 for
applying a thermoplastic adhesive material 68 to the substrate 64 and the
absorbent particulate
polymer 66 material thereon.
The second printing unit 134 may comprise a second auxiliary adhesive
applicator 148
for applying an auxiliary adhesive to a second substrate 72, a second
rotatable support roll 152
for receiving the second substrate 72, a second hopper 154 for holding an
absorbent particulate
polymer material 74, a second printing roll 156 for transferring the absorbent
particulate
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polymer material 74 from the hopper 154 to the second substrate 72, and a
second thermoplastic
adhesive material applicator 158 for applying a thermoplastic adhesive
material 76 to the second
substrate 72 and the absorbent particulate polymer material 74 thereon.
The printing system 130 also includes a guide roller 160 for guiding the
formed
absorbent core from a nip 162 between first and second rotatable support rolls
140 and 152.
The first and second auxiliary applicators 136 and 148 and the first and
second
thermoplastic adhesive material applicators 146 and 158 may be a nozzle system
which can
provide a relatively thin but wide curtain of thermoplastic adhesive material.
Turning to Fig. 7, portions of the first hopper 142, first support roll 140,
and first printing
roll 144 are illustrated. As also shown in Fig. 10, the first rotatable
support roll 140, which has
the same structure as the second rotatable support roll 152, comprises a
rotatable drum 164 and a
peripheral vented support grid 166 for receiving the first substrate 64.
As also illustrated in Fig. 8, the first printing roll 144, which has the same
structure as
the second printing roll 156, comprises a rotatable drum 168 and a plurality
of absorbent
particulate polymer material reservoirs 170 in a peripheral surface 172 of the
drum 168. The
reservoirs 170 best illustrated in Fig. 9, may have a variety of shapes, but
in a particular
embodiment, are conical. The reservoirs 170 may lead to an air passage 174 in
the drum 168
and comprise a vented cover 176 for holding adhesive particulate polymer
material 66 in the
reservoir and preventing the adhesive particulate polymer material 66 from
falling or being
pulled into the air passage 174.
A second nip 163 between first and second rotatable compression rolls 165 and
167 can
form one or more compression strips, such as 15 in Fig. 1, in the absorbent
core 14. In a certain
embodiment, the compression rolls 165 and 167 may be a suitable width for
forming a similarly
sized compression strip in the absorbent core 14. In other certain
embodiments, at least one of
the compression rolls 165 and 167 may include a suitable pattern for forming a
correspondingly
sized compression strip in the absorbent core 14. In yet other certain
embodiments, one or more
jets of pressurized air or another medium could be used to form at least one
compression strip in
the absorbent core 14.
In operation, the printing system 130 receives the first and second substrate
64 and 72
into the first and second printing units 132 and 134, respectively, the first
substrate 64 is drawn
by the rotating first support roll 140 past the first auxiliary adhesive
applicator 136 which
applies the first auxiliary adhesive to the first substrate 64 in a pattern
such as described
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hereinabove. A vacuum (not shown) within the first support roll 140 draws the
first substrate 64
against the vertical support grid 166 and holds the first substrate 64 against
the first support roll
140. This presents an uneven surface on the first substrate 64. Due to
gravity, or by using the
vacuum means, the substrate 64 will follow the contours of the uneven surface
and thereby the
substrate 64 will assume a mountain and valley shape. The absorbent
particulate polymer
material 66 may accumulate in the valleys presented by the substrate 64. The
first support roll
140 then carries the first substrate 64 past the rotating first printing roll
144 which transfers the
absorbent particulate polymer material 66 from the first hopper 142 to the
first substrate 64 in a
grid pattern 92. A vacuum (not shown) in the first printing roll 144 may hold
the absorbent
particulate polymer material 66 in the reservoirs 170 until time to deliver
the absorbent
particulate polymer material 66 to the first substrate 64. The vacuum may then
be released or air
flow through the air passages 174 may be reversed to eject the absorbent
particulate polymer
material 66 from the reservoirs and onto the first substrate 64. The absorbent
particulate polymer
material 66 may accumulate in the valleys presented by the substrate 64. The
support roll 140
then carries the printed first substrate 64 past the thermoplastic adhesive
material applicator 136
which applies the thermoplastic adhesive material 68 to encase the absorbent
particulate polymer
material 66 on the first substrate 64.
Hence, the uneven surface of the vented support grid 166 of the support rolls
140 and
152 determines the distribution of absorbent particulate polymeric material 66
and 74
throughout the absorbent core 14 and likewise determines the pattern of
junction areas.
Meanwhile, the second rotatable support roll draws the second substrate 72
past the
second auxiliary adhesive applicator 148 which applies an auxiliary adhesive
to the second
substrate 72 in any predefined pattern. The second rotatable support roll 152
then carries the
second substrate 72 past the second printing roll 156 which transfers the
absorbent particulate
polymer material 74 from the second hopper 154 to the second substrate 72 and
deposits the
absorbent particulate polymer material 74 in a grid pattern on the second
substrate 72 in the
same manner as described with regard to the first printing unit 132 above. The
second
thermoplastic adhesive material applicator 158 then applies the thermoplastic
adhesive material
76 to encase the absorbent particulate polymer material 74 on the second
substrate 72. The
printed first and second substrates 64 and 72 then pass through the nip 162
between the first and
second support rolls 140 and 152 for compressing the first absorbent layer 60
and second
absorbent layer 62 together to form the absorbent core 14. The absorbent core
14 then passes
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through nip 163 between the first and second compression rolls 165 and 167 for
forming at least
one compression strip in the absorbent core 14. As needed, various lengths of
the absorbent
core 14 can be cut into predefined sections for use in an absorbent article,
such as a diaper 10.
In a further process step, an outer covering 16 may be placed upon or
otherwise
combined with the substrates 64 and 72, the absorbent particulate polymer
material 66 and 74,
and the thermoplastic adhesive material 68 and 76. In another embodiment, the
outer covering
16 and the respective substrate 64 and 72 may be provided from a unitary sheet
of material.
As shown in Fig. 11, after the formed absorbent core 14 is combined with the
outer
covering 16, the unfinished diaper 200 can be fed to a folding device 202 or
process, wherein the
unfinished diaper 200 is folded and compressed. In a certain embodiment, the
unfinished diaper
200 is folded and compressed along a longitudinal axis 204, similar to 36 in
Fig. 1, wherein at
least one crease 206 can be formed in the diaper 208. In certain other
embodiments, an
unfinished diaper 200 can be folded and compressed along one or more lines
substantially
parallel with the longitudinal axis 204, wherein a corresponding number of
creases can be
formed in the diaper. When unfolded, the diaper 208 can include a preformed
concave V-shape,
similar to 58 shown in Fig. 2, within the crotch region of the diaper 208.
For certain embodiments when the absorbent core 14 may be relatively
incompressible,
such as an airfelt free core, i.e. with little or no wood pulp or cellulosic
material, an auxiliary
adhesive can be applied to any portion of the crease 206 by an adhesive
application device 210.
The auxiliary adhesive may be deposited in the crease 206 when the diaper 208
is folded or
compressed along the crease 206 by the folding device 202 or process. The
auxiliary adhesive
may aid in maintaining the relative shape of the crease 206 in the diaper 208.
All patents and patent applications (including any patents which issue
thereon) assigned
to the Procter & Gamble Company referred to herein are hereby incorporated by
reference to the
extent that it is consistent herewith.
The dimensions and values disclosed herein are not to be understood as being
strictly
limited to the exact numerical values recited. Instead, unless otherwise
specified, each such
dimension is intended to mean both the recited value and a functionally
equivalent range
surrounding that value. For example, a dimension disclosed as "40 mm" is
intended to mean
"about 40 mm."
All documents cited in the Detailed Description of the Invention are, in
relevant part,
incorporated herein by reference; the citation of any document is not to be
construed as an
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admission that it is prior art with respect to the present invention. To the
extent that any
meaning or definition of a term in this document conflicts with any meaning or
definition of the
same term in a document incorporated by reference, the meaning or definition
assigned to that
term in this document shall govern.
While particular embodiments of the present invention have been illustrated
and
described, it would be obvious to those skilled in the art that various other
changes and
modifications can be made without departing from the spirit and scope of the
invention. It is
therefore intended to cover in the appended claims all such changes and
modifications that are
within the scope of this invention.
