U.S. patent application number 15/627494 was filed with the patent office on 2017-10-05 for absorbent core with high superabsorbent material content.
The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to Blanca ARIZTI, Ernesto BIANCHI, Bruno Johannes EHRNSPERGER, Hans Adolf JACKELS, Carsten Heinrich KREUZER, Rodrigo ROSATI.
Application Number | 20170281426 15/627494 |
Document ID | / |
Family ID | 47294799 |
Filed Date | 2017-10-05 |
United States Patent
Application |
20170281426 |
Kind Code |
A1 |
ARIZTI; Blanca ; et
al. |
October 5, 2017 |
ABSORBENT CORE WITH HIGH SUPERABSORBENT MATERIAL CONTENT
Abstract
An absorbent core includes a core wrap enclosing an absorbent
material, and one or more channels extending from the crotch region
to the back region. The core wrap is at least partially sealed. The
absorbent core has a Wet Compression Force of about 5N or less.
Inventors: |
ARIZTI; Blanca; (Frankfurt
am Main, DE) ; BIANCHI; Ernesto; (Oberursel, DE)
; EHRNSPERGER; Bruno Johannes; (Bad Soden, DE) ;
JACKELS; Hans Adolf; (Mechernich, DE) ; KREUZER;
Carsten Heinrich; (Hofheim, DE) ; ROSATI;
Rodrigo; (Frankfurt am Main, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company |
Cincinnati |
OH |
US |
|
|
Family ID: |
47294799 |
Appl. No.: |
15/627494 |
Filed: |
June 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14100062 |
Dec 9, 2013 |
9713556 |
|
|
15627494 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 13/539 20130101;
A61F 13/4942 20130101; A61F 13/538 20130101; A61F 13/532
20130101 |
International
Class: |
A61F 13/538 20060101
A61F013/538; A61F 13/539 20060101 A61F013/539; A61F 13/532 20060101
A61F013/532; A61F 13/494 20060101 A61F013/494 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2012 |
EP |
12196343.3 |
Claims
1. An absorbent core, wherein the absorbent core comprises a core
wrap enclosing an absorbent material; a front edge, a back edge,
two longitudinal edges, a front region, a back region and a crotch
region, the absorbent core having a longitudinal axis oriented in a
longitudinal direction, and a length (L) as measured between the
front edge and back edge along the longitudinal axis which is at
least 320 mm; at least a pair of channels symmetrically disposed
relative to the longitudinal axis of the core, wherein neither
channel coincides with the longitudinal axis and wherein the
channels are substantially free of the absorbent material, and
wherein the channels extend from the crotch region into the back
region; wherein the absorbent core has a Wet Compression Force of
about 5.0 N or less; and wherein the core wrap is at least
partially sealed along the edges of the core.
2. The absorbent core of claim 1, wherein at least one channel has
a length projected on the longitudinal axis of the core which is at
least 10% of the length L of the absorbent core.
3. The absorbent core according claim 1, wherein at least one
channel is comprises a width of at least about 2 mm.
4. The absorbent core of claim 1, wherein the absorbent material
comprises less than about 10% of natural or synthetic fibers by
total weight of the absorbent material.
5. The absorbent core of claim 1, wherein the first substrate
comprises a first nonwoven and the second substrate comprises a
second nonwoven, and wherein the first nonwoven forms a C-wrap
around the second nonwoven.
6. The absorbent core of claim 1, wherein the absorbent material
defines an absorbent material deposition area within the core wrap,
wherein the absorbent material deposition area is rectangular or
shaped with a width having a minimum in the crotch region.
7. The absorbent core of claim 6, wherein the basis weight of the
superabsorbent polymers is not homogenously distributed along the
longitudinal axis of the core, and wherein the basis weight of the
superabsorbent polymers is at least 10% percent higher at the
crotch point of the core than at another point of the absorbent
material deposition area on the longitudinal axis.
8. The absorbent core of claim 1 wherein the absorbent material is
at least partially immobilized on the core wrap.
9. The absorbent core of claim 1 comprising a first absorbent layer
and a second absorbent layer, wherein the first absorbent layer
comprises a first substrate and a first layer of superabsorbent
polymers, wherein the second absorbent layer comprises a second
substrate and a second layer of superabsorbent polymers.
10. The absorbent core of claim 1 wherein the Wet Compression Force
from about 1.00 N to about 3.00 N.
11. The absorbent core of claim 1, comprising from about 5 g to
about 60 g of superabsorbent polymers.
12. An absorbent article comprising: a liquid permeable topsheet, a
liquid impermeable backsheet, and an absorbent core positioned
between the topsheet and the backsheet; wherein the absorbent core
comprises the absorbent core of claim 1.
13. The absorbent core of claim 1, wherein the caliper of the core,
as measured at the crotch point, is from about 0.25 mm to about 5.0
mm.
14. An absorbent core, wherein the absorbent core comprises a core
wrap enclosing an absorbent material; the absorbent core comprising
a front edge, a back edge, two longitudinal edges, a front region,
a back region and a crotch region, the absorbent core having a
longitudinal axis oriented in a longitudinal direction, and a
length (L) as measured between the front edge and back edge along
the longitudinal axis which is at least 320 mm; at least a pair of
channels symmetrically disposed relative to the longitudinal axis
of the core, wherein neither channel coincides with the
longitudinal axis and wherein the channels are substantially free
of the absorbent material, and wherein the channels extend from the
crotch region into the back region; wherein the absorbent core has
a Relative Wet Caliper Increase (RWCI) after compression of less
than 10.0%; and wherein the core wrap is at least partially sealed
along the edges of the core.
15. The absorbent core of claim 14, wherein the absorbent material
comprises at least about 90% of the superabsorbent polymers by
total weight of the absorbent material.
16. The absorbent core of claim 14, wherein the absorbent material
is substantially free of natural or synthetic fibers.
17. The absorbent core of claim 14, comprising from about 5 g to
about 60 g of superabsorbent polymers.
18. The absorbent core of claim 14, wherein the caliper of the
core, as measured at the crotch point, is from about 0.25 mm to
about 5.0 mm.
19. The absorbent core of claim 14 further comprising a Wet
Compression Force of about 5 N or less.
20. An absorbent article comprising: a liquid permeable topsheet, a
liquid impermeable backsheet, and an absorbent core positioned
between the topsheet and the backsheet; wherein the absorbent core
comprises the absorbent core of claim 14.
Description
FIELD OF THE INVENTION
[0001] The invention is for an absorbent core for personal hygiene
absorbent products such as, but not limited to, baby diapers,
training pants, feminine pads or adult incontinence products.
BACKGROUND OF THE INVENTION
[0002] Absorbent articles for personal hygiene, such as disposable
diapers for infants, training pants for toddlers or adult
incontinence undergarments, are designed to absorb and contain body
exudates, in particular large quantity of urine. These absorbent
articles comprise several layers providing different functions, for
example a topsheet, a backsheet and in-between an absorbent core,
among other layers.
[0003] The function of the absorbent core is to absorb and retain
the exudates for a prolonged amount of time, for example overnight
for a diaper, minimize re-wet to keep the wearer dry and avoid
soiling of clothes or bed sheets. The majority of currently
marketed absorbent articles comprise as absorbent material a blend
of comminuted wood pulp with superabsorbent polymers (SAP) in
particulate form, also called absorbent gelling materials (AGM),
see for example U.S. Pat. No. 5,151,092 (Buell). Absorbent articles
having a core consisting essentially of SAP as absorbent material
(so called "airfelt-free" cores) have also been proposed but are
less common than traditional mixed cores (see e.g. WO2008/155699
(Hundorf), WO95/11652 (Tanzer), WO2012/052172 (Van Malderen)).
[0004] Absorbent articles comprising an absorbent core with slits
or grooves have also been proposed, typically to increase the fluid
acquisition properties of the core or to act as a folding guide.
WO95/11652 (Tanzer) discloses absorbent articles which include
superabsorbent material located in discrete pockets having
water-sensitive and water-insensitive containment structure.
WO2009/047596 (Wright) discloses an absorbent article with a slit
absorbent core.
[0005] Absorbent products which are flexible in the crotch region
provide the benefits of improved freedom of movement for the
wearer, especially when the user's legs compress the crotch region
of the article laterally. However the inventors have found that
highly flexible products may in generally have a poor resiliency
when becoming wet, and thus tend to lose their shape when
compressed by the movement of the wearer's legs. As the absorbent
core is deformed, the product can fail performing properly and this
increases the chance of failure such as fluid leakages. The
inventors have now found a new absorbent core structure which can
provide the benefit of good flexibility combined with good
resiliency when loaded with fluid.
SUMMARY OF THE INVENTION
[0006] The invention is for an absorbent core as defined in the
claims and an absorbent article comprising this absorbent core. The
absorbent core comprises a core wrap enclosing an absorbent
material, wherein the absorbent material may comprise at least 80%
of superabsorbent polymers ("SAP") by weight of the absorbent
material. The absorbent core comprises a front edge, a back edge
and two longitudinal edges, and has a longitudinal axis oriented in
a longitudinal direction. The absorbent material comprises at least
one channel, which is at least present in the crotch region and may
extend to the front and/or back regions. The absorbent core have a
Wet Compression Force below 5.00 N, in particular from 1.00 to
3.00N, as measured by the WCACF Test.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a top view of an absorbent article in the form of
a diaper comprising an exemplary absorbent core according to the
invention;
[0008] FIG. 2 is a transversal cross-section of the diaper of FIG.
1;
[0009] FIG. 3 is a top view of the exemplary absorbent core of the
diaper of FIG. 1 taken in isolation;
[0010] FIG. 4 is a transversal cross-section of the core of FIG.
3;
[0011] FIG. 5 is a longitudinal cross-section of the core of FIG.
3;
[0012] FIG. 6 shows a top view of an alternative absorbent core of
the invention.
[0013] FIG. 7 is a schematic description of an apparatus used to
carry out the Wet Caliper And Compression Force Test, further
detailed below.
DETAILED DESCRIPTION OF THE INVENTION
Introduction
[0014] As used herein, the term "absorbent article" refers to
disposable products such as infant or adult diapers, training
pants, and the like which are placed against or in proximity to the
body of the wearer to absorb and contain the various exudates
discharged from the body. Typically these articles comprise a
topsheet, backsheet, an absorbent core and optionally an
acquisition layer and/or distribution layer and typically other
components, with the absorbent core normally placed between the
backsheet and the acquisition system or topsheet.
[0015] As used herein, the term "absorbent core" refers to an
individual component, which is placed or is intended to be placed
within an absorbent article and which comprises an absorbent
material enclosed in a core wrap. The term "absorbent core" does
not cover an acquisition or distribution layer or any other
component of an absorbent article which is not either integral part
of the core wrap or placed within the core wrap. The absorbent core
is typically the component of an absorbent article which comprises
all, or at least the majority of, superabsorbent particles (SAP)
and has the most absorbent capacity of all the components of the
absorbent article.
[0016] A "nonwoven web" as used herein means 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 such as 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 (yam). Nonwoven webs
can be formed by many processes such as meltblowing, spunbonding,
solvent spinning, electrospinning, carding and airlaying. The basis
weight of nonwoven webs is usually expressed in grams per square
meter (g/m.sup.2 or gsm).
[0017] "Comprise," "comprising," and "comprises" are open ended
terms, each specifies the presence of the feature that 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. These terms based on the verb "comprise" should
be read as encompassing the narrower terms "consisting essential
of" which excludes any element, step or ingredient not mentioned
which materially affect the way the feature performs its function,
and the term "consisting of" which excludes any element, step, or
ingredient not specified. Any preferred or exemplary embodiments
described below are not limiting the scope of the claims, unless
specifically indicated to do so. The words "typically", "normally",
"advantageously" and the likes also qualify features which are not
intended to limit the scope of the claims unless specifically
indicated to do so.
[0018] Unless indicated otherwise, the description refers to the
absorbent core and absorbent article before use (i.e. dry, and not
loaded with a fluid) and conditioned at least 24 hours at
21.degree. C. +/-2.degree. C. and 50+/-20% Relative Humidity
(RH).
General description of the absorbent article 20
[0019] An exemplary absorbent article 20 in which the absorbent
core 28 of the invention can be used is an infant taped diaper 20
as represented in FIG. 1. FIG. 1 is a top plan view of the
exemplary diaper 20, in a flat-out state, with portions of the
structure being cut-away to more clearly show the construction of
the diaper 20. This diaper 20 is shown for illustration purpose
only as the invention may be used for making a wide variety of
diapers or other absorbent articles.
[0020] The absorbent article 20 comprises a liquid permeable
topsheet 24, a liquid impermeable backsheet 25, an absorbent core
28 between the topsheet 24 and the backsheet 25. The absorbent
article may also comprise further typical components such as an
acquisition layer 52 and/or a distribution layer 54 (collectively
referred to as acquisition-distribution system "ADS", designated as
50 in FIG. 2), and elasticized gasketing cuffs 32 present between
topsheet and backsheet and upstanding barrier leg cuffs 34, which
will be further detailed in the following. FIGS. 1-2 also show
other typical taped diaper components such as a fastening system
comprising fastening tabs 42 attached towards the back edge 12 of
the article and cooperating with a landing zone 44 towards the
front edge of the article. The absorbent article may also comprise
other typical components, which are not represented in the Figures,
such as a back elastic waist feature, a front elastic waist
feature, transverse barrier cuff(s), a lotion application, etc . .
.
[0021] The absorbent article 20 comprises a front edge 10, a back
edge 12, and two longitudinal edge edges. The front edge 10 is the
edge of the article which is intended to be placed towards the
front of the user when worn, and the back edge 12 is the opposite
edge. The absorbent article may be notionally divided by a
longitudinal axis 80 extending from the front edge to the back edge
of the article and dividing the article in two substantially
symmetrical halves relative to this axis, when viewing the article
from the wearer facing side in a flat out configuration, as
exemplarily shown in FIG. 1. If some part of the article is under
tension due to elasticized components, the article may be typically
flattened using clamps along the periphery of the article and/or a
sticky surface, so that the topsheet and backsheet can be pulled
taut so as to be substantially flat. The absorbent article 20 can
also be notionally divided by a transversal axis 90 in a front
region and a back region of equal length measured on the
longitudinal axis, when the article is in such a flat state. This
article's transversal axis 90 is perpendicular to the longitudinal
axis 80 and placed at half the length of the article. The length of
the article can be measured along the longitudinal axis 80 from
front edge 10 to back edge 12.
[0022] The topsheet 24, the backsheet 25, the absorbent core 28 and
the other article components may be assembled in a variety of well
known configurations, in particular by gluing and/or heat
embossing. Exemplary diaper assemblies are for example generally
described in U.S. Pat. No. 3,860,003, U.S. Pat. No. 5,221,274, U.S.
Pat. No. 5,554,145, U.S. Pat. No. 5,569,234, U.S. Pat No.
5,580,411, and U.S. Pat. No. 6,004,306. The absorbent article is
preferably thin. The article may be advantageously thin at the
intersection of the longitudinal and transversal axis, for example
with a caliper of from 1.0 mm to 8.0 mm, in particular from 1.5 mm
to 6.0 mm, as measured using the Absorbent Article Caliper Test
described below.
[0023] These and other components of the articles will now be
discussed in more details. Absorbent core 28
[0024] The absorbent core of the invention comprises absorbent
material with a high amount of superabsorbent polymers (herein
abbreviated as "SAP") enclosed within a core wrap. The SAP content
represents at least 80% by weight of the absorbent material
contained in the core wrap. The core wrap is not considered as
absorbent material for the purpose of assessing the percentage of
SAP in the absorbent core. The absorbent material defines an
absorbent material deposition area 8 as seen when the core is
placed substantially flat. As used herein, the term "absorbent
core" does not include the topsheet, the backsheet and (if present)
an acquisition-distribution system or layer which is not integral
part of the absorbent core, in particular which is not placed
within the core wrap. The core may consist essentially of, or
consist of, the core wrap, the absorbent material and optionally
glue. The term "absorbent core" and the term "core" are herein used
interchangeably.
[0025] The exemplary absorbent core 28 of the absorbent article of
FIG. 1 is shown in isolation in FIGS. 3-5. The absorbent core of
the invention comprises a front edge 280, a back edge 282 and two
longitudinal edges 284, 286 joining the front edge 280 and the back
edge 282. The front edge 280 of the core is the edge of the core
intended to be placed towards the front edge 10 of the absorbent
article. Typically the absorbent material will be advantageously
distributed in higher amount towards the front edge than towards
the back edge as more absorbency is required at the front.
Typically the front and back edges of the core 280, 282 are shorter
than the longitudinal edges 284, 286 of the core. The absorbent
core may also comprise a top side and a bottom side. The top side
288 of the core is the side intended to be placed towards the
topsheet and the bottom side 290 the side intended to be placed
towards the backsheet in the finished article 20. The top side 288
of the core is typically more hydrophilic than the bottom side 290.
The width of the core at the crotch point as measured between the
two longitudinal edges 284,286 should be sufficient for the WCACF
Test to be conducted, i.e. should be at least 40 mm. The width of
the core at the crotch point may in particular be of from 45 mm to
200 mm, or from 50 mm to 150 mm.
[0026] The absorbent core may be notionally divided by a
longitudinal axis 80' extending from the front edge to the back
edge of the core and dividing the core in two substantially
symmetrical halves relative to this axis, when viewing the core
from the topside in a flat out configuration, as exemplarily shown
in FIG. 3. Typically the longitudinal axis 80' of the core and the
longitudinal axis 80 of the article in which the core is intended
to be placed will be contiguous, when viewed from the top as in
FIG. 1. The transversal axis of the core (herein also referred to
as "crotch line"), is perpendicular to the longitudinal axis and is
passing through the crotch point C of the core. The crotch point C
is the point of the absorbent core placed at a distance of 0.45 of
L from the front edge of the absorbent core, L being the length of
the core as measured from its front edge to its back edge on the
longitudinal axis 80', as illustrated in FIG. 3. The full length L
of the core is measured from the front edge 280 to the back edge
282 of the core along its longitudinal axis 80' and also includes
the region of the core wrap which does not enclose the absorbent
material, in particular at the front and back end seals when
present. The length of the core L is of at least 320 mm, for
example from 320 mm to 600 mm.
[0027] The crotch region 81 is defined herein as the region of the
core extending from the crotch line, i.e. at the level of the
crotch point C, towards the back edge and front edge of the core by
a distance of a quarter of L (L/4) in both directions for a total
length of L/2. The front region 82 and back region 83 of the core
are the remaining regions of the deposition area towards the front
and back edges of the core respectively.
[0028] The core wrap may be formed by two nonwoven material 16, 16'
which may be at least partially sealed along the edges of the
absorbent core. The core wrap may be at least partially sealed
along the core's front edge, back edge and two longitudinal edges
so that substantially no absorbent material leaks out of the
absorbent core wrap when performing the compression step of the
WCACF test described below. It is not excluded that the core wrap
can be sealed with a seal line further inboard than the core's
edge, for example as in a gift wrapping if the core wrap comprises
a single substrate. The absorbent core may also advantageously
achieve an SAP loss of no more than about 70%, 60%, 50%, 40%, 30%,
20%, 10% according to the Wet Immobilization Test described in
WO2010/0051166A1. Further aspects of the absorbent core will now be
described in further details.
[0029] The absorbent core of the invention may be relatively thin
and thinner than can conventional airfelt cores. In particular the
caliper of the core (before use) as measured at the crotch point
(C) according to the Core Caliper Test as described herein may be
from 0.25 mm to 5.0 mm, in particular from 0.5 mm to 4.0 mm.
[0030] By "absorbent material" it is meant a material which has at
least some absorbency and/or liquid retaining properties, such as
SAP, cellulosic fibers as well as some hydrophilically treated
synthetic fibers. Typically, glues used in making absorbent cores
have no absorbency properties and are not considered as absorbent
material. The SAP content may be higher than 80%, for example at
least 85%, at least 90%, at least 95% and even up to and including
100% of the weight of the absorbent material contained within the
core wrap. This high SAP content may provide a relatively thin core
compared to conventional core typically comprising between 40-60%
SAP and the rest of cellulose fibers. The absorbent material of the
invention may in particular comprises less than 10% weight percent,
or less than 5% weight percent, or even be substantially free of
natural and/or synthetic fibers. The absorbent material may
advantageously comprise little or no airfelt (cellulosic) fibers,
in particular the absorbent core may comprise less than 15%, 10%,
or 5% airfelt (cellulose) fibers by weight of the absorbent core,
or even be substantially free of cellulose fibers.
[0031] The absorbent core of the invention may further comprise
adhesive for example to help immobilizing the SAP within the core
wrap and/or to ensure integrity of the core wrap, in particular
when the core wrap is made of two or more substrates. The core wrap
will typically extend to a larger area than strictly needed for
containing the absorbent material within.
[0032] Cores comprising relatively high amount of SAP with various
core designs have been proposed in the past, see for example in
U.S. Pat. No. 5,599,335 (Goldman), EP1,447,066 (Busam), WO95/11652
(Tanzer), US2008/0312622A1 (Hundorf), WO2012/052172 (Van Malderen).
In some embodiments, the absorbent material may be continuously
present within the core wrap. In this case, the absorbent material
may be for example obtained by the application of a single
continuous layer of absorbent material. In other embodiments, the
absorbent material may be comprised of individual pockets or
stripes of absorbent material enclosed within the core wrap and
separated by junction areas.
[0033] The continuous layer of absorbent material, in particular of
SAP, may also be obtained by combining two "half" absorbent layers
having discontinuous absorbent material application pattern wherein
the resulting layer is substantially continuously distributed
across the absorbent particulate polymer material area, as taught
in US2008/0312622A1 (Hundorf) for example. The absorbent core 28
may for example, as illustrated in FIG. 5, comprise a first
absorbent layer and a second absorbent layer, the first absorbent
layer comprising a first substrate 16 and a first layer 61 of
absorbent material, which may be 100% SAP, and the second absorbent
layer comprising a second substrate and a second layer of absorbent
material, which may also be 100% SAP, and a fibrous thermoplastic
adhesive material 51 at least partially bonding each layer of
absorbent material 61, 62 to its respective substrate. The first
substrate 16 and the second substrate 16' form the core wrap. The
first and second absorbent layers may be deposited on their
respective substrate in a deposition pattern comprising land areas
comprising absorbent material and junction areas between the land
areas which are free of absorbent material. The land areas as
exemplified in FIG. 5 for example may be for example transversally
orientated and span the width of the absorbent material deposition
area 8. The fibrous thermoplastic adhesive material 51 may be at
least partially in contact with the absorbent material 61, 62 in
the land areas and at least partially in contact with the substrate
layer in the junction areas. This imparts an essentially
three-dimensional structure to the fibrous layer of thermoplastic
adhesive material 51, which in itself is essentially a
two-dimensional structure of relatively small thickness, as
compared to the dimension in length and width directions. Thereby,
the fibrous thermoplastic adhesive material may provide cavities to
cover the absorbent material in the land area, and thereby
immobilizes this absorbent material, which as already indicated may
be 100% SAP.
[0034] The thermoplastic adhesive material may comprise, in its
entirety, a single thermoplastic polymer or a blend of
thermoplastic polymers, having a softening point, as determined by
the ASTM Method D-36-95 "Ring and Ball", in the range between
50.degree. C. and 300.degree. C., and/or the thermoplastic adhesive
material may be a hotmelt adhesive comprising at least one
thermoplastic polymer in combination with other thermoplastic
diluents such as tackifying resins, plasticizers and additives such
as antioxidants.
[0035] The thermoplastic polymer has typically a molecular weight
(Mw) of more than 10,000 and a glass transition temperature (Tg)
usually below room temperature or -6.degree. C.<Tg<16.degree.
C. Typical concentrations of the polymer in a hotmelt are in the
range of about 20 to about 40% by weight. The thermoplastic
polymers may be water insensitive. Exemplary polymers are
(styrenic) block copolymers including A-B-A triblock structures,
A-B diblock structures and (A-B)n radial block copolymer structures
wherein the A blocks are non-elastomeric polymer blocks, typically
comprising polystyrene, and the B blocks are unsaturated conjugated
diene or (partly) hydrogenated versions of such. The B block is
typically isoprene, butadiene, ethylene/butylene (hydrogenated
butadiene), ethylene/propylene (hydrogenated isoprene), and
mixtures thereof. Other suitable thermoplastic polymers that may be
employed are metallocene polyolefins, which are ethylene polymers
prepared using single-site or metallocene catalysts. Therein, at
least one comonomer can be polymerized with ethylene to make a
copolymer, terpolymer or higher order polymer. Also applicable are
amorphous polyolefins or amorphous polyalphaolefins (APAO) which
are homopolymers, copolymers or terpolymers of C2 to C8 alpha
olefins.
[0036] The tackifying resin may exemplarily have a Mw below 5,000
and a Tg usually above room temperature, typical concentrations of
the resin in a hotmelt are in the range of about 30 to about 60%,
and the plasticizer has a low Mw of typically less than 1,000 and a
Tg below room temperature, with a typical concentration of about 0
to about 15%.
[0037] The thermoplastic adhesive 51 used for the fibrous layer
preferably has elastomeric properties, such that the web formed by
the fibers on the SAP layer is able to be stretched as the SAP
swell. Exemplary elastomeric, hotmelt adhesives include
thermoplastic elastomers such as ethylene vinyl acetates,
polyurethanes, polyolefin blends of a hard component (generally a
crystalline polyolefin such as polypropylene or polyethylene) and a
Soft component (such as ethylene-propylene rubber); copolyesters
such as poly (ethylene terephthalate-co-ethylene azelate); and
thermoplastic elastomeric block copolymers having thermoplastic end
blocks and rubbery mid blocks designated as A-B-A block copolymers:
mixtures of structurally different homopolymers or copolymers,
e.g., a mixture of polyethylene or polystyrene with an A-B-A block
copolymer; mixtures of a thermoplastic elastomer and a low
molecular weight resin modifier, e.g., a mixture of a
styrene-isoprenestyrene block copolymer with polystyrene; and the
elastomeric, hot-melt, pressure-sensitive adhesives described
herein. Elastomeric, hot-melt adhesives of these types are
described in more detail in U.S. Pat. No. 4,731,066 issued to
Korpman on Mar. 15, 1988.
[0038] The thermoplastic adhesive material is advantageously
applied as fibers. The fibers may exemplarily have an average
thickness of about 1 to about 50 micrometers or about 1 to about 35
micrometers and an average length of about 5 mm to about 50 mm or
about 5mm to about 30 mm. To improve the adhesion of the
thermoplastic adhesive material to the substrate or to any other
layer, in particular any other nonwoven layer, such layers may be
pre-treated with an auxiliary adhesive. The fibers adhere to each
other to form a fibrous layer, which can also be described as a
mesh.
[0039] In certain embodiments, the thermoplastic adhesive material
will meet at least one, or several, or all of the following
parameters. An exemplary thermoplastic adhesive material may have a
storage modulus G' measured at 20.degree. C. of at least 30,000 Pa
and less than 300,000 Pa, or less than 200,000 Pa, or between
140,000 Pa and 200,000 Pa, or less than 100,000 Pa. In a further
aspect, the storage modulus G' measured at 35.degree. C. may be
greater than 80,000 Pa. In a further aspect, the storage modulus G'
measured at 60.degree. C. may be less than 300,000 Pa and more than
18,000 Pa, or more than 24,000 Pa, or more than 30,000 Pa, or more
than 90,000 Pa. In a further aspect, the storage modulus G'
measured at 90.degree. C. may be less than 200,000 Pa and more than
10,000 Pa, or more than 20,000 Pa, or more then 30,000 Pa. The
storage modulus measured at 60.degree. C. and 90.degree. C. may be
a measure for the form stability of the thermoplastic adhesive
material at elevated ambient temperatures. This value is
particularly important if the absorbent product is used in a hot
climate where the thermoplastic adhesive material would lose its
integrity if the storage modulus G' at 60.degree. C. and 90.degree.
C. is not sufficiently high.
[0040] G' can be measured using a rheometer as indicated in
WO2010/27719. The rheometer is capable of applying a shear stress
to the adhesive and measuring the resulting strain (shear
deformation) response at constant temperature. The adhesive is
placed between a Peltier-element acting as lower, fixed plate and
an upper plate with a radius R of e.g., 10 mm, which is connected
to the drive shaft of a motor to generate the shear stress. The gap
between both plates has a height H of e.g., 1500 micron. The
Peltier-element enables temperature control of the material
(+0.5.degree. C.). The strain rate and frequency should be chosen
such that all measurements are made in the linear viscoelastic
region.
Absorbent material deposition area 8
[0041] The absorbent core may comprise an absorbent material
deposition area 8 defined by the periphery of the layer formed by
the absorbent material 60 within the core wrap, as seen from the
top when the absorbent core is laid flat, as illustrated in FIG. 3.
The absorbent material 60 may be applied continuously or
discontinuously in the absorbent material deposition area 8. If
absorbent material free channels or junction areas between pockets
or stripes of absorbent material are present, these are considered
to be part of the absorbent material deposition area 8, for example
for the purpose of measuring the width or the length L of the
absorbent material deposition area. The shape of the absorbent
material deposition area 8 can vary, in particular it can be
rectangular as shown in FIG. 3 or shaped with a so-called "dog
bone" or "hour-glass" shape, which shows a tapering along its width
at least in the crotch region 81 of the absorbent material
deposition area, as shown in FIG. 6. When shaped (non-rectangular),
the absorbent material deposition area 8 may have a relatively
narrow width in the crotch region 81 of the core as this may
provide for example better wearing comfort in the finished article
incorporating the core. The absorbent material deposition area 8
may thus have a width (as measured in the transversal direction
perpendicular to the longitudinal axis 80') at its narrowest point
which is less than about 100 mm, 90 mm, 80 mm, 70 mm, 60 mm or even
less than about 50 mm. This narrowest width may typically be in the
crotch region and may further be for example at least 5 mm, or at
least 10 mm, or at least 20 mm smaller than the maximum width of
the absorbent material deposition area 8 at its largest point in
the front region 82 and/or back region 83 of the absorbent
core.
[0042] The basis weight (amount deposited per unit of area) of the
absorbent material may also be varied along the absorbent material
deposition area 8 to create a profiled distribution of the
absorbent material in the longitudinal direction, in the
transversal direction, or both directions of the core. Hence the
basis weight of the absorbent material may vary along the
longitudinal axis of the core 80', as well as along the transversal
axis, or any axis parallel to any of these axes. The basis weight
of absorbent material in area of relatively high basis weight such
as the crotch point may thus be for example at least 10%, or 20%,
or 30%, or 40%, or 50% higher than in an area of relatively low
basis weight. In particular the absorbent material present in the
absorbent material deposition area 8 at the level of the crotch
point C may have more SAP per unit of area deposited as compared to
any other area of the front region 82 or back region 83 of the
deposition area 8. The basis weight of the SAP may be at least 10%,
or 20%, or 30%, or 40%, or 50% higher at the crotch point (C) of
the core than at an another point of the absorbent material
deposition area on the longitudinal axis, in particular in the
front or back region of the core.
[0043] The absorbent material 60 may be deposited using known
techniques, which may allow relatively precise deposition of SAP at
relatively high speed. In particular the SAP printing technology as
disclosed for example in US2006/24433 (Blessing), US2008/0312617
and US2010/0051166A1 (both to Hundorf et al.) may be used. This
technique uses a printing roll to deposit SAP onto a substrate
disposed on a grid of a support which may include a plurality of
cross bars extending substantially parallel to and spaced from one
another so as to form channels extending between the plurality of
cross-bars. This technology allows high-speed and precise
deposition of SAP on a substrate. The channels of the absorbent
core can be formed for example by modifying the pattern of the grid
and receiving drums so that no SAP is applied in areas
corresponding to the channels. EP application number 11169396.6 for
example discloses this modification in more details.
Superabsorbent polymer (SAP)
[0044] "Superabsorbent polymers" ("SAP") as used herein refer to
absorbent material which are cross-linked polymeric materials that
can absorb at least 10 times their weight of an aqueous 0.9% saline
solution as measured using the Centrifuge Retention Capacity (CRC)
test (EDANA method WSP 241.2-05E). The SAP of the invention may in
particular have a CRC value of more than 20 g/g, or more than 24
g/g, or of from 20 to 50 g/g, or from 20 to 40 g/g, or 24 to 30
g/g. The SAP useful in the present invention include a variety of
water-insoluble, but water-swellable polymers capable of absorbing
large quantities of fluids.
[0045] The superabsorbent polymer can be in particulate form so as
to be flowable in the dry state. Typical particulate absorbent
polymer materials are made of poly(meth)acrylic acid polymers.
However, e.g. starch-based particulate absorbent polymer material
may also be used, as well polyacrylamide copolymer, ethylene maleic
anhydride copolymer, cross-linked carboxymethylcellulose, polyvinyl
alcohol copolymers, cross-linked polyethylene oxide, and starch
grafted copolymer of polyacrylonitrile. The superabsorbent polymer
may be polyacrylates and polyacrylic acid polymers that are
internally and/or surface cross-linked. Suitable materials are
described in the PCT Patent Application WO07/047598 or for example
WO07/046052 or for example WO2009/155265 and WO2009/155264. In some
embodiments, suitable superabsorbent polymer particles may be
obtained by current state of the art production processes as is
more particularly as described in WO 2006/083584. The
superabsorbent polymers are preferably internally cross-linked,
i.e. the polymerization is carried out in the presence of compounds
having two or more polymerizable groups which can be free-radically
copolymerized into the polymer network. Useful crosslinkers include
for example ethylene glycol dimethacrylate, diethylene glycol
diacrylate, allyl methacrylate, trimethylolpropane triacrylate,
triallylamine, tetraallyloxyethane as described in EP-A 530 438,
di- and triacrylates as described in EP-A 547 847, EP-A 559 476,
EP-A 632 068, WO 93/21237, WO 03/104299, WO 03/104300, WO 03/104301
and in DE-A 103 31 450, mixed acrylates which, as well as acrylate
groups, include further ethylenically unsaturated groups, as
described in DE-A 103 31 456 and DE-A 103 55 401, or crosslinker
mixtures as described for example in DE-A 195 43 368, DE-A 196 46
484, WO 90/15830 and WO 02/32962 as well as cross-linkers described
in WO2009/155265. The superabsorbent polymer particles may be
externally surface cross-linked, or: post cross-linked). Useful
post-crosslinkers include compounds including two or more groups
capable of forming covalent bonds with the carboxylate groups of
the polymers. Useful compounds include for example alkoxysilyl
compounds, polyaziridines, polyamines, polyamidoamines, di- or
polyglycidyl compounds as described in EP-A 083 022, EP-A 543 303
and EP-A 937 736, polyhydric alcohols as described in DE-C 33 14
019, cyclic carbonates as described in DE-A 40 20 780,
2-oxazolidone and its derivatives, such as
N-(2-hydroxyethyl)-2-oxazolidone as described in DE-A 198 07 502,
bis- and poly-2-oxazolidones as described in DE-A 198 07 992,
2-oxotetrahydro-1,3-oxazine and its derivatives as described in
DE-A 198 54 573, N-acyl-2-oxazolidones as described in DE-A 198 54
574, cyclic ureas as described in DE-A 102 04 937, bicyclic amide
acetals as described in DE-A 103 34 584, oxetane and cyclic ureas
as described in EP1,199,327 and morpholine-2,3-dione and its
derivatives as described in WO03/031482.
[0046] In some embodiments, the SAP are formed from polyacrylic
acid polymers/polyacrylate polymers, for example having a
neutralization degree of from 60% to 90%, or about 75%, having for
example sodium counter ions.
[0047] The SAP useful for the present invention may be of numerous
shapes. The term "particles" refers to granules, fibers, flakes,
spheres, powders, platelets and other shapes and forms known to
persons skilled in the art of superabsorbent polymer particles. In
some embodiments, the SAP particles can be in the shape of fibers,
i.e. elongated, acicular superabsorbent polymer particles. In those
embodiments, the superabsorbent polymer particles fibers have a
minor dimension (i.e. diameter of the fiber) of less than about 1
mm, usually less than about 500 .mu.m, and preferably less than 250
.mu.m down to 50 .mu.m. The length of the fibers is preferably
about 3 mm to about 100 mm. The fibers can also be in the form of a
long filament that can be woven.
[0048] Typically, SAP are spherical-like particles. In contrast to
fibers, "spherical-like particles" have a longest and a smallest
dimension with a particulate ratio of longest to smallest particle
dimension in the range of 1-5, where a value of 1 would equate a
perfectly spherical particle and 5 would allow for some deviation
from such a spherical particle. The superabsorbent polymer
particles may have a particle size of less than 850 .mu.m, or from
50 to 850 .mu.m, preferably from 100 to 710 .mu.m, more preferably
from 150 to 650 .mu.m, as measured according to EDANA method WSP
220.2-05. SAP having a relatively low particle size help to
increase the surface area of the absorbent material which is in
contact with liquid exudates and therefore support fast absorption
of liquid exudates. The SAP may have a particle sizes in the range
from 45 .mu.m to 4000 .mu.m, more specifically a particle size
distribution within the range of from 45 .mu.m to about 2000 .mu.m,
or from about 100 .mu.m to about 1000, 850 or 600 .mu.m. The
particle size distribution of a material in particulate form can be
determined as it is known in the art, for example by means of dry
sieve analysis (EDANA 420.02 "Particle Size distribution).
[0049] In some embodiments herein, the superabsorbent material is
in the form of particles with a mass medium particle size up to 2
mm, or between 50 microns and 2 mm or to 1 mm, or preferably from
100 or 200 or 300 or 400 or 500 .mu.m, or to 1000 or to 800 or to
700 .mu.m; as can for example be measured by the method set out in
for example EP-A-0,691,133. In some embodiments of the invention,
the superabsorbent polymer material is in the form of particles
whereof at least 80% by weight are particles of a size between 50
.mu.m and 1200 .mu.m and having a mass median particle size between
any of the range combinations above. In addition, or in another
embodiment of the invention, said particles are essentially
spherical. In yet another or additional embodiment of the invention
the superabsorbent polymer material has a relatively narrow range
of particle sizes, e.g. with the majority (e.g. at least 80% or
preferably at least 90% or even at least 95% by weight) of
particles having a particle size between 50.mu.m and 1000.mu.m,
preferably between 100.mu.m and 800.mu.m, and more preferably
between 200.mu.m and 600.mu.m.
[0050] Suitable SAP may for example be obtained from inverse phase
suspension polymerizations as described in U.S. Pat. No. 4,340,706
and U.S. Pat. No. 5,849,816 or from spray- or other gas-phase
dispersion polymerizations as described in US Patent Applications
No. 2009/0192035, 2009/0258994 and 2010/0068520. In some
embodiments, suitable SAP may be obtained by current state of the
art production processes as is more particularly described from
page 12, line 23 to page 20, line 27 of WO 2006/083584.
[0051] The surface of the SAP may be coated, for example, with a
cationic polymer. Preferred cationic polymers can include polyamine
or polyimine materials. In some embodiments, the SAP may be coated
with chitosan materials such as those disclosed in U.S. Pat. No.
7,537,832. In some other embodiments, the SAP may comprise
mixed-bed Ion-Exchange absorbent polymers such as those disclosed
in WO 99/34841 and WO 99/34842.
[0052] The absorbent core will typically comprise only one type of
SAP, but it is not excluded that a blend of SAPs may be used. The
fluid permeability of a superabsorbent polymer can be quantified
using its Urine Permeability Measurement (UPM) value, as measured
in the test disclosed European patent application number
EP12174117.7. The UPM of the SAP may for example be of at least
10.times.10.sup.-7 cm.sup.3.sec/g, or at least 30.times.10.sup.-7
cm.sup.3.sec/g, or at least 50.times.10.sup.-7 cm.sup.3.sec/g, or
more, e.g. at least 80 or 100.times.10.sup.-7 cm.sup.3.sec/g. The
flow characteristics can also be adjusted by varying the quantity
and distribution of the SAP used in the second absorbent layer.
[0053] For most absorbent articles, the liquid discharge occurs
predominately in the front half of the article, in particular for
diaper. The absorbent core may be thus placed in the absorbent
article so that the front half of the absorbent article comprises
most of the absorbent capacity of the core. Thus, at least: 60%, or
65%, or 70%, or 75%, or 80% of the SAP by weight may be present in
the front half of the absorbent article, the remaining SAP being
disposed in the back half of the absorbent article. The front half
region of the absorbent article can be defined as the region
between the front edge 10 of the absorbent article and the
transversal axis 90 of the absorbent article. The transversal axis
90 is perpendicular to the longitudinal axis 80 and placed at a
distance of half the length of the article as measured on
longitudinal axis of the article from the front or back edge
thereof.
[0054] The total amount of SAP present in the absorbent core may
also vary according to expected user. Diapers for newborns may
require less SAP than infant or adult incontinence diapers. The
amount of SAP in the core may be for example comprised from about 5
to 60 g, in particular from 5 to 50 g. The average SAP basis weight
within the (or "at least one", if several are present) deposition
area 8 of the SAP may be for example of at least 50, 100, 200, 300,
400, 500 or more g/m.sup.2. The areas of the channels present in
the absorbent material deposition area 8 are deduced from the
absorbent material deposition area to calculate this average basis
weight.
Core wrap (16, 16')
[0055] The core wrap may be made of a single substrate folded
around the absorbent material, or may advantageously comprise two
(or more) substrates which are attached to another. Typical
attachments are the so-called C-wrap and/or sandwich wrap. In a
C-wrap, as exemplarily shown in FIGS. 2 and 4, the longitudinal
and/or transversal edges of one of the substrate are folded over
the other substrate to form flaps. These flaps are then bonded to
the external surface of the other substrate, typically by
gluing.
[0056] The core wrap may be formed by any materials suitable for
receiving and containing the absorbent material. Typical substrate
materials used in the production of conventional cores may be used,
in particular paper, tissues, films, wovens or nonwovens, or
laminate of any of these. The core wrap may in particular be formed
by a nonwoven web, such as a carded nonwoven, spunbond nonwoven
("S") or meltblown nonwoven ("M"), and laminates of any of these.
For example spunmelt polypropylene nonwovens are suitable, in
particular those having a laminate web SMS, or SMMS, or SSMMS,
structure, and having a basis weight range of about 5 gsm to 15
gsm. Suitable materials are for example disclosed in U.S. Pat. No.
7,744,576, US2011/0268932A1, US2011/0319848A1 or US2011/0250413A1.
Nonwoven materials provided from synthetic fibers may be used, such
as PE, PET and in particular PP.
[0057] If the core wrap comprises a first substrate 16 and a second
substrate 16' these may be made of the same type of material, or
may be made of different materials or one of the substrate may be
treated differently than the other to provide it with different
properties. As the polymers used for nonwoven production are
inherently hydrophobic, they are preferably coated with hydrophilic
coatings if placed on the fluid receiving side of the absorbent
core. It is advantageous that the top side of the core wrap, i.e.
the side placed closer to the wearer in the absorbent article, be
more hydrophilic than the bottom side of the core wrap. A possible
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. An alternative possible way to produce
nonwovens with durably hydrophilic coatings is to coat the nonwoven
with hydrophilic nanoparticles, e.g. as described in WO
02/064877.
[0058] Permanently hydrophilic nonwovens are also useful in some
embodiments. Surface tension, as described in U.S. Pat. No.
7,744,576 (Busam et al.), can be used to measure how permanently a
certain hydrophilicity level is achieved. Liquid strike through, as
described in U.S. Pat. No. 7,744,576, can be used to measure the
hydrophilicity level. The first and/or second substrate may in
particular have a surface tension of at least 55, preferably at
least 60 and most preferably at least 65 mN/m or higher when being
wetted with saline solution. The substrate may also have a liquid
strike through time of less than 5 s for a fifth gush of liquid.
These values can be measured using the test methods described in
U.S. Pat. No. 7,744,576B2: "Determination Of Surface Tension" and
"Determination of Strike Through" respectively.
[0059] Hydrophilicity and wettability are typically defined in
terms of contact angle and the strike through time of the fluids,
for example through a nonwoven fabric. This is discussed in detail
in the
[0060] American Chemical Society publication entitled "Contact
angle, wettability and adhesion", edited by Robert F. Gould
(Copyright 1964). A substrate having a lower contact angle between
the water and the surface of substrate may be said to be more
hydrophilic than another.
[0061] The substrates may also be air-permeable. Films useful
herein may therefore comprise micro-pores. The substrate may have
for example an air-permeability of from 40 or from 50, to 300 or to
200 m.sup.3/(m.sup.2x min), as determined by EDANA method 140-1-99
(125 Pa, 38.3 cm.sup.2). The material of the core wrap may
alternatively have a lower air-permeability, e.g. being
non-air-permeable, for example to facilitate handling on a moving
surface comprising vacuum.
[0062] In the present invention, the core wrap may be at least
partially sealed along all the sides of the absorbent core or
otherwise so that substantially no absorbent material leaks out of
the core wrap while performing the WCACF Test indicated below. By
"substantially no absorbent material" it is meant that less than
5%, advantageously less than 2%, or less than 1% or 0% by weight of
absorbent material escapes the core wrap. In particular the core
wrap should not in an appreciable way burst open while the test is
conducted.
[0063] The term "seal" is to be understood in a broad sense. The
seal does not need to be continuous along the whole periphery of
the core wrap but may be discontinuous along part or the whole of
it, such as formed by a series of closely spaced apart seal points
on a line. While the seal may be at the periphery of the core, it
is not excluded that a seal may also be at other locations of the
core, for example close to the longitudinal centerline 80'.
Typically a seal may be formed by gluing and/or thermal
bonding.
[0064] If the core wrap is formed by two substrates 16, 16', one
seal per edge of the core may be typically be used to enclose the
absorbent material 60 within the core wrap. This is exemplified in
the FIGS. 4 and 5. As shown in FIG. 4, for example, the first
substrate 16 may be placed on one side of the core (the top side as
represented therein) and extends around the core's longitudinal
edges to at least partially wrap the opposed (bottom) side of the
core. The second substrate 16' can be present between the wrapped
flaps of the first substrate 16 and the absorbent material 60 of
the core. The flaps of the first substrate 16 may be glued to the
second substrate 16' to provide a strong seal. This so called
C-wrap construction can provide benefits such as improved
resistance to bursting in a wet loaded state compared to a sandwich
seal. The front edge and back edge of the core wrap may then also
be sealed for example by gluing the first substrate and second
substrate flat to another to provide more complete enclosure of the
absorbent material across the whole of the periphery of the core.
It can be advantageous to use the C-wrap at least on the
longitudinal edges of the core which are longer than the front and
end edges. In the so-called sandwich construction, the first and
second substrates may also extend outwardly on all edges of the
core and be sealed flat along the whole or parts of the periphery
of the core typically by gluing and/or heat/pressure bonding.
Typically neither first nor second substrates need to be shaped, so
that they can be rectangularly cut for ease of production but of
course other shapes are possible.
[0065] The core wrap may also be formed by a single substrate which
may enclose as in a parcel wrap the absorbent material and be for
example sealed along the front edge and back edge of the core and
one longitudinal seal.
Channels 26, 26'
[0066] The absorbent core comprises at least one channel which is
at least partially oriented in the longitudinal direction of the
core. If the following the plural form "channels" will be used to
mean "at least one channel". The channels may be formed in various
ways. For example the channels may be formed by zones within the
absorbent material deposition area which may be substantially or
completely free of absorbent material, in particular SAP. In
addition or alternatively, the channel(s) may also be formed by
continuously or discontinuously bonding the material forming the
top side of the core wrap to the material forming the bottom side
of the core wrap through the absorbent material deposition area.
The channels may be advantageously continuous but it is not
excluded that the channels are intermittent. The
acquisition-distribution system or any sub-layer between the
topsheet and the absorbent core, or another layer of the article,
may also comprise channels, which may or not correspond to the
channels of the absorbent core. The channels may be in particular
fully encompassed within the absorbent material deposition area
8.
[0067] The channel or channels may in particular be present within
the crotch region (81) of the core, in particular at least at the
same longitudinal level as the crotch point C, as represented in
FIG. 3 by the two longitudinally extending channels 26, 26'. Some
channels may also extend from the crotch region 81 into the back
region 82 and/or front region 83 of the core or may be solely
present in the front region and/or in the back region of the core,
as represented in FIG. 6 by the smaller channels 27, 27'.
[0068] The absorbent core 28 may also comprise more than two
channels, for example at least 3, or at least 4 or at least 5 or at
least 6. Shorter channels may also be present, for example in the
back region or the front region of the core as represented by the
pair of channels 27, 27' in FIG. 6 towards the front of the core.
The channels may comprise one or more pairs of channels
symmetrically arranged relative to the longitudinal axis 80'.
[0069] The channels may be particularly useful in the absorbent
core when the absorbent material deposition area is rectangular, as
the channels can improve the flexibility of the core to an extent
that there is less advantage in using a non-rectangular (shaped)
core. Of course channels may also be present in a layer of SAP
having a shaped deposition area.
[0070] The channels may extend substantially longitudinally, which
means typically that each channel extends more in the longitudinal
direction than in the transverse direction, and typically at least
twice as much in the longitudinal direction than in the transverse
direction (as measured after projection on the respective axis).
The channels may have a length L' projected on the longitudinal
axis 80' of the core that is at least 10% of the length L of the
absorbent material deposition area 8. It may be advantageous that
at least some or all of the channels are not completely or
substantially completely transversely oriented channels in the
core.
[0071] The channels may be completely oriented longitudinally and
parallel to the longitudinal axis but also may be curved. In
particular some or all the channels, in particular the channels
present in the crotch region, may be concave towards the
longitudinal axis 80', as for example represented in FIGS. 3 and 7
for the pair of channels 26, 26'. The radius of curvature may
typically be at least equal (and preferably at least 1.5 or at
least 2.0 times this average transverse dimension) to the average
transverse dimension of the absorbent material deposition area 8;
and also straight but under an angle of (e.g. from)5.degree. up to
30.degree. , or for example up to 20.degree. , or up to 10.degree.
with a line parallel to the longitudinal axis. The radius of
curvature may be constant for a channel, or may vary along its
length. This may also includes channels with an angle therein,
provided said angle between two parts of a channel is at least
120.degree. , preferably at least 150.degree. ; and in any of these
cases, provided the longitudinal extension of the channel is more
than the transverse extension. The channels may also be branched,
for example a central channel superposed with the longitudinal axis
in the crotch region which branches towards the back and/or towards
the front of the article.
[0072] In some embodiments, there is no channel that coincides with
the longitudinal axis 80' of the core. When present as symmetrical
pairs relative to the longitudinal axis, the channels may be spaced
apart from one another over their whole longitudinal dimension. The
smallest spacing distance may be for example at least 5 mm, or at
least 10 mm, or at least 16 mm.
[0073] Furthermore, in order to reduce the risk of fluid leakages,
the longitudinal main channels typically do not extend up to any of
the edges of the absorbent material deposition area 8, and are
therefore fully encompassed within the absorbent material
deposition area of the core. Typically, the smallest distance
between a channel and the closest edge of the absorbent material
deposition area is at least 5 mm.
[0074] The channels may have a width We along at least part of its
length which is at least 2 mm, or at least 3 mm or at least 4 mm,
up to for example 20 mm, or 16 mm or 12 mm. The width of the
channel may be constant through substantially the whole length of
the channel or may vary along its length.
[0075] At least some or all the channels are advantageously
permanent channels, meaning their integrity is at least partially
maintained both in the dry state and in the wet state. Permanent
channels may be obtained by provision of one or more adhesive
material, for example the fibrous layer of adhesive material or a
construction glue that helps adhering for example a substrate with
an absorbent material within the walls of the channel. Permanent
channels may be also in particular formed by bonding the upper side
and lower side of the core wrap (e.g. first substrate 16 and the
second substrate 16') together through the channels. Typically, an
adhesive can be used to bond both sides of the core wrap through
the channels, but it is possible to bond via other known means,
such as pressure bonding, ultrasonic bonding or heat bonding or
combination thereof. The core wrap can be continuously bonded or
intermittently bonded along the channels. The channels may
advantageously remain or become visible at least through the
topsheet and/or backsheet when the absorbent article is fully
loaded with a fluid as disclosed in the Wet Channel Integrity Test
below. This may be obtained by making the channels substantially
free of SAP, so they will not swell, and sufficiently large so that
they will not close when wet. Furthermore bonding the core wrap to
itself through the channels may be advantageous. The Wet Channel
Integrity Test described below can be used to test if channels are
permanent and visible following wet saturation and to what extent.
Advantageously, a permanent channel according to the invention has
a percentage of integrity of at least: 20%, or 30%, or 40%, or 50%,
or 60, or 70%, or 80%, or 90%, according to the Wet Channel
Integrity Test described below.
Topsheet 24
[0076] The topsheet 24 is the part of the absorbent article that is
directly in contact with the wearer's skin. The topsheet 24 can be
joined to the backsheet 25, the core 28 and/or any other layers as
is known in the art (as used herein, the term "joined" encompasses
configurations whereby an element is directly secured to another
element by affixing the element directly to the other element, and
configurations whereby an element is indirectly secured to another
element by affixing the element to intermediate member(s) which in
turn are affixed to the other element). Usually, the topsheet 24
and the backsheet 25 are joined directly to each other in some
locations (e.g. on or close to the periphery of the article) and
are indirectly joined together in other locations by directly
joining them to one or more other elements of the article 20.
[0077] The topsheet 24 is preferably compliant, soft-feeling, and
non-irritating to the wearer's skin. Further, at least a portion of
the topsheet 24 is liquid permeable, permitting liquids to readily
penetrate through its thickness. A suitable topsheet may be
manufactured from a wide range of materials, such as porous foams,
reticulated foams, apertured plastic films, or woven or nonwoven
materials of natural fibers (e.g., wood or cotton fibers),
synthetic fibers or filaments (e.g., polyester or polypropylene or
bicomponent PE/PP fibers or mixtures thereof), or a combination of
natural and synthetic fibers. If the topsheet 24 includes fibers,
the fibers may be spunbond, carded, wet-laid, meltblown,
hydroentangled, or otherwise processed as is known in the art, in
particular spunbond PP nonwoven. A suitable topsheet comprising a
web of staple-length polypropylene fibers is manufactured by
Veratec, Inc., a Division of International Paper Company, of
Walpole, Mass. under the designation P-8.
[0078] Suitable formed film topsheets are also described in U.S.
Pat. No. 3,929,135, U.S. Pat. No. 4,324,246, U.S. Pat. No.
4,342,314, U.S. Pat. No. 4,463,045, and U.S. Pat. No. 5,006,394.
Other suitable topsheets may be made in accordance with U.S. Pat.
Nos. 4,609,518 and 4,629,643 issued to Curro et al. Such formed
films are available from The Procter & Gamble Company of
Cincinnati, Ohio as "DRI-WEAVE" and from Tredegar Corporation,
based in Richmond, Va., as "CLIFF-T".
[0079] Any portion of the topsheet may be coated with a lotion as
is known in the art. Examples of suitable lotions include those
described in U.S. Pat. No. 5,607,760, U.S. Pat. No. 5,609,587, U.S.
Pat. No. 5,643,588, U.S. Pat. No. 5,968,025 and U.S. Pat. No.
6,716,441. The topsheet 24 may also include or be treated with
antibacterial agents, some examples of which are disclosed in PCT
Publication WO95/24173. Further, the topsheet, the backsheet or any
portion of the topsheet or backsheet may be embossed and/or matte
finished to provide a more cloth like appearance.
[0080] The topsheet 24 may comprise one or more apertures to ease
penetration of exudates therethrough, such as urine and/or feces
(solid, semi-solid, or liquid). The size of at least the primary
aperture is important in achieving the desired waste encapsulation
performance. If the primary aperture is too small, the waste may
not pass through the aperture, either due to poor alignment of the
waste source and the aperture location or due to fecal masses
having a diameter greater than the aperture. If the aperture is too
large, the area of skin that may be contaminated by "rewet" from
the article is increased. Typically, the total area of the
apertures at the surface of a diaper may have an area of between
about 10 cm.sup.2 and about 50 cm.sup.2, in particular between
about 15 cm.sup.2 and 35 cm.sup.2. Examples of apertured topsheet
are disclosed in U.S. Pat. No. 6632504, assigned to BBA NONWOVENS
SIMPSONVILLE. WO2011/163582 also discloses suitable colored
topsheet having a basis weight of from 12 to 18 gsm and comprising
a plurality of bonded points. Each of the bonded points has a
surface area of from 2 mm.sup.2 to 5 mm.sup.2 and the cumulated
surface area of the plurality of bonded points is from 10 to 25% of
the total surface area of the topsheet.
[0081] Typical diaper topsheets have a basis weight of from about
10 to about 28 gsm, in particular between from about 12 to about 18
gsm but other basis weights are possible.
Backsheet 25
[0082] The backsheet 25 is generally that portion of the absorbent
article 20 which forms the majority of the external surface of the
article when worn by the user. The backsheet is positioned towards
the bottom side of the absorbent core and prevents the exudates
absorbed and contained therein from soiling articles such as
bedsheets and undergarments. The backsheet 25 is typically
impermeable to liquids (e.g. urine). The backsheet may for example
be or comprise a thin plastic film such as a thermoplastic film
having a thickness of about 0.012 mm to about 0.051 mm. Exemplary
backsheet films include those manufactured by Tredegar Corporation,
based in Richmond, Va., and sold under the trade name CPC2 film.
Other suitable backsheet materials may include breathable materials
which permit vapors to escape from the diaper 20 while still
preventing exudates from passing through the backsheet 25.
Exemplary breathable materials may include materials such as woven
webs, nonwoven webs, composite materials such as film-coated
nonwoven webs, microporous films such as manufactured by Mitsui
Toatsu Co., of Japan under the designation ESPOIR NO and by
Tredegar Corporation of Richmond, Va., and sold under the
designation EXAIRE, and monolithic films such as manufactured by
Clopay Corporation, Cincinnati, Ohio under the name HYTREL blend
P18-3097. Some 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; U.S. Pat. No. 5,938,648 to
LaVon et al., U.S. Pat. No. 4,681,793 to Linman et al., U.S. Pat.
No. 5,865,823 to Curro; and U.S. Pat. No. 5,571,096 to Dobrin et
al, U.S. Pat. No. 6,946,585B2 to London Brown.
[0083] The backsheet 25 may be joined to the topsheet 24, the
absorbent core 28 or any other element of the diaper 20 by any
attachment means known in the art. Suitable attachment means are
described above with respect to means for joining the topsheet 24
to other elements of the article 20. For example, the attachment
means may include a uniform continuous layer of adhesive, a
patterned layer of adhesive, or an array of separate lines,
spirals, or spots of adhesive. Suitable attachment means comprises
an open pattern network of filaments of adhesive as disclosed in
U.S. Pat. No. 4,573,986. Other suitable attachment means include
several lines of adhesive filaments which are swirled into a spiral
pattern, as is illustrated by the apparatus and methods shown in
U.S. Pat. No. 3,911,173, U.S. Pat. No. 4,785,996; and U.S. Pat. No.
4,842,666. Adhesives which have been found to be satisfactory are
manufactured by H. B. Fuller Company of St. Paul, Minn. and
marketed as HL-1620 and HL 1358-XZP. Alternatively, the attachment
means may comprise heat bonds, pressure bonds, ultrasonic bonds,
dynamic mechanical bonds, or any other suitable attachment means or
combinations of these attachment means as are known in the art.
Acquisition-Distribution System
[0084] The absorbent articles of the invention may comprise an
acquisition layer 52, a distribution layer 54, or combination of
both (all herein collectively referred to as
acquisition-distribution system "ADS"). The function of the ADS is
typically to quickly acquire the fluid and distribute it to the
absorbent core in an efficient manner. The ADS may comprise one,
two or more layers, which may form a unitary layer or remain
discrete layers which may be attached to each other. In the
examples below, the ADS comprises two layers: a distribution layer
54 and an acquisition layer 52 disposed between the absorbent core
and the topsheet, but the invention is not restricted to this
example. Typically, the ADS will not comprise SAP as this may slow
the acquisition and distribution of the fluid. The prior art
discloses many type of acquisition-distribution system, see for
example WO2000/59430 (Daley), WO95/10996 (Richards), U.S. Pat. No.
5,700,254 (McDowall), WO02/067809 (Graef). The ADS may comprise,
although not necessarily, two layers: a distribution layer 54 and
an acquisition layer 52, which will now be exemplified in more
details.
Distribution layer 54
[0085] The function of a distribution layer 54 is to spread the
insulting fluid liquid over a larger surface within the article so
that the absorbent capacity of the core can be more efficiently
used. Typically distribution layer are made of a nonwoven material
based on synthetic or cellulosic fibers and having a relatively low
density. The density of the distribution layer may vary depending
on the compression of the article, but may typically range from
0.03 to 0.25 g/cm.sup.3, in particular from 0.05 to 0.15 g/cm.sup.3
measured at 0.30 psi (2.07 kPa). The distribution layer 54 may also
be a material having a water retention value of from 25 to 60,
preferably from 30 to 45, measured as indicated in the procedure
disclosed in U.S. Pat. No. 5,137,537. The distribution layer may
typically have an average basis weight of from 30 to 400 g/m.sup.2,
in particular from 100 to 300 g/m.sup.2.
[0086] The distribution layer may for example comprise at least 50%
by weight of cross-linked cellulose fibers. The cross-linked
cellulosic fibers may be crimped, twisted, or curled, or a
combination thereof including crimped, twisted, and curled. This
type of material has been used in the past in disposable diapers as
part of an acquisition system, for example US 2008/0312622 A1
(Hundorf). The cross-linked cellulosic fibers provide higher
resilience and therefore higher resistance to the first absorbent
layer against the compression in the product packaging or in use
conditions, e.g. under baby weight. This provides the core with a
higher void volume, permeability and liquid absorption, and hence
reduced leakage and improved dryness.
[0087] Exemplary chemically cross-linked cellulosic fibers suitable
for a distribution layer are disclosed in U.S. Pat. No. 5,549,791,
U.S. Pat. No. 5,137,537, WO9534329 or US2007/118087. Exemplary
cross-linking agents include polycarboxylic acids such as citric
acid and/or polyacrylic acids such as acrylic acid and maleic acid
copolymers. For example, the crosslinked cellulosic fibers may have
between about 0.5 mole % and about 10.0 mole % of a C2-C9
polycarboxylic acid cross-linking agent, calculated on a cellulose
anhydroglucose molar basis, reacted with said fibers in an
intrafiber ester crosslink bond form. The C2-C9 polycarboxylic acid
cross-linking agent may be selected from the group consisting of:
[0088] aliphatic and alicyclic C2-C9 polycarboxylic acids having at
least three carboxyl groups per molecule; and [0089] aliphatic and
alicyclic C2-C9 polycarboxylic acids having two carboxyl groups per
molecule and having a carbon-carbon double bond located alpha, beta
to one or both of the carboxyl groups, wherein one carboxyl group
in said C2-C9 polycarboxylic acid crosslinking agent is separated
from a second carboxyl group by either two or three carbon atoms.
The fibers may have in particular between about 1.5 mole % and
about 6.0 mole % crosslinking agent, calculated on a cellulose
anhydroglucose molar basis, reacted therewith in the form of
intrafiber ester crosslink bonds. The cross-linking agent may be
selected from the group consisting of citric acid, 1, 2, 3, 4
butane tetracarboxylic acid, and 1, 2, 3 propane tricarboxylic
acid, in particular citric acid.
[0090] Polyacrylic acid cross-linking agents may also be selected
from polyacrylic acid homopolymers, copolymers of acrylic acid, and
mixtures thereof. The fibers may have between 1.0 weight % and 10.0
weight %, preferably between 3 weight % and 7 weight %, of these
cross-linking agents, calculated on a dry fiber weight basis,
reacted therewith in the form of intra-fiber crosslink bonds. The
cross-linking agent may be a polyacrylic acid polymer having a
molecular weight of from 500 to 40,000, preferably from 1,000 to
20,000. The polymeric polyacrylic acid cross-linking agent may be a
copolymer of acrylic acid and maleic acid, in particular wherein
the weight ratio of acrylic acid to maleic acid is from 10:1 to
1:1, preferably from 5:1 to 1.5:1. An effective amount of citric
acid may be further mixed with said polymeric polyacrylic acid
cross-linking agent.
[0091] The distribution layer comprising cross-linked cellulose
fibers may comprise other fibers, but this layer may advantageously
comprise at least 50%, or 60%, or 70%, or 80%, or 90% or even up to
100%, by weight of the layer, of cross-linked cellulose fibers
(including the cross-linking agents). Examples of such mixed layer
of cross-linked cellulose fibers may comprise about 70% by weight
of chemically cross-linked cellulose fibers, about 10% by weight
polyester (PET) fibers, and about 20% by weight untreated pulp
fibers. In another example, the layer of cross-linked cellulose
fibers may comprise about 70% by weight chemically cross-linked
cellulose fibers, about 20% by weight lyocell fibers, and about 10%
by weight PET fibers. In another example, the layer may comprise
about 68% by weight chemically cross-linked cellulose fibers, about
16% by weight untreated pulp fibers, and about 16% by weight PET
fibers. In another example, the layer of cross-linked cellulose
fibers may comprise from about 90-100% by weight chemically
cross-linked cellulose fibers.
Acquisition Layer 52
[0092] The absorbent article 20 may comprise an acquisition layer
52, whose function is to quickly acquire the fluid away from the
topsheet so as to provide a good dryness for the wearer. The
acquisition layer 52 is typically placed directly under the
topsheet. If present, the distribution layer may be at least
partially disposed under the acquisition layer. The acquisition
layer may typically be or comprise a non-woven material, for
example a SMS or SMMS material, comprising a spunbonded, a
melt-blown and a further spunbonded layer or alternatively a carded
chemical-bonded nonwoven. The non-woven material may in particular
be latex bonded. Exemplary upper acquisition layers 52 are
disclosed in U.S. Pat. No. 7,786,341. Carded, resin-bonded
nonwovens may be used, in particular where the fibers used are
solid round or round and hollow PET staple fibers (50/50 or 40/60
mix of 6 denier and 9 denier fibers). An exemplary binder is a
butadiene/styrene latex. Non-wovens have the advantage that they
can be manufactured outside the converting line and stored and used
as a roll of material.
[0093] Further useful non-wovens are described in U.S. Pat. No.
6,645,569 to Cramer et al., U.S. Pat. No. 6,863,933 to Cramer et
al., U.S. Pat. No. 7,112,621 to Rohrbaugh et al., and co patent
applications US2003/148684 to Cramer et al. and US2005/008839 to
Cramer et al.
[0094] The acquisition layer 52 may be stabilized by a latex
binder, for example a styrene-butadiene latex binder (SB latex).
Processes for obtaining such lattices are known, for example, from
EP 149 880 (Kwok) and US 2003/0105190 (Diehl et al.). In certain
embodiments, the binder may be present in the acquisition layer 52
in excess of about 12%, about 14% or about 16% by weight. SB latex
is available under the trade name GENFLOTM 3160 (OMNOVA Solutions
Inc.; Akron, Ohio).
[0095] A further acquisition layer may be used in addition to a
first acquisition layer described above. For example a tissue layer
may be placed between the first acquisition layer and the
distribution layer. The tissue may have enhanced capillarity
distribution properties compared to the acquisition layer described
above. The tissue and the first acquisition layer may be of the
same size or may be of different size, for example the tissue layer
may extend further in the back of the absorbent article than the
first acquisition layer. An example of hydrophilic tissue is a
13-15 gsm high wet strength made of cellulose fibers from supplier
Havix.
Fastening System 42-44
[0096] The absorbent article may include a fastening system. The
fastening system can be used to provide lateral tensions about the
circumference of the absorbent article to hold the absorbent
article on the wearer. This fastening system is not necessary for
training pant article since the waist region of these articles is
already bonded. The fastening system usually comprises a fastener
such as tape tabs, hook and loop fastening components, interlocking
fasteners such as tabs & slots, buckles, buttons, snaps, and/or
hermaphroditic fastening components, although any other known
fastening means are generally acceptable. A landing zone is
normally provided on the front waist region of the article for the
fastener to be releasably attached. Some exemplary surface
fastening systems are disclosed in U.S. Pat. No. 3,848,594, U.S.
Pat. No. 4,662,875, U.S. Pat. No. 4,846,815, U.S. Pat. No.
4,894,060, U.S. Pat. No. 4,946,527, U.S. Pat. No. 5,151,092 and
U.S. Pat. No. 5,221,274 issued to Buell. An exemplary interlocking
fastening system is disclosed in U.S. Pat. No. 6,432,098. The
fastening system may also provide a means for holding the article
in a disposal configuration as disclosed in U.S. Pat. No. 4,963,140
issued to Robertson et al.
[0097] The fastening system may also include primary and secondary
fastening systems, as disclosed in U.S. Pat. No. 4,699,622 to
reduce shifting of overlapped portions or to improve fit as
disclosed in U.S. Pat. No. 5,242,436, U.S. Pat. No. 5,499,978, U.S.
Pat. No. 5,507,736, and U.S. Pat. No. 5,591,152.
Front and Back Ears 46, 40
[0098] The absorbent article may comprise front ears 46 and back
ears 40 as is known in the art. The ears can be integral part of
the chassis, for example formed from the topsheet and/or backsheet
as side panel. Alternatively, as represented on FIG. 1, they may be
separate elements attached by gluing and/or heat embossing. The
back ears 40 are advantageously stretchable to facilitate the
attachment of the tabs 42 on the landing zone 40 and maintain the
taped diapers in place around the wearer's waist. The back ears 40
may also be elastic or extensible to provide a more comfortable and
contouring fit by initially conformably fitting the absorbent
article to the wearer and sustaining this fit throughout the time
of wear well past when absorbent article has been loaded with
exudates since the elasticized ears allow the sides of the
absorbent article to expand and contract.
Barrier Leg Cuffs 34 and Gasketing Cuffs 32
[0099] Absorbent articles such as diapers or training pants may
typically further comprise components that increase the fit of the
article around the legs of the wearer, in particular barrier leg
cuffs 34 and gasketing cuffs 32. The barrier leg cuffs 32 may be
formed by a piece of material, typically a nonwoven, which is
partially bonded to the rest of the article and can be partially
raised away and thus stand up from the plane defined by the
topsheet, when the article is pulled flat as shown e.g. in FIGS.
1-2. The barrier leg cuffs can provide improved containment of
liquids and other body exudates approximately at the junction of
the torso and legs of the wearer. The barrier leg cuffs extend at
least partially between the front edge and the back edge of the
absorbent article on opposite sides of the longitudinal axis and
are at least present at the level of the crotch point (C).
[0100] The barrier leg cuffs may be delimited by a proximal edge 64
joined to the rest of the article, typically the topsheet and/or
the backsheet, and a free terminal edge 66, which is intended to
contact and form a seal with the wearer's skin. The barrier leg
cuffs 34 may be joined at the proximal edge 64 with the chassis of
the article by a bond 65 which may be made for example by gluing,
fusion bonding or combination of known bonding means. The bond 65
at the proximal edge 64 may be continuous or intermittent.
[0101] The barrier leg cuffs 32 can be integral with (i.e. formed
from) the topsheet or the backsheet, or more typically be formed
from a separate material joined to the rest of the article.
Typically the material of the barrier leg cuffs may extend through
the whole length of the article but is "tack bonded" to the
topsheet towards the front edge and back edge of the article so
that in these sections the barrier leg cuff material remains flush
with the topsheet. Each barrier leg cuff 34 may comprise one, two
or more elastic strings 35 close to this free terminal edge 66 to
provide a better seal. In addition to the barrier leg cuffs 34, the
article may comprise gasketing cuffs 32, which are formed in the
same plane as the chassis of absorbent article, in particular may
be at least partially enclosed between the topsheet and the
backsheet, and may be placed transversely outwardly relative to the
barrier leg cuffs. The gasketing cuffs can provide a better seal
around the thighs of the wearer. Usually each gasketing leg cuff
will comprise one or more elastic string or elastic element
comprised in the chassis of the diaper for example between the
topsheet and backsheet in the area of the leg openings.
[0102] U.S. Pat. No. 3,860,003 describes a disposable diaper which
provides a contractible leg opening having a side flap and one or
more elastic members to provide an elasticized leg cuff (a
gasketing cuff). U.S. Pat. No. 4,808,178 and U.S. Pat. No.
4,909,803 issued to Aziz et al. describe disposable diapers having
"stand-up" elasticized flaps (barrier leg cuffs) which improve the
containment of the leg regions. U.S. Pat. No. 4,695,278 and U.S.
Pat. No. 4,795,454 issued to Lawson and to Dragoo respectively,
describe disposable diapers having dual cuffs, including gasketing
cuffs and barrier leg cuffs. All or a portion of the barrier leg
and/or gasketing cuffs may be treated with a lotion.
Elastic Waist Feature
[0103] The absorbent article may also comprise at least one elastic
waist feature (not represented) that helps to provide improved fit
and containment. The elastic waist feature is generally intended to
elastically expand and contract to dynamically fit the wearer's
waist. The elastic waist feature preferably extends at least
longitudinally outwardly from at least one waist edge of the
absorbent core 28 and generally forms at least a portion of the
back side of the absorbent article. Disposable diapers can be
constructed so as to have two elastic waist features, one
positioned in the front waist region and one positioned in the back
waist region. The elastic waist feature may be constructed in a
number of different configurations including those described in
U.S. Pat. No. 4,515,595, U.S. Pat. No. 4,710,189, U.S. Pat. No.
5,151,092 and U.S. Pat. No. 5,221,274.
Relations Between the Layers and Components
[0104] Typically, adjacent layers will be joined together using
conventional bonding method such as adhesive coating via slot
coating or spraying on the whole or part of the surface of the
layer, or thermo-bonding, or pressure bonding or combinations
thereof. This bonding is not represented in the Figures (except for
the bonding 65 between the raised element of the leg cuffs 34 with
the topsheet 24) for clarity and readability but bonding between
the layers of the article should be considered to be present unless
specifically excluded. Adhesives may be typically used to improve
the adhesion of the different layers, for example between the
backsheet and the core wrap. The glue may be any standard hotmelt
glue as known in the art.
[0105] If an acquisition layer 52 is present, it may be
advantageous that this acquisition layer is larger than or least as
large as the distribution layer 54 in the longitudinal and/or
transversal dimension. Thus the distribution layer 54 can be
deposited on the acquisition layer 52. This simplifies handling, in
particular if the acquisition layer is a nonwoven which can be
unrolled from a roll of stock material. The distribution layer may
also be deposited directly on the absorbent core's upper side of
the core wrap or another layer of the article. Also, an acquisition
layer 52 larger than the distribution layer allows to directly glue
the acquisition layer to the storage core (at the larger areas).
This can provide an increased article integrity and better liquid
communication.
[0106] The absorbent core and in particular its absorbent material
deposition area 8 may advantageously be at least as large and long
and advantageously at least partially larger and/or longer than any
of the layer in the ADS. This is because the absorbent material in
the core can usually more effectively retain fluid and provide
dryness benefits across a larger area than the ADS. The absorbent
article may have a rectangular SAP layer and a non-rectangular
(shaped) ADS. The absorbent article may also have a rectangular
(non-shaped) ADS and a rectangular layer of SAP.
Method of making
[0107] The absorbent cores and articles of the invention may be
made by any conventional methods known in the art. In particular
the articles may be hand-made or industrially produced at high
speed on a modern converting line.
Experimental Settings
[0108] The values indicated herein are measured according to the
methods indicated herein below, unless specified otherwise. All
measurements are performed at 21.degree. C..+-.2.degree. C. and
50%.+-.20% RH, unless specified otherwise. All samples should be
kept at least 24 hours in these conditions to equilibrate before
conducting the tests, unless indicated otherwise. All measurements
should be reproduced on at least 4 samples and the average value
obtained indicated, unless otherwise indicated.
Centrifuge Retention Capacity (CRC)
[0109] The CRC measures the liquid absorbed by the superabsorbent
polymer particles for free swelling in excess liquid. The CRC is
measured according to EDANA method WSP 241.2-05.
Dry Absorbent Core Caliper Test
[0110] This test may be used to measure the caliper of the
absorbent core (before use i.e. without fluid loading) in a
standardized manner.
[0111] Equipment: Mitutoyo manual caliper gauge with a resolution
of 0.01 mm--or equivalent instrument.
[0112] Contact Foot: Flat circular foot with a diameter of 17.0 mm
(.+-.0.2 mm). A circular weight may be applied to the foot (e.g., a
weight with a slot to facilitate application around the instrument
shaft) to achieve the target weight. The total weight of foot and
added weight (including shaft) is selected to provide 2.07 kPa
(0.30 psi) of pressure to the sample.
[0113] The caliper gauge is mounted with the lower surface of the
contact foot in an horizontal plane so that the lower surface of
the contact foot contacts the center of the flat horizontal upper
surface of a base plate approximately 20.times.25 cm. The gauge is
set to read zero with the contact foot resting on the base
plate.
[0114] Ruler: Calibrated metal ruler graduated in mm.
[0115] Stopwatch: Accuracy 1 second
[0116] Sample preparation: The core is conditioned at least 24
hours as indicated above.
[0117] Measurement procedure: The core is laid flat with the bottom
side, i.e. the side intended to be placed towards the backsheet in
the finished article facing down. The point of measurement (e.g.
the crotch point C) is carefully drawn on the top side of the core
taking care not to compress or deform the core.
[0118] The contact foot of the caliper gauge is raised and the core
is placed flat on the base plate of the caliper gauge with the top
side of the core up so that when lowered, the center of the foot is
on the marked measuring point.
[0119] The foot is gently lowered onto the article and released
(ensure calibration to "0" prior to the start of the measurement).
The caliper value is read to the nearest 0.01 mm, 10 seconds after
the foot is released.
[0120] The procedure is repeated for each measuring point. If there
is a fold at the measuring point, the measurement is done in the
closest area to this point but without any folds. Ten articles are
measured in this manner for a given product and the average caliper
is calculated and reported with an accuracy of one tenth mm.
[0121] Absorbent Article Caliper Test
[0122] The Absorbent Article Caliper Test can be performed as for
the Dry Absorbent Core Caliper Test with the difference that the
caliper of the finished absorbent article is measured instead of
the caliper of the core. The point of measurement may be the
intersection of the longitudinal axis (80) and transversal axis
(90) of the absorbent article. If the absorbent articles were
provided folded and/or in a package, the articles to be measured
are unfolded and/or removed from the center area of the package. If
the package contains more than 4 articles, the outer most two
articles on each side of the package are not used in the testing.
If the package contains more than 4 but fewer than 14 articles,
then more than one package of articles is required to complete the
testing. If the package contains 14 or more articles, then only one
package of articles is required to perform the testing. If the
package contains 4 or fewer articles then all articles in the
package are measured and multiple packages are required to perform
the measurement. Caliper readings should be taken 24.+-.1 hours
after the article is removed from the package, unfolded and
conditioned. Physical manipulation of product should be minimal and
restricted only to necessary sample preparation.
[0123] Any elastic components of the article that prevent the
article from being laid flat under the caliper foot are cut or
removed. These may include leg cuffs or waistbands. Pant-type
articles are opened or cut along the side seams as necessary. Apply
sufficient tension to flatten out any folds/wrinkles. Care is taken
to avoid touching and/or compressing the area of measurement.
[0124] Wet Channel Integrity Test
[0125] This test is designed to check the integrity of a channel in
an absorbent core following wet saturation.
[0126] 1. The full length (in millimeters) of the channel is
measured in the dry state (if the channel is not straight, the
curvilinear length through the middle of the channel is
measured).
[0127] 2. The absorbent core is then completely immersed in a large
excess (e.g. 5 liters) of synthetic urine "Saline", with a
concentration of 9.00 g NaCl per 1000 ml solution prepared by
dissolving the appropriate amount of sodium chloride in distilled
water. The temperature of the solution must be 20 +/-5.degree.
C.
[0128] 3. After 1 minute in the saline, the core is removed and
held vertically by one end for 5 seconds to drain, then extended
flat on an horizontal surface with the top side (the side intended
to be facing the wearer in the article) facing up. If the core
comprises stretch elements, it is pulled taut so that no
contraction is observed. The core can be fixed to an horizontal
surface by clamps at its front edge and back edge, so that no
contraction can happen.
[0129] 4. The absorbent core is covered with a rectangular suitably
weighted rigid plate, with dimensions as follows: length equal to
the full length of the core, and width equal to the maximum core
width at the widest point.
[0130] 5. A pressure of 18.0 kPa is applied for 30 seconds over the
area of the rigid plate above mentioned. Pressure is calculated on
the basis of overall area encompassed by the rigid plate. Pressure
is achieved by placing additional weights in the geometric center
of the rigid plate, such that the combined weight of the rigid
plate and the additional weights result in a pressure of 18.0 kPa
over the total area of the rigid plate.
[0131] 6. After 30 seconds, the additional weights and the rigid
plate are removed.
[0132] 7. Immediately afterwards, the cumulative length of the
portions of the channel which remained intact is measured (in
millimeters; if the channel is not straight, the curvilinear length
through the middle of the channel is measured). If no portions of
the channel remained intact then the channel is not permanent.
[0133] The percentage of integrity of the permanent channel is
calculated by dividing the cumulative length of the portions of the
channel which remained intact by the length of the channel in the
dry state, and then multiplying the quotient by 100.
[0134] Wet Caliper And Compression Force (WCACF) Test
[0135] This test measures a) the percentage of increase in caliper
of a saturated absorbent core following one lateral compression,
and b) the force required to laterally compress the saturated
absorbent core to a width of 40 mm. The WCACF Test is to be
performed on an absorbent core according to the following
instructions. [0136] 1. Mark the longitudinal axis on the absorbent
core on the top side of the core. The longitudinal axis generally
divides the top side of the core into two roughly symmetric pieces
along the length of the absorbent core when the core is viewed from
the top as exemplarily shown on FIG. 3. The top side of the core is
the side intended to be placed towards the wearer-facing side of
the absorbent article. In doubt, the top side is normally more
hydrophilic than the bottom side. If the top side still cannot be
identified, the test is then conducted on an equal number of cores
on alternative sides and the results averaged. Marking can be made
with any pen taking care not to damage the core while marking.
[0137] 2. Mark the crotch line on the same side of the absorbent
core as the longitudinal centerline. The crotch line is
perpendicular to the longitudinal axis and crosses the longitudinal
axis at a distance equal to 45% of the length L of the absorbent
core (0.45 L). This distance is measured from the front side of the
absorbent core (see FIG. 3 for an exemplary illustration). The
front side of the absorbent core is the side of the core intended
to be placed towards the front of the absorbent article. If the
intended orientation of the core is not known, the front edge is on
the side of the core where the amount of SAP is higher. If the
front edge can still not be identified, then half the samples can
be tested with the distance starting from one side and the other
half with the distance starting from the other side, and the
results averaged. The intersection of the crotch line and the
longitudinal axis is the crotch point C. [0138] 3. The absorbent
core is then immersed in a large excess, e.g. 5 l, of synthetic
urine "Saline", with a concentration of 9.00 g NaCl per 1000 ml
solution prepared by dissolving the appropriate amount of sodium
chloride in distilled water. The container must be large enough to
accommodate the core in a flat configuration. The marked side of
the core faces up during the immersion. [0139] 4. After 1 minute in
the saline, the absorbent core is removed and held vertically by
the front side for 10 seconds to drain. [0140] 5. The absorbent
core is left to equilibrate for 10 minutes by pulling it flat on a
horizontal surface, with the top side facing down. Clamps placed on
the front and back sides of the core may be used to keep the loaded
core flat. [0141] 6. The caliper of the loaded absorbent core
before compression is then measured at the crotch point and
reported as Cinitial. For this purpose, a presser foot with a
diameter of 17.0 mm is used, and a pressure of 2.07 kPa (0.30 psi)
is applied. The absorbent core is laid flat on a plexiglas plate
the marked side facing up, and the presser foot is gently lowered
so that it is centered on the crotch point C. The thickness
Cinitial is measured 30.+-.2 seconds after initial contact between
the foot and the core and reported to the nearest 0.1 mm. [0142] 7.
The loaded absorbent core with its top side facing up is then fixed
on a rigid-plastic cylinder as schematically represented in FIG. 7.
The cylinder 600 has a diameter d of 150 mm (+-1 mm). The last 20.0
mm (+-0.5 mm) of the front edge 280 of the core 28 is first
attached to the external surface of the cylinder closest to the
operator via a double sided tape previously applied on the cylinder
or other fastening means so that the absorbent core can be securely
and releasably attached to the cylinder. The last 20.0 mm (+-0.5
mm) of the back edge 282of the core 28 is then attached at the
diametrically opposed external surface of the cylinder at a high
sufficient for the crotch point C to coincide with the central axis
610 of the cylinder 600. [0143] 8. One understands that the
cylinder needs to be sufficiently high so that the back edge of the
core can be attached to it. [0144] 9. The absorbent core is then
laterally compressed as detailed below. Compressive forces are
applied to the absorbent core by an assembly comprised of a pair of
compression plates 630, 640, which simulate the portion of the legs
compressing the absorbent core during use. Each compression plate
should have dimensions 90 mm (+-1 mm).times.90 mm (+-1 mm). The
plates can be made from any suitable material that can be formed
into the required flat, square shape (e.g. aluminum, Plexiglas).
The plates should be placed lined up opposite one another. The
compression plates are placed so that the Crotch Line on the top
side of the core and the geometrical center of each compression
plate are aligned and are in a horizontal plane.
[0145] 10. Each compression plate is driven toward the crotch point
at constant rate of 100 mm/min. (total closing speed is 200
mm/min). The gap between both compression plates starts at a
distance of 140.0 mm +-0.5 mm, or more if the width of the core so
requires, and then narrows to a final gap of 40.0 mm +-0.5 mm when
the absorbent core is compressed. The compression plates may for
example use an apparatus such as a Zwick Z 1.0 or similar. The
testing instrument includes a right clamp for securing one
compression plate, and a left clamp for securing another
compression plate. The equipment should include a force cell with
an appropriate measurement range e.g. up to 100 N and a precision
of at least +/-0.01 N. [0146] 11. Once the absorbent core has been
compressed to 40 mm, compression is maintained for 30 seconds. The
force at the end of the 30 seconds immediately before the
compression is released is recorded to the nearest 0.01 N and
reported as the "Wet Compression Force". The compression plates can
then be returned to their initial positions at a speed of 100
mm/min for each plate. [0147] 12. Immediately afterwards, the
absorbent core is removed from the cylinder 600, taking care to not
touch the area that has been compressed. If some absorbent material
leaked out of the core wrap during the compression step this leaked
out absorbent material is collected and weighted. [0148] 13. The
caliper at the crotch point C is measured again using the thickness
measuring procedure as described above on step 6. This caliper
value is reported as Cfinal.
[0149] This procedure is repeated for at least 4 core samples. The
Relative Wet Caliper Increase (RWCI) of the absorbent core is then
calculated as follows:
Relative Wet Caliper Increase
(%)=(.SIGMA.Cfinal-.SIGMA.Cinitial)*100/.SIGMA.Cinitial
where .SIGMA.Cfinal is the sum of Cfinal values measured for all
the samples and .SIGMA.Cinitial is the sum of the Cinitial values
measured for all the samples. The Relative Wet Caliper Increase
value of the cores according to the invention is less than 10.0%,
in particular it may range of from 1.0% to 9.5%, or 2.0% to 9.0%,
or from to 2.5% to 8.0%.
[0150] If some absorbent material leaked at step 12, the rest of
the absorbent material still contained in the core can be extracted
and also weighted. If the amount that leaked represents less than
5% by weight of the total absorbent material of the core (leaked
and extracted) then it is considered that "substantially no
absorbent material" leaked during the test. Advantageously less
than 2%, or less than 1% or even 0% by weight of absorbent material
escapes the core wrap during step 12. In particular the core wrap
should not in an appreciable way burst open while the test is
conducted.
EXPERIMENTALS
[0151] The following absorbent core according to the invention was
prepared:
Invention example 1:
[0152] The absorbent cores tested in this example were similar to
the core illustrated in FIG. 3. The cores contained SAP as
absorbent material, without cellulosic fibers. The core wrap
comprised two substrates forming the top and bottom sides of the
core, the upper substrate forming a C-wrap along the longitudinal
edges of the core and the front and back edges of the core being
attached flat. The core comprised two absorbent material free
channels in the crotch region. The channels were symmetric in
relation to the longitudinal axis 80 had a projected length thereon
of about 227 mm, a width of about 8 mm and a shortest distance from
each other of 20 mm. The core wrap was further attached to itself
through the channels.
[0153] The absorbent core comprised in total 14.1 g fast absorbing
SAP applied in an area of deposition having a length of 360 mm and
a width of 110 mm (rectangular profile). The SAP was distributed so
that the basis weight of SAP was higher in the crotch region than
at the front region and still lower towards the back region. There
was no profiling of the SAP in the transversal direction
("cross-machine direction" or "CD", except of the channels which
were free of absorbent material). The absorbent core was formed by
SAP printing technology, as disclosed in US2010/0051166A1, which
combines two nonwoven substrates each supporting a SAP layer and
having a microfiber elastic glue applied on each SAP layer which
immobilizes the SAP layer on the substrate. The channels were
formed by using a suitable printing drum delimiting the channels
shape, further information on how to form channels can be found in
EP application number EP12174117.7 using printed SAP
technology.
[0154] Auxiliary glue was applied between the SAP layer and the
upper substrate 16, and was slot coated with 41 slots 1 mm wide
with a distance of 1 mm between the slots along the whole length of
the core wrap (390 mm). 0.211 g and 0.168 g of microfiber glue
(from H. B. Fuller) were respectively applied on the upper and
lower SAP layer, the area of application having a width of 110 mm
and length of 390 mm on each SAP layer.
[0155] The core wrap had a length of 390 mm with two end flaps free
of absorbent material having a length of 15 mm at the back and at
the front edge of the absorbent core. The front and back end seals
of the core were slot glued together, the glue slots having a
length of 30mm from the front end seal and 20mm from the back end
seal. The folded width of the core wrap was 120 mm.
[0156] The upper substrate 16 was a 10 gsm hydrophilically treated
SMMS nonwoven and the lower substrate 16' was a 10 gsm SMMS
nonwoven. The upper substrate was cut at a length of 390 mm and a
cut width of 165 mm. The lower substrate had a cut length of 390 mm
and a cut width of 130 mm. The upper substrate was C-wrapped around
the lower substrate on the lateral edges of the core and the
lateral edges of the lower layer was slightly formed upwards on the
edge of the absorbent material of the core so that the overall
width of the folded core wrap was about 120 mm. The C-wrap was made
permanent by application between the substrates of a core folding
glue applied at 20 gsm with 2 slots having a slot width of 3 mm and
390 mm long on each side of the core. The two substrates were
additionally bonded together through the channels. The bond was
formed by applying pressure and the auxiliary and microfiber glue.
The bond was strong. The core wrap seals resisted compression and
no absorbent material escaped the core wrap during the WCACF
Test.
Invention Example 2
[0157] The cores tested in this example had two pair of channels
and a shaped deposition area similar to the one shown in FIG. 6.
The width of the absorbent material deposition area was 110 mm at
the front and the back region and 90 mm at the crotch point of the
absorbent material deposition area.
[0158] The projected lengths of the long and short channels on the
longitudinal axis of the core were about 170 mm and 40 mm
respectively. The smallest distance between the longer channels was
about 16 mm. The smallest distance between the shorter channels was
about 14 mm. The cores comprised 11.53 g of SAP. The core wrap
comprised two nonwovens, the top substrate (16) was a 10 gsm SMMS
nonwoven treated by a surfactant to be hydrophilic. The lower
substrate (16') was a 11 gsm SMMS nonwoven. Auxiliary glue was
applied between the lower SAP layer and its respective lower
substrate which was slot coated with 41 slots 1 mm wide with a
distance of 1 mm between the slots along the whole length of the
core wrap (390 mm). The microfiber glue (from H. B. Fuller) applied
on each SAP layer was uniformly applied at width of 108 mm and
length of 390 mm on each SAP layer, 0.211 g of microfiber glue was
used on the core cover side and 0.211 g on the dusting layer side.
The rest of the core construction was substantially similar as the
cores in Invention Example 1.
COMPARATIVE EXAMPLE
[0159] The comparative example 1 was substantially similar to
Invention Example 2 with the difference that the absorbent core did
not comprise material free channels.
[0160] Test Results
[0161] Four samples of each above mentioned products were tested
according to the WCACF Test described above to measure the Relative
Wet Caliper Increase and the Wet Compression Force of the core. The
averaged results are compiled below:
TABLE-US-00001 Relative Wet .SIGMA.Cinitial/4 .SIGMA.Cfinal/4 wet
caliper Compression [mm] [mm] increase Force (N) Invention 13.0
13.8 6.2% 4.83 Example 1 Invention 10.8 11.5 6.5% 2.81 Example 2
Comparative 10.8 11.9 10.2% 3.05 example 1
[0162] Discussion
[0163] While not wishing to be bound by theory it is believed that
the following features can provide alone or in combinations an
increase in the relative wet caliper to an absorbent core missing
one or more of the below features. None of these features should be
considered as being limited the scope of the claims, unless
specifically claimed. [0164] 1) The top side of the wrap and the
bottom side of the wrap may advantageously be at least partially
bonded to each other through the channels. These bonds may be
continuous or intermittent, and may be made via gluing and/or heat
bonding, and may advantageously be sufficiently strong to at least
partially resist delamination upon fluid loading ("permanent
channels"), as discussed above. By constraining the core wrap in
the channels, these bonds increase the strain of the core wrap and
can diminish the wet caliper increase upon core loading. [0165] 2)
The core wrap may comprise a first substrate (16) and a second
substrate (16'), both typically made of a nonwoven, wherein the
first substrate forms a C-wrap around the second substrate. The
first substrate may form the top side of the core wrap and the
second substrate may form at least part of the bottom side of the
core wrap. Typically the substrates may be bonded, for example by
gluing, along the wrapped flaps of the first substrate together
with the bottom side of the second substrate. The inventors believe
that a C-wrap, especially along part or whole of the longitudinal
sides of the absorbent core, can better restrain the absorbent
material from breaking out of the core upon compression. [0166] 3)
The Wet Compression Force is influenced by the amount of absorbent
material and the shape of the deposition area of the core in the
crotch region. It is believed that a lower amount of absorbent
material and/or a narrower deposition area at the crotch region of
the core (as in a shaped area) can provide a decreased Wet
Compression Force. The absorbent core of the invention may
exemplarily have a Wet Compression Force below 5.00 N, in
particular less than 3.00 N, or from 1.00 N to 5.00 N, as measured
by the WCACF Test.
[0167] 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."
[0168] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that it alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, 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.
[0169] 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.
* * * * *