U.S. patent application number 15/477408 was filed with the patent office on 2017-11-02 for absorbent article with a distribution layer comprising channels.
The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to Ernesto Gabriel BIANCHI, Joerg ENDRES, Alexander FEDOTOV, Julien Rene GARCIA, Ryo MINOGUCHI.
Application Number | 20170312149 15/477408 |
Document ID | / |
Family ID | 55860763 |
Filed Date | 2017-11-02 |
United States Patent
Application |
20170312149 |
Kind Code |
A1 |
BIANCHI; Ernesto Gabriel ;
et al. |
November 2, 2017 |
ABSORBENT ARTICLE WITH A DISTRIBUTION LAYER COMPRISING CHANNELS
Abstract
An absorbent article such as a diaper extending in a
longitudinal direction parallel to a longitudinal axis (80') and a
transversal direction (90') perpendicular to the longitudinal
direction and comprising a distribution layer (54) between a
topsheet (24) and an absorbent core (28). The distribution layer
comprises a fibrous material and a first and second
longitudinally-extending channels (86a,b) substantially free of
fibrous material. The fibrous material is profiled in the
transversal direction so that average basis weight between the
channels differs from the average basis weight in the lateral areas
outward of the channels by at least 50 g/m.sup.2 and/or wherein the
distribution layer comprises a first region having a first basis
weight (bw1) and a second region having a second basis weight
(bw2), wherein the first basis weight and the second basis weight
differ by at least 20 g/m.sup.2, preferably by at least 50
g/m.sup.2, and these regions are present in different areas of the
distribution layer but in the same longitudinally extending
transversal section. The absorbent core may comprise
channel-forming areas (26a,b). The article further comprises a
backsheet (25).
Inventors: |
BIANCHI; Ernesto Gabriel;
(Oberursel, DE) ; ENDRES; Joerg; (Frankfurt am
Main, DE) ; FEDOTOV; Alexander; (Schwalbach, DE)
; GARCIA; Julien Rene; (Frankfurt, DE) ;
MINOGUCHI; Ryo; (Cincinnati, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company |
Cincinnati |
OH |
US |
|
|
Family ID: |
55860763 |
Appl. No.: |
15/477408 |
Filed: |
April 3, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 13/53747 20130101;
A61F 2013/15406 20130101; B65D 85/62 20130101; B65D 85/07 20180101;
A61F 2013/5349 20130101; A61F 13/535 20130101; A61F 13/537
20130101; A61F 13/15203 20130101; A61F 13/49 20130101; A61F 13/551
20130101; A61F 13/55105 20130101; A61F 2013/53778 20130101; A61F
2013/530138 20130101; A61F 13/53717 20130101; A61F 2013/530481
20130101; A61L 15/28 20130101; A61F 13/532 20130101 |
International
Class: |
A61F 13/537 20060101
A61F013/537; A61F 13/535 20060101 A61F013/535; A61F 13/537 20060101
A61F013/537; A61F 13/551 20060101 A61F013/551; A61F 13/551 20060101
A61F013/551; A61L 15/28 20060101 A61L015/28; A61F 13/15 20060101
A61F013/15; B65D 85/62 20060101 B65D085/62; B65D 85/16 20060101
B65D085/16; A61F 13/49 20060101 A61F013/49 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 29, 2016 |
EP |
16167640.8 |
Claims
1. An absorbent article extending in a longitudinal direction
parallel to a longitudinal axis and a transversal direction
perpendicular to the longitudinal direction, wherein the absorbent
article comprises: a fluid permeable topsheet on the wearer-facing
side; an absorbent core comprising an absorbent material; a
fluid-impermeable backsheet on the garment-facing side; a
distribution layer between the topsheet and the absorbent core,
wherein the distribution layer comprises a fibrous material, the
distribution layer comprising: a first and second
longitudinally-extending channels substantially free of fibrous
material; wherein the first channel is on one side of the
longitudinal axis and the second channel is on the other side of
the longitudinal axis; a central area comprising fibrous material
disposed between the first and second longitudinally-extending
channels at an average central area basis weight; a first and
second lateral areas comprising fibrous material disposed
transversally outwardly of the first channel and the second channel
respectively, wherein the first and second lateral areas have an
average lateral areas basis weight; wherein the average central
area basis weight differs from the average lateral areas basis
weight by at least 50 g/m.sup.2.
2. An absorbent article according to claim 1, wherein the local
basis weight of the fibrous material is maximum at the P point,
wherein the P point is situated on the longitudinal axis at a
distance of 0.30 of the length of the article from the front edge
of the article, and the local basis weight is measured on an
circular area having a diameter of 10 mm centered on the P
point.
3. An absorbent article according to claim 1, wherein the average
central area basis weight differs from the average lateral areas
basis weight by at least 60 g/m.sup.2.
4. An absorbent article according to claim 1, wherein the higher of
the average central area basis weight and the average lateral areas
basis weight ranges from about 150 g/m.sup.2 to about 300 g/m.sup.2
and the lower of the average central area basis weight and the
average lateral areas basis weight ranges from about 50 g/m.sup.2
to about 200 g/m.sup.2.
5. An absorbent article according to claim 1, wherein the
distribution layer comprises a first region having a first basis
weight and a second region having a second basis weight, wherein
the first basis weight and the second basis weight differ by at
least 50 g/m.sup.2, and wherein the first basis weight region and
the second basis weight region are longitudinally separated by a
transition area.
6. An absorbent article according to claim 1, wherein the channels
are discontinuous transversal transition areas for the basis weight
in the central area and the basis weight in the lateral areas, at
least along a portion of the length of the channels.
7. An absorbent article according to claim 1, wherein the fibrous
material has a Water Retention Value of from about 2 to about 60,
as measured by the Water Retention Value Procedure.
8. An absorbent article according to claim 1, wherein the fibrous
material comprises cellulosic fibers.
9. An absorbent article according to claim 1, wherein the first and
second longitudinally-extending channels are curved and wherein the
minimum distance between the first and the second
longitudinally-extending channels is of at least 10 mm.
10. An absorbent article according to claim 1, wherein the
absorbent core comprises a core wrap having a top side and a bottom
side, the absorbent material being between the top side and bottom
side of the core wrap, and wherein the absorbent core further
comprises a first and second longitudinally-extending
channel-forming areas, wherein the first channel-forming area is on
one side of the longitudinal axis and the second channel-forming
side is on the other side of the longitudinal axis; a central
absorbent zone comprising absorbent material and disposed between
the first and the second channel-forming areas; and a first lateral
absorbent zone and a second lateral absorbent zone comprising
absorbent material and disposed respectively laterally outwardly of
the first channel-forming area and the second channel-forming
area.
11. An absorbent article according to claim 10, wherein the
channel-forming areas of the absorbent core are substantially free
of absorbent material, and the top side of the core wrap is
attached to the bottom side of the core wrap through the
channel-forming areas.
12. An absorbent article according to claim 10, wherein the first
and second channels of the distribution layer are at least
partially superposed with the first and second channel-forming
areas of the absorbent core.
13. An absorbent article according to claim 10, wherein the average
basis weight of the absorbent material in the central absorbent
zone differs from the average basis weight of the absorbent
material in the first and second lateral absorbent zones by at
least 50%.
14. A package comprising a plurality of absorbent articles
according to claim 1.
15. An absorbent article extending in a longitudinal direction
parallel to a longitudinal axis and a transversal direction
perpendicular to the longitudinal direction, wherein the absorbent
article comprises: a fluid permeable topsheet on the wearer-facing
side; an absorbent core comprising an absorbent material; a
fluid-impermeable backsheet on the garment-facing side; a
distribution layer between the topsheet and the absorbent core,
wherein the distribution layer comprises a fibrous material, the
distribution layer comprising: a first and second
longitudinally-extending channels substantially free of fibrous
material; wherein the first channel is on one side of the
longitudinal axis and the second channel is on the other side of
the longitudinal axis; a central area comprising fibrous material
disposed between the first and second longitudinally-extending
channels at an average central area basis weight; a first and
second lateral areas comprising fibrous material disposed
transversally outwardly of the first channel and the second channel
respectively, wherein the first and second lateral areas have an
average lateral areas basis weight; wherein the distribution layer
comprises a first region having a first basis weight and a second
region having a second basis weight, wherein the first basis weight
and the second basis weight differ by at least 20 g/m.sup.2, and
the first region of first basis weight and the second region of
second basis weight are present in different areas of the
distribution layer but are at least partially in the same
longitudinally-extending transversal section of the distribution
layer where the channels are present, and the length of this
transversal section ranges from about 30% to about 100% of the
length of the channels.
16. An absorbent article according to claim 15 wherein the first
basis weight and the second basis weight differ by at least 50
g/m.sup.2.
17. An absorbent article according to claim 15, wherein the
absorbent core comprises a core wrap having a top side and a bottom
side, the absorbent material being between the top side and bottom
side of the core wrap, and wherein the absorbent core further
comprises a first and second longitudinally-extending
channel-forming areas, wherein the first channel-forming area is on
one side of the longitudinal axis and the second channel-forming
side is on the other side of the longitudinal axis; a central
absorbent zone comprising absorbent material and disposed between
the first and the second channel-forming areas; and a first lateral
absorbent zone and a second lateral absorbent zone comprising
absorbent material and disposed respectively laterally outwardly of
the first channel-forming area and the second channel-forming
area.
18. An absorbent article according to claim 17, wherein the
channel-forming areas of the absorbent core are substantially free
of absorbent material, and the top side of the core wrap is
attached to the bottom side of the core wrap through the
channel-forming areas.
19. An absorbent article according to claim 17, wherein the first
and second channels of the distribution layer are at least
partially superposed with the first and second channel-forming
areas of the absorbent core.
20. A package comprising a plurality of absorbent articles
according to claim 1.
Description
FIELD OF THE INVENTION
[0001] The invention relates to personal hygiene absorbent articles
such as, but not limited to, baby diapers, training pants, feminine
pads or adult incontinence products. The invention is in a first
aspect directed to an improved distribution layer that efficiently
uses a fibrous distribution material.
BACKGROUND OF THE INVENTION
[0002] Absorbent articles for personal hygiene are designed to
absorb and contain body exudates, in particular large quantity of
urine. These absorbent articles typically comprise several layers
that provide different functions, for example a topsheet for
quickly acquiring the fluid and feel soft on the wearer's skin, a
backsheet for protection the wearer's clothes, an absorbent core
for retaining fluid, and an acquisition or distribution layer
between the topsheet and the absorbent core for pulling the liquid
away from the topsheet and bringing it into the absorbent core.
[0003] Absorbent cores traditionally comprise as absorbent material
a blend of cellulose fibers with superabsorbent polymer (SAP)
particles, also called absorbent gelling materials (AGM), see for
example U.S. Pat. No. 5,151,092 (Buell). Absorbent articles having
cores consisting essentially of SAP without cellulose fibers as
absorbent material (so called "airfelt-free" cores) have been more
recently proposed. For example WO2008/155699 (Hundorf) discloses
absorbent cores with a patterned layer of SAP immobilized by a net
of fibrous thermoplastic adhesive material deposited over the layer
of SAP. The fibrous thermoplastic material helps maintaining the
SAP in position within the absorbent core prior to and during use
of the article, without substantially restricting the ability of
the SAP to absorb large volumes of urine. More recently,
WO2012/170783 (Hundorf et al.) discloses absorbent cores comprising
absorbent material having a basis weight that varies across the
absorbent core. WO2012/170778 (Rosati et al.) discloses absorbent
structures that comprise superabsorbent polymers, optionally a
cellulosic material, and at least a pair of substantially
longitudinally-extending channels (see also WO2012/170779,
WO2012/170781 and WO2012/170808). The core wrap can be adhesively
bonded through the channels to form a channel bond. The integrity
of the channel bonds may be at least partially maintained in wet
state.
[0004] It is also known to provide an intermediate layer between
the topsheet and the absorbent core. These intermediate layers are
designed to quickly acquire and/or distribute the fluid away from
the topsheet and bring it into the core. These intermediate layers
are sometimes called "wicking layer", "surge layer", "acquisition
layer" or "distribution layer". These intermediate layers typically
do not comprise superabsorbent material.
[0005] Absorbent articles having only one of these intermediate
layers are known. WO94/23761 (Payne) for example discloses an
acquisition layer comprising an homogeneous composition of
hydrophilic fibrous material comprising stiffened, twisted, and
curled cellulose fibers and having a densified distribution zone.
Other examples are found in U.S. Pat. No. 5,486,166 and U.S. Pat.
No. 5,490,846 (Bishop). Articles having two intermediate layers or
more, in particular an acquisition layer having a high capillarity
which pulls the fluid quickly away from the topsheet and a
distribution layer having a larger void area to distribute the
fluid over a large surface over the core, are also known. For
example WO2014/93323 (Bianchi et al.) discloses an absorbent
article with a profiled acquisition-distribution system. Other
exemplary references disclosing such intermediate layers are
US2008/0312621 and US2008/0312622 (both Hundorf et al.), WO99/17679
(Everett et al.). Absorbent articles comprising channels in the
absorbent core and partially overlapping channels in a liquid
management system have been more recently disclosed in
WO2015/31225, WO2015/31229, WO2015/31243, WO2015/31256 (Roe et
al.).
[0006] While the known absorbent articles can have good overall
properties, there is a continuous need to improve comfort, fit and
efficiency of the current articles while reducing the usage of raw
material to keep the price of manufacture as low as possible. The
present invention addresses these problems.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to an improved absorbent
article having a fibrous distribution layer. The article extends in
a longitudinal direction parallel to a longitudinal axis and a
transversal direction perpendicular to the longitudinal direction.
The absorbent core comprises a fluid permeable topsheet on the
wearer-facing side, an absorbent core comprising an absorbent
material, in particular a superabsorbent polymer material, a
fluid-impermeable backsheet on the garment-facing side and a
distribution layer between the topsheet and the absorbent core. The
distribution layer has: [0008] a first and second
longitudinally-extending channels substantially free of fibrous
material; wherein the first channel is on one side of the
longitudinal axis and the second channel is on the other side of
the longitudinal axis; [0009] a central area comprising fibrous
material disposed between the first and second
longitudinally-extending channels at an average central area basis
weight; [0010] a first and second lateral areas comprising fibrous
material and disposed transversally outwardly of the first and
second channel respectively, wherein the first and second lateral
areas have an average lateral areas basis weight.
[0011] In a first aspect of the invention, the average central area
basis weight differs from the average lateral areas basis weight in
the first and second lateral areas by at least 50 g/m.sup.2 (grams
per square meter or "gsm"). The average central area basis weight
may be higher or lower than the average lateral areas basis weight
of the first and second lateral areas. The relative amount of
distribution material can be adapted to the types of absorbent
articles considered, including the type of absorbent cores disposed
underneath the distribution layer. For most absorbent articles, the
higher average basis weight may typically range from 150 g/m.sup.2
to 450 g/m.sup.2, and the lower average basis weight may typically
range from 50 g/m.sup.2 to 300 g/m.sup.2.
[0012] In a second aspect, the distribution layer comprises a first
region having a first basis weight (bw1) and a second region having
a second basis weight (bw2), wherein the first basis weight and the
second basis weight differ by at least 20 g/m.sup.2, advantageously
by at least 50 g/m.sup.2. The first region of first basis weight
and the second region of second basis weight are present in
different areas of the distribution layer but in a same
longitudinally-extending transversal section of the distribution
layer where the channels are present. The length of this
transversal section may in particular range from 30% to 100% of the
length of the channels, thus providing a CD profiling in at least
30% of the length of the channels up to 100%. The region of first
basis weight may for example be a region of higher basis weight
comprised in the central area of the distribution layer, and the
region of second basis weight may be comprised in the lateral
areas, both regions being comprised in the same longitudinally
extending transversal section of the core. This is for example
illustrated in FIGS. 4-7. Alternatively, the second region may be
of lower basis weight bw2 and may be comprised in the central area
while the first region is comprised in the lateral areas, both
first and second regions being comprised in the same longitudinally
extending transversal section of the distribution layer. This is
for example illustrated in FIGS. 13-15. There may be of course
further regions of different basis weight (bw3, bw4). The first
aspect may be of course combined with the second aspect or may be
used independently of the second aspect.
[0013] The distribution layer may in particular be used with an
absorbent core having channel-forming areas that are at least
partially superposed with the channels of the distribution layer.
The absorbent core may thus comprise a central absorbent zone and
lateral absorbent zones defined relative to the channel-forming
areas of the core. The central absorbent zone and the lateral
absorbent zones may advantageously have different average basis
weight. In this way, the higher basis weight area of the
distribution layer may match the higher basis weight zone of the
absorbent core, and likewise for the lower basis weight area. The
absorbent core may be free of cellulose fibers.
[0014] The distribution material may be typically distributed in
regions having different pre-determined basis weight. These regions
may overlap different areas of the distribution layer. These
regions may be typically separated by continuous transition areas
in the longitudinal direction, whereas the channels may act as
discontinuous transition areas between these regions of different
basis weight in the transversal direction, at least along a portion
of the length of the channels. It may be advantageous to have a
relatively high amount of distribution material in the central area
at the P point of the article, which is defined as the point on the
longitudinal axis situated at a distance of 0.30 of L'' from the
front edge of the article, L'' being the length of the article
measured along the longitudinal axis. The distribution material may
be comprised of cellulose fibers, in particular cross-linked
cellulose fibers, but other materials are possible, in particular
fibrous materials having a Water Retention Value of from 2 to 60,
as measured by Water Retention Value Procedure described
herein.
[0015] The first and second channels may be at least partially
curved or angled so that the width of the central area varies at
least along a portion of the length of the distribution layer.
Alternatively the first and second channels may be straight and
oriented parallel to the longitudinal axis. This and further
aspects will now be further described in the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a top view of an exemplary article of the
invention in the form of a taped diaper which has been pulled flat,
with some layers partially removed.
[0017] FIG. 2 shows an exploded view of the taped diaper of FIG.
1.
[0018] FIG. 3 shows a transversal cross-section of the diaper of
FIG. 1.
[0019] FIG. 4 shows a top view of the distribution layer of the
diaper of FIGS. 1-3 in isolation.
[0020] FIG. 5 shows a transversal cross-section of FIG. 4.
[0021] FIGS. 6 and 7 shows two longitudinal cross-sections of the
distribution layer of FIG. 4.
[0022] FIG. 8 is a top view of an absorbent core comprising two
curved channel-forming areas, with the top layer of the core wrap
partially removed.
[0023] FIG. 9 is a schematic transversal cross-section of the core
of FIG. 8.
[0024] FIG. 10 is a schematic longitudinal cross-section of the
core showing an optional dual absorbent layer construction.
[0025] FIG. 11 is a schematic close-up view of a section of FIG.
10.
[0026] FIG. 12 shows in superposition the distribution layer of
FIG. 4 with the absorbent core of FIG. 8.
[0027] FIG. 13 shows an alternative distribution layer taken in
isolation.
[0028] FIGS. 14-15 show two longitudinal cross-sections of the
distribution layer of FIG. 13.
[0029] FIG. 16 shows in superposition the distribution layer of
FIG. 12 with the absorbent core of FIG. 8.
[0030] FIGS. 17-19 show an alternative distribution layer taken in
isolation.
[0031] FIGS. 20-22 show an alternative distribution layer taken in
isolation.
[0032] FIG. 23 shows a portion of a laying drum that can be used to
form a distribution layer as shown on FIG. 20.
[0033] FIG. 24 schematically shows an article in the form of a
pant.
[0034] FIG. 25 schematically shows a pant article with the side
seams opened.
DETAILED DESCRIPTION OF THE INVENTION
General Description of an Absorbent Article
[0035] An exemplary absorbent article according to the invention in
the form of a baby taped diaper 20 is represented in FIGS. 1-3.
FIG. 1 is a top plan view of the exemplary diaper in a flat-out
state, with portions of the structure being cut-away to more
clearly show the construction of the diaper. FIG. 2 is an exploded
view showing the different layers of the diaper of FIG. 1. FIG. 3
is transversal cross-sectional view of the diaper 20 taken along
line 2-2 in FIG. 1. 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 such as training
pants, adult incontinence pants or feminine sanitary pads. FIGS.
24-25 for example schematically show a pant type absorbent article
that may also use the invention.
[0036] The absorbent article 20 comprises a liquid permeable
topsheet 24, a liquid impermeable backsheet 25 and an absorbent
core 28 between the topsheet and the backsheet. The absorbent
article represented also comprises an acquisition layer 52 directly
underneath the topsheet and a distribution layer 54 according to
invention. The acquisition layer 52 is optional. The distribution
layer 54 has a pair of longitudinally-extending channels 86a,b
which are substantially free of absorbent material. The
distribution layer 54 will be further discussed in details in the
next section. Other typical diaper components are represented such
as elasticized gasketing cuffs 32, upstanding barrier leg cuffs 34,
fastening tabs 42 and landing zone 44, an urine indicator 70. These
further components will be discussed in more details further below.
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
cuffs, a lotion application, etc.
[0037] The absorbent article 20 comprises a front edge 10, a back
edge 12, and two longitudinally-extending side (lateral) edges 13,
14. 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 is notionally
divided by a longitudinal axis 80' extending along a longitudinal
direction from the middle of the front edge to the middle of 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. This axis 80' may
typically be concomitant with the longitudinal axis 80 of the core.
If some parts of the article are 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 article can be pulled taut so as to be substantially flat.
Closed articles such as training pants or adult incontinent pants
may be cut open along the side seams to apply them on a flat
surface (as illustrated on FIG. 25). Unless otherwise indicated,
dimensions and areas disclosed herein apply to the article in this
flat-out configuration.
[0038] The article has a length L'' as measured along the
longitudinal axis 80' from the back edge to the front edge. The
absorbent article can also be notionally divided by a transversal
axis 90' into a front region and a back region of equal length
measured on the longitudinal axis, when the article is in such a
flat state. The transversal axis 90' is perpendicular to the
longitudinal axis 80' and placed at half the length of the article.
The intersection of the longitudinal axis 80' and the transversal
axis 90' is defined herein as the centerpoint C' of the article.
The P point is further defined herein as the point on the
longitudinal axis situated at a distance of 0.30 of the length of
the article (L'') from the front edge of the article. The P point
typically corresponds in many articles to a zone of relatively high
volume of fluid insult.
[0039] The absorbent core represented comprises a pair of
channel-forming areas 26, which may be substantially free of
absorbent material and through which the top side of the core wrap
is bonded to the bottom side of the core wrap. The absorbent core
can alternatively comprise channels without core wrap bonds, or may
be devoid of channels or channel-forming areas. However the
channels of the distribution layer according to the invention can
advantageously cooperate with such channel-forming areas present in
an absorbent core, especially when these are at least partially
superposed with the channels of the distribution layer as
illustrated in FIG. 3.
[0040] 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, fusion and/or
pressure bonding. The topsheet 24 and the distribution layer 52, if
present, may be attached to the top side 288 of the absorbent core
through the channel of the distribution layer if desired (not shown
in FIG. 3) for example by gluing. The absorbent article is
preferably thin. The article may for example have a caliper of from
1.0 mm to 8.0 mm, in particular from 1.5 mm to 6.0 mm, at the
centerpoint C' as measured using the Absorbent Article Caliper Test
described below.
Distribution Layer 54
[0041] The absorbent article comprises a distribution layer 54
between the topsheet 24 and the absorbent core 28. There may be
other layers between the distribution layer and any of the topsheet
and the absorbent core, for example an acquisition layer 52. The
function of the distribution layer 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. The
distribution layer is made of a fibrous material typically based on
synthetic or cellulosic fibers and has a relatively low density.
The fibrous material may be manufactured by air-laying the fibers
on a drum comprising several molds each having the required depth
profile for the desired fibrous material configuration. The formed
distribution layer can then be directly un-molded onto another
component of the article such as nonwoven and then integrated with
the rest of the chassis of the article. When a nonwoven acquisition
layer 52 is present in the article, the distribution layer may be
for example deposited on this acquisition layer, the two layers
being further joined to absorbent core and the rest of the article,
as is known in the art. The fibrous material used to make the
distribution layer may have a Water Retention Value of from 2 to
60, in particular from 3 to 40, more particularly from 4 to 20, as
measured by the Water Retention Value Procedure described further
below. The density of the distribution layer may vary depending on
the compression of the article, but may typically range from 0.03
g/cm.sup.3 to 0.25 g/cm.sup.3, in particular from 0.05 g/cm.sup.3
to 0.15 g/cm.sup.3, measured at 0.30 psi (2.07 kPa), and may be for
example measured at the centerpoint C' or the P point. A
particularly preferred distribution material comprises or consists
of cross-linked cellulose fibers, as will be detailed further
below, but other typical distribution materials can also be
used.
[0042] The distribution layer of the invention comprises a first
longitudinally-extending channel 86a substantially free of fibrous
material on one side of the longitudinal axis, and a second
longitudinally-extending channel 86b on the other side of the
longitudinal axis. These channels define between them a central
area 82 comprising fibrous material. The central area has an
average central area basis weight. The channels further define a
first lateral area 81 comprising fibrous material disposed
transversally outwardly of the first channel 86a and a second
lateral area 83 comprising fibrous material disposed transversally
outwardly of the second channel 86b. The central and the lateral
areas thus have about the same length, which is the length of the
channels. The basis weight in the first lateral area is typically
about equal to the basis weight in the second lateral area because
the article is normally symmetrically arranged relative to the
longitudinal axis. The distribution layer also comprises a front
area 84 disposed longitudinally in front of the channels 86, and a
back area 85 disposed longitudinally behind the channels 86.
[0043] The channel may be typically at least partially curved. In
particular the channels may be concave (inwardly curved) towards
the longitudinal axis 80' as illustrated in FIG. 4. Alternatively,
it is not excluded that the channels may be partially or entirely
straight, and in particular longitudinally oriented parallel to the
longitudinal axis 80', or curved in the other direction. The
channels are typically disposed as one or more symmetrical pair(s)
relative to the longitudinal axis, and are spaced apart from one
another over their whole longitudinal dimension. The shortest
spacing distance between the channels may be for example at least 5
mm, or at least 10 mm, or at least 16 mm. It is however not
excluded that the channels may be joined together, for example at
their front or back extremities. Furthermore, in order to reduce
the risk of fluid leakages, the channels optionally do not extend
up to any of the edges of the distribution layer, and are therefore
surrounded by and fully encompassed within the distribution layer.
The smallest distance between a channel and the closest edge of the
distribution layer may be at least 5 mm.
[0044] It has been suggested in the past to profile the
distribution layer in the longitudinal direction and to provide two
material-free channels in the distribution layer on either side of
the longitudinal axis (see e.g. WO2014/93323, Bianchi et al. and
WO2015/31225, Roe et al). The present invention now provides a
distribution layer having a profiled basis weight configuration in
the transversal direction. According to a first aspect of the
invention, the average central area basis weight differs from the
average lateral areas basis weight by at least 50 g/m.sup.2 (grams
per square meter, or gsm), in particular at least 60 g/m.sup.2, or
at least 70 g/m.sup.2, or at least 80 g/m.sup.2. The central area
may be the area having the higher average basis weight relative to
the first and second lateral areas. This will be exemplified when
discussing for example the distribution layer of FIGS. 4-7.
Alternatively, the average central area basis weight may be at
least 50 g/m.sup.2, in particular at least 60 g/m.sup.2, or at
least 70 g/m.sup.2, or at least 80 g/m.sup.2 lower than the average
lateral areas basis weight. This is exemplified for example in the
distribution layer of FIGS. 13-15. For most absorbent articles, the
average basis in the higher basis weight area may typically range
from 150 g/m.sup.2 and 300 g/m.sup.2 and the average basis weight
in the lower basis weight area would be between 50 g/m.sup.2 and
200 g/m.sup.2. For some articles like adult incontinence products
having to deal with relatively high amount of fluid, these values
may be higher. The average basis weight in the higher basis weight
area may also range from 150 g/m.sup.2 and 450 g/m.sup.2 and the
average basis weight in the lower basis weight area would be
between 50 g/m.sup.2 and 300 g/m.sup.2 for these products.
[0045] The average basis weight in each area of the distribution
layer can be measured experimentally by removing and weighing the
fibrous material in the area considered (central area or both
lateral areas) and dividing this weight by the surface of the area
considered. The surface of the area can be determined by taking a
picture and analyzing it using any commercial image analysis
software, or by any other conventional methods. The channels and
any other areas which are substantially free of fibrous
distribution material are disregarded for calculating the average
basis weight of the different areas. It is unlikely that the
average basis weights in the first and second lateral area
substantially differs, but in any case the combined weight of the
distribution material if both areas and the combined surface of
both lateral areas is used to determine the average lateral areas
basis weight.
[0046] Independently of the relation between the basis weigh of the
central and the lateral areas, it may be further advantageous that
the basis weight of the distribution material measured at the P
point (P) is maximum relative to the rest of the distribution
layer. By maximum, it is meant that the distribution layer does not
comprise another point having a higher basis weight, but of course
there may be other point or regions in the distribution layer
having the same basis weight. The P point may in particular belong
to a region of higher basis weight (bw1) in the distribution layer.
The P point is defined herein as the point of the distribution
layer on the longitudinal axis disposed at a distance of 0.30 of
the length of the article (L'') from the front edge 10 of the
article. The basis weight at the P point or on any the other
regions of the distribution layer can be typically directly
determined from the manufacturer's specification of the layer
making machine. If the specification is not known, the local basis
weight at the P point may be measured by taking a circular sample
having a diameter of 10 mm and centered on the P point. The
distribution material in this area is weighed and divided by the
surface area of the circle to provide the local basis weight
value.
[0047] The basis weight transition in the transversal direction
between regions of the distribution layer having different basis
weight can be typically discontinuous (in other word discrete). The
channels in the distribution layer can act along at least a portion
of their length as boundaries between regions of the distribution
layer having different basis weight. The profiling of the
distribution layer in the transversal direction can be used to
provide an improvement of the performance of the article and/or a
cost reduction. Of course, the distribution layer may still be
profiled in the longitudinal direction in each area. This may be
advantageous to have more distribution material in regions of the
article that are more susceptible to receive fluid for example. The
basis weight transition in the longitudinal direction between
regions of the distribution layer having different basis weight can
typically be continuous. This means that may typically be
transition zones in the longitudinal direction as will be
exemplified further below.
[0048] The general shape of the distribution layer as seen from
above may be generally rectangular, as is typical in the art, but
may be also shaped (that is non-rectangular), for example having a
bullet shape as illustrated on FIG. 4 with a back edge that is
rounded, or may have a tapered outline in its middle as illustrated
on FIG. 20. The different configurations can be used to maximize
the efficiency of the distribution layer for different
applications.
[0049] The distribution layer is a fibrous layer. The distribution
layer may be a nonwoven material comprising fibers that are bonded
to another so that the layer has a strong integrity and may be
manipulated independently of a substrate. However the distribution
layer is more typically not a nonwoven layer, but preferably
comprises or consists of loose fibers with no or weak intra-fiber
bonds that are deposited on a supporting substrate at varying basis
weight to form a profiled distribution. A typical example of
distribution material comprises or consists of cross-linked
cellulose fibers. 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 against
the compression in the product packaging or in use conditions, e.g.
under baby weight.
[0050] 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, WO95/34329 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 cross-linked 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:
[0051] aliphatic and alicyclic C2-C9 polycarboxylic acids having at
least three carboxyl groups per molecule; and [0052] 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 cross-linking 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 % cross-linking 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.
[0053] 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.
[0054] The distribution layer comprising cross-linked cellulose
fibers may comprise other fibers, but this layer may 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.
[0055] FIGS. 4-7 illustrate a first example of distribution layer
represented in isolation without the substrate such as an
acquisition layer or the core cover on which it may be deposited.
FIG. 4 shows a top, planar view of the distribution layer. The
front edge of the distribution layer is the straight edge and the
back edge of the distribution layer is the rounded edge. The
rounded edge oriented toward the back of the article in the
finished product. FIG. 5 shows schematically a transversal
cross-section through the middle of the distribution layer. FIG. 6
shows a longitudinal cross-section of the distribution layer
parallel to the longitudinal axis of the article and FIG. 7 shows a
longitudinal cross-section through the first lateral area 81.
[0056] In this example, the fibrous material is deposited in a
first region having a relatively high basis weight bw1, and a
second region having a relatively low basis weight bw2. The region
of higher basis weight bw1 extends across the whole of the front
area 84 of the distribution layer, most of the central area 82 and
to a small at extent the front part of the lateral areas 81, 83.
The region of lower basis weight bw2 is present through most of the
length of the lateral areas 81, 83 and the back area 85. These
regions of constant basis weight are separated by gradual
transition zones t1, 12 in the longitudinal direction. These
transition zones may be relatively short compared to the rest of
the layer. On the other hand, the transition is discrete in the
transversal direction between the regions of the central area and
the lateral areas having different basis weight, with the channels
acting as boundaries serving as discrete transition zones.
[0057] These considerations may be generalized beyond this example
for any distribution layers according to the invention. The length
(measured in the longitudinal direction) of the
longitudinally-extending transversal section of the core where both
regions of different basis weight are present in the areas of the
channels may in particular be range from 30% to 100% of the length
of the channels (L'). The regions of higher basis weight may also
be alternatively on the lateral areas of the distribution layer,
while the region of lower basis weight being on the central area.
This is for example illustrated in FIG. 13.
[0058] The fibrous material of the distribution layer may also be
deposited in more than two regions of different basis weight, and
that may extend to different areas. The regions of different basis
weight can be separated longitudinally by gradual transition zones,
while the transition may be discrete in the transversal direction
between the regions across at least along a portion of the length
of the channels, with the channels acting as boundaries serving as
discrete transition zones.
[0059] The dimensions and basis weight values for the different
areas, regions and channels of the distribution layer can be of
course adapted for the different types of absorbent articles
considered. Typically, the more fluid needs to be distributed, the
higher the basis weight is required to provide the performance
desired. To give purely exemplary values, a size 4 baby diaper
(recommended for babies weighing 7-18 kg) may have for example a
higher basis weight bw1 of 220 gsm and a lower basis weight of 120
gsm, but other values are of course possible. Typically, the
distribution layer may comprise a first region having a first basis
weight (bw1) and a second region having a second basis weight
(bw2), wherein the first basis weight and the second basis weight
differ by at least 20 g/m.sup.2, in particular at least 50
g/m.sup.2, or at least 60 g/m.sup.2, or at least 70 g/m.sup.2, or
at least 80 g/m.sup.2. The first basis weight region and the second
basis weight region may be typically longitudinally separated by a
continuous transition area (t1, t2). Of course there may be further
regions of constant basis weight.
[0060] The distribution layer as a whole (including for
simplification the channel areas) may typically have an average
basis weight of from 30 g/m.sup.2 to 400 g/m.sup.2, in particular
from 100 g/m.sup.2 to 300 g/m.sup.2, for the whole distribution
layer. Heavy adult incontinence products may for example have a
higher basis weight, and smaller sizes diaper a lower basis weight.
The underlying absorbent core also plays a role when deciding the
shape and amount of material of the distribution layer. Typically
higher amount of absorbent material in the absorbent core requires
higher amount of distribution material superposed therewith and
vice versa. Before discussing the further examples of distribution
layer of FIGS. 17-22, an example of absorbent core will be
generally described in the following section.
General Description of the Absorbent Core 28
[0061] The distribution layer may advantageously cooperate with the
underlying absorbent core to provide improved performance in terms
of fluid handling and/or wearing comfort. Thus before discussing
other examples of distribution layers, an exemplary absorbent core
and its combination with the distribution layer of FIGS. 4-7 will
be briefly discussed with exemplary reference to the FIGS. 8-12.
The absorbent core 28 may in particular advantageously comprise at
least two longitudinally-extending areas that are substantially
free of absorbent material, which are herein referred as
channel-forming areas 26a, 26b. The channel-forming areas 26 may be
longer or shorter than the channels 86 of the distribution layer,
but advantageously the channel-forming areas of the core correspond
at least along a portion of their length to the channels in the
distribution layer. In this way, the fluid can be directly
transferred vertically via the channels to the center of the
absorbent core, as well as being spread longitudinally along its
length.
[0062] An exemplary absorbent core taken in isolation is
illustrated on FIGS. 8-11. As used herein, the term "absorbent
core" or "core" refers to a component of an absorbent article which
comprises an absorbent material contained in a core wrap. As used
herein, the term "absorbent core" does not include the topsheet,
the backsheet, and the distribution layer. The absorbent core has
typically the most absorbent capacity of all the components of the
absorbent article, and comprises all or at least the majority of
superabsorbent polymer (SAP) in the article. The core typically
thus consists essentially of, or consists of, the core wrap, the
absorbent material and optionally adhesives. The absorbent material
may consist of SAP in particulate form as exemplified in the
present description but it is not excluded that other type of
absorbent material may be used. The terms "absorbent core" and
"core" are herein used interchangeably.
[0063] The absorbent core may be substantially planar so that it
can be laid flat on a surface. The absorbent core may also be
typically thin and conformable, so that it can also be laid on a
curved surface for example a drum during its making process or
stored as a continuous roll of stock material before being
converted into an absorbent article. FIGS. 8-11 schematically show
an absorbent core as known from the prior art, e.g. as in
WO2012/170,778 (Rosati et al.). The absorbent cores of the
invention may comprise the same basic features as this absorbent
core. For ease of discussion, the exemplarily absorbent core of
FIG. 8 is represented in a flat state and extending in a plane
along a transversal direction (x) and a longitudinal direction (y).
Unless otherwise indicated, dimensions and areas disclosed herein
apply to the core in this flat-out configuration. The same applies
to an absorbent article, as exemplarily represented in FIG. 1, in
which the core is integrated. For ease of discussion, the absorbent
cores and articles of the invention will be discussed with
reference to the Figures and the numerals referred to in these
Figures, however these are not intended to limit the scope of the
claims unless specifically indicated.
[0064] The outline of the absorbent core is typically defined by
the core wrap. The core wrap may comprise two individual substrates
16, 16' as illustrated in the Figures, but it is also common and
possible to have a single substrate forming the core wrap. The
absorbent core typically comprises a front edge 280, a back edge
282 and two longitudinally-extending side edges 284, 286 joining
the front edge and the back edge. The front edge is the edge of the
core placed towards the front edge 10 of the absorbent article.
Typically the absorbent material 60 of the core may be
advantageously distributed in somewhat higher amount towards the
front edge than towards the back edge as more absorbency is
typically required towards the front half of the article. Typically
the front and back edges 280, 282 may be shorter than the
longitudinally-extending side edges 284, 286. The absorbent core
also comprises a top side 288 and a bottom side 290. The top side
of the core is the side placed or intended to be placed towards the
topsheet 24 of the article and the bottom side is the side placed
or intended to be placed towards the backsheet 25 in the finished
article. The top side of the core wrap may be typically treated to
be more hydrophilic than the bottom side.
[0065] The absorbent core can notionally (i.e. virtually) comprise
a longitudinal axis 80 extending from the front edge 280 to the
back edge 282 and dividing the core in two substantially
symmetrical halves relative to this axis, when viewing the core in
the plane formed by the longitudinal and transversal direction (x,
y). The absorbent core can typically be generally rectangular with
a width W in the transversal direction and a length L in the
longitudinal direction as measured from edge to edge, including the
region of the core wrap which does not enclose the absorbent
material, in particular at the front and back end seals 280', 282'
when present. In case the core is not rectangular, the maximum
dimension measured along the transversal direction and the
longitudinal direction can be used to report the width and length
of the core respectively. The width and length of the core may vary
depending on the intended usage. For baby and infant diapers, the
width W may for example in the range from 40 mm to 200 mm and the
length L from 100 mm to 600 mm. Adult incontinence products may
have higher maximum dimensions.
[0066] The transversal axis 90 of the core (also referred to as
"crotch line") is defined as the virtual line perpendicular to the
longitudinal axis 80 and bisecting the diaper at a distance of 0.45
of L from the front edge 280 of the absorbent core, L being the
length of the core as measured from the front edge 280 in direction
of the back edge 282, as shown on FIG. 8. The crotch point C of the
core is herein defined as the point of intersection of these two
axis. The crotch region of the core is defined herein as the region
of the core extending from the transversal axis 90, 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 and back
region of the core are the remaining regions of the core towards
the front and back edges of the core respectively.
[0067] The absorbent material 60 may be any conventional absorbent
material used in absorbent articles. The absorbent material may
consist of SAP particles immobilized by an adhesive to provide a
relatively thin core. The absorbent core may thus be relatively
thin, in particular thinner than conventional cores comprising
cellulosic fibers. In particular, the caliper of the core (dry,
i.e. before use) as measured at the crotch point (C) or at any
other points of the surface of the core according to the Dry 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. However other types of absorbent
material are more commonly used, the absorbent material may be in
particular a mix of cellulose fibers and SAP particles.
[0068] The absorbent material 60 may be deposited within the core
wrap as one layer, or as represented in FIGS. 10-11 as two
absorbent layers applied on the top substrate 16 and bottom
substrate 16' respectively in a pattern of land areas 75,75'
separated by junction areas 76,76'. This advanced way of making
cores free of cellulose fibers is for example generally disclosed
in WO2008/155699. In particular, two absorbent layers having offset
land 75, 75' and junction areas 76, 76' may be combined to form an
absorbent material deposition area in which the absorbent material
is substantially continuous, as shown in FIG. 8. If the absorbent
core is made according to this process, it may further
advantageously comprise a fibrous thermoplastic adhesive 74, 74' to
further immobilize the absorbent material. However the absorbent
cores of the present invention are not limited to a particular
process for making them, and the cores of the invention may be more
conventionally by air-laying a mix of cellulose fibers and
superabsorbent particles on a conventional air-laying drum.
[0069] The absorbent material 60 defines an absorbent material
deposition area as seen from above within the plane of the core.
The deposition area may be generally rectangular as shown in the
FIG. 8, or may be shaped so that it has a tapered section in the
crotch region, as is known in the art in so-called shaped cores.
The absorbent core may comprise within the deposition area at least
a first longitudinally-extending area 26a and a second
longitudinally-extending area 26b, which are substantially free of
absorbent material and are each disposed on opposite side of the
longitudinal axis. These areas will be designated herein as
channel-forming areas 26a, 26b. The channel-forming areas may be
typically mirror image of each other relative to the longitudinal
axis. The top side 288 of the core wrap may be advantageously
bonded to the bottom side 290 of the core wrap through these
channel-forming areas 26 which are substantially free of absorbent
material. The bonds 27 may be provided by an auxiliary glue 72
applied directly to the inner surface of at least one of the
substrate, as illustrated in FIG. 9, and/or by any other bonding
means such as fusion bonding or ultra-sonic bonding. Typically the
bonds 27 may generally have the same outline and shape as the
absorbent material free areas 26 in which they are contained, but
may be slightly smaller to allow for a safety margin (e.g. by a few
mm) as some deviations from the optimal registration may happen
during high speed process. It is however not excluded that the
channel bonds 27 may be provided in areas containing absorbent
material, in those cases the bonds may however be substantially
less strong and more easily delaminate when the absorbent material
swells. The channel-forming areas 26 may be also be provided
without such bonds, but then the absorbent material may relatively
quickly fill into these areas so that the fluid handling properties
of the channels may be relatively quickly compromised.
[0070] The two channel-forming areas 26a,b define a central
absorbent zone 62 disposed between them, and a first and second
lateral absorbent zones 61, 63 respectively disposed laterally
outwardly of the first and second channel-forming areas. The
central, first and second lateral absorbent zones comprise
absorbent material. The first and second lateral absorbent zones
typically extend laterally up to the longitudinal side edges 284,
286 of the absorbent core. As defined herein, the central absorbent
zone 62 and the lateral absorbent zones 61, 63 do not extend beyond
the longitudinal extremities of the channel-forming areas 26, and
thus the central and the lateral zones typically all have the same
length L' as the length of the channel-forming areas 26. The rest
of the absorbent core comprising absorbent material may thus define
a front absorbent zone 64 extending longitudinally forward of the
front extremities of the channel-forming areas and up to the front
end seal 280' and a back absorbent zone 65 extending longitudinally
backward from the back extremities of the channel-forming areas to
the back end seal 282' of the core.
[0071] The longitudinal axis 80 of the core is typically superposed
with the longitudinal axis 80' of the article. As the absorbent
material 60 swells when it absorbs a liquid such as urine, the bond
27 in the channel-forming areas 26 remain at least initially in
place between the top and bottom sides of the core wrap, so that
the channel-forming areas 26 form easily recognizable
three-dimensional channels. These three-dimensional channels may
further cooperate with the channels of the distribution layer 54
disposed above the absorbent core 28 to guide the fluid inside the
core and longitudinally towards the front and back of the
article.
[0072] The absorbent core and the distribution layer are shown
superposed in FIG. 12. In this view, the channel-forming areas 26
of the core extend longitudinally further than the channels of the
distribution layer 86, but the channels and channel-forming areas
are otherwise superposed. Typically the absorbent core may be
longer and wider than the distribution layer, so that the
channel-forming areas can extend further than the channels of the
distribution layer. It may be advantageous that the channels 86 or
channel-forming areas 26 do not reach any of the edges of the layer
in which they are formed, to reduce the risk of fluid escaping the
layer. Thus the channels and channel-forming areas may be designed
to stop at a distance of at least 5 mm from any edges of the layer
in which they are formed. It is however also not excluded that the
distribution layer may be as wide and/or as long as the absorbent
core, and the channels and the channel-forming areas may have
similar dimensions. It is also not excluded that the
channel-forming areas 26 of the core when present are not
superposed with the channels 86 of the distribution layer 54.
[0073] As illustrated in FIG. 10, the absorbent core may have a
profiled distribution of material in the longitudinal direction,
especially having a higher basis weight in the crotch region than
in the front region, and still higher in the front region than in
the back region. The absorbent core may also be profiled in the
transversal direction, in particular, the absorbent core and the
distribution layer may be similarly profiled in the transversal
direction. Thus, the average basis weight of the absorbent material
in the central absorbent zone of the core may also differ (higher
or lower) than the average basis weight in the first and second
lateral absorbent zones of the core. The average basis weight of
the absorbent material in the central absorbent zone may differ by
at least 10% than the average basis weight in the first and second
lateral absorbent zones, in particular by at least 25%, or by at
least 50%, or by at least 100%.
[0074] Some executions may have relatively less absorbent material
in the central absorbent zone. The average basis weight of the
lateral absorbent zones may then be at least 25% higher than the
average basis weight in the central absorbent zone. In particular,
the average basis weight of the absorbent material in the central
absorbent zone may range from about 20% to about 70% of the average
basis weight in the first and second lateral absorbent zones. The
amount of absorbent material in the central absorbent zone may also
range from about 5% to about 25% of the total amount of absorbent
material in the absorbent core, and the combined amount of
absorbent material in both lateral absorbent zones ranges from
about 30% to 80% of the total amount of absorbent material in the
absorbent core.
[0075] Alternatively, other executions may have relatively more
absorbent material in the central zone. The average basis weight of
the lateral absorbent zones may then be at least 25% lower than the
average basis weight in the central absorbent zone. The amount of
absorbent material in the central absorbent zone may then also
range from about 15% to about 60% of the total amount of absorbent
material in the absorbent core, and the combined amount of
absorbent material in both lateral absorbent zones ranges from
about 25% to 70% of the total amount of absorbent material in the
absorbent core.
[0076] The average basis weight for each absorbent zone of the core
can be, similarly as for the areas of the distribution layer,
calculated by taking the weight of absorbent material in the zone
considered and dividing this weight by the surface of this zone.
The channel-forming areas and any other areas which are
substantially free of absorbent material are disregarded for
calculating the average basis weight of the different zones. The
average basis weight may be typically the same in the first lateral
absorbent zone and in the second lateral absorbent zone. If
exceptionally there was a significant difference of basis weight in
the first lateral zone and the second lateral zone, the weight of
the absorbent material in both lateral absorbent zones is anyway
added and divided by the combined surfaces of both lateral
absorbent zones to provide an average value.
[0077] When the average basis weight of the central zone of the
absorbent core is higher than the average basis weight of the
lateral zones, the average basis weight of the distribution layer
is advantageously similarly higher in the central area relative to
the lateral areas of the distribution layer. Inversely, when the
average basis weight of the central zone of the absorbent core is
lower than the basis weight of the lateral zones of the core, the
average basis weight of the distribution layer may be
advantageously lower in the central area relative to the lateral
area of the distribution layer. By increasing the basis weight of
the distribution material in the areas superposed with the zones of
the absorbent core of relatively higher basis weight, the fluid may
be more efficiently distributed and absorbed by the absorbent core.
For example, the distribution layer of FIGS. 4-7 having a
relatively higher basis weight in the central area 82 is
particularly adapted for an absorbent core having a higher basis
weight of absorbent material in the central zone 62.
[0078] The total amount of absorbent material should be sufficient
for the application considered. For baby diapers for example, the
amount SAP should be sufficient to provide overnight dryness. For
children having a weight range of 8-17 kg, as an example, the total
amount of SAP in the core may be about 12 g, distributed as
follows: 11.5% in the front absorbent zone, 28% in the central
absorbent zone, 25% in each lateral absorbent zone, and 10.5% in
the back absorbent zone (for a total of 100%). More generally, the
amount of absorbent material may be for example distributed as
indicated in the following Table, the percentage being reported by
total weight of the absorbent material in the absorbent core:
TABLE-US-00001 Range in weight % In particular Front absorbent zone
64 0*-25 5-20 Central absorbent zone 62 15-60 20-45 Lateral
absorbent zone 61, 20-70 15-30 63 (combined) Back absorbent zone 65
0*-25 5-15 * although not preferred, it is possible that the
channel-forming areas extend up to the front and back edges of the
absorbent core, so that the front and/or are the back absorbent
zones not existent.
[0079] For absorbent cores having a relatively low amount of
absorbent material in their central absorbent zones, exemplary
values for the same type of baby diaper may be as follows. The
total amount of SAP in the core may be about 12 g, distributed as
follows: 13% in the front absorbent zone, 12% in the central
absorbent zone, 32% in each lateral absorbent zone, and 11% in the
back absorbent zone (for a total of 100%). The average lateral
zones basis weight may be for this particular example about 500 gsm
and the average central zone basis weight may be about 175 gsm.
More generally, the amount of absorbent material may be for example
distributed as indicated in the following Table, the percentage
being reported by total weight of the absorbent material in the
absorbent core:
TABLE-US-00002 Range in weight % In particular Front absorbent zone
64 0*-25 5-20 Central absorbent zone 62 5-25 10-20 Lateral
absorbent zone 61, 30-80 20-40 63 (combined) Back absorbent zone 65
0*-25 5-15 * although not preferred, it is possible that the
channel-forming areas extend up to the front and back edges of the
absorbent core, so that the front and/or are the back absorbent
zones not existent.
Other Examples of Distribution Layers
[0080] FIGS. 13-15 show another example of distribution layer,
wherein the average basis weight in the lateral areas 81, 83 is
higher than the average basis weight in the central area 82, thus
having the opposite relationship as for the previous example of
FIGS. 4-7. Such a distribution layer may be particularly adapted to
an absorbent core with channel-forming areas and having a
transversally profiled distribution of absorbent material with a
relatively low basis weight in the central absorbent zone compared
to the lateral absorbent zones. This type of core may be beneficial
if it is desired that the central absorbent zone does not become
too stiff in the longitudinal direction when it absorbs fluid and
swells. Although the stiffness may thus be reduced in the central
zone, the core may remain sufficiently rigid in the lateral areas
so that overall the absorbent core refrains from excessive sagging
in the crotch region when wet. Excessive sagging may cause the
barrier leg cuffs or the gasketing cuffs to lose contact with the
skin of the users, thus raising the risk of side leakage outside of
the article, and should be avoided. The same general considerations
as for the previous example otherwise apply for this example. FIG.
16 shows the superposition of the distribution layer of FIG. 13-15
with an absorbent core comprising channel-forming areas as
previously discussed.
[0081] FIGS. 17-19 show another example of distribution layer
having three regions of different basis weight. In this example,
the distribution layer is rectangular (thus not shaped), as seen
from above. The region of high basis weight bw1 of the distribution
layer is entirely contained in the central area 82 between the
channels 86a, 86b. The region of medium basis weight bw2 is present
in most of the lateral areas 81, 83 and in the front area 84. The
basis weight further diminishes towards the back edge of the
distribution layer in the central and lateral areas. The region
having the lowest basis weight bw3 comprises the back area 85 of
the distribution layer and a small portion of the adjoining central
and lateral areas. Gradual transition zones t1, t2, t3 separate the
different regions of constant basis weight in the longitudinal
direction. The basis weight transition is discrete in the
transversal direction between the central area and the lateral
areas. Such a distribution layer may be particularly useful for use
together with an absorbent core having a rectangular absorbent
material deposition area and concentrating the absorbent material
in a central zone between its channel-forming areas (if there are
present).
[0082] FIGS. 20-22 show another example of distribution layer. This
distribution layer is shaped (in other words not rectangular), in
particular it tapers transversally towards its middle. This
distribution layer also comprises four different regions having
different basis weight separated by transition zones. The region of
highest basis weight bw1 is entirely contained between the channels
86a, 86b in the central area 82. The basis weight gradually tapers
towards the front and back end of the central area until it reaches
a region of medium basis weight bw2 on each side. The distribution
material in the lateral areas 81, 83 also has a medium basis weight
bw2 for almost the whole length of the lateral areas. The basis
weight further gradually diminishes through a transition zone t2
towards the front edge of the distribution layer to a region of
lower basis weight bw3. Similarly, the basis weight of the
distribution layer gradually diminishes towards the back edge of
the distribution layer through a transition zone t3 until it
reaches a region where the basis weight bw4 is lowest. The region
of lowest basis weight bw4 is entirely comprised in the back area
85. Different gradual transition zones t1, t2, t3, t4 separate the
different regions of constant basis weight in the longitudinal
direction. The basis weight transition is discrete in the
transversal direction through the channels between the central area
and the lateral areas along the majority of the length of the
channels. Such a distribution layer may be particularly useful for
use together with an absorbent core having a shaped absorbent
material deposition area which has a relatively high concentration
of the absorbent material in a central zone between its
channel-forming areas (if these are present).
Method for Making the Distribution Layer
[0083] The distribution layer of the invention may be made and
integrated in an absorbent article using any typical manufacturing
methods known in the art. FIG. 23 shows schematically an individual
receptacle or mold 200 that can be used for depositing the fibrous
material having a configuration similar to the distribution layer
exemplified in FIG. 17. A plurality of such molds may be arranged
in a repeating manner along the circumference of a drum in an
air-laying chamber, as is known in the art. The bottom of the mold
may comprise a grid connected to a source of vacuum so that the
fibers are pulled and deposited in the mold. Two elongated
protuberances 286a, 286b are flush with the frame of the
receptacle, so that substantially no fibers deposit in these areas,
thus forming the material-free channels 86a, 86b of the
distribution layer. The mold further comprises zones of different
depths, for example a zone of lowest depth zone 285 which will form
the back area 85 of the distribution layer, a zone of maximum depth
282 corresponding to the central area 82 of the distribution layer,
and two lateral zones 281, 283 of medium depth corresponding to the
lateral areas 81, 83 of the distribution layer.
Example of Article in a Pant Form
[0084] As indicated previously, the invention may be also used in
absorbent articles presented in the form of a pant or underwear
(herein "pant"). In these articles, the waist and the leg openings
are pre-formed during manufacture so that the article can be put on
like underwear. These pant articles typically have a front waist
panel and a back waist panel which are sealed together via side
seams. The side seams can be broken to remove and discard the
article and are typically not re-fastenable. The front and back
waist panels are typically elasticized. Pants are used as taped
diapers on babies and younger children for day wear and for
overnight dryness, as training pant for older children at the
toilet training stage, and also as adult incontinence
protection.
[0085] The outline of such a pant article is schematically
illustrated in perspective on FIG. 24. The pant comprises a front
waist panel 110 and a back waist panel 120 shown in dotted lines.
The front and back waist panels are joined together at side seams
(not represented) to form the waist opening and the leg openings.
The waist panels are typically elasticized, either using a material
which is inherently elastic to make them (such as a laminate
comprising an elastomeric layer between two nonwoven layers) or by
sandwiching a plurality of elastic strands 130 between two
nonwovens along the width of the panels, as is known in the art.
The pants may further comprise a chassis comprising the remaining
components of the article, in particular the topsheet 24, the
backsheet 25, the absorbent core 28 and barrier cuffs 30 including
upstanding barrier leg cuffs. These components may be generally
constructed as in previously disclosed for the taped diaper.
[0086] FIG. 25 shows a top view of the wearer-facing side of the
pant with the side seams opened and the pant flattened out. For
clarity of the view, the barrier cuffs 30, the topsheet 24 and an
acquisition layer are not shown in FIG. 25. These and the
components represented may be generally as previously discussed.
For example, the distribution layer 54 comprises a pair of
material-free channel areas 86 which can be superposed with a pair
of generally parallel channel-forming areas 26 in the absorbent
core. The channels in the distribution layer may be typically
shorter or have the same length as the channel-forming areas 26 in
the core. Of course, many other constructions for pants are known
in the art and possible to use in the present invention.
[0087] Having described in details the key features of the
invention, the following sections provide more details on some of
the typical components found in absorbent articles. The materials
described below are of course optional and non-limiting, unless
explicitly indicated otherwise.
Core Wrap 16, 16'
[0088] The absorbent core comprises a core wrap which encloses the
absorbent material. The core wrap can typically comprise a
substrate for receiving the absorbent material when the core is
made. Various core wrap constructions are possible. The core wrap
may in particular comprise as represented in the Figures two
separate substrates 16, 16' forming the top side and the bottom
side of the core wrap respectively. Having two different substrates
for example allows separately depositing about half of the
absorbent material on each substrate before combining these to form
the core wrap. The two substrates may be attached in a C-wrap
configuration with two longitudinal seals 284', 286', and
optionally a front seal 280' and a back seal 282' as will be
detailed further below. However this core wrap construction is not
limiting of the invention, as any conventional core wrap
construction may also be used, for example a single substrate on a
portion of which the absorbent material is deposited and then the
rest of the substrate folded over the deposited absorbent material
to form the other side of the core. This single substrate
construction can then be sealed longitudinally with a single
longitudinal edge seal. The core wrap may also comprise two
substrates disposed flat in a face to face relation (sandwich).
[0089] The substrates 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, US 2011/0268932A1, US2011/0319848A1 and
US2011/0250413A1. Nonwoven materials are typically made of
synthetic fibers, such as PE, PET and in particular PP fibers. It
is also possible than the core wrap may be at least partially
formed from a component of the article having another function than
substrate for the absorbent material. For example, it is possible
that the backsheet may form the bottom side of the core wrap and/or
that a distribution layer or the topsheet may form the top side of
the core wrap. However, typically the core wrap is made of one or
more substrates whose only function is to receive and enclose the
absorbent material, as indicated previously.
[0090] As used herein, the terms "nonwoven layer" or "nonwoven web"
generally 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 synthetic 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).
[0091] As illustrated in FIG. 9, a first substrate 16 may
substantially form the whole of the top surface 288 of the core
wrap and a second substrate 16' substantially form the whole of the
bottom surface 290 of the core wrap, but it is not excluded that
this may be the other way round. By "substantially forming the
whole of the surface" it is meant that the outwardly extending
flaps of the other substrate that have been folded longitudinally
may also form part of the surface considered. The substrates are
typically substantially planar in the same plane as the absorbent
core, and each comprises an external surface and an internal
surface. The internal surface is orientated towards the absorbent
material and the external surface is the opposite surface. At least
one of the substrate comprises at least one, and advantageously two
outwardly extending flaps, which are folded around the front, back
or side edges of the absorbent core and then attached to the
external surface of the other substrate to form at least one
so-called C-wrap seal. As seen in FIG. 9, the first substrate 16
may comprise two side flaps laterally extending along the length of
the core and which are folded inwardly over each side edge 284, 286
of the absorbent core. The flaps may be attached to the outer
surface of the second substrate 16' for example by using an
adhesive seal along each C-wrap seal 284', 286'. One or two
continuous or semi-continuous lines of glue may be typically
applied along the length of the flaps to bond the inner surface of
the flaps to the external surface of the other substrate.
[0092] As exemplarily represented in FIG. 10, the core may also
comprise so-called sandwich seals 280', 282' where the two
substrates are bonded along one edge of the core to each other in
face-to-face relationship with the inner surface of each substrate
bonded to the inner surface of the other substrate. These sandwich
seals can for example be formed using a hotmelt glue applied in a
series of stripes in a direction perpendicular of the edge, as
shown on the front edge 280 and back edge 282 of the core on FIG. 8
for example.
[0093] The substrates may typically be commercially supplied as
rolls of material of several hundred meters of length. Each roll is
then integrated in the converting line and unrolled at high speed
while the auxiliary adhesive, the absorbent material and the
fibrous thermoplastic adhesive layer if present are deposited or
applied on the substrate and then further converted into an
absorbent core when a core wrap enclosing the absorbent material is
formed by the second substrate. Typically the machine direction
(MD) of the converting line may correspond to the longitudinal
direction (y) of the substrate/core and the cross-machine direction
(CD) to the transversal direction (x) of the substrate/core. The
substrates may be cut along the front and back edges of the core
280, 282 to individualize the core.
Absorbent Material 60
[0094] The absorbent material may be any known absorbent material
known in the art, but will typically comprise or consist of
superabsorbent polymers (herein referred to as "SAP"). The SAP may
be typically in particulate forms (superabsorbent polymer
particles), optionally mixed with cellulose fibers, but it not
excluded that other forms of SAP may be used such as a
superabsorbent polymer foam for example. The SAP useful in the
present invention includes a variety of water-insoluble, but
water-swellable polymers capable of absorbing large quantities of
fluids. The term "superabsorbent polymer" refers herein to
absorbent materials, which may be cross-linked polymeric materials,
that can typically 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.R3 (12). The
SAP 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.
[0095] The absorbent material may comprise a relative high amount
of SAP, in particular the absorbent material may comprise at least
80%, in particular at least 85%, 90%, 95% and up to 100% of SAP by
weight of the absorbent material. The absorbent material may in
particular comprise no or only small amount of cellulose fibers,
such as less than 20%, in particular less than 10%, 5% or even 0%
of cellulose fibers by weight of the absorbent material. The
absorbent material may thus consist or consist essentially of SAP.
The core wrap is not considered as absorbent material for the
purpose of calculating the percentage of SAP in the absorbent core.
When the absorbent material comprises cellulose fibers, the content
of SAP may typically range from 60% to 80% by weight of the
absorbent material.
[0096] The superabsorbent polymers may be in particulate form so as
to be flowable in the dry state and thus easily deposited on a
substrate. Typical particulate absorbent polymer materials are made
of poly(meth)acrylic acid polymers. However, starch-based
particulate absorbent polymer materials 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 WO07/047598,
WO07/046052, WO2009/155265 and WO 2009/155264. Suitable
superabsorbent polymer particles may be obtained by current state
of the art production processes, for example as described in
WO2006/083584. 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.
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.
[0097] The SAP particles may be relatively small (under 1 mm in
their longest dimension) in their dry state and may be roughly
circular in shape, but granules, fibers, flakes, spheres, powders,
platelets and other shapes and forms are also known to persons
skilled in the art. Typically, the SAP may be in the form of
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 .mu.m to 850 .mu.m,
preferably from 100 .mu.m to 710 .mu.m, more preferably from 150
.mu.m 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.
[0098] The absorbent core typically comprises only one type of SAP,
but it is not excluded that a blend of different 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 in US patent application number
US2014/005622A1. The UPM of the SAP may for example be of at least
10.times.10.sup.-7 cm.sup.3sec/g, or at least 30.times.10.sup.-7
cm.sup.3sec/g, or at least 50.times.10.sup.-7 cm.sup.3sec/g, or
more, e.g. at least 80 or 100.times.10.sup.-7 cm.sup.3sec/g. The
SAP particles may have a time to reach an uptake of 20 g/g (T20) of
less than 240 s, preferably from 40 s to less than 240 s, more
preferably from 65 s to 215 s, as measured according to the K(t)
test method as described in WO2015/041784 (Peri et al).
Absorbent Material Deposition Area
[0099] The absorbent material 60 defines as seen from above as in
FIG. 8 an absorbent material deposition area having a periphery
that may generally follow the front, back and longitudinal side
edges of the core. The absorbent material deposition area can be
generally rectangular, for example as shown in FIG. 8, but other
shapes can also be used such as a "T" or "Y" or "sand-hour" or
"dog-bone" shape. In particular the deposition area may be tapered
along its width towards the crotch region of the core. In this way,
the absorbent material deposition area may have a relatively narrow
width in an area of the core intended to be placed in the crotch
region of the absorbent article. This may provide for example
better wearing comfort. The absorbent material deposition area may
for example have a width (as measured in the transversal direction
x) 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 be for example at least 5 mm, or at least 10 mm, smaller
than the width of the deposition area at its largest point in the
front and/or back regions of the deposition area. The
channel-forming areas 26 are typically encompassed within the
absorbent material area, and are typically completely surrounded by
absorbent material, i.e. the channel-forming areas do not extend to
any edges of the absorbent material deposition area.
[0100] The absorbent material 60 may be deposited on any of the
substrates using known techniques, which may allow relatively
precise deposition of absorbent material at relatively high speed.
In particular the SAP printing technology as disclosed for example
in US2006/024433 (Blessing), US2008/0312617 and US2010/0051166A1
(both to Hundorf et al.) may be used. This technique uses a
transfer device such as a printing roll to deposit SAP onto a
substrate disposed on a grid of a support which may include a
plurality of cross-bars 36 extending substantially parallel to each
other and spaced apart from one another. The zones 26 substantially
free of absorbent material through which the bonding 27 is executed
can be formed for example by modifying the pattern of the grid and
receiving drums so that no SAP is applied in the selected areas, as
exemplary disclosed in US2012/0312491 (Jackels). This technology
allows high-speed and precise deposition of SAP on a substrate in
particular to provide one or more area(s) substantially free of
absorbent material surrounded by absorbent material.
[0101] The absorbent material may be substantially continuously
distributed in the deposition area. By "substantially continuous"
it is meant that at least 50%, or at least to 70% and up to 100% of
the deposition area comprises a continuous layer of absorbent
material as seen from the top side of the core. The absorbent
material may be for example applied as a single continuous layer on
one of the substrate, the layer thus directly forming the material
deposition area. A continuous layer of absorbent material, in
particular of SAP, may also be obtained by combining two absorbent
layers having matching (offset) discontinuous absorbent material
application pattern wherein the resulting layer is substantially
continuously distributed across the absorbent material deposition
area, as exemplarily taught in US2008/0312622A1 (Hundorf), and as
exemplarily shown on FIGS. 10-11. Each individual absorbent
material layer comprises a pattern having absorbent material land
areas 75, 75' separated by absorbent material-free junction areas
76, 76'. The absorbent material areas 75 of the first layer
correspond substantially to the absorbent material-free junction
areas 76' of the second layer and vice versa. As exemplary shown in
FIGS. 10-11, the absorbent core 28 may thus comprise a first
absorbent layer and a second absorbent layer deposited respectively
on the first substrate 16 and second substrate 16' and combined
together. The first and second absorbent layers may be deposited as
series of transversally oriented dots which immediately after
deposition merge into transversal stripes or "land areas" having
the desired width. Each absorbent layer may comprise for example
between 5 and 50 of these generally transversally orientated land
areas. These land areas may have for example a width ranging from 4
to 20 mm, in particular 10 mm, as measured in the longitudinal
direction (y). The land areas 75 may be of uniform length in the
transversal direction (x) but they may have different width, in
particular towards the center or crotch section of the absorbent
structure to form so called "dog bone" or "hour-glass" shape, which
shows a tapering along its width at least in the crotch zone of the
structure. The width of the junction areas 76 between the land
areas 75 may typically be shorter than the width of the land areas,
for example having a width exemplarily ranging from 0.5 to 6 mm,
for example 1 to 2 mm. Of course other patterns of deposition for
the absorbent material are possible, for example the absorbent
material may be deposited as an array of circular or ovoid land
areas, or combination of rectangular land areas with circular or
ovoid land areas.
[0102] In many applications, the liquid discharge occurs
predominantly in one area of the core. For diapers, the liquid may
predominantly be released towards the crotch region of the core and
to a lesser extent the front of the core. Relatively less liquid
may be released towards the back of the core. Thus it may be
beneficial to profile the amount of absorbent material along the
longitudinal direction of the absorbent structure so that more
absorbent material is present in the areas where the liquid is more
likely to insult the core.
Channel-Forming Areas 26
[0103] The absorbent material deposition area of the core
encompasses at least two channel-forming areas 26 which are
substantially free of absorbent material and through which core
wrap bonds 27 may be formed. By "substantially free" it is meant
that zones do not comprise absorbent material except possibly for
minimal amount such as involuntary contaminations with absorbent
material particles that may occur during the core making process.
The top side 288 of the core wrap is attached to the bottom side
290 of the core wrap by core wrap bonds 27 in the channel-forming
areas, in particular through these areas substantially free of
absorbent material. The channel-forming areas 26 are advantageously
surrounded by absorbent material 60. When the absorbent material 60
swells upon absorbing a liquid, the core wrap bonds 27 remain at
least initially attached in the channel-forming areas 26. The
absorbent material 60 swells in the rest of the core when it
absorbs a liquid, so that the core wrap forms one or more visible
channels along the channel-forming areas 26 comprising the core
wrap bond 27. These channels are three dimensional and can serve to
distribute an insulting fluid along their length to a wider area of
the core. They may provide a quicker fluid acquisition speed and a
better utilization of the absorbent capacity of the core. It is not
excluded that the channel-forming areas may be without a core wrap
bond, as this may be easier to manufacture, but these non-bonded
areas will typically not form permanent three-dimensional channels
when wet.
[0104] The inner surface of the top side 288 and the inner surface
of the bottom side 290 of the core wrap may be bonded together
continuously along the channel-forming areas 26, but the core wrap
bond 27 may also be discontinuous (intermittent) such as formed by
series of point bonds. An auxiliary glue 72 may be used to at least
partially form the substrates bond 27. In this case, some pressure
may be applied on the substrates in the zones 26 to improve the
adhesive bonds between the substrates. If an optional fibrous
adhesive 74, 74' is present, it may also help forming the bond 27.
If the auxiliary glue is applied as a series of longitudinally
orientated continuous slots, the width and frequency of these slots
may advantageously be such that at least one slot of auxiliary glue
is present at any level of the channel-forming area 26 in the
longitudinal direction. For example the slots may be 1 mm wide with
a 1 mm distance between each slots, and the channel-forming areas
have a width of about 8 mm. Such on average for 4 slots of
auxiliary glue will be present in each of the channel-forming area
26. It is of course also possible to form the bonds 27 via other
known attachment means, such as pressure bonding, ultrasonic
bonding, heat bonding or combination thereof.
[0105] The channel-forming areas 26 extend substantially
longitudinally, meaning that each zone extends at least as much in
the longitudinal direction (y) than in the transversal direction
(x), 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 channel-forming areas 26
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 core, in
particular from 20% to 80%. The absorbent material-free
channel-forming areas may have a width Wc along at least part of
their 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 Wc of
each areas substantially free of absorbent material may be constant
through substantially its whole length or may vary along its
length.
[0106] The channel-forming areas may be typically at least
partially curved. In particular the channel-forming areas present
in the crotch region may be concave towards the longitudinal axis
80 as illustrated in FIG. 8. Alternatively, it is not excluded that
the channel-forming areas may be partially or entirely straight,
and in particular longitudinally oriented parallel to the
longitudinal axis 80, or curved in the other direction. The
channel-forming areas are typically disposed as one or more
symmetrical pair(s) relative to the longitudinal axis, and are
spaced apart from one another over their whole longitudinal
dimension. The shortest spacing distance between the
channel-forming areas may be for example at least 5 mm, or at least
10 mm, or at least 16 mm. Furthermore, in order to reduce the risk
of fluid leakages, the areas substantially free of absorbent
material may advantageously not extend up to any of the edges of
the absorbent material deposition area, and are therefore
surrounded by and fully encompassed within the absorbent material
deposition area of the core. The smallest distance between a
channel-forming area and the closest edge of the absorbent material
deposition area may be at least 5 mm.
Auxiliary Glue 72
[0107] The auxiliary glue 72 is optional. When present, the
auxiliary glue may be applied directly over the inner surface of
the top side and/or bottom side of the core wrap. The auxiliary
glue may at least partially form the bonds 27 between the two sides
of the core wrap, through the areas substantially free of absorbent
material of the channel-forming areas. The auxiliary glue may also
be useful to improve the adhesion between the inner surface of the
core wrap and the absorbent material. If a fibrous thermoplastic
material 74 is present, such an auxiliary glue may also help
adhering the fibrous thermoplastic material to the material-free
junction areas 76.
[0108] The auxiliary glue may comprise or consist of any kind of
thermoplastic hot-melt adhesives used in the field of absorbent
core making. Such an adhesive generally includes one or more
polymers to provide cohesive strength (e.g., aliphatic polyolefins
such as ethylene-propylene copolymers, polyetheramides,
polyetheresters, and combinations thereof; ethylene vinyl acetate
copolymers; styrene-butadiene or styrene-isoprene block copolymers;
etc.), a resin or analogous material (sometimes called a tackifier)
to provide adhesive strength (e.g., hydrocarbons distilled from
petroleum distillates; rosins and/or rosin esters; terpenes
derived, for example, from wood or citrus, etc.); and optional
waxes, plasticizers or other materials to modify viscosity (e.g.,
mineral oil, polybutene, paraffin oils, ester oils, and the like),
and/or other additives including, but not limited to, antioxidants
or other stabilizers. Exemplary suitable commercial adhesives are
available from Fuller under reference number 1358L0 and from Henkel
under reference numbers DM3800 and DM526. Further information about
hotmelt adhesive chemistry is discussed below for the fibrous
thermoplastic adhesive layer. The auxiliary glue can be applied by
any adhesive applicator known in the field, in particular bead,
slot or spray nozzles.
[0109] The auxiliary glue 72 was discussed above with reference to
the first absorbent substrate 16 which forms the upper side 288 of
the absorbent core, and which is placed towards the topsheet 24 in
the finished absorbent article 20. This is however not limiting, as
the first substrate may alternatively form the bottom side 290 of
the absorbent core which is placed towards the backsheet 25 of the
article 20. It is also considered that a second auxiliary glue may
be applied directly on the second substrate 16' in addition to the
first auxiliary glue applied directly on the first substrate 16, in
particular in any of the configurations discussed above. This may
be particular useful when the absorbent material within the core
wrap is formed by two absorbent layers 61, 62 as discussed
above.
Microfiber Glue 74, 74'
[0110] The absorbent core may comprise a fibrous thermoplastic
adhesive material 74 which can be used to further immobilize the
absorbent material 60 during the making process of the core and
usage of the article. The fibrous thermoplastic adhesive material
74, 74' may be in particular useful to immobilize the layers of
absorbent material onto their respective substrate 16, 16' where
they have been deposited. These absorbent layers may comprise land
areas 75, 75' separated by junction areas 76, 76' as discussed
above and the fibrous thermoplastic adhesive material 74 may then
be at least partially in contact with the absorbent material in the
land areas and at least partially in contact with the substrate
layer 16, 16' in the junction areas. This imparts an essentially
three-dimensional net-like structure to the fibrous layer of
thermoplastic adhesive material, 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 areas, and thereby
immobilizes this absorbent material. The fibrous adhesive may be
for example sprayed on an absorbent layer after it has been
deposited on its substrate during the core making process.
[0111] The fibrous thermoplastic adhesive material may have 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.
[0112] 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%. Exemplary commercial suitable adhesives are NW1151
ex. HB Fuller and H2898 ex. Bostik.
[0113] The thermoplastic adhesive 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. 4,81,066 (Korpman).
[0114] The thermoplastic adhesive material 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 5 mm to about 30 mm. The auxiliary glue may
improve the adhesion of the thermoplastic adhesive material to the
substrate. The fibers adhere to each other to form a fibrous layer,
which can also be described as a mesh.
Exemplary Method and Apparatus for Making the Absorbent Core
[0115] The absorbent cores may be made by any conventional methods
known in the art that allow a relative precise and controlled
deposition of absorbent material. The articles may be hand-made or
industrially produced at high speed on a modern converting line. As
mentioned above, the absorbent core of the invention can in
particular be made industrially by combining two absorbent
structures using the SAP printing method first disclosed in
WO2008/155699 (Hundorf et al.) and further developed in
WO2012/170798A1 (Jackels et al.), with the adaptations required to
obtain the desired distribution of the absorbent material.
Topsheet 24
[0116] The topsheet typically forms the majority of the
wearer-contacting surface of the article and is the first layer
that the body exudates contact. The topsheet is preferably
compliant, soft-feeling, and non-irritating to the wearer's skin.
Further, at least a portion of the topsheet is liquid permeable,
permitting liquids to readily penetrate through its thickness. Any
known topsheet may be used in the present invention. A suitable
topsheet may be manufactured from a wide range of materials. Most
topsheets are nonwoven materials or apertured formed films, but
other materials are possible such as porous foams, reticulated
foams, woven materials. Typical diaper topsheets have a basis
weight of from about 10 gsm to about 28 gsm, in particular between
from about 12 gsm to about 18 gsm but higher basis weights are
possible if it is desired to provide a very soft feeling
wearer-contacting surface for example.
[0117] Nonwoven topsheets may be made 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
includes nonwoven fibers, the fibers may be spunbond, carded,
wet-laid, meltblown, hydroentangled, or otherwise processed as is
known in the art. In particular the topsheet may be a 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.
[0118] 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.
No. 4,609,518 and U.S. Pat. No. 4,629,643. 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". The topsheet may also have a three-dimensional
appearance and feel, or there may be an additional, smaller,
three-dimensional layer placed on top of the topsheet. Such
three-dimensional additional layers may be for example particularly
useful to receive low viscous exudates such as the stool of young
babies Examples of such fluid entangled dual layered
three-dimensional materials and processes to obtain them have been
disclosed for example in US2014/0121623A1, US2014/0121621A1,
US2014/0121624A1, US2014/0121625A1.
[0119] The topsheet may also be treated with a wetting agent to
make it more hydrophilic. The wetting agent may be a surfactant as
is known in the art. Other possible treatments are for example
special coating by nanoparticles, as for example described in U.S.
Pat. No. 6,645,569, U.S. Pat. No. 6,863,933, US2003/148684 and
US2005/008839 (Cramer et al.) and U.S. Pat. No. 7,112,621
(Rohrbaugh et al). Any portion of the topsheet may also 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 may also include or be
treated with antibacterial agents, some examples of which are
disclosed in 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.
[0120] The topsheet 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. 6,632,504. WO 2011/163582 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.
Backsheet 25
[0121] The backsheet may be any backsheet known in the art for
absorbent articles. The backsheet may be positioned directly
adjacent the garment-facing surface of the absorbent core. The
backsheet prevents, or at least inhibits, the exudates absorbed and
contained therein from soiling articles such as bedsheets and
undergarments. The backsheet is typically impermeable, or at least
substantially 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. The basis weight of those films is usually as low as
possible to save material costs, typically from 10 gsm to 30 gsm,
in particular below 20 gsm. A covering low basis weight nonwoven
may be attached to the external surface of the film to provide for
a softer touch.
[0122] Suitable backsheet materials include breathable materials
which permit vapors to escape from the absorbent article while
still preventing, or at least inhibiting, exudates from passing
through the backsheet. Example 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.
[0123] The film may include at least about 20 weight percent filler
particles, for example filler particles that include calcium
carbonate, so that wherein the film has been stretched in the
machine direction, e.g. to at least about 150 percent, fractures
are formed where said filler particles are located. The films may
be biaxially stretched at least about 150 percent in the machine
direction and a transverse direction to cause fractures to form
where said filler particles are located. Breathable films may
generally have Water Vapor Transmission Rates (WVTR) in excess of
300 grams per square meter per 24 hours. The WVTR may be measured
by the Desiccant Method as indicated in ASTM E96/E96M-14.
[0124] U.S. Pat. No. 6,075,179 for example discloses a suitable
multilayer film comprising: a core layer made from an extrudable
thermoplastic polymer, the core layer having a first exterior
surface and a second exterior surface, a first skin layer attached
to the first exterior surface of said core layer to form the
multilayer film, the multilayer film defining an overall thickness.
The first skin layer defines a first skin thickness, and comprising
less than about ten percent of said overall thickness. The overall
thickness is not exceeding about 30 micrometers and the multilayer
film is a liquid barrier and has a WVTR of at least 300
g/m.sup.2/24 hours.
[0125] The backsheet may further typically comprise a nonwoven on
its most external side to improve softness. Exemplary laminates
comprising a breathable film and a nonwoven layer are for example
disclosed in WO2014/022,362A1, WO2014/022,652A1 and U.S. Pat. No.
5,837,352. The nonwoven web may in particular comprise a spunbond
nonwoven web and/or a laminate of a spunbond nonwoven web and a
meltblown nonwoven web. The laminate may also have a water vapor
transmission rate of at least 300 g/m.sup.2/24 hours. U.S. Pat. No.
5,843,056 for example discloses substantially liquid impermeable,
vapor permeable composite backsheet.
Acquisition Layer 52
[0126] The absorbent article 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 is typically placed directly under the topsheet.
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
nonwoven material may in particular be latex bonded. Exemplary
upper acquisition layers 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. Nonwovens have the advantage
that they can be manufactured outside the converting line and
stored and used as a roll of material. Further useful nonwovens are
described in U.S. Pat. No. 6,645,569 (Cramer et al.), U.S. Pat. No.
6,863,933 (Cramer et al.), U.S. Pat. No. 7,112,621 (Rohrbaugh et
al.), US2003/148684 (Cramer et al.) and US2005/008839 (Cramer et
al.). The acquisition layer may be stabilized by a latex binder,
for example a styrene-butadiene latex binder (SB latex). Processes
for obtaining such latices are known, for example, from EP 149880
(Kwok) and US 2003/0105190 (Diehl et al.). The binder may typically
be present in the acquisition layer in amount ranging from about
12% to about 50%, for example about 30%, by total weight of the
acquisition layer. SB latex is available under the trade name
GENFLO.TM. 3160 (OMNOVA Solutions Inc.; Akron, Ohio).
[0127] Another typical acquisition layer, sometimes referred to as
secondary topsheet, may for example be a through-air bonded carded
web ("TABCW") but many other alternatives material are known in the
art and may be used instead. "Bonded carded web" refers to webs
that are made from staple fibers that are sent through a combing or
carding unit, which breaks apart and aligns the staple fibers in
the machine direction to form a generally machine
direction-oriented fibrous nonwoven web. This web is then drawn
through a heated drum, creating bonds throughout the fabric without
applying specific pressure (thru air bonding process). The TABCW
material provides a low density, lofty through-air bonded carded
web. The web may for example have a specific weight basis level at
about 15 gsm to about 120 gsm (gram per m.sup.2), in particular
about 30 gsm to about 80 gsm. The TABCW material can for example
comprise about 3 to about 10 denier staple fibers. Examples of such
TABCW are disclosed in WO2000/71067 (KIM DOO-HONG et al.). TABCW
are available directly from all usual suppliers of nonwoven webs
for use in absorbent articles, for example Fitesa Ltd or Fiberweb
Technical Nonwovens.
[0128] A further acquisition layer (not shown) may be used in
addition to the 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
layers 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 a
hydrophilic tissue is a 13 to 15 gsm high wet strength tissue made
of cellulose fibers from supplier Havix.
Fastening System 42, 44
[0129] The absorbent article may include a fastening system,
especially when the article is a taped diaper as exemplified in
FIG. 1. 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. Such a fastening system is not
necessary for pant articles such as training pants and adult
incontinence pants since the waist region of these articles is
already bonded and elasticized. The fastening system usually
comprises a fastener 42 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 44 is normally provided on the front
waist region of the article for the fastener 42 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 (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 (Robertson et al.)
[0130] 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. 5,507,86, and U.S. Pat. No. 5,591,152.
Front and Back Ears 46, 40
[0131] The absorbent article may comprise front ears 46 and back
ears 40 as is known in the art in taped diapers. Training pants
which are already sealed along the waist edges typically do not
require front ears and back ears. The ears can be integral part of
the chassis, for example formed from the topsheet and/or backsheet
as side panel. Alternatively, as represented in FIG. 1, they may be
separate elements attached by gluing and/or heat embossing. The
back ears 40 are optionally stretchable to facilitate the
attachment of the tabs 42 on the landing zone 44 and maintain the
taped diapers in place around the wearer's waist. The front ears 46
may also be optionally elastic or extensible to provide a more
comfortable and contouring fit.
Barrier Leg Cuffs 34 and Gasketing Cuffs 32
[0132] Absorbent articles such as taped diapers, training pants or
adult incontinence pants may typically further comprise cuff
components 30 that improve the fit of the article around the legs
of the wearer. Such cuffs typically comprise barrier leg cuffs 34
and gasketing cuffs 32. The cuffs 30 may comprise a piece of
material, typically a nonwoven, which is one side partially bonded
to the article and on the other side can be partially raised away
from the topsheet and thus stand up from the plane defined by the
topsheet as shown for example in FIG. 3. Both parts of the cuffs
may be advantageously elasticized. The raised part of the cuff
components is referred to herein as barrier leg cuffs 34 and 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 34 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 adjacent to
the center point C' of the article.
[0133] The barrier leg cuffs 34 may be delimited by a proximal edge
36 joined to the rest of the article, typically the topsheet, and a
free terminal edge 38 intended to contact and form a seal with the
wearer's skin. The barrier leg cuffs 34 may be joined at the
proximal edge 36 with the chassis of the article by a bond 37 which
may be made for example by adhesive bonding, fusion bonding or
combination of known bonding means, for example as disclosed in
WO2014/168810A1 (Bianchi et al.). The bond 37 at the proximal edge
36 may be continuous or intermittent.
[0134] The barrier leg cuffs 34 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 its free terminal edge 38 to
provide a better seal.
[0135] 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 the absorbent article, in particular may be at least
partially enclosed between the topsheet and the backsheet, and
typically placed further laterally outwardly relative to the
barrier leg cuffs 34. The gasketing cuffs 32 can provide a better
seal around the thighs of the wearer. Usually each gasketing leg
cuff 32 will comprise one or more elastic string or elastic element
33 comprised in the chassis of the diaper for example between the
topsheet and backsheet in the area of the leg openings. Typically
the barrier leg cuffs 34 are disposed more internally than the
gasketing cuffs 32. The barrier leg cuffs are thus also referred to
as inner cuffs and the gasketing cuffs as outer cuffs.
[0136] For example, 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 (Aziz) and U.S. Pat.
No. 4,909,803 (Aziz) 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 (Lawson) and U.S. Pat.
No. 4,795,454 (Dragoo) 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.
Other Components
[0137] The absorbent articles of the invention can further comprise
any other typical components known for the intended purpose of the
article that are not illustrated in the Figures, such as a
transverse barrier element extending across the topsheet to form a
receptacle for bowel movement, a lotion application on the
topsheet, a wetness indicator comprising a pH indicator disposed
between the absorbent core and the backsheet, etc. These components
are well-known in the art and will not be further discussed herein.
Reference is made to WO2014/093310 where several examples of these
components are disclosed in more details.
[0138] The absorbent article may also comprise at least one elastic
waist band (also called elastic waist feature) disposed parallel to
and along the back edge of the article and less commonly parallel
to and along the front edge of the article. Such waistbands help
providing improved fit and containment at the back and/or front
edge of the article. The elastic waist feature is generally
intended to elastically expand and contract to dynamically fit the
wearer's waist. The elastic waist feature may be constructed in a
number of different configurations. Non-limiting examples of back
and front waistbands can be found in WO2012/177400 and
WO2012/177401 (Lawson), and U.S. Pat. No. 4,515,595, U.S. Pat. No.
4,710,189, U.S. Pat. No. 5,221,274 and U.S. Pat. No. 6,336,922
(VanGompel et al.).
Packages
[0139] A plurality of articles according to the invention may be
packaged in a package for transport and sale. At least 50% of the
articles in the package may be according to the invention, and
preferably substantially all the articles. The articles may be
folded and packaged as is known in the art. The package may be for
example a plastic bag or a cardboard box. Diapers may typically
bi-folded along the transversal axis and the ears folded inwardly
before being packaged. The absorbent articles may be packed under
compression so as to reduce the size of the packages, while still
providing an adequate amount of absorbent articles per package. By
packaging the absorbent articles under compression, caregivers can
easily handle and store the packages, while also providing
distribution and inventory savings to manufacturers owing to the
size of the packages.
[0140] The absorbent articles may thus be packaged compressed at an
In-Bag Compression Rate of at least 10%, in particular of from 10%
to 50%, in particular from 20% to 40%. The "In-Bag Compression
Rate" as used herein is one minus the height of a stack of 10
folded articles measured while under compression within a bag
("In-Bag Stack Height") divided by the height of a stack of 10
folded articles of the same type before compression, multiplied by
100; i.e. (1-In-Bag Stack Height/stack height before
compression)*100, reported as a percentage. Of course, the stack in
the bag does not need to have exactly 10 articles, rather the value
measured for the height of stack of article in the package is
divided by the number of articles in the stack and then multiplied
by 10. The method used to measure the In-Bag Stack Height is
described in further details in the Test Procedures. The articles
before compression may be typically sampled from the production
line between the folding unit and the stack packing unit. The stack
height before compression is measured by taking 10 articles before
compression and packing, and measuring their stack height as
indicated for the IBSH.
[0141] Packages of the absorbent articles of the present disclosure
may in particular have an In-Bag Stack Height of less than 110 mm,
less than 105 mm, less than 100 mm, less than 95 mm, less than 90
mm, specifically reciting all 0.1 mm increments within the
specified ranges and all ranges formed therein or thereby,
according to the In-Bag Stack Height Test described herein. For
each of the values indicated in the previous sentence, it may be
desirable to have an In-Bag Stack Height of greater than 60, or
greater than 70 mm, or greater than 75 mm, or greater than 80 mm.
Alternatively, packages of the absorbent articles of the present
disclosure may have an In-Bag Stack Height of from 60 mm to 110 mm,
from 75 mm to 110 mm, from 80 mm to 110 mm, from 80 mm to 105 mm,
or from 80 mm to 100 mm, specifically reciting all 0.1 mm
increments within the specified ranges and all ranges formed
therein or thereby, according to the In-Back Stack Height Test
described herein.
Relations Between the Layers and Components
[0142] 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. Most of the bonding between components is for clarity and
readability not represented in the Figure. 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 adhesives used may be any standard
hotmelt glue as known in the art. The individual components may be
converted into an absorbent article according to any of the
processes known in the art.
Test Procedures
[0143] 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%.+-.5% 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)
[0144] 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.R3 (12).
Dry Absorbent Core Caliper Test
[0145] This test may be used to measure the caliper of the
absorbent core (before use i.e. without fluid loading) in a
standardized manner.
[0146] Equipment: Mitutoyo manual caliper gauge with a resolution
of 0.01 mm, or equivalent instrument.
[0147] 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.
[0148] 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.
[0149] Ruler: Calibrated metal ruler graduated in mm.
[0150] Stopwatch: Accuracy 1 second.
[0151] Sample preparation: The core is conditioned at least 24
hours as indicated above.
[0152] 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.
[0153] 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.
[0154] 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.+-.1 seconds
after the foot is released.
[0155] 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.
Absorbent Article Caliper Test
[0156] 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 C' 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.
[0157] 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.
Water Retention Value Measurement Procedure
[0158] The following procedure is utilized to determine the water
retention value of fibers using a centrifugal method. A sample of
0.35.+-.0.05 grams of fibers is soaked in a covered container with
100 mL distilled water at 23.+-.2.degree. C. for 17 hours. The
soaked fibers are collected on a filter and transferred to a US
standard 80-mesh wire basket supported 40 mm above a 60-mesh
screened bottom of a centrifuge tube. The tube is covered with a
plastic cover and the sample is centrifuged at a relative
centrifuge acceleration of 1600.+-.100 gravities (15.7.+-.1.0
km/s.sup.2) for 20 minutes. The centrifuged fibers are then removed
from the basket and weighed. The weighed fibers are dried to a
constant weight at 105.degree. C. in a forced-air oven located in a
controlled temperature and humidity environment at 23.+-.2.degree.
C. and 50.+-.5% RH. The water retention value (WRV) is calculated
as follows:
WRV = ( W - D ) D .times. 100 ##EQU00001##
[0159] where
[0160] W=wet weight of centrifuged fibers
[0161] D=dry weight of centrifuged fibers, and
[0162] W-D=weight of absorbed water
In-Bag Stack Height Test
[0163] The In-Bag stack height of a package of absorbent articles
is determined as follows:
[0164] Equipment:
[0165] A thickness tester with a flat, rigid horizontal sliding
plate is used. The thickness tester is configured so that the
horizontal sliding plate moves freely in a vertical direction with
the horizontal sliding plate always maintained in a horizontal
orientation directly above a flat, rigid horizontal base plate. The
thickness tester includes a suitable device for measuring the gap
between the horizontal sliding plate and the horizontal base plate
to within .+-.0.5 mm. The horizontal sliding plate and the
horizontal base plate are larger than the surface of the absorbent
article package that contacts each plate, i.e. each plate extends
past the contact surface of the absorbent article package in all
directions. The horizontal sliding plate exerts a downward force of
850.+-.1 gram-force (8.34 N) on the absorbent article package,
which may be achieved by placing a suitable weight on the center of
the non-package-contacting top surface of the horizontal sliding
plate so that the total mass of the sliding plate plus added weight
is 850.+-.1 grams. Such a testing apparatus is for example
illustrated on FIG. 19 of US2008/0312624A1.
[0166] Test Procedure:
[0167] Absorbent article packages are equilibrated at
21.+-.2.degree. C. and 50.+-.5% relative humidity prior to
measurement. The horizontal sliding plate is raised and an
absorbent article package is placed centrally under the horizontal
sliding plate in such a way that the absorbent articles within the
package are in a horizontal orientation. Any handle or other
packaging feature on the surfaces of the package that would contact
either of the plates is folded flat against the surface of the
package so as to minimize their impact on the measurement. The
horizontal sliding plate is lowered slowly until it contacts the
top surface of the package and then released. The gap between the
horizontal plates is measured to within .+-.0.5 mm ten seconds
after releasing the horizontal sliding plate. Five identical
packages (same size packages and same absorbent articles counts)
are measured and the arithmetic mean is reported as the package
width. The "In-Bag Stack Height"=(package width/absorbent article
count per stack).times.10 is calculated and reported to within
.+-.0.5 mm.
Determination of the Basis Weight of the Absorbent Material in the
Absorbent Core
[0168] The distribution of the absorbent material in the central
and the lateral absorbent zones of the absorbent core is determined
by the manufacturer based on the desired product specification. For
example, if a SAP printing process is used, the SAP distribution
will be determined by the distribution of the cavities on the
printing roll and the size of the depressions between the bars. If
an air-laid core making process is used, for example to deposit a
mix of cellulose fibers and SAP particles as absorbent material,
the absorbent material distribution will be determined by the shape
of the core mold on which the fibers and SAP particles are
deposited. The local basis weight of the absorbent material in the
different areas of the absorbent core can be thus directly
determined from the manufacturer's specification for the absorbent
core's manufacturing tool. For the purpose of calculating the basis
weight in the different absorbent zones of the core, any absorbent
material-free areas in the plane of the absorbent core such as in
the channel-forming areas or any material free recesses at the
longitudinal sides of the core (in a profiled core, not
represented) are disregarded.
[0169] If the manufacturer specifications are not known for a given
absorbent core, in particular if the absorbent core was made by a
third party, the basis weight of the absorbent material in
different sections of the different absorbent zones can be
determined in the following manner. The absorbent core is carefully
separated from the other components of the article (topsheet,
backsheet, . . . ) so as not to damage the absorbent core or modify
the distribution of the absorbent material. Then a particular area
of interest of the core can be cut out using a die or another
suitable means to avoid loss of material, and the area weighted.
The absorbent material basis weight in the cut-out area is
calculated by dividing the weight of the area (minus the weight of
the core wrap) by the size of the area. The basis weight of the
core wrap can be determined by taking a sample in an area of the
core wrap not comprising the absorbent material and weighing this
sample. This procedure can further be repeated on a sufficient
amount of similar articles to obtain a good approximation of the
basis weight distribution across different sections of the
absorbent zones and to smooth out any small variations between
individual articles due to process variability.
Misc
[0170] As used herein, the terms "comprise(s)" and "comprising" are
open-ended; 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
essentially 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", "preferably", "advantageously", "in
particular" and the likes also qualify features which are not
intended to limit the scope of the claims unless specifically
indicated to do so.
[0171] Unless indicated otherwise, the description and claims refer
to the absorbent core and 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+/-5% Relative Humidity
(RH).
[0172] 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".
[0173] Every document cited herein, including any cross referenced
or related patent or application and any patent application or
patent to which this application claims priority or benefit
thereof, 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.
[0174] 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.
* * * * *