U.S. patent application number 13/902265 was filed with the patent office on 2013-10-10 for absorbent core.
This patent application is currently assigned to The Procter & Gamble Company. The applicant listed for this patent is The Procter & Gamble Company. Invention is credited to Giovanni Carlucci, Alessandro Gagliardini, Maurizio Tamburro, Evelina Toro, Pancrazio Veronese.
Application Number | 20130267922 13/902265 |
Document ID | / |
Family ID | 38740508 |
Filed Date | 2013-10-10 |
United States Patent
Application |
20130267922 |
Kind Code |
A1 |
Carlucci; Giovanni ; et
al. |
October 10, 2013 |
Absorbent Core
Abstract
Absorbent core for disposable absorbent articles, particularly
for the absorption of menses or blood.
Inventors: |
Carlucci; Giovanni; (Chieti,
IT) ; Tamburro; Maurizio; (San Giovanni Teatino,
IT) ; Gagliardini; Alessandro; (Villa Vomano
(Teramo), IT) ; Toro; Evelina; (Chieti, IT) ;
Veronese; Pancrazio; (Pescara, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
The Procter & Gamble Company |
Cincinnati |
OH |
US |
|
|
Assignee: |
The Procter & Gamble
Company
Cincinnati
OH
|
Family ID: |
38740508 |
Appl. No.: |
13/902265 |
Filed: |
May 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12180751 |
Jul 28, 2008 |
8263820 |
|
|
13902265 |
|
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13588614 |
Aug 17, 2012 |
8466336 |
|
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12180751 |
|
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Current U.S.
Class: |
604/366 ;
604/370 |
Current CPC
Class: |
A61F 13/539 20130101;
A61F 2013/530562 20130101; A61F 13/5323 20130101; A61F 13/534
20130101 |
Class at
Publication: |
604/366 ;
604/370 |
International
Class: |
A61F 13/534 20060101
A61F013/534; A61F 13/539 20060101 A61F013/539 |
Claims
1. An absorbent core for an absorbent article, the core comprising
a substrate layer; the substrate layer comprising a substrate layer
first surface and a substrate layer second surface; the absorbent
core further comprising a layer of absorbent material, the
absorbent material comprising an absorbent polymer material; the
layer of absorbent material comprising a layer of absorbent
material first surface and a layer of absorbent material second
surface; the absorbent core further comprising a layer of a
thermoplastic material; and the layer of thermoplastic material
comprising a layer of thermoplastic material first surface and a
layer of thermoplastic material second surface, wherein the layer
of absorbent material second surface is in at least partial contact
with the substrate layer first surface, wherein portions of the
layer of thermoplastic material second surface are in direct
contact with the substrate layer first surface and portions of the
layer of thermoplastic material second surface are in direct
contact with the layer of absorbent material first surface, and
wherein the substrate layer comprises a fibrous material
substantially free of cellulose fibers; said absorbent article
having in use a body facing surface and a garment facing surface,
wherein said substrate layer in said absorbent core provides the
function of a top layer to the absorbent core; wherein the top
layer to the absorbent core correspond to the body facing surface
of the core; wherein said absorbent article further comprises a
fibrous layer positioned below said core towards said garment
facing surface of said absorbent article, wherein said fibrous
layer comprises greater than zero and not more than 60% of
cellulose fibres; and wherein the absorbent core comprises at least
a cover layer in direct contact with the layer of thermoplastic
material first surface.
2. An absorbent core according to claim 1, wherein the layer of
absorbent material is a non uniform layer.
3. An absorbent core according to claim 1, wherein the substrate
layer has a basis weight from about 25 g/m.sup.2 to about 120
g/m.sup.2.
4. An absorbent core according to claim 1, wherein the layer of
absorbent material is a discontinuous layer of absorbent
material.
5. An absorbent core according to claim 1, wherein the absorbent
polymer material is present throughout the area of the absorbent
core in an average basis weight of greater than zero and less than
about 200 g/m.sup.2.
6. An absorbent core according to claim 1, wherein the absorbent
polymer material is present throughout the area of the absorbent
core in an average basis weight of greater than zero and less than
about 160 g/m.sup.2.
7. An absorbent core according to claim 1, wherein the absorbent
polymer material is present throughout the area of the absorbent
core in an average basis weight from about 60 g/m.sup.2 to about
120 g/m.sup.2.
8. An absorbent core according to claim 1, wherein the absorbent
polymer material is present throughout the area of the absorbent
core in an average basis weight from about 80 g/m.sup.2 to about
100 g/m.sup.2.
9. An absorbent core according to claim 1, wherein the
thermoplastic material is a hot melt adhesive.
10. An absorbent core according to claim 1, wherein the
thermoplastic material is fiberized.
11. An absorbent core according to claim 1, wherein the
thermoplastic material comprises a net-like structure.
12. An absorbent article according to claim 1, wherein the fibrous
layer comprises from about 30% to about 50% cellulose fibers.
13. A core according to claim 1, in an absorbent article, wherein
the absorbent article further comprises a fluid acquisition layer
positioned over the absorbent core towards the body facing surface,
wherein the fluid acquisition layer is substantially free of
cellulose fibers.
14. An absorbent core for an absorbent article intended for
absorption of menses or blood, the core comprising a substrate
layer; the substrate layer comprising a substrate layer first
surface and a substrate layer second surface; the absorbent core
further comprising a layer of absorbent material, the absorbent
material comprising an absorbent polymer material; the layer of
absorbent material comprising a layer of absorbent material first
surface and a layer of absorbent material second surface; the
absorbent core further comprising a layer of a thermoplastic
material; and the layer of thermoplastic material comprising a
layer of thermoplastic material first surface and a layer of
thermoplastic material second surface, wherein the layer of
absorbent material second surface is in at least partial contact
with the substrate layer first surface, wherein portions of the
layer of thermoplastic material second surface are in direct
contact with the substrate layer first surface and portions of the
layer of thermoplastic material second surface are in direct
contact with the layer of absorbent material first surface, and
wherein the substrate layer comprises a fibrous material
substantially free of cellulose fibers; said absorbent article
having in use a body facing surface and a garment facing surface,
wherein said substrate layer in said absorbent core provides the
function of a top layer to the absorbent core; wherein the top
layer to the absorbent core correspond to the body facing surface
of the core; wherein said absorbent article further comprises a
fibrous layer positioned below said core towards said garment
facing surface of said absorbent article, wherein said fibrous
layer comprises greater than zero and not more than 60% of
cellulose fibres; and wherein the absorbent core comprises at least
a cover layer in direct contact with the layer of thermoplastic
material first surface, and wherein the fibrous layer is provided
by the cover layer of the absorbent core.
15. An absorbent article according to claim 14, wherein the fibrous
layer comprises from about 30% to about 50% cellulose fibers.
16. An absorbent article according to claim 14, wherein the
absorbent article further comprises a fluid acquisition layer
positioned over the absorbent core towards the body facing surface,
wherein the fluid acquisition layer is substantially free of
cellulose fibers.
17. An absorbent core according to claim 14, wherein the absorbent
polymer material is present throughout the area of the absorbent
core in an average basis weight of greater than zero and less than
about 200 g/m.sup.2.
18. An absorbent core according to claim 14, wherein the layer of
absorbent material is a discontinuous layer of absorbent
material.
19. An absorbent core according to claim 14, wherein the
thermoplastic material is a hot melt adhesive.
20. An absorbent core according to claim 14, wherein the
thermoplastic material is fiberized.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application Ser.
No. 13/588,614, filed Aug. 17, 2012, pending, which is a
continuation of U.S. application Ser. No. 12/180,751, filed Jul.
28, 2008, issued as U.S. Pat. No. 8,263,820 on Aug. 22, 2012; both
herein incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an absorbent core for
absorbent articles, for example sanitary napkins and the like.
BACKGROUND OF THE INVENTION
[0003] Absorbent articles for absorption of body fluids such as
menses or blood are well known in the art, and comprise for example
feminine hygiene articles such as sanitary napkins, panty liners,
tampons, interlabial devices, as well as wound dressings, and the
like. When considering for example sanitary napkins, these articles
typically comprise a liquid-pervious topsheet as wearer-facing
layer, a backsheet as garment-facing layer and an absorbent core
between topsheet and backsheet. The body fluids are acquired
through the topsheet and subsequently stored in the absorbent core.
The backsheet typically prevents the absorbed fluids from wetting
the wearer's garment.
[0004] An absorbent core can typically comprise one or more fibrous
absorbent material, which in turn can comprise natural fibers, such
as for example cellulose fibers, typically wood pulp fibers,
synthetic fibers, or combinations thereof.
[0005] Absorbent articles can further comprise, typically in the
absorbent core, superabsorbent materials, such as absorbent gelling
materials (AGM), usually in finely dispersed form, e.g. typically
in particulate form, in order to improve their absorption and
retention characteristics. Superabsorbent materials for use in
absorbent articles typically comprise water-insoluble,
water-swellable, hydrogel-forming crosslinked absorbent polymers
which are capable of absorbing large quantities of liquids and of
retaining such absorbed liquids under moderate pressure. Absorbent
gelling materials can be incorporated in absorbent articles,
typically in the core structure, in different ways; for example,
absorbent gelling materials in particulate form can be dispersed
among the fibers of fibrous layers comprised in the core, or rather
localized in a more concentrated arrangement between fibrous
layers.
[0006] Absorbent cores for absorbent articles having a thin
structure can further provide an improved immobilization of
absorbent gelling materials, particularly when the article is fully
or partially loaded with liquid, and an increased wearing comfort.
Such thinner structures provide absorbent articles combining better
comfort, discreetness and adaptability, such as for example, thin
absorbent structures where the absorbent gelling material is
located and somehow kept in selected, e.g. patterned regions of the
structure itself.
[0007] EP 724418 (Tanzer) for example, discloses an absorbent
article which includes superabsorbent material located in discrete
pockets. The absorbent article comprises a first and a second
carrier layer and water-sensitive attaching means for securing
together the carrier layers and to provide a plurality of pocket
regions. The article comprises high-absorbency material located
within said pocket regions. The water-sensitive attachment means
provides a wet strength which is less than a separating force
imparted by a swelling of that high-absorbency material when that
high-absorbency material is exposed to an aqueous liquid. The
absorbent article is said to provide an absorbent structure which
more securely locates and contains the high-absorbency material in
said pockets when the article is dry. However, due to the
construction of the pockets, it is believed that this absorbent
article does not provide a very satisfactory immobilization of the
absorbent material in the fully or partially urine loaded state. EP
1447067, assigned to the Procter & Gamble Company, describes an
absorbent article, typically a disposable absorbent article, such
as a diaper, having an absorbent core which imparts increased
wearing comfort to the article and makes it thin and dry. The
absorbent core comprises a substrate layer, the substrate layer
comprising a first surface and a second surface, the absorbent core
further comprising a discontinuous layer of absorbent material, the
absorbent material comprising an absorbent polymer material, the
absorbent material optionally comprising an absorbent fibrous
material which does not represent more than 20 weight percent of
the total weight of the absorbent polymer material. The
discontinuous layer of absorbent material comprises a first surface
and a second surface, the absorbent core further comprising a layer
of thermoplastic material, the layer of thermoplastic material
comprising a first surface and a second surface and wherein the
second surface of the discontinuous layer of absorbent material is
in at least partial contact with the first surface of the substrate
layer and wherein portions of the second surface of the layer of
thermoplastic material are in direct contact with the first surface
of the substrate layer and portions of the second surface of the
layer of thermoplastic material are in direct contact with the
first surface of the discontinuous layer of absorbent material.
[0008] While absorbent articles according to EP 1447067 and
comprising thin absorbent cores with relatively high amounts of
absorbent gelling materials and rather low content of fibrous
materials commonly have good absorption and retention
characteristics to body fluids like urine, there still remains room
for improvement of absorption and retention towards other body
fluids. In particular, menses and blood are particularly difficult
to be effectively absorbed and retained into absorbent cores
containing superabsorbent materials in major amounts since such
materials do not show optimal absorption and retention
characteristics towards such body fluids.
[0009] It is believed that the non-optimal absorption and retention
are mainly caused by poor permeability of superabsorbent materials
towards menses and blood due to the viscosity and/or to the complex
nature of these fluids. Menses and blood are water based fluids
comprising components having molecular weights higher than water
and also corpuscular components, including red cells, white cells,
soluble proteins, cellular debris and mucus, which slow down the
absorption of these fluids by superabsorbents. Menses and blood are
rather thick, and more difficult to absorb in conventional
absorbent structures comprising absorbent gelling materials;
moreover, corpuscular components like red cells may decrease the
absorption capacity of certain superabsorbent particles. This
translates into a slower initial uptake rate of the fluid into the
superabsorbent material, and in turn in the absorbent structure
comprising the superabsorbent material, which can result in a lower
final absorption and retention capacity.
[0010] Also when considering more in general fibrous absorbent
materials, different fibers and different fibrous structures may
show different behaviors and effectiveness towards various body
fluids, particularly towards menses and blood. For example,
cellulose fibers, such as for example wood pulp fibers, show a
greater absorption and diffusion capacity towards the water
fraction of menses and blood, which may be very rapidly acquired
and may be transported within the fibrous structure, far from the
initial acquisition area, while the corpuscular and higher
molecular weight components do not diffuse equally well, and may
remain closer to the initial acquisition area. Such corpuscular and
higher molecular weight components tend to travel preferentially in
a direction perpendicular to the plane of the absorbent structure.
Also, natural and synthetic fibrous materials can be more or less
suitable to provide compact, or alternatively bulkier, absorbent
structures to be employed in absorbent cores.
[0011] Hence, there is still the need for an improved, thin
absorbent core structure for an absorbent article, particularly for
absorption of menses or blood, which comprises the absorbent
gelling material in a non uniform layer stably provided onto a
substrate layer, and which takes advantage of the peculiarities of
the different fibrous and non-fibrous absorbent materials in the
absorption and management of these complex body fluids, achieving a
better result in terms of fluid acquisition and distribution. Such
a structure could also be stably thin, or in any case should not
significantly change (for example increase) its thickness upon
absorption throughout its normal use.
SUMMARY OF THE INVENTION
[0012] The present invention addresses the above need by providing
an absorbent core for an absorbent article intended for absorption
of menses or blood, comprising a substrate layer including a first
surface and a second surface. The absorbent core further comprises
a non uniform layer of absorbent material including an absorbent
polymer material. The non uniform layer of absorbent material
comprises a first surface and a second surface. The absorbent core
further comprises a layer of a thermoplastic material including a
first surface and a second surface, wherein the second surface of
the non uniform layer of absorbent material is in at least partial
contact with the first surface of the substrate layer. Portions of
the second surface of the layer of thermoplastic material are in
direct contact with the first surface of the substrate layer and
portions of the second surface of the layer of thermoplastic
material are in direct contact with the first surface of the non
uniform layer of absorbent material. Further, the substrate layer
comprises a fibrous material substantially free of cellulose
fibers, and the substrate layer has a basis weight from 25
g/m.sup.2 to 120 g/m.sup.2, preferably from 35 g/m.sup.2 to 90
g/m.sup.2.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a plan view of a sanitary napkin showing an
absorbent core according to an embodiment of the present
invention.
[0014] FIG. 2 is a schematic cross section of the sanitary napkin
of FIG. 1 taken in the transverse axis A-A'.
[0015] FIG. 3 shows a schematic cross section of an absorbent core
according to one embodiment of the present invention.
[0016] FIG. 4 shows a schematic cross section of an absorbent core
according to one embodiment of the present invention.
[0017] FIG. 5 shows a perspective view of an exemplary absorbent
core according to the present invention.
[0018] FIG. 6 shows a schematic cross section of an absorbent core
according to one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] The present invention relates to an absorbent core for
absorbent articles such as sanitary napkins, panty liners, tampons,
interlabial devices, wound dressings, and the like, which are
intended for the absorption of body fluids, such as menses and
blood. Exemplary absorbent articles in the context of the present
invention are disposable absorbent articles. The term "disposable"
is used herein to describe articles, which are not intended to be
laundered or otherwise restored or reused as an article (i.e. they
are intended to be discarded after a single use and preferably to
be recycled, composted or otherwise disposed of in an
environmentally compatible manner). The absorbent core of the
present invention will be herein described in the context of a
typical absorbent article, such as, for example, a sanitary napkin
20 as illustrated in FIG. 1. Typically, such articles as shown in
FIG. 1 can comprise the elements of a liquid pervious topsheet 30,
a backsheet 40 and an absorbent core 28 intermediate said topsheet
30 and said backsheet 40.
[0020] In the following description the term "cellulose fibers" is
used. Cellulose fibers comprise naturally occurring fibers based on
cellulose, such as, for example cotton, linen, etc. Wood pulp
fibers are one example of cellulose fibers according to the present
invention. Man-made fibers derived from cellulose, such as
regenerated cellulose (rayon), or partially or fully acetylated
cellulose derivatives (e.g. cellulose acetate or triacetate), are
also considered as cellulose fibers according to the present
invention.
[0021] In the following description of the invention, the surface
of the article, or of each element thereof, which in use faces in
the direction of the wearer is called wearer-facing surface.
Conversely, the surface facing in use in the direction of the
garment is called garment-facing surface. The absorbent article of
the present invention, as well as any element thereof, such as, for
example the absorbent core, has therefore a wearer-facing surface
and a garment-facing surface.
Topsheet
[0022] According to the present invention, the absorbent article
can comprise a liquid pervious topsheet. The topsheet suitable for
use herein can comprise wovens, non-wovens, and/or
three-dimensional webs of a liquid impermeable polymeric film
comprising liquid permeable apertures. In FIG. 1 the topsheet is
indicated with reference numeral 30. For example, the wearer-facing
and contacting surface can be provided by a film material having
apertures which are provided to facilitate liquid transport from
the wearer facing surface towards the absorbent structure. Such
liquid permeable, apertured films are well known in the art. They
provide a resilient three-dimensional fiber-like structure. Such
films have been disclosed in detail for example in U.S. Pat. No.
3,929,135, U.S. Pat. No. 4,151,240, U.S. Pat. No. 4,319,868, U.S.
Pat. No. 4,324,426, U.S. Pat. No. 4,343,314, U.S. Pat. No.
4,591,523, U.S. Pat. No. 4,609,518, U.S. Pat. No. 4,629,643, U.S.
Pat. No. 4,695,422 or WO 96/00548.
[0023] The topsheet for use herein can be a single layer or may
have a multiplicity of layers. In an embodiment of the present
invention, the topsheet across its full extension is a single
layer, which provides both the wearer-facing surface and the
garment-facing surface of the topsheet. Optionally, on the
wearer-facing surface of the topsheet but only extending in the
peripheral zone of the article an additional layer may be desirable
to provide extra softness or extra liquid handling/retaining
abilities (this design is usually referred to as "hybrid
topsheet"). The topsheet typically extends across the whole of the
absorbent structure and can extend into and form part of or all of
the preferred but optional side flaps, side-wrapping elements,
wings or ears. Also the topsheet can wrap around the absorbent core
edges.
[0024] The topsheet as a whole shall be compliant, soft feeling,
and non-irritating to the wearer's skin. It also can have elastic
characteristics allowing it to be stretched in one or more
directions. The topsheet may provide for acquisition and transport
of fluid from the wearer towards the absorbent core and containment
of the absorbent core. In addition to liquid permeability, the
topsheet may have a high vapor permeability and/or air
permeability.
Absorbent Core
[0025] In an embodiment of the present invention the absorbent core
28 comprises a substrate layer 100, absorbent polymer material 110
and a layer of thermoplastic material 120, typically a layer of
fiberized hot melt adhesive 120. The substrate layer 100 is
typically provided from a non-woven material, as will be explained
in detail below.
[0026] The substrate layer 100 comprises a first surface and a
second surface. At least portions of the first surface of the
substrate layer 100 are in direct contact with a layer of absorbent
polymer material 110. This layer of absorbent polymer material 110
can be typically a non uniform layer, and comprises a first surface
and a second surface, wherein by "non uniform" it is meant that the
absorbent polymer material 110 is distributed over the substrate
layer 100 with non uniform basis weight. According to an embodiment
of the present invention, the non uniform layer of absorbent
polymer material 110 can be a discontinuous layer that is a layer
typically comprising openings, i.e. areas substantially free of
absorbent polymer material, which in certain embodiments can be
typically completely surrounded by areas comprising absorbent
polymer material, as will be explained in more detail later on.
Typically these openings have a diameter or largest span of less
than 10 mm, or less than 5 mm, or 3 mm, or 2 mm, or 1.5 mm and of
more than 0.5 mm, or 1 mm At least portions of the second surface
of the absorbent polymer material layer 110 are in contact with at
least portions of the first surface of the substrate layer material
100. The first surface of the absorbent polymer material 112
defines a certain height of the layer of absorbent polymer material
above the first surface of the layer of substrate material 100.
When the absorbent polymer material layer 110 is provided as a non
uniform layer, typically for example as a discontinuous layer, at
least some portions of the first surface of the substrate layer 100
are not covered by absorbent polymer material 110. The absorbent
core 28 further comprises a layer of a thermoplastic material 120.
This thermoplastic material 120 serves to at least partially
immobilize the absorbent polymer material 110.
[0027] In a typical embodiment of the present invention the
thermoplastic material 120 is provided as a fibrous layer which is
partially in contact with the absorbent polymer material 110 and
partially in contact with the substrate layer 100. FIG. 3 shows
such a structure. In this structure the absorbent polymer material
layer 110 is provided as a discontinuous layer, a layer of
fiberized thermoplastic material 120 is laid down onto the layer of
absorbent polymeric material 110, such that the thermoplastic layer
120 is in direct contact with the first surface of the layer of
absorbent polymer material 110, but also in direct contact with the
first surface of the substrate layer 100, where the substrate layer
is not covered by the absorbent polymeric material 110, i.e. in
correspondence of the openings of the discontinuous layer of the
polymer material 120. This imparts an essentially three-dimensional
structure to the fibrous layer of thermoplastic material 120 which
in itself is essentially a two-dimensional structure of relatively
small thickness (in z-direction), as compared to the extension in
x- and y-direction. In other words, the fibrous thermoplastic
material layer 120 undulates between the first surface of the
absorbent polymer material 110 and the first surface of the
substrate layer 100. The areas where the fibrous thermoplastic
material 120 is in contact with the substrate layer 100 are the
areas of junction 140.
[0028] Thereby, the thermoplastic material 120 provides spaces to
hold the absorbent polymer material 110 typically towards the
substrate layer 100, and thereby immobilizes this material. In a
further aspect, the thermoplastic material 120 bonds to the
substrate 100 and thus affixes the absorbent polymer material 110
to the substrate 100. Typical thermoplastic materials will also
penetrate into both the absorbent polymer material 110 and the
substrate layer 100, thus providing for further immobilization and
affixation.
[0029] Of course, while the thermoplastic materials disclosed
herein can provide a much improved wet immobilization, i.e.
immobilization of absorbent polymer material when the article is
wet or at least partially loaded, these thermoplastic materials can
also provide a very good immobilization of absorbent polymer
material when the article is dry.
[0030] In accordance with an embodiment of the present invention,
the absorbent polymer material 110 may also be optionally mixed
with fibrous material, which can provide a matrix for further
immobilization of the absorbent polymer material. However,
typically a relatively low amount of fibrous material can be used,
for example less than 40 weight %, less than 20 weight %, or less
than 10 weight % of the total weight of the absorbent polymer
material 110, positioned within the areas of absorbent polymer
material.
[0031] According to an embodiment of the present invention, in a
typically discontinuous layer of absorbent polymer material 110 the
areas of absorbent polymer material can be connected to one
another, while the areas of junction 140 can be areas, which in an
embodiment may correspond to the openings in the discontinuous
layer of absorbent polymer material, as shown for example in FIG.
5. The areas of absorbent material are then referred to as
connected areas. In an alternative embodiment, the areas of
junction 140 can be connected to one another. Then, the absorbent
material can be deposited in a discrete pattern, or in other words
the absorbent material represents islands in a sea of thermoplastic
material 120. Hence, in summary, a discontinuous layer of absorbent
polymer material 110 may comprise connected areas of absorbent
polymer material 110, as e.g. illustrated in FIG. 5, or may
alternatively comprise discrete areas of absorbent polymer material
110.
[0032] In a further aspect of the present invention, it has been
found that absorbent cores providing for a good wet immobilization
can be formed by combining two layers as shown in FIG. 3 and as
described in the context thereof. Such an embodiment is shown in
FIG. 6. The absorbent core material shown in FIG. 6 comprises two
substrate layers 100, two layers of absorbent polymer material 110
and two layers of fibrous thermoplastic material 120. When two e.g.
discontinuous layers of an absorbent polymer material 110 are used,
they would be typically arranged in such a way that the absorbent
polymer material of the one layer faces the areas of junction 140
of the other layer, which in the two combined layers can be then
offset without facing each other. Hence typically, when two storage
layers are joined, this is done such that the first surface of the
substrate layer 100 of the first storage layer faces the first
surface of the substrate layer 100 of the second storage layer.
[0033] An alternative embodiment of the present invention is shown
in FIG. 4. The absorbent core shown in FIG. 4 can further comprise
a cover layer 130. This cover layer may be provided of the same
material as the substrate layer 100, or may be provided from a
different material. Suitable materials for the cover layer are for
example nonwoven materials, as will be better explained further on.
In these embodiment portions of the cover layer 130 bond to
portions of the substrate layer 100 via the thermoplastic material
120. Thereby, the substrate layer 100 together with the cover layer
130 provides spaces to immobilize the absorbent polymer material
110.
[0034] The present invention, and specifically the embodiments
described with reference to FIGS. 3, 4 and 6 can be used to provide
a storage layer of an absorbent core. However, they can also be
used to provide the full absorbent core 28 as illustrated in FIGS.
1 and 2. In that case, no further materials wrapping the core, such
as a top layer and a bottom layer are being used. With reference to
the embodiment of FIG. 3 the substrate layer 100 may provide the
function of a top layer and the layer of fiberized thermoplastic
material 120 may provide the function of a bottom layer of an
absorbent core 28, wherein top and bottom layers respectively
correspond to the body facing and garment facing surfaces of the
core 28. With reference to FIG. 4 the cover layer 130 may provide
the function of a bottom layer and the substrate layer 100 may
provide the function of a top layer of an absorbent core. With
reference to FIG. 6, the two substrate layers 100 used may provide
the functions of a top layer and of a bottom layer of an absorbent
core, respectively.
[0035] With reference to FIGS. 3 and 4 the areas of direct contact
between the thermoplastic material 120 and the substrate material
100 are referred to as areas of junction 140. The shape, number and
disposition of the areas of junction 140 will influence the
immobilization of the absorbent polymer material 110. The areas of
junction can be for example of squared, rectangular or circular
shape. Areas of junction of circular shape can have a diameter of
more than 0.5 mm, or more than 1 mm, and of less than 10 mm, or
less than 5 mm, or less than 3 mm, or less than 2 mm, or less than
1.5 mm If the areas of junction 140 are not of circular shape, they
can be of a size as to fit inside a circle of any of the diameters
given above.
[0036] The areas of junction 140 can be disposed in a regular or
irregular pattern. For example, the areas of junction 140 may be
disposed along lines as shown in FIG. 5. These lines may be aligned
with the longitudinal axis of the absorbent core, or alternatively
they may have a certain angle in respect to the longitudinal edges
of the core. A disposition along lines parallel with the
longitudinal edges of the absorbent core 28 might create channels
in the longitudinal direction which can lead to a lesser wet
immobilization, hence for example the areas of junction 140 can be
arranged along lines which form an angle of 20 degrees, or 30
degrees, or 40 degrees, or 45 degrees with the longitudinal edges
of the absorbent core 28. Another pattern for the areas of junction
140 can be a pattern comprising polygons, for example pentagons and
hexagons or a combination of pentagons and hexagons. Also typical
can be irregular patterns of areas of junction 140, which also can
give a good wet immobilization. Irregular patterns of areas of
junction 140 can also give a better fluid handling behavior in case
of absorption of menses or blood, since fluid can start diffusing
in whichever direction from any initial acquisition point with
substantially the same probability of contacting the absorbent
polymer material in the e.g. discontinuous layer. Conversely,
regular patterns might create preferential paths the fluid could
follow with lesser probability of actually contacting the absorbent
polymer material.
[0037] According to the present invention the thermoplastic layer
120 can comprise any thermoplastic material, typically adhesive
thermoplastic materials, also referred to as hot melt adhesives. A
variety of thermoplastic materials are suitable to immobilize the
absorbent material. Some initially thermoplastic materials may
later lose their thermoplasticity due to a curing step, e.g.
initiated via heat, UV radiation, electron beam exposure or
moisture or other means of curing, leading to the irreversible
formation of a crosslinked network of covalent bonds. Those
materials having lost their initial thermoplastic behavior are
herein also understood as thermoplastic materials 120.
[0038] Without wishing to be bound by theory it has been found that
those thermoplastic materials, i.e. the hot melt adhesives, can be
most useful for immobilizing the absorbent polymer material 110,
which combine good cohesion and good adhesion behavior. Good
adhesion is critical to ensure that the thermoplastic layer 120
maintains good contact with the absorbent polymer material 110 and
in particular with the substrate. Good adhesion is a challenge,
namely when a non-woven substrate is used. Good cohesion ensures
that the adhesive does not break, in particular in response to
external forces, and namely in response to strain. The adhesive is
subject to external forces when the absorbent product has acquired
liquid, which is then stored in the absorbent polymer material 110
which in response swells. An exemplary adhesive should allow for
such swelling, without breaking and without imparting too many
compressive forces, which would restrain the absorbent polymer
material 110 from swelling. It may be desirable that the adhesive
not break, which would deteriorate the wet immobilization.
Exemplary suitable thermoplastic materials are described below.
[0039] The thermoplastic material may comprise, in its entirety, a
single thermoplastic polymer or a blend of thermoplastic polymers,
having a softening point, as determined by the ASTM Method D-36-95
"Ring and Ball", in the range between 50.degree. C. and 300.degree.
C., or alternatively the thermoplastic composition may be a hot
melt adhesive comprising at least one thermoplastic polymer in
combination with other thermoplastic diluents such as tackifying
resins, plasticizers and additives such as antioxidants.
[0040] The thermoplastic polymer can have typically a molecular
weight (Mw) of more than 10,000 and a glass transition temperature
(Tg) usually below room temperature. Typical concentrations of the
polymer in a hot melt are in the range of 20-40% by weight. A wide
variety of thermoplastic polymers can be suitable for use in the
present invention. Such thermoplastic polymers can be typically
water insensitive. Exemplary polymers can be (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 can be non-elastomeric polymer blocks, typically
comprising polystyrene, and the B blocks can be unsaturated
conjugated diene or (partly) hydrogenated versions of such. The B
block can be typically isoprene, butadiene, ethylene/butylene
(hydrogenated butadiene), ethylene/propylene (hydrogenated
isoprene), and mixtures thereof.
[0041] 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 can be
amorphous polyolefins or amorphous polyalphaolefins (APAO) which
are homopolymers, copolymers or terpolymers of C2 to C8
alphaolefins.
[0042] The resin can typically have a Mw below 5,000 and a Tg
usually above room temperature, typical concentrations of the resin
in a hot melt can be in the range of 30-60%. The plasticizer has a
low Mw of typically less than 1,000 and a Tg below room
temperature, a typical concentration is 0-15%.
[0043] The thermoplastic material, typically a hotmelt adhesive,
can be present in the form of fibers throughout the core, being
provided with known means, i.e. the adhesive can be fiberized.
Typically, the fibers can have an average thickness of 1-100
micrometer and an average length of 5 mm to 50 cm. In particular
the layer of thermoplastic material, typically e.g. a hot melt
adhesive, can be provided such as to comprise a net-like
structure.
[0044] To improve the adhesiveness of the thermoplastic material
120 to the substrate layer 100 or to any other layer, in particular
any other non-woven layer, such layers may be pre-treated with an
auxiliary adhesive.
[0045] Typically, a hot melt adhesive can meet at least one or more
of the following parameters. A typical hot melt adhesive can have a
storage modulus G' measured at 20.degree. C. of at least 30,000 Pa
and less than 300,000 Pa, less than 200,000 Pa, or less than
100,000 Pa. The storage modulus G' at 20.degree. C. is a measure
for the permanent "tackiness" or permanent adhesion of the
thermoplastic material used. Good adhesion will ensure a good and
permanent contact between the thermoplastic material and for
example the substrate layer 100. In a further aspect, the storage
modulus G' measured at 60.degree. C. should be less than 300,000 Pa
and more than 18,000 Pa, or more than 24,000 Pa, or also more than
30,000.
[0046] The storage modulus measured at 60.degree. C. is a measure
for the form stability of the thermoplastic material at elevated
ambient temperatures. This value may be important if the absorbent
product is used in a hot climate where the thermoplastic
composition could lose its integrity if the storage modulus G' at
60.degree. C. is not sufficiently high.
[0047] In a further aspect, the loss angle tan Delta of the
adhesive at 60.degree. C. should be below the value of 1, or below
the value of 0.5. The loss angle tan Delta at 60.degree. C. is
correlated with the liquid character of an adhesive at elevated
ambient temperatures. The lower tan Delta, the more an adhesive
behaves like a solid rather than a liquid, i.e. the lower its
tendency to flow or to migrate and the lower the tendency of an
adhesive superstructure as described herein to deteriorate or even
to collapse over time. This value is hence particularly important
if the absorbent article is used in a hot climate.
[0048] In a further aspect, a typical hot melt adhesive should have
a glass transition temperature Tg of less than 25.degree. C., less
than 22.degree. C., less than 18.degree. C., or less than
15.degree. C. A low glass transition temperature Tg is generally
beneficial for good adhesion. In a further aspect a low glass
transition temperature Tg may help ensure that the adhesive
thermoplastic material does not become too brittle.
[0049] In yet a further aspect, a typical hot melt adhesive can
have a sufficiently high cross-over temperature Tx. The cross-over
temperature parameter Tx is measured using the Dynamical Mechanical
Analysis (DMA)--Temperature Sweep Test as referred to hereinafter.
A sufficiently high cross-over temperature Tx has been found
beneficial for high temperature stability of the thermoplastic
material and hence it can ensure good performance of the absorbent
product and in particular good wet immobilization even under
conditions of hot climates and high temperatures. Therefore, Tx
should typically be above 80.degree. C., above 85.degree. C., or
above 90.degree. C.
[0050] In a further aspect, hot melt adhesives in accordance with
the present invention may have a sufficient cohesive strength
parameter .gamma.. The cohesive strength parameter y is measured
using the Rheological Creep Test as referred to hereinafter. A
sufficiently low cohesive strength parameter .gamma. is
representative of elastic adhesive which, for example, can be
stretched without tearing. If a stress of .tau.=1,000 Pa is
applied, the cohesive strength parameter y can be less than 100%,
less than 90%, or less than 75%. For a stress of .tau.=125,000 Pa,
the cohesive strength parameter y can be less than 1,200%, less
than 1,000%, or less than 800%.
[0051] An exemplary process for producing absorbent cores 28 in
accordance with the present invention can comprise the following
steps:
[0052] In one step, the substrate layer 100 is laid onto a
formation surface. The absorbent polymeric material 110 is disposed
by means known in the art, for example by means of a lay-down drum,
in the selected non uniform e.g. discontinuous layer onto the
substrate layer 100, optionally after providing a stabilizing
adhesive on the substrate layer 100, for example in longitudinal
stripes. In a further process step, a hot melt adhesive is placed
with known means onto the absorbent polymer material, for example
in form of fibers.
[0053] While any adhesive application means known in the art can be
used to place the hot melt adhesive onto the absorbent polymer
material, the hot melt adhesive can be typically applied by a
nozzle system. For example, a nozzle system can be utilized, which
can provide a relatively thin but wide curtain of adhesive. This
curtain of adhesive is than placed onto the substrate layer 100 and
the absorbent polymer material 110.
[0054] In an optional further process step, a cover layer 130 can
be placed upon the substrate layer 100, the absorbent polymer
material and the hot melt adhesive layer. The cover layer 130 will
be in adhesive contact with the substrate layer 100 in the areas of
junction 140. In these areas of junction 140 the adhesive is in
direct contact with the substrate layer 100. The cover layer 130
will typically not be in direct adhesive contact with the substrate
layer 100 where the absorbent polymer material 110 is present.
[0055] In one alternative embodiment, the cover layer 130 and the
substrate layer 100 can be provided from a unitary sheet of
material. The placing of the cover layer 130 onto the substrate
layer 100 can then involve the folding of the unitary piece of
material.
[0056] Hence, the uneven service of the lay-down system, which may
be a lay-down drum, typically determines the distribution of
absorbent polymer material in the non uniform, for example
discontinuous layer and likewise can determine the pattern of areas
of junction 140. The distribution of absorbent polymer material may
be influenced by vacuum means.
[0057] The distribution of absorbent polymeric material can be
profiled, for example profiled in the longitudinal direction, or in
the lateral direction, or in both. Hence, for example, along the
longitudinal axis of the absorbent core, which is normally
coincident with the longitudinal axis of the absorbent article, for
example a sanitary napkin, the basis weight of the absorbent
polymer material can change. For example, the basis weight of
absorbent polymer material in at least one freely selected first
square measuring 1 cm.times.1 cm can be at least 10%, 20%, 30%, 40%
or 50% higher than the basis weight of absorbent polymer material
in at least one freely selected second square measuring 1
cm.times.1 cm. Typically the criterion is met if the first and the
second square are centered about the longitudinal axis.
[0058] Typically the absorbent polymer material for absorbent cores
according to the present invention can comprise absorbent polymer
particles. Without whishing to be bound by theory it is believed
that such material, even in the swollen state, i.e. when liquid has
been absorbed, does not substantially obstruct the liquid flow
throughout the material, particularly when further the permeability
of said material, as expressed by the saline flow conductivity of
the absorbent polymer material, is greater than 10, 20, 30 or 40
SFC-units, where 1 SFC unit is 1.times.10.sup.-7
(cm.sup.3.times.s)/g. Saline flow conductivity is a parameter well
recognized in the art and is to be measured in accordance with the
test disclosed in EP 752 892 B.
[0059] According to an embodiment of the present invention, the
absorbent core can be provided as a single structure by known
means. Thermo bonding or felting or combinations of these combining
steps can for example create it. Hence, a core constituted by a
single structure can be provided by laying the various materials
described above onto each other in a continuous process, for
example by air laying techniques, then a calendaring can take place
in order to reduce the thickness and bulkiness of the structure as
desired. The calendaring step can create a densification, which can
provide the same force throughout the whole of the structure. This
calendaring can be then optionally followed by thermo bonding or
felting with needles or a combination such as felting with hot
needles and a hot air exposure of the absorbent core structure, in
order to attain a desired level of calliper, density and structure
stabilization, which will in turn reflect on the final dimensional
stabilization of the absorbent core.
[0060] The substrate layer 100 of the absorbent core 28 in FIGS. 2,
3, 4, and 6 can advantageously comprise a fibrous material
substantially free of cellulose fibers. By saying that a layer of
the absorbent core is "substantially free" of cellulose fibers, it
is meant in the context of the present invention that the layer
should not comprise any significant amount of cellulose fibers
within its inner structure. While cellulose fibers which can be
present at an outer surface of the specified layer, for example at
the interface between the specified layer and an adjacent one,
which could be for example an outer layer wrapping the core 28, in
some cases can accidentally and slightly penetrate the structure of
the specified layer, such shall not be considered significant.
Significant amount can correspond to less than 10% by weight, less
than 5% by weight, less than 3% by weight, or less than 1% by
weight, based on the dry weight of the specified layer of the
absorbent core. The substrate layer 100 can also have a basis
weight from 25 g/m.sup.2 to 120 g/m.sup.2, or from 35 g/m.sup.2 to
90 g/m.sup.2.
[0061] In certain embodiments of the present invention the
absorbent polymer material 110 in the absorbent core 28 is present
throughout the area of the absorbent core in an average basis
weight of less than 200 g/m.sup.2, of less than 160 g/m.sup.2, from
60 g/m.sup.2 to 120 g/m.sup.2, or from 80 g/m.sup.2 to 100
g/m.sup.2. An average basis weight is typically based on the whole
area interested by the layer of absorbent polymer material, hence
comprising possible openings included in an e.g. discontinuous
layer.
[0062] Typical materials for the substrate layer 100 can be
nonwoven materials, for example spunbonded or carded nonwoven
materials, or also airlaid materials, such as for example latex
and/or thermal bonded airlaid materials. Exemplary nonwoven
materials can be provided from synthetic fibers, such as
polyethylene (PE), polyethylene terephthalate (PET), polypropylene
(PP). As the polymers used for nonwoven production are inherently
hydrophobic, they can be typically coated with hydrophilic
coatings, for example with durably hydrophilic coatings to provide
permanently hydrophilic nonwovens. Other nonwoven materials can
comprise composite structures such as a so called SMS material,
comprising a spunbonded, a melt-blown and a further spunbonded
layer.
[0063] In another embodiment of the present invention illustrated
in FIG. 4, the absorbent core 28 can further comprise at least one
cover layer 130 in direct contact with the first surface of the
layer of thermoplastic material 120. According to an embodiment of
the present invention, the cover layer 130 can comprise a same or
similar fibrous material as that of the substrate layer 100, which
hence can be substantially free of cellulose fibers and can e.g.
have a basis weight from 25 g/m.sup.2 to 120 g/m.sup.2, or from 35
g/m.sup.2 to 90 g/m.sup.2.
[0064] Without being bound to any theory, it is believed that the
absorbent core of the present invention has an improved capacity
for the acquisition, management and retention of complex body
fluids, particularly menses and blood, owing to the particular
combination and composition of its material components and to the
respective arrangement thereof, in addition to the already improved
structure stability due to the better immobilization of the
absorbent polymer material also when the article is fully of
partially liquid loaded. The above advantages are achieved by a
core structure which is particularly thin and flexible, and
substantially shape stable, hence providing an absorbent article,
typically a sanitary napkin, with an increased wearing comfort by
being thin and dry.
[0065] In the absorbent core of the present invention, at least the
fibrous substrate layer and the non uniform, e.g. discontinuous
layer of absorbent material comprising the absorbent polymer
material can each provide specific liquid absorption and management
characteristics. Typically, as shown for example in FIG. 2, the
absorbent core 28 can be positioned in the sanitary napkin 20 with
the substrate layer 100 towards the wearer facing surface of the
article. An absorbent core having the structure as shown in FIG. 6
is instead substantially symmetrical and can have in any case a
substrate layer 100 towards the wearer facing surface of the
article. In use the body fluid, typically menses or blood, can be
hence directly received by a fibrous layer being substantially free
of cellulose fibers, typically a substrate layer 100 as in the
embodiment of FIG. 2. In the exemplary embodiment of FIGS. 1 and 2,
the fluid can directly reach the fibrous substrate layer 100. The
same occurs in the other embodiments where the absorbent core is as
shown in FIG. 4 or 6, wherein the absorbent core of FIG. 4 can be
typically positioned in an absorbent article with the substrate
layer 100 towards the body facing surface of the article. In both
cases the body fluid directly reaches a substrate layer 100
first.
[0066] The fibrous substrate layer being substantially free of
cellulose fibers and having the selected basis weight and hence
thickness typically comprises synthetic fibers which have a certain
filtration capacity towards the corpuscular and complex fraction of
menses or blood, typically red cells, white cells, soluble
proteins, cellular debris and mucus. Upon receiving body fluid,
said corpuscular and complex fraction of menses or blood is hence
intercepted minimizing its direct interaction with the underlying
absorbent polymer material, which could otherwise cause gel
blocking. The complex body fluid is in fact at least partially
"filtered" by the fibrous layer being free of cellulose fibers and
having the selected basis weight, owing to the combined effect of
its component synthetic fibers, and to its basis weight which in
turn provides sufficient volume for an effective entrapment and
immobilization of the corpuscular and complex components. In the
exemplary embodiment of FIG. 2 the body fluid is directly acquired
by the fibrous substrate layer 100, where the corpuscular part can
be at least partially intercepted. The body fluid, typically menses
or blood, is hence made less thick by this sort of filtration step,
and can be subsequently released and more efficiently absorbed by
the absorbent polymer material 120. In this exemplary embodiment
the fluid can hence contact the absorbent polymer material after
being previously "filtered" by the fibrous material substantially
free of cellulose fibers and provided with the necessary volume in
order to effectively entrap the corpuscular and complex fraction
thereof. This substantially prevents complex components of menses
or blood, particularly corpuscular components, from accumulating on
the outer surface of the absorbent polymer material, for example
superabsorbent particles, with a sort of shielding effect which
causes gel blocking and makes further absorption problematic. The
absorption capacity of the absorbent polymer material is instead
directed more efficiently towards the water fraction of menses or
blood.
[0067] This is achieved in a structure which is typically thin and
is capable of employing more completely the absorption capacity of
the different materials, which can hence be present in a typically
lesser amount, thus also providing a particularly thin structure
having improved dimensional stability during absorption and
therefore increased comfort during use.
[0068] According to an embodiment of the present invention the
absorbent polymer material can be selected among the polyacrylate
based polymers described in the PCT Patent Application
WO2007/047598, which are polyacrylate based materials very slightly
crosslinked, or substantially not crosslinked at all, this further
improving the above mentioned synergistic effect. Particularly,
said polyacrylate based materials can have an extractable fraction
of at least about 30% by weight, between 30% and 80% by weight, or
between 32% and 70% by weight, evaluated according to the
Extractables test method described in the above referenced
application. Alternatively, said polyacrylate based materials can
have a retention capacity of at least about 30 g/g, at least about
35 g/g, or at least about 40 g/g, evaluated according to the
Centrifuge Retention Capacity test described in the above
referenced application. Said polymers in fact are particularly
effective in absorbing complex body fluids such as menses or blood,
and upon absorption of such fluids do not generally show a marked
swelling, followed by gel blocking, like traditional
superabsorbents, but rather act to a certain extent as thickeners
of the body fluid, immobilizing it as a sort of gelatinous mass
within the absorbent structure, namely in the interstices among the
fibers, without causing substantial swelling and in turn a sensible
increase of the overall thickness of the absorbent core.
[0069] According to a further embodiment of the present invention,
an absorbent article for absorption of body fluids such as menses
or blood comprising an absorbent core 28, typically positioned such
as to have the substrate layer 100 oriented towards the body facing
surface of the article, can further comprise a fibrous acquisition
layer between the absorbent core 28 and the topsheet, hence
typically onto the body facing surface of the substrate layer 100.
According to an embodiment of the present invention the acquisition
layer can also comprise a fibrous material substantially free of
cellulose fibers, namely for example nonwoven materials made by air
laying or wet laying of synthetic fibers such as polyethylene (PE),
polyethylene terephthalate (PET), or polypropylene (PP). Such a
fluid acquisition layer substantially free of cellulose fibers
would further improve the fluid acquisition and absorption
mechanism as described above with reference to the
intercepting/filtering capability of synthetic fibers towards the
complex components of menses or blood.
[0070] Exemplary materials for the fluid acquisition layer could
comprise spunbonded or carded nonwoven materials, or airlaid
materials such as for example latex bonded or thermal bonded
airlaid materials. Basis weights can typically range from 10
g/m.sup.2 to 60 g/m.sup.2, or from 25 g/m.sup.2 to 40
g/m.sup.2.
[0071] According to another embodiment of the present invention the
absorbent article can comprise a further fibrous layer comprised
between the absorbent core 28 and the backsheet, i.e. typically
provided at the garment facing surface of the core. This optional
layer can be provided by a fibrous material comprising cellulose
fibers, typically not more than 60% by weight of cellulose fibers,
or from 30% to 50% by weight of cellulose fibers.
[0072] Examples of fibrous materials for this optional fibrous
layer can be nonwoven materials, such as for example carded
nonwovens, airlaid or wetlaid fibrous materials, such as for
example latex or thermal bonded airlaid fibrous materials. Basis
weights for this optional fibrous layer can typically range from 10
g/m.sup.2 to 100 g/m.sup.2, or from 40 g/m.sup.2 to 80 g/m.sup.2.
This optional fibrous layer according to this further embodiment of
the present invention can act as an added wicking layer receiving
and distributing excess fluid which might not be fully retained by
the absorbent core 28. Without being bound to any theory, the
presence of cellulose fibers can make the layer particularly
effective in acquiring and diffusing the water fraction of body
fluids like menses or blood which is not completely absorbed by the
absorbent polymer material of the absorbent core 28, moreover after
at least a part of the complex fraction, particularly the
corpuscular components, have been retained by the substrate layer
100 as explained above.
[0073] The further fibrous layer can be a separate layer, distinct
from the core 28, and combined thereto in a known way while
assembling the absorbent article, or can be part of the absorbent
core, for example it can be provided by a suitably selected cover
layer 130.
Backsheet
[0074] The absorbent article comprising the core according to the
present invention can also comprise a backsheet 40. The backsheet
primarily has to prevent the extrudes absorbed and contained in the
absorbent structure from wetting materials that contact the
absorbent article such as underpants, pants, pajamas,
undergarments, and shirts or jackets, thereby acting as a barrier
to fluid transport. The backsheet according to an embodiment of the
present invention can also allow the transfer of at least water
vapor, or both water vapor and air through it and thus allow the
circulation of air into and water vapor out of the article. The
backsheet can typically extend across the whole of the absorbent
structure and can extend into and form part or all of side flaps,
side wrapping elements or wings, if present.
[0075] The elements of the article may be joined by any means
suitable for affixing two adjacent layers of material, such that
the layers are directly attached to one another or directly
attached to one another via the joining means. Suitable joining
means include adhesive, fusion bonding, ultrasonic bonding,
stitching, heat (e.g. thermo bonding by welding fibers at
intersections or melting a polymer to attach fibers or films to
each other), embossing, crimping, pressure bonds, dynamic
mechanical bonds or combinations thereof.
[0076] Especially if the absorbent article finds utility as a
sanitary napkin or panty liner, the absorbent article can be also
provided with a panty fastening means, which provides means to
attach the article to an undergarment. For example the panty
fastening means may comprise a panty fastening adhesive on the
garment facing surface of the backsheet, or alternatively a
mechanical fastener such as hook and loop fasteners such as
marketed under the trade name VELCRO, snaps or holders. The panty
fastening adhesive provides a means for securing the article to the
panty and optionally also a means for securing the article when
soiled, to a fold and wrap package for convenient disposal.
[0077] The absorbent article comprising the absorbent core of the
present invention can be used beneficially in the context of
sanitary napkins. The absorbent article may thus also have all
those features and parts, which are typical for products in the
context of their intended use. For sanitary napkins this includes
particularly wings or side flaps which are provided on the side
edges of the napkin and which fold around the crotch edge of an
undergarment. The side flaps can be provided as extensions of one
or several of the elements of the napkin such as the topsheet
and/or backsheet. They can also be made separately and be joined to
the side margin of the napkin.
EXAMPLE
[0078] A sanitary napkin comprising an absorbent core according to
an embodiment of the present invention is similar to that
illustrated in FIGS. 1 and 2 and comprises a topsheet constituted
by a polyethylene perforated formed film, a backsheet constituted
by a 25 g/m.sup.2 polyethylene film, a core comprising a substrate
layer constituted by a 45 g/m.sup.2 carded nonwoven comprising
polyester fibers and PP/PE bicomponent fibers, available from BBA
Fiberweb under the code TBPL 50/50 6dpf philic PET/BICO, a
discontinuous layer of absorbent polymer material constituted by a
particulate superabsorbent material available from Nippon Shokubai
under the trade name Aqualic L520 distributed onto the substrate
layer in a non uniform layer having overall an average basis weight
of 100 g/m.sup.2, and a layer of thermoplastic material constituted
by a hot melt adhesive available from HB Fuller under the trade
name NV 1151 Zeropack applied in fibers having an average thickness
of about 50 um at a basis weight of 9 g/m.sup.2.
[0079] The sanitary napkin further comprises a fibrous layer
between the absorbent core and the backsheet, constituted by a 65
g/m.sup.2 latex bonded airlaid (LBAL) material comprising 30% by
weight cellulose fibers, 40% by weight PET fibers and 30% by weight
latex binder, available from Concert GmbH under the code
WHXX65.
[0080] The Rheological Creep Test and the Dynamical Mechanical
Analysis (DMA)--Temperature Sweep Test mentioned hereinabove for
measuring the cohesive strength parameter y and the cross-over
temperature parameter Tx respectively, are as described in the
copending patent application EP 1447067, assigned to the Procter
& Gamble Company.
Artificial Menstrual Fluid (AMF)
[0081] Artificial Menstrual Fluid is based on modified sheep's
blood that has been modified to ensure it closely resembles human
menstrual fluid in viscosity, electrical conductivity, surface
tension and appearance. It is prepared as explained in U.S. Pat.
No. 6,417,424, assigned to The Procter & Gamble Company, from
line 33 of column 17 to line 45 of column 18, to which reference is
made.
[0082] 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".
[0083] Every document cited herein, including any cross referenced
or related patent or application, is hereby incorporated herein by
reference in its entirety unless expressly excluded or otherwise
limited. The citation of any document is not an admission that it
is prior art with respect to any invention disclosed or claimed
herein or that is alone, or in any combination with any other
reference or references, teaches, suggests or discloses any such
invention. Further, to the extend that any meaning or definition of
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.
[0084] 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.
* * * * *