U.S. patent application number 13/879454 was filed with the patent office on 2013-08-29 for absorbent structure.
This patent application is currently assigned to ROMANOVA BVBA STARTER. The applicant listed for this patent is Marleen Van De Maele. Invention is credited to Marleen Van De Maele.
Application Number | 20130226120 13/879454 |
Document ID | / |
Family ID | 45937916 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130226120 |
Kind Code |
A1 |
Van De Maele; Marleen |
August 29, 2013 |
ABSORBENT STRUCTURE
Abstract
The present invention relates to an absorbent structure,
preferably for use in absorbent products, such as used in the food,
consumer, household, building and construction, beauty and medical
industry, and as used in the personal hygiene industry. The
substantially cellulose free absorbent structures continuously
immobilise absorbent polymer material via initial smaller pockets
and subsequently larger compartments allowing excellent fluid
management of the absorbent polymer material in dry, partially and
fully liquid loaded state. Preferably such absorbent structure
volume increases are result of temporary secondary attachment
patterns made in combination with substantially permanent primary
attachment grids allowing the release of bigger volumes from the
initial smaller volumes by detachment of the secondary attachments.
Furthermore the absorbent structure according to an embodiment of
the invention non-homogeneously swells to form a liquid-managing
surface structure as a result of exposing the absorbent structure
to liquid. The present invention foresees in the need for improved
flexible, thin, lightweight absorbent structures which overcome the
absorbency problems of the prior art during absorption,
distribution and retention of liquids with optimal fit.
Inventors: |
Van De Maele; Marleen;
(Buggenhout, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Van De Maele; Marleen |
Buggenhout |
|
BE |
|
|
Assignee: |
ROMANOVA BVBA STARTER
Buggenhout
BE
|
Family ID: |
45937916 |
Appl. No.: |
13/879454 |
Filed: |
October 13, 2011 |
PCT Filed: |
October 13, 2011 |
PCT NO: |
PCT/EP2011/005139 |
371 Date: |
April 15, 2013 |
Current U.S.
Class: |
604/372 ; 156/70;
28/104; 428/206; 428/76 |
Current CPC
Class: |
A61F 13/15658 20130101;
D04H 1/465 20130101; B05D 1/32 20130101; Y10T 428/24893 20150115;
A61F 2013/530591 20130101; B32B 3/28 20130101; B32B 37/0076
20130101; A61F 2013/530562 20130101; A61F 13/5323 20130101; B32B
2555/02 20130101; A61F 13/15585 20130101; B05C 19/04 20130101; B32B
37/24 20130101; B32B 5/16 20130101; B05D 2401/32 20130101; B05C
1/10 20130101; Y10T 428/239 20150115; B32B 5/30 20130101; A61F
13/539 20130101 |
Class at
Publication: |
604/372 ;
428/206; 428/76; 156/70; 28/104 |
International
Class: |
A61F 13/539 20060101
A61F013/539; D04H 1/46 20060101 D04H001/46; B32B 37/00 20060101
B32B037/00; B32B 3/28 20060101 B32B003/28; B32B 5/16 20060101
B32B005/16 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 13, 2010 |
EP |
10 447 020.8 |
Oct 13, 2010 |
EP |
10 447 021.6 |
Oct 13, 2010 |
EP |
10 447 022.4 |
Oct 13, 2010 |
EP |
10 447 023.2 |
Oct 13, 2010 |
EP |
10 447 024.0 |
Feb 3, 2011 |
EP |
11 153 268.5 |
Claims
1. A substantially cellulose free absorbent structure comprising a
carrier layer, an auxiliary layer and an absorbent polymer material
there between, the carrier layer and auxiliary layer being at least
partially joined together by attachments made up of substantially
permanent primary attachment grids and/or substantially temporary
secondary attachment patterns, so as to form a sandwich-like
composite structure containing patterned absorbent particulate
polymer materials provided in at least some of the unattached
regions between the carrier layer and auxiliary layer forming an
absorbent polymer material area, the plurality of smaller-sized
pockets made up by at least substantially temporary secondary
attachments define spaces which immobilize the available dry volume
absorbent polymer material, the substantially temporary secondary
attachment being gradually releasable as a result of exposing the
surrounding absorbent polymer material to liquid so as phase in an
intermediate volume increase to fewer and medium-sized compartments
immobilising the partially wetted absorbent polymer material, and
resulting in still fewer maximum-sized compartments immobilising
the wetted absorbent polymer material to obtain continuous fluid
management.
2. An absorbent structure according to claim 1 characterized in
that its substantially permanent primary attachments are provided,
in combination with the substantially temporary secondary
attachment to make up the initial small-sized pockets, which remain
substantially intact.
3. An absorbent structure according to claim 1, characterized in
that the substantially permanent primary attachment grid and/or
substantially temporary secondary attachment pattern is distributed
over substantially the majority of the surface area of the
absorbent polymer material area.
4. An absorbent structure according to claim 1, characterized in
that the absorbent structure non-homogeneously swells to form a
liquid management surface structure due to release of the
substantially temporary secondary attachments.
5. An absorbent structure according to claim 1, characterized in
that the absorbent structure non-homogeneously swells to form a
liquid management surface structure due to phased swelling of the
absorbent polymer material area.
6. An absorbent structure according to claim 1, wherein the
attachments are at least partially formed via a mechanical,
thermal, physical, chemical, thermo-mechanical and/or most
preferably an ultrasonic process.
7. An absorbent structure according to claim 1, wherein at least
some or all of the substantially permanent primary attachments
and/or substantially temporary secondary attachments are formed
with at least an adhesive or binder as an attachment medium.
8. An absorbent structure according to claim 1, wherein the
substantially permanent primary attachments and/or substantially
temporary secondary attachments have different locations, sizes
and/or shapes.
9. An absorbent structure according claim 1, wherein at least 80%
of the absorbent material is absorbent polymer material.
10. An absorbent structure according to claim 1, wherein the
absorbent structure has on average within the absorbent polymer
material area at least one pocket per about 0.10 cm.sup.2,
preferably 1 per about 0.50 cm.sup.2, preferably 1 per about 1
cm.sup.2; preferably 1 per about 2.5 cm.sup.2, preferably 1 per
about 5 cm.sup.2 and/or at least 1 compartment per about 5
cm.sup.2, preferably 1 per about 10 cm.sup.2, preferably 1 per
about 20 cm.sup.2, preferably 1 per about 30 cm.sup.2, preferably 1
per about 45 cm.sup.2
11. An absorbent structure according to claim 1, wherein at least
some or all of the substantially permanent primary attachments
and/or substantially temporary secondary attachments have an
average surface size of at least 0.3 mm.sup.2, preferably at least
0.5 mm.sup.2, preferably at least 1.0 mm.sup.2 and more preferably
at least 3.0 mm.sup.2.
12. Absorbent structure according to claim 1, wherein the absorbent
structure has a flexure-resistance of less than 500.0 grams, more
preferably less than 250.0 grams, and still more preferably less
than about 175.0 grams and most preferably less than 130.0 grams or
100.0 grams.
13. Absorbent structure according to claim 1, with a wet
immobilization of more than 50 wt %, preferably more than 60 wt %,
preferably more than 7 wt %, more preferably more than 80 wt %.
14. An absorbent article comprising an absorbent structure
according to claim 1, wherein said absorbent article is a feminine
hygiene garment, baby diaper, baby pants or adult incontinence
garment.
15. An absorbent article according to claim 1, comprising a liquid
pervious topsheet, a liquid impervious backsheet and a liquid
absorbing absorbent structure situated in between the liquid
pervious topsheet and liquid impervious backsheet.
16. A method for the manufacturing of an absorbent structure
according to claim 1 which comprises: providing a carrier layer,
covering the carrier layer with an absorbent material, covering the
absorbent material with an auxiliary layer which is joinable to the
carrier layer; and in at least one position substantially temporary
and/or substantially permanently attaching the auxiliary layer to
the carrier layer, and by means of at least substantially temporary
secondary attachments defining small-sized pocket wherein dry
absorbent material is immobilized, such that by means of gradual
release of substantially temporary secondary attachment patterns
bigger-sized intermediate and final compartments are provided,
thereby continuously immobilising the absorbent material from dry
to wetted state.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an absorbent structure
having a high concentration of absorbent polymer material within an
integrated fluid management system, preferably for use in an
absorbent product, such as for example used in the food industry
(e.g. coffee pads), the consumer industry (e.g. disposable body
warmers), the household industry (e.g. sheet formed detergent
articles), building and construction (e.g. filter materials and
insulation), beauty and medical industry (e.g. make-up pads,
anti-septic wads) and absorbent articles as used in the personal
hygiene industry (e.g. feminine hygiene garments, baby diapers and
pants, adult incontinence garments). The present invention also
relates to an absorbent article comprising such absorbent structure
and to a method and apparatus for manufacturing such absorbent
structure.
BACKGROUND OF THE INVENTION
[0002] Disposable absorbent articles have an absorbent structure
for absorbing bodily exudates, a soft liquid-permeable top sheet on
the wearer side and a liquid-impermeable back sheet on the garment
side. The absorbent structure in between is normally made from a
mixture of cellulose fibers or other fibrous substance and an
absorbent polymer material. These fibrous substances make these
absorbent articles typically quite fluffy and bulky.
[0003] In recent years there has been increasing demand for
flexible, thinner, lightweight absorbent structures to resolve
various problems of manufacturing, marketing, design, fit, wearing
comfort, distribution, garbage disposal, material and energy
consumption, transportation and storage costs and the like.
[0004] The most common method currently used to meet these demands
in disposable absorbent articles is to reduce the amount of
cellulose fibre or other support material within and surrounding
the absorbent structure and/or use larger amounts of absorbent
polymer materials. Consequently such absorbent articles have a
smaller proportion of hydrophilic cellulose fibres and/or a higher
proportion of absorbent polymers materials. Some of these absorbent
articles may be better at storing liquid, however they are not
necessarily good at absorbing and distributing liquid when the
absorbent article is actually being used. It will thus be apparent
from the above that the absolute and relative proportions of the
fibrous material and absorbent polymer material are closely linked
in light of article performance. Hence there are limits on reducing
the amount of hydrophilic cellulose fibre and reducing the
thickness of absorbent cores.
[0005] Many attempts have been undertaken to manufacture flexible,
thin, lightweight absorbent structures, consisting of a high amount
of absorbent polymer material. In order to obtain good absorbency,
distribution and retention within such absorbent structures it has
found to be important to at least partially immobilize the
absorbent material. Failing to provide sufficient structural
integrity results in loss of functional performance characteristics
such as coherence, absorption, distribution and/or retention and
results in failures related but not limited to for instance
leakages, high rewet values, etc. On the other hand however the
presence of this physical and/or chemical interaction in between
the absorbent material and the restraining material often also
leads to a reduced absorption, distribution and/or retention
performance. This is especially the case when such flexible, thin,
lightweight absorbent structures, consisting of an absorbent
polymer material are placed in between multiple enveloping
layers.
[0006] The larger proportion of absorbent polymer materials and
related immobilisation requirements in substantially cellulose free
absorbent articles may thus greatly inhibit the absorption,
distribution and/or retention of liquids if inadequately managed.
It will be clear that the absolute and relative proportions of the
hydrophilic cellulose fibres and absorbent polymer materials need
to be tightly controlled in order to maintain the absorbent
properties of the absorbent structures. Certainly decreased
absorption speed and fluid distribution are common causes of
failure. Since such hygienic absorbent articles are generally also
disposable and need in some instances to be worn over many hours
they require performance in a dry state as well as in a partially
and fully bodily exudates loaded state.
[0007] The ability and capacity of an absorbent polymer material to
absorb, distribute and retain liquid is dependent upon the form,
position and/or manner in which the absorbent polymer material is
incorporated into the absorbent structure. Since many absorbent
structures have a relatively homogeneous and continuous
distribution of absorbent polymer material, and thus exhibit a
substantial homogeneous swelling, for second, third and next liquid
insults such absorbent layers may actually act as a liquid barrier.
This gel-blocking occurs when the absorbent polymer material
located in regions of first contact starts to increase in volume as
a consequence of imbibing the fluid, thereby forming a hydro-gel.
Gel blocking in and adjacent a zone of the absorbent layer of
initial liquid contact prevents liquid from rapidly dispersing or
wicking past the "blocking" material into the rest of the absorbent
layer and further liquid uptake by the absorbent layer must then
take place via for instance a diffusion process that is much slower
than the rate at which liquid is applied to the absorbent layer.
Especially when absorbent polymer material concentrations are
absolutely or relatively high and wetted, the hydro-gel can block
the initial and/or additional fluid from reaching other still more
absorbent regions of the absorbent core, thus leading to
unappreciated, underused or unused absorbent capacity. The
diminished capacity results in leakages, well before the absorbent
core is fully saturated.
[0008] Gel-blocking is even increased in thin substantially
cellulose free structures where the liquid find little or limited
macroscopic voids and/or spaces which can be used for temporary,
intermediate or final liquid storage. Also the structural volume
restrictions of these absorbent structures lead to a further
reduced absorbent performance due to limited swelling capacity of
the absorbent polymer material increasing the tendency to
functional failures and leakages. To remedy, absorbent article
designers have and typically use additional side cuffs and
acquisition layers which are expensive, inefficient and can only
partly remedy these limitations. By not completely abandoning the
use of hydrophilic fibrous materials next to the use of absorbent
polymer materials this problem can be partially resolved, however,
it will be clear that in such case the absolute and relative
proportions of absorbent materials will unwillingly be restricted
and thus any thickness reduction of the absorbent structure not
fully optimised.
[0009] Multiple attempts have been made to provide the above
flexible, thinner, light-weight absorbent articles comprising from
low cellulose to substantially cellulose to completely cellulose
free absorbent structures combining absolute and/or relative high
proportions absorbent polymer material versus remaining absorbent
materials: WO95/17868, hereby incorporated by reference, discloses
an absorbent structure comprising two fibre layers and an
intermediate layer comprising an absorbent polymer material in an
amount exceeding 120 g/m.sup.2 and particles of a thermoplastic
material. While this construction may provide good immobilisation
of the absorbent polymer material in the dry state, it seems that
only a lesser immobilisation can be achieved in the liquid loaded
state. The thermoplastic material appears to stretch to a much
lesser extent than the potential swelling of the absorbent polymer
materials. Therefore, in particular when the absorbent structure is
to be used in an absorbent article to absorb and retain high
amounts of bodily exudates, for example a diaper or pants, the
absorbent structure disclosed herein may not be fully satisfactory.
Furthermore the fibrous bulk material increases thickness and
weight, reduces flexibility and raises the cost and environmental
footprint of the absorbent structure which is highly unfavourable
and undesirable.
[0010] WO95/26209, hereby incorporated by reference, describes an
absorbent structure having a region containing absorbent polymer
material in high homogenous and continuous quantities in the
absence of any significant fibrous support material which however
typically leads poor fluid management. By poor fluid management it
is meant that the regions of absorbent polymer material have
insufficient integrity in dry, partially wet and/or wetted state.
This results in the physical continuity (and thus the capability of
acquiring and transporting fluids through interstitial voids and
capillaries) of the hydrogel formed upon swelling in the presence
of fluids being substantially disrupted and altered, leading to the
hydrogel layers being unintentionally separated, having gaps being
introduced, having areas that are significantly thinned and/or
broken up into a plurality of underperforming segments. Obviously
this minimizing or completely negating coherence, permeability and
flow conductivity properties of the absorbent structure results in
highly undesirable performance and unacceptable product
failure.
[0011] EP1447066, hereby incorporated by reference, describes an
absorbent structure for the use in an absorbent article which aims
to provide an improved immobilization of absorbent polymer
material. An absorbent structure is disclosed comprising a
non-woven substrate layer, a layer of thermoplastic material in the
form of a hot melt adhesive which bonds to the substrate layer to
define a thermoplastic immobilizing web which captures the
absorbent polymer material. However, in order to adequately secure
the absorbent material, one needs to use a significant amount of
thermoplastic material, which obviously leads to much higher costs
and unappreciated stiffness and rigidity, thereby reducing good
product fit, comfort and discreetness. Also, due to its internal
cohesion, the layer of thermoplastic material exerts pressure and
offers resistance against the free and complete swelling and
take-up capacity and thus overall absorption performance of the
absorbent material. Furthermore the very high quantities of
thermoplastic material lead to physical and chemical shielding of
the absorbent polymer materials from the fluids, leading to
unavoidable reduced absorption, distribution and retention
performance and importantly due to their single use put forward a
significant burden on society, industry and families from economic,
environmental and sustainability view. Therefore, such absorbent
structures are considered to be unfavourable.
[0012] Whilst the above attempts describe various approaches to
various problems, it is believed that none of these absorbent
structures leads to very favourable and performing absorbent
structures or articles. The inefficient use of the absorbent
material capacity and complex manufacturing processes makes neither
of the above absorbent articles economically, technically and/or
environmentally advantageous.
[0013] Hence, there is still an need in the art for an improved
thin, flexible, lightweight absorbent structure with high
concentrations of absorbent polymer material which overcomes the
problems of the prior art which is discreet, sustainable and/or
relatively inexpensive taking in mind manufacturing, marketing,
design, fit, comfort, distribution, packaging, disposal, material,
energy and transportation costs while preserving the required fluid
absorption, distribution, transport, coherence and retention
properties. There is furthermore also a need for a method and
apparatus to produce such absorbent structures at high production
speed and low energy and raw material consumption.
SUMMARY OF THE INVENTION
[0014] As a result of exhaustive research to address the
above-identified, derived and related problems, the inventor has
found that substantially cellulose free absorbent structures
continuously immobilising absorbent polymer material via initial
smaller pockets (preferably more in amount compared to later
compartments) and subsequently larger compartments (preferably less
in amount compared to initial pockets) allows excellent fluid
management in relation to the available absorbent polymer material
in dry, partially and fully liquid loaded state. In a preferred
embodiment according to the invention, the absorbent structures
according to the present invention allow excellent fluid management
of absorbent polymer material by providing a plurality of initial
smaller-sized pockets adequately immobilizing dry absorbent polymer
clusters thus avoiding unwanted migration and movement thereof in
dry state, while during liquid uptake and expansion of the
absorbent polymer materials, the absorbent structure swells
non-homogenously by gradually unleashing and combining the pockets
into fewer and bigger-sized compartments immobilizing the wet
absorbent polymer materials thereby avoiding excess restraining or
restriction in wet state; thereby advantageously creating an
internal fluid management as well as an external liquid management
surface structure.
[0015] Such absorbent structure volume increases are preferably
result of temporary secondary attachment patterns made up for
instance from ultrasonic bonds, preferably in combination with the
substantially permanent primary attachment grids for instance also
made up by ultrasonic bonds, allowing the release of bigger volumes
from the initial smaller volumes by detachment of the secondary
attachments. In an alternative embodiment however these absorbent
structure volume increases are the result of using flexible,
extensible, elastic, stretchable and/or elastomeric materials such
as for instance elastic non-woven and/or breakable materials such
as for instance semi-rigid, rigid and/or stiff paper or tissue
respectively allowing additional expansion of and/or breaking up to
larger volumes.
[0016] In a preferred embodiment the absorbent structure
immobilizes, retains and/or restrains the particulate material and
the attachments seal, bond and/or join at least part of the outer
layers together via ultrasonic bonding, thermo-bonding,
pressure-bonding and/or glue-bonding means. These attachments
preferably form and/or define pockets which can contain particulate
material, whereby the attachment regions comprise essentially and
preferably no particulate material. Preferably the absence of an
excess or the complete elimination of synthetic immobilisation
admixtures (e.g. adhesive and binders, such as thermoplastic glues
and webs) used for covering, restraining or bonding absorbent
polymers makes the structure technically, environmentally and
economically very favourable. In an alternative embodiment however,
the composite structure is covered with such thermoplastic
materials, glues, binders and/or adhesives to fixate, pocket,
encapsulate, bind and/or join these particulate material clusters
to and/or in between one or more layers. Additional materials
and/or layers to provide extra functional and/or structural
advantages such as strength, acquisition, absorption, distribution,
transport, retention, etc. may also be incorporated.
[0017] In a preferred embodiment a substantially cellulose free
absorbent structure is provided comprising a carrier layer, an
auxiliary layer and an absorbent polymer material there between,
the carrier layer and auxiliary layer being at least partially
joined together by attachments made up of substantially permanent
primary attachment grids and/or substantially temporary secondary
attachment patterns, so as to form a sandwich-like composite
structure containing patterned absorbent particulate polymer
materials provided in at least some of the unattached regions
between the carrier layer and auxiliary layer forming an absorbent
polymer material area, the plurality of smaller-sized pockets made
up by at least substantially temporary secondary attachments define
spaces which immobilize the available dry volume absorbent polymer
material, the substantially temporary secondary attachment being
gradually releasable as a result of exposing the surrounding
absorbent polymer material to liquid so as phase in an intermediate
volume increase to fewer and medium-sized compartments immobilising
the partially wetted absorbent polymer material, and resulting in
still fewer maximum-sized compartments immobilising the wetted
absorbent polymer material to obtain continuous fluid
management.
[0018] In a preferred embodiment a method for the manufacturing of
an absorbent structure is provided which comprises: providing a
carrier layer, covering the carrier layer with an absorbent
material, covering the absorbent material with an auxiliary layer
which is joinable to the carrier layer; and in at least one
position substantially temporary and/or substantially permanently
attaching the auxiliary layer to the carrier layer, and by means of
at least substantially temporary secondary attachments defining
small-sized pocket wherein dry absorbent material is immobilized,
such that by means of gradual release of substantially temporary
secondary attachment patterns bigger-sized intermediate and final
compartments are provided, thereby continuously immobilising the
absorbent material from dry to wetted state.
[0019] In a further aspect, the invention provides an absorbent
article comprising an absorbent structure as provided by the
invention. In another aspect the present invention provides a
method and apparatus for the manufacturing of such an absorbent
structure.
[0020] As also described in EP priority application 10447020.8 and
hereby incorporated by reference, an absorbent sandwich-like
structure is provided which comprises a distribution layer with an
absorbent capacity and an immobilisation layer which joins to the
distribution layer to define compartments there between containing
intermediate absorbent material. In particular an absorbent
structure for use in an absorbent article comprises a distribution
layer having an absorbent capacity of at least about 5 g/m.sup.2,
an immobilisation layer which is joined to the distribution layer
to define compartments there between, and an absorbent material
held in at least one of the compartments, wherein said absorbent
material comprises an absorbent polymer material and from zero to
an amount less than about 40 weight percent absorbent fibrous
material, based on the weight of absorbent polymer material. The
absorbent structure provides in particular an increased fluid
communication structure including better adsorption and dispersion
in and between the absorbent polymer material pockets, due to the
additional wicking and mass flow of liquids caused by the
distribution layer, limiting gel blocking, reducing rewet and
minimizing leakages. It further provides for a method and apparatus
to produce such absorbent structures at high production speed with
low energy and raw material consumption.
[0021] As also described in EP priority application 10447021.6 and
hereby incorporated by reference, an absorbent sandwich-like
structure is provided which comprises a substantially
liquid-impermeable wicking layer and an immobilisation layer which
joins to the wicking layer to define compartments there between
containing intermediate absorbent material. In particular an
absorbent structure for use in an absorbent article comprises a
substantially liquid-impermeable wicking layer, and an
immobilisation layer which is joined to the substantially
liquid-impermeable wicking layer to define compartments there
between, and an absorbent material held in at least one of the
compartments, wherein said absorbent material comprises an
absorbent polymer material, and from zero to an amount less than
about 40 weight percent absorbent fibrous material, based on the
weight of absorbent polymer material. The substantially
liquid-impermeable wicking layer allows unbound liquids such as
water, urine and/or other bodily exudates to more easily spread
out, which allows better distribution and transport so as to wet
the side and lower sides of the absorbent polymer materials within
the pockets. It ensure lower rewet values, less leakage risk and
less surface wetness and thus increased reliability of the overall
structure. It further provides for a method and apparatus to
produce such absorbent structures at high production speed with low
energy and raw material consumption.
[0022] As also described in EP priority application 10447022.4 and
hereby incorporated by reference, an absorbent sandwich-like
structure is provided which comprises a carrier layer, an auxiliary
layer and an intermediate absorbent particulate material there
between wherein substantially primary attachments and substantially
secondary attachments join the carrier layer and auxiliary layer
together, whereby the secondary attachments are loosened as a
result of exposing the absorbent structure to liquid whereas the
primary attachments remain substantially intact. It further
provides for a method and apparatus to produce such absorbent
structures at high production speed with low energy and raw
material consumption.
[0023] As also described in EP priority application 10447023.2 and
hereby incorporated by reference, an absorbent sandwich-like
structure is provided which comprises a carrier layer, an auxiliary
layer and an intermediate absorbent material there between wherein
substantially permanent primary attachments and substantially
temporary secondary attachments join the carrier layer and
auxiliary layer together, whereby the absorbent structure is made
to in-homogeneously swell as a result of exposing the absorbent
structure to liquid to form a liquid-managing surface structure. It
further provides for a method and apparatus to produce such
absorbent structures at high production speed with low energy and
raw material consumption.
[0024] As also described in EP priority application 10447024.0 and
hereby incorporated by reference, a method and apparatus is
provided for forming a sandwich-like structure, by depositing
particulate material in a desired pattern onto a moving carrier
layer. In particular a method for depositing particulate material
in a desired pattern onto a moving carrier layer is provided, which
provides a clustering means with perforations corresponding to a
desired pattern, driving the clustering means in the same direction
as and in close proximity to the moving carrier layer, feeding a
particle material stream from a particulate material supply means
and directing the particle material stream through the clustering
means onto the carrier layer. Preferably the particulate materials
are clustered via the inlet regions of the perforations and
released via the outlet regions of the clustering means. The method
allows accurate forming of a pre-determined pattern of particulate
material clusters at high production speed, with reduced raw
material usage and relative low cost. It furthermore provides the
improved thin, flexible, lightweight particulate material absorbent
structures with discretely deposited particulate material clusters
thereon, complemented with an auxiliary layer, such as for instance
non-woven, tissue, paper, thermoplastic material and the like
and/or affixed by attachment means, such as for instance glue,
bonds, joints and the like, with particulate material clusters
relatively immobilized there between so as to obtain a sandwich
structure usable in the form of an absorbent structure.
[0025] As also described in EP priority application 10447027 and
hereby incorporated by reference, a method and apparatus is
provided for forming a sandwich-like structure, by positioning
particulate material in a desired pattern onto a moving carrier
layer. In particular a method for positioning particulate material
in a desired pattern onto a moving carrier layer is provided,
providing a first material, an intermediate material and a second
material, whereby prior to joining the first material to the second
material, the distribution of the intermediate particulate material
is altered through an airflow. In a preferred embodiment the
intermediate particulate material is provided substantially
homogeneously on the first material prior to applying the
positioning airflow. When the intermediate material is undesirable
in the attachment area, the method describes the use of airflows,
resulting from blowing and/or suction holes to evacuate the
intermediate material from the attachment area prior to or during
bonding, leading to improved and controllable attachment
properties, thus increasing attachment quality and utilisation of
energy or materials. It furthermore provides improved thin,
flexible, lightweight absorbent particulate structures.
[0026] The product, method and apparatus according to preferred
embodiments of the invention lead to highly appreciated thin,
flexible and/or light-weight absorbent structures which are
economically, environmentally, technically and/or commercially
advantageous, not in the least since they are obtained without the
need for substantial and bulky amounts of fibrous absorbent
materials such as fluff and wood pulp (allowing "fluffless"
advertisement claims) and are not using substantial and expensive
amounts of glue, binder, adhesive and/or other thermoplastic
materials (allowing "glueless" advertisement claims). This is
unprecedented within the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 A-D provides cross-sectional schematic illustrations
of absorbent structures according to embodiments of the
invention.
[0028] FIG. 2 provides a top view schematic illustration of an
absorbent structure according to an embodiment of the
invention.
[0029] FIG. 3 provides a top view schematic illustration of an
absorbent structure in a partially wetted state according to an
embodiment of the invention, indicating substantial permanent
primary attachments; and the gradual release by the still joined
and already loosened temporary secondary attachments.
[0030] FIG. 4 provides a top view schematic illustration of
differently located and sized clusters of absorbent material
according to an embodiment of the invention.
[0031] FIG. 5 provides top view schematic illustrations of an
absorbent structure according to an embodiment of the invention
indicating different cluster patterns.
[0032] FIG. 6 A-B provides top view schematic illustrations of
absorbent structures according to an embodiment of the invention in
intact (A) en loosened (B) state.
[0033] FIG. 7 provides a top view schematic illustration of an
absorbent structure according to an embodiment of the present
invention, illustrating a built-in phased expansion by primary
attachment grids and secondary attachment patterns.
[0034] FIG. 8 provides a cross-sectional schematic illustration of
a dry absorbent structure having phased expansion according to an
embodiment of the invention.
[0035] FIG. 9 provides a cross-sectional schematic illustration of
a wetted absorbent structure having phased expansion according to
an embodiment of the invention.
[0036] FIG. 10 A-B provides a top view schematic illustration of
absorbent structures according to the invention, in dry state with
a plurality of smaller-sized pockets (A) and in wet state with
fewer and larger-sized compartments (B).
[0037] FIG. 11 provides a schematic process for manufacturing
absorbent structures according to the invention.
[0038] FIG. 12 is a top plan view of a diaper as a preferred
embodiment of an absorbent structure according to the invention,
with the upper layers partially cut away.
DETAILED DESCRIPTION OF THE INVENTION
[0039] The present invention relates to an absorbent structure for
use in absorbent products, such as coffee pads, disposable body
warmers, sheet formed detergent articles, filter material,
insulation material, make-up pads, anti-septic wads, and preferably
absorbent articles from the personal hygiene industry such as but
not limited to feminine hygiene garments, baby diapers and pants,
adult incontinence garments, various absorbent holders, liners,
towels, inserts and the like; and to a method and manufacturing of
the same.
[0040] Unless otherwise defined, all terms used in disclosing the
invention, including technical and scientific terms, have the
meaning as commonly understood by one of ordinary skill in the art
to which this invention belongs. By means of further guidance, term
definitions are included to better appreciate the teaching of the
present invention.
[0041] As used herein, the following terms have the following
meanings:
[0042] "A", "an", and "the" as used herein refers to both singular
and plural referents unless the context clearly dictates otherwise.
By way of example, "a compartment" refers to one or more than one
compartment.
[0043] "About" as used herein referring to a measurable value such
as a parameter, an amount, a temporal duration, and the like, is
meant to encompass variations of +/-20% or less, preferably +/-10%
or less, more preferably +/-5% or less, even more preferably +/-1%
or less, and still more preferably +/-0.1% or less of and from the
specified value, insofar such variations are appropriate to perform
in the disclosed invention. However, it is to be understood that
the value to which the modifier "about" refers is itself also
specifically disclosed.
[0044] "Absorbent article", "absorbent garment", "absorbing
article", "absorbing garment", and the like as used herein are used
interchangeably and refer to devices that absorb and contain bodily
exudates, and more specifically, refers to devices that are placed
against or in proximity to the body of the wearer to absorb and
contain the various liquids discharged from the body. Absorbent
articles include but are not limited to feminine hygiene garments,
baby diapers and pants, adult incontinence garments, various diaper
and pants holders, liners, towels, absorbent inserts and the
like.
[0045] "Absorbent core" as used herein refers to a
three-dimensional part of the absorbent structure, comprising
liquid-absorbing material, useful to absorb and/or retain bodily
exudates.
[0046] "Absorbent component" as used herein refers to a structural
constituent of an absorbent structure, e.g., a piece of an
absorbent core, such as one of multiple pieces in a multi-piece
absorbent core.
[0047] "Absorbent element" as used herein refers to a part of a
functional constituent of an absorbent structure, e.g., a liquid
acquisition layer, a liquid distribution layer, or a liquid storage
layer formed of a material or materials having particular liquid
handling characteristics suitable for the specific function.
[0048] "Absorbent insert" as used herein refers to a device adapted
for insertion into an absorbent article and to serve as an
absorbent structure when so inserted.
[0049] "Absorbent layer" as used herein refers to a term referring
to a discrete, identifiable sheet-like or web-like element of an
absorbent structure which may remain detached and relatively
movable with respect to another such element or may be attached or
joined so as to remain permanently associated with another such
element. Each absorbent layer may itself include a laminate or
combination of several layers, sheets and/or webs of similar or
diverse compositions.
[0050] "Absorbent polymer material", "absorbent gelling material",
"AGM", "superabsorbent", "superabsorbent material", "superabsorbent
polymer", "SAP" and the like as used herein are used
interchangeably and refer to any suitable particulate (e.g.,
flaked, particulate, granular, or powdered) or fibrous cross linked
polymeric materials that can absorb at least 5 times and preferably
at least about 10 times or more its weight of an aqueous 0.9%
saline solution as measured using the Centrifuge Retention Capacity
test (EDANA 441.2-01).
[0051] "Absorbent polymer material area" as used herein refers to
the area of the absorbent structure wherein adjacent layers are
separated by a multiplicity of absorbent polymer material.
Incidental contact areas between these adjacent layers within the
absorbent particulate polymer material area may be intentional (e.g
bond area's) or unintentional (e.g. manufacturing artefacts).
[0052] "Absorbent particulate polymer material" as used herein
refers to an absorbent polymer material which is in particulate
form such as powders, granules, flakes and the like so as to be
flowable in the dry state.
[0053] "Absorbent structure" as used herein refers to those
elements of an absorbent article comprising material or a
combination of materials suitable to absorb, distribute and retain
bodily exudates.
[0054] "Absorption" as used herein refers to the process by which a
liquid is taken up within a material.
[0055] "Acquisition layer", "acquisition region", "acquisition
surface" or "acquisition material" and the like as used herein
refer to a layer having a faster liquid uptake capability.
[0056] "Absorbency" is the ability of a material to take up fluids
by various means including capillary, osmotic, solvent, chemical or
other action.
[0057] "Adult incontinence garment" as used herein refers to
absorbent articles intended to be worn by incontinent adults, for
absorbing and containing bodily exudates.
[0058] "Adhesion" as used herein refers to the force that holds
different materials together at their interface.
[0059] "Adhesive" as used herein refers to a material, which may or
may not be flowable in solution or when heated, that is used to
bond materials together.
[0060] "Adsorption" as used herein refers to the process by which a
liquid is taken up by the surface of a material.
[0061] "Airlaying" as used herein refers to forming a web by
dispersing fibres or particles in an air stream and condensing them
from the air stream onto a moving screen by means of a pressure or
vacuum; a web of fibres produced by airlaying is herein referred to
an "airlaid"; an airlaid web bonded by one or more techniques to
provide fabric integrity is herein referred to an "airlaid
nonwoven".
[0062] "Apparent density" as used herein refers to the basis weight
of the sample divided by the calliper with appropriate unit
conversions incorporated therein. Apparent density used herein has
the unit g/cm.sup.3.
[0063] "Attach", "attached" and "attachment" as used herein are
synonymous with their counterparts of the terms "fasten", "affix",
"secure", "bind", "join" and "link".
[0064] "Baby diaper" as used herein refers to absorbent articles
intended to be worn by children, for absorbing and containing
bodily exudates which the user draws up between the legs and
fastens about the waist of the wearer.
[0065] "Baby pants" as used herein refers to absorbent articles
marketed for use in transitioning children from diapers to
underwear intended to cover the lower torso of children, so as to
absorb and contain body exudates which article is generally
configured like a panty garment and manufactured with a completed
waist encircling portion, thereby eliminating the need for the user
to fasten the article about the waist of the wearer.
[0066] "Back region" as used herein refers to the portion of an
absorbent article or part thereof that is intended to be positioned
proximate the back of a wearer.
[0067] "Backing" as used herein refers to a web or other material
that supports and reinforces the back of a product.
[0068] "Basis weight" is the weight per unit area of a sample
reported in grams per square meter, g/m.sup.2 or gsm.
[0069] "Bodily exudates", "body exudates", "bodily fluids", "body
fluids", "bodily discharges", "body discharges", "liquids" and the
like as used herein are used interchangeably and refer to, but are
not limited to urine, blood, vaginal discharges, breast milk,
sweats and faecal matter.
[0070] "Binder", "adhesive", "glue", "resins", "plastics" and the
like as used herein are used interchangeably and refer to
substances, generally in a solid form (e.g. powder, film, fibre) or
as a foam, or in a liquid form (e.g. emulsion, dispersion,
solution) used for example by way of impregnation, spraying,
printing, foam application and the like used for attaching or
bonding functional and/or structural components, elements and
materials, for example including heat and/or pressure sensitive
adhesives, hot-melts, heat activated adhesives, thermoplastic
materials, chemical activated adhesives/solvents, curable materials
and the like.
[0071] "Bond strength" as used herein refers to the amount of
adhesion between bonded surfaces. It is a measure of the stress
required to separate a layer of material from the base to which it
is bonded.
[0072] "Capillary action", "capillarity", or "capillary motion" and
the like as used herein are used to refer to the phenomena of the
flow of liquid through porous media.
[0073] "Chassis" as used herein refers to a foundational
constituent of an absorbent article upon which the remainder of the
structure of the article is built up or overlaid, e.g., in a
diaper, the structural elements that give the diaper the form of
briefs or pants when configured for wearing, such as a backsheet, a
topsheet, or a combination.
[0074] "Cellulose fibres" as used herein refers to naturally
occurring fibres based on cellulose, such as, for example cotton,
linen, etc.; wood pulp fibres are one example of cellulose fibres;
man-made fibres 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 fibres.
[0075] "Cluster" or the like as used herein refers to an
agglomeration of particles and/or fibres.
[0076] "Chemically stiffened fibres", chemically modified fibres",
"chemically cross-linked fibres", "curly fibres" and the like as
used herein are used interchangeably and refer to any fibres which
have been stiffened by chemical means to increase stiffness of the
fibres under both dry and aqueous conditions, for example by way of
addition of chemical stiffening agents (e.g. by coating,
impregnating, etc.), altering the chemical structure of the fibres
themselves (e.g. by cross-linking chains, etc.) and the like.
[0077] "Cohesion" as used herein refers to the resistance of
similar materials to be separated from each other.
[0078] "Comprise," "comprising," and "comprises" and "comprised of"
as used herein are synonymous with "include", "including",
"includes" or "contain", "containing", "contains" and are inclusive
or open-ended terms that specify the presence of what follows e.g.
a component and do not exclude or preclude the presence of
additional, non-recited components, features, elements, members,
steps, known in the art or disclosed therein.
[0079] "Coverstock" as used herein refers to a lightweight
non-woven material used to contain and conceal an underlying
absorbent core material; examples are the facing layer or materials
that cover the absorbent cores of feminine hygiene garments, baby
diapers and pants and adult incontinence garments.
[0080] "Crotch region" of an absorbent article as used herein
refers to about 50% of the absorbent article's total length (i.e.,
in the y-dimension), where the crotch point is located in the
longitudinal centre of the crotch region. That is, the crotch
region is determined by first locating the crotch point of the
absorbent article, and then measuring forward and backward distance
of 25% of absorbent article's total length.
[0081] "Cross direction (CD)", "lateral" or "transverse" and the
like as used herein are used interchangeably and refer to a
direction which is orthogonal to the longitudinal direction and
includes directions within .+-.45.degree. of the transversal
direction.
[0082] "Curing" as used herein refers to a process by which resins,
binders or plastics are set into or onto fabrics, usually by
heating, to cause them to stay in place; the setting may occur by
removing solvent or by cross-linking so as to make them
insoluble.
[0083] "Diaper", "conventional diaper", "diaper-like", "diaper-like
garment" and the like as used herein are used interchangeably and
refer to disposable absorbent articles, which typically include a
front waist portion and a back waist portion which may be
releasably connected about the hips of the wearer during use by
conventional fasteners such as adhesive tape fasteners or hook and
loop type fasteners. In use, the article is positioned between the
legs of the wearer and the fasteners are releasably attached to
secure the back waist portion to the front waist portion of the
diaper, thereby securing the diaper about the waist of the wearer.
The front waist portion and a back waist portion are connected by
relatively non-stretchable or stretchable members (the term
"stretchable" as used herein refers to materials that are
extensible when forces are applied to the material, and offer some
resistance to extension). Hence, such articles are generally not
configured to be pulled up or down over the hips of the wearer when
the fasteners are attached.
[0084] "Disposable" is used herein to describe articles that are
generally not intended to be laundered or otherwise restored or
reused (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).
[0085] "Distribution layer", "distribution region", "distribution
surface" or "distribution material" and the like as used herein are
used interchangeably and refer to a layer having a larger capacity
in wicking, dispersing and distributing liquids.
[0086] "Drylaying" as used herein refers to a process for making a
nonwoven web from dry fibre; these terms apply to the formation of
carded webs, as well as to the air laying formation of random webs;
a web of fibres produced by drylaying is herein referred to as a
"drylaid"; a drylaid web bonded by one or more techniques to
provide fabric integrity is herein referred to a "drylaid
nonwoven".
[0087] "Dry strength" as used herein refers to the strength of an
adhesive attachment determined in dry state conditions, immediately
after drying under specified conditions or after a period of
conditioning in the standard laboratory atmosphere.
[0088] "Fabric" as used herein refers to a sheet structure made
from fibres, filaments and/or yarns.
[0089] "Feminine hygiene garments" as used herein refer to
absorbent hygiene articles intended to be worn by woman, for
absorbing and containing body exudates.
[0090] "Fibre" as used herein refers to the basic threadlike
structure from which nonwovens, yarns and textiles are made. It
differs from a particle by having a length at least 4 times its
width; "Natural fibres" are either of animal (wool, silk),
vegetable (cotton, flax, jute) or mineral (asbestos) origin, while
"Man-made fibres" may be either polymers synthesised from chemical
compounds (polyester, polypropylene, nylon, acrylic etc.) or
modified natural polymers (rayon, acetate) or mineral (glass).
"Fibre" and "filament" are used interchangeably.
[0091] "Film", "foil" and the like as used herein are used
interchangeably and refer to a thin sheet of essentially
non-absorbent material such as plastic or closed foams. In this
invention it particularly refers to materials that do not
correspond to non-wovens.
[0092] "Fluff pulp" as used herein refers to wood pulp specially
prepared to be drylaid.
[0093] "Front region" as used herein refers to the portion of an
absorbent article or part thereof that is intended to be positioned
proximate the front of a wearer.
[0094] "Garment facing layer" as used herein refers to elements of
the chassis that form the outer surface of the absorbent article,
such as the back sheet, the side panels, the waist fasteners, and
the like, when such elements are present.
[0095] "Heat activated adhesive" as used herein refers to a dry
adhesive that is rendered tacky or fluid by application of heat or
heat and pressure to the assembly.
[0096] "Heat sealing adhesive" as used herein refers to a
thermoplastic adhesive which is melted between the adherent
surfaces by heat application to one or both of the adjacent
adherent surfaces.
[0097] "Highloft" as used herein refers to general term of low
density, thick or bulky fabrics.
[0098] "Hot-melt adhesive" as used herein refers to a solid
material that melts quickly upon heating, then sets to a firm bond
upon cooling; used for almost instantaneous bonding.
[0099] "Hydrophilic" as used herein refers to having an affinity
for being wetted by water or for absorbing water.
[0100] "Hydrophobic" as used herein refers to lacking the affinity
for being wetted by water or for absorbing water.
[0101] "Immobilisation layer" as used herein refers to a layer able
to be applied to the absorbent polymer material or absorbent
polymer material area with the intent to compartmentalize, bond
and/or immobilize absorbent material and/or layer.
[0102] "Join", "joined" and "joining" as used herein refers to
encompassing configurations wherein an element is directly secured
to another element by affixing the element directly to the other
element, as well as configurations wherein the element is
indirectly secured to the other element by affixing the element to
an intermediate member or members which in turn is or are affixed
to the other element.
[0103] "Knitting" as used herein refers to the technique for
interlocking loops of fibres with needles or similar devices.
[0104] "Layer" refers to identifiable components of the absorbent
article, and any part referred to as a "layer" may actually
comprise a laminate or combination of several sheets or webs of the
requisite type of materials. As used herein, the term "layer"
includes the terms "layers" and "layered." "Upper" refers to the
layer of the absorbent article which is nearest to and faces the
wearer facing layer; conversely, the term "lower" refers to the
layer of the absorbent article which is nearest to and faces the
garment facing layer. "Layer" is three dimensional structure with a
x dimension width, y dimension length, and z-dimensions thickness
or calliper, said x-y dimensions being substantially in the plane
of the article, however it should be noted that the various
members, layers, and structures of absorbent articles according to
the present invention may or may not be generally planar in nature,
and may be shaped or profiled in any desired configuration.
[0105] "Machine direction (MD)", "longitudinal" and the like as
used herein are used interchangeably and refer to a direction
running parallel to the maximum linear dimension of the structure
and includes directions within .+-.45.degree. of the longitudinal
direction.
[0106] "Major surface" as used herein refers to a term used to
describe the surfaces of greatest extent of a generally planar or
sheet-like structural element and to distinguish these surfaces
from the minor surfaces of the end edges and the side edges, i.e.,
in an element having a length, a width, and a thickness, the
thickness being the smallest of the three dimensions, the major
surfaces are those defined by the length and the width and thus
having the greatest extent.
[0107] "Mass flow" as used herein refers to the flow of a liquid
from one absorbent element or component to another absorbent
element or component by channel flow action.
[0108] "Mechanical bonding" as used herein refers to a method of
bonding fibres by entangling them. This can be achieved by
needling, stitching with fibres or by the use of high-pressure air
or water jets and the like.
[0109] "Non-woven" as used herein refers to manufactured sheet, web
or batt of directionally or randomly orientated fibres, 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 fibres may be of natural
or man-made origin and may be staple or continuous filaments or be
formed in situ. Commercially available fibres have diameters
ranging from less than about 0.001 mm to more than about 0.2 mm and
they come in several different forms: short fibres (known as
staple, or chopped), continuous single fibres (filaments or
monofilaments), untwisted bundles of continuous filaments (tow),
and twisted bundles of continuous filaments (yarn). Nonwoven
fabrics can be formed by many processes such as melt blowing,
spunbonding, solvent spinning, electro-spinning, and carding. The
basis weight of nonwoven fabrics is usually expressed in grams per
square meter (gsm).
[0110] "Pant", "training pant", "closed diapers", "pre-fastened
diapers", "pull-on diapers" and "diaper-pants" and the like as used
herein are used interchangeably and refer to absorbent articles
which are typically applied to the wearer by first leading the feet
into the respective leg openings and subsequently pulling the pants
from the feet to waist area over the hips and buttocks of the
wearer and which are capable of being pulled up or down over the
hips of the wearer. Typically, such articles may include a front
waist portion and a back waist portion which may be connected about
the hips of the wearer by integral or releasable members. A pant
may be preformed by any suitable technique including, but not
limited to, joining together portions of the article using
refastenable and/or non-refastenable bonds (e.g., seam, weld,
adhesive, cohesive bond, fastener, etc.). A pant may be preformed
anywhere along the circumference of the article (e.g., side
fastened, front waist fastened).
[0111] "Polymer" as used herein refers to but is not limited to,
homopolymers, copolymers, such as for example, block, graft, random
and alternating copolymers, terpolymers, etc. and blends and
modifications thereof. Unless otherwise specifically limited, the
term "polymer" includes all possible spatial configurations of the
molecule and include, but are not limited to isotactic,
syndiotactic and random symmetries.
[0112] "Rear" as used herein refers to the portion of an absorbent
article or part thereof that is intended to be positioned proximate
the back of the wearer.
[0113] "Resin" as used herein refers to a solid or semisolid
polymeric material.
[0114] "Substantially cellulose free" as used herein refers to an
absorbent article, structure or core, that contains less than 40%
by weight cellulosic fibres, less than 20% cellulosic fibres, less
than 5% cellulosic fibres, no cellulosic fibres, or no more than an
immaterial amount of cellulosic fibres which do not materially
affect the thinness, flexibility or absorbency thereof. This also
encompasses completely cellulose free.
[0115] "Thermobonding" as used herein refers to a method of bonding
fibres by the use of heat and/or high-pressure.
[0116] "Thermoplastic" as used herein refers to polymeric materials
that have a melting temperature and can flow or be formed into
desired shapes on the application of heat at or below the melting
point.
[0117] "Ultrasonic" as used herein refers to the use of high
frequency sound to generate localised heat through vibration
thereby causing fibres to bond to one another.
[0118] "Water-absorbing", "liquid-absorbing", "absorbent",
"absorbing" and the like as used herein are used interchangeably
and refer to compounds, materials, products that absorb at least
water, but typically also other aqueous fluids and typically other
parts of bodily exudates such as at least urine or blood.
[0119] "Wearer facing layer" as used herein refers to elements of
the chassis that form the inner surface of the absorbent article,
such as the topsheet, the leg cuffs, and the side panels, etc.,
when such elements are present.
[0120] "Weaving" as used herein refers to the process of
interlacing two or more sets of yarns at right angles to form a
fabric; a web of fibres produced by weaving is herein referred to
as a "Woven".
[0121] "Web material" as used herein refers to an essentially
endless material in one direction, i.e. the longitudinal extension
or the length, or the x-direction in Cartesian coordinates relative
to the web material. Included in this term is an essentially
unlimited sequence of pieces cut or otherwise separated from an
essentially endless material. Often, though not necessarily, the
web materials will have a thickness dimension (i.e. the
z-direction) which is significantly smaller than the longitudinal
extension (i.e. in x-direction). Typically, the width of web
materials (the y-direction) will be significantly larger than the
thickness, but less than the length. Often, though not necessarily,
the thickness and the width of such materials is essentially
constant along the length of the web. Without intending any
limitation, such web materials may be cellulosic fibre materials,
tissues, woven or non-woven materials and the like. Typically,
though not necessarily, web materials are supplied in roll form, or
on spools, or in a folded state in boxes. The individual deliveries
may then be spliced together to form the essentially endless
structure. A web material may be composed of several web materials,
such as multilayer non-woven, coated tissues, nonwoven/film
laminates. Web materials may comprise other materials, such as
added binding material, particles, hydrophilizing agents and the
like.
[0122] "Wet burst strength" is a measure of a layer's ability to
absorb energy, when wet and subjected to deformation normal to the
plane of the web.
[0123] "Wet strength" as used herein refers to the strength of an
adhesive attachment determined immediately after removal from a
liquid in which it has been immersed under specified conditions of
time, temperature and pressure. The term is commonly used in the
art to designate strength after immersion in water.
[0124] "Wetlaying" as used herein refers to the forming a web from
an aqueous dispersion of fibres by applying modified paper making
techniques; a web of fibres produced by wetlaying is herein
referred to as a "wetlaid".
[0125] "Wood pulp" as used herein refers to cellulosic fibres used
to make viscose rayon, paper and the absorbent cores of products
such as feminine hygiene garments, baby diapers and pants and adult
incontinence garments.
[0126] "X-y dimension" as used herein refers to the plane
orthogonal to the thickness of the article, structure or element.
The x- and y-dimensions correspond generally to the width and
length, respectively, of the article, structure or element.
[0127] "Z-dimension" as used herein refers to the dimension
orthogonal to the length and width of the article, structure or
element. The z-dimension corresponds generally to the thickness of
the article, structure or element.
[0128] The recitation of numerical ranges by endpoints includes all
numbers and fractions subsumed within that range, as well as the
recited endpoints.
[0129] The absorbent structure according to the invention,
preferably a substantially cellulose free structure, comprises a
carrier layer, an auxiliary layer and an absorbent material
provided between said carrier layer and said auxiliary layer to
form a sandwich wherein initial smaller pockets (preferably more in
relative amount as compared to later compartments) and subsequently
larger compartments (preferably less in relative amount as compared
to initial pockets) allows excellent fluid management of the
absorbent polymer material in dry, partially and fully liquid
loaded state. The absorbent structures according to the present
invention allow sufficient internal immobilization of the absorbent
polymer material in dry state by providing well-designable
customized smaller pockets containing the unexpanded dry materials
and subsequently by providing well-designable customised bigger
compartments containing the wetted materials, while avoiding
restraining or restriction of the swelling and volume-expanding
absorbent material in wetted state, thereby preventing
underutilisation, loss or negative impact on their absolute and
relative performance, giving rise to superficial liquid management
surfaces.
[0130] In a preferred embodiment according to the invention the
fluid and liquid management absorbent structure contains a
pre-defined pattern of secondary attachments at least partially
joining said enveloping layers together characterized in that the
secondary attachments are loosened, dissolved, weakened and/or
broken up as a result of exposing said absorbent structure to
liquid, vapour and/or moisture. It should be noted that the
secondary attachment can but do not have to be water-sensitive, in
other words they can thus also be water-insensitive or
wet-resistant, as the secondary attachments should preferably be
allowed to detach by bringing the absorbent structure in contact
with liquid, thus not necessarily the secondary attachments
themselves have to be wetted before the absorbent structures
displays its fluid and liquid management. Next to more accurate
prediction and development of customised release times of the
secondary attachments, this is also advantageous since developing
and controlling water-sensitive secondary attachments bring much
more complexity to the manufacturing process of the absorbent
structures leading to slower production speeds, additional energy
and material consumption, gives rise to higher prevalence of
dysfunctional and non-performing secondary attachment thus to be
disposed failing absorbent structures. The mere forces exerted by
the swelling absorbent material should thus preferably be
sufficient to detach the secondary attachments, independent of them
being dry, partially wetted or fully wetted. Preferably the
smaller-sized pockets in dry state release under the influence of
bringing the absorbent structure into contact with water, thereby
forming intermediate-sized compartment made up by the release
expanded smaller-sized pockets and/or by the combination of
multiple smaller-sized pockets. Preferably these intermediate-sized
pockets are formed when the absorbent structure is partially
loaded. Even more preferably the medium-sized compartments from
partially wetted state enlarge even further under the influence of
bringing the absorbent structure into contact with water or upon
additional swelling of the absorbent polymer material, thereby
forming maximum-sized compartments made up by the release expanded
smaller-sized pockets and by the combination of multiple
smaller-sized pockets and medium sized compartments. Preferably
these maximum-sized pockets are formed when the absorbent structure
is almost fully wetted. This controlled and continuous expansion
during the wetting process results in unseen fluid management
qualities and moreover allows for liquid management superficial
structures. This is unseen in the prior art and is highly
desirable. Preferably also a pre-defined grid of primary
attachments is present throughout the majority of the surface area
of the absorbent structure which remain substantially intact under
normal usage conditions. The primary attachment can serve the
overall structural and functional integrity of the absorbent
structure, increase the fluid management systems and/or help with
the creation of in-homogenous liquid management surface structure
of the absorbent structure. Absorbent structures according to a
preferred embodiment of the invention contain absorbent polymer
material, more preferably absorbent particulate polymer material
such as highly permeable SAP.
[0131] In a preferred embodiment according to the invention a
single absorbent layer substantially cellulose free absorbent
structure for use in an absorbent article is measuring about 10 cm
in width by about 40 cm in length, having an average dry thickness
from about 0.1 to about 10 mm, more preferably from about 0.5 to
about 5 mm, most preferably from about 1-3 mm would contain about
5-25 grams absorbent polymer material, more preferably about 10-20
grams, more preferably 11-15 gram, most preferably about 12-14
grams which would initially be pocketed in about 50-800 small
pockets, more preferably about 100-700 pockets, more preferably
about 200-600 pockets, more preferably about 300-500 pockets, more
preferably about 350-450 pockets and most preferably around 1
pocket per cm.sup.2 absorbent structure surface, which would
subsequently be gradually released to ultimately form about 1-50
compartments, more preferably about 3-30 compartments, more
preferably about 5-25 compartments, more preferably about 10-20
compartment and most preferably about 1 compartment per 15 cm.sup.2
absorbent structure surface. Pockets are preferably identical and
square-, round- or honeycomb shaped and uniformly and homogenously
distributed across the absorbent structure, the compartments are
preferably longitudinally distributed and rectangle- or
ellipsoid-like shaped having adequate perimeter sealing at the
absorbent article edges to avoid liquid management structures
guiding and channelling the liquid to edges of the absorbent
structure, where certainly the edges of the crotch regions have to
be avoided. In essence the shape of the smaller pockets try to
accommodate the maximum amount of absorbent polymer on the
available surface area, while the bigger compartments try to
accommodate the maximum expansion volume of the wetted absorbent
polymer materials while ensuring internal fluid management and
external liquid management via surface structures. The absorbent
polymer material will furthermore preferably be profiled throughout
the surface in these dry pockets, hence the need for primary
attachment grid and secondary attachment patterns having
well-defined and accurate bonding strength to accommodate fluid
management and liquid management surface structures according to
the invention. The absorbent structure will preferably be
complemented by about 30-70 gsm, more preferably about 40-60 gsm
and most preferably about 50 gsm highloft acquisition layer and/or
similar amounts of curly fibers as distribution layer to allow fast
uptake and distribution within the absorbent article, subsequently
being enveloped in a liquid permeable topsheet and liquid
impermeable breathable backsheet to allow implementation within an
absorbent article such as baby diaper or pants.
[0132] While preferably such absorbent structure volume increases
are result of temporary secondary attachment patterns made up for
instance from ultrasonic bonds, preferably the absorbent structures
are designed in combination with substantially permanent primary
attachment grids for instance also made up by ultrasonic bonds,
allowing the release of bigger volumes from the initial smaller
volumes by detachment of the secondary attachments, while keeping
absorbent polymer integrity and coherence in light of excellent
fluid management via the primary attachment pattern safeguarding
structural and functional integrity. In an alternative embodiment
however these absorbent structure volume increases are the result
of using flexible, extensible, elastic, stretchable and/or
elastomeric materials such as for instance elastic non-woven and/or
breakable material such as for instance semi-rigid, rigid and/or
stiff paper or tissue respectively allowing additional expansion
from and/or breaking up from smaller to larger volumes.
[0133] In certain embodiments according to the present invention
all or some of the secondary attachments may for instance be
maintained during partial loading of the absorbent structure, while
they will only become detached in fully bodily exudates loaded
state. In this way initial contact is maintained until swelling
forces of the absorbent structure take the upper hand. This
de-bonding does preferably not influence the primary attachments,
thereby still ensuring functional and/or structural integrity of
the absorbent structure and absorbent polymer material area, while
however not restraining the swelling of the absorbent polymer
material so as to decrease liquid absorption and retention
capacity. By preferably not relying on wet-soluble, wet-sensitive
or not-wet-resistant secondary attachments the detachment process
of the secondary attachment patterns according to the invention can
be better controlled and predicted, since such absorbent structures
and secondary attachment patterns in use, such as for instance used
in absorbent articles such as a baby diaper or pants, will not be
prematurely released due to the mere wetting of the (wet-sensitive)
attachment means but will only be released when the to be expected
and required forces deriving from movement, article strain and
absorbent polymer material swelling have been reached. This is
especially advantageous in substantially cellulose free absorbent
articles as they specifically have to avoid free migration and
movement of dry or partially dry absorbent polymer materials in
light of lumping, gel blocking and overall absorbent material
performance.
[0134] In a preferred embodiment the absorbent structure
immobilizes, retains and/or restrains the particulate material and
the attachments seal, bond and/or join at least part of the pockets
and/or outer layers together via ultrasonic bonding,
thermo-bonding, pressure-bonding and/or glue-bonding means. These
attachments preferably form and/or define pockets which can contain
particulate material, whereby the attachment regions comprise
essentially and preferably no particulate material. Preferably
these attachments are made up from discrete shape rather than
substantially continuous lines so as to better control the bonding
and debonding process in line with specified bonding strengths for
those primary attachments grids and secondary attachment patterns
within that absorbent structure according to that embodiment of the
present invention. The use well-design dots for instance can be
located, shaped and sized in such a manner so as to gradually
release the secondary attachment pattern while steadily preserving
the primary attachment patterns during any given absorbent
structure embodiment. Preferably this is done by the very accurate
ultrasonic bonding as opposed to the thermo-mechanical calendaring
for instance which are very difficult to control in light of their
generated attachment tenacity. Also such calendar systems are
caused to be performing very poorly in case any absorbent material
is trapped in between the attachments. The absorbent structure
according to the present invention overcome these problems.
Preferably the absence of an excess or the complete elimination of
synthetic immobilisation admixtures (e.g. adhesive and binders,
such as thermoplastic glues and webs) used for covering,
restraining or bonding absorbent polymer materials makes the
structure technically, environmentally and economically very
favourable. In an alternative embodiment, the composite structure
is covered with such thermoplastic materials, glues, binders and/or
adhesives to fixate, pocket, encapsulate, bind and/or join these
particulate material clusters to and/or in between one or more
layers. Additional materials and/or layers to provide extra
functional and/or structural advantages such as strength,
acquisition, absorption, distribution, transport, retention, etc.
may also be incorporated.
[0135] The absorbent structure, preferably substantially cellulose
free, according to the invention has several embodiments and
preferred embodiments for use in absorbent products such as for
instance:
[0136] An absorbent structure comprising: [0137] a) a carrier
layer; and [0138] b) an auxiliary layer; and [0139] c) an absorbent
material provided between said carrier layer and said auxiliary
layer wherein pockets release extra volume as a result of exposing
said absorbent structure to liquid.
[0140] An absorbent structure comprising: [0141] a) a carrier
layer; and [0142] b) an auxiliary layer; and [0143] c) an absorbent
material provided between said carrier layer and said auxiliary
layer wherein relative smaller sized pockets release extra volume
so as to form relative bigger sized compartments as a result of
exposing said absorbent structure to liquid.
[0144] An absorbent structure comprising: [0145] a) a carrier
layer; and [0146] b) an auxiliary layer; and [0147] c) an absorbent
material provided between said carrier layer and said auxiliary
layer wherein a plurality of smaller sized pockets release extra
volume so as to form relative fewer bigger sized compartments as a
result of exposing said absorbent structure to liquid.
[0148] An absorbent structure for use in an absorbent article
comprising: [0149] a) a carrier layer; and [0150] b) an auxiliary
layer; and [0151] c) an absorbent material provided between said
carrier layer and said auxiliary layer wherein a plurality of
smaller sized pockets release extra volume so as to form relative
fewer bigger sized compartments as a result of exposing said
absorbent structure to liquid wherein at least some secondary
attachments form pockets characterized in that when the secondary
attachments are loosened as a result of exposing said absorbent
structure to liquid they form compartments.
[0152] An absorbent structure for use in an absorbent article
comprising: [0153] a) a carrier layer; and [0154] b) an auxiliary
layer; and [0155] c) an absorbent material provided between said
carrier layer and said auxiliary layer wherein a plurality of
smaller sized pockets release extra volume so as to form relative
fewer bigger sized compartments as a result of exposing said
absorbent structure to liquid wherein at least some secondary
attachments join said carrier layer and said auxiliary layer
together to form pockets characterized in that when the secondary
attachments are loosened as a result of exposing said absorbent
structure to liquid they form compartments.
[0156] An absorbent structure for use in an absorbent article
comprising: [0157] a) a carrier layer; and [0158] b) an auxiliary
layer; and [0159] c) an absorbent material provided between said
carrier layer and said auxiliary layer wherein a plurality of
smaller sized pockets release extra volume so as to form relative
fewer bigger sized compartments as a result of exposing said
absorbent structure to liquid wherein at least some primary and
secondary attachments join said carrier layer and said auxiliary
layer together to form pockets characterized in that when the
secondary attachments are loosened as a result of exposing said
absorbent structure to liquid they form compartments, whereas the
primary attachments remain substantially intact.
[0160] An absorbent structure for use in an absorbent article
comprising: [0161] a) a carrier layer; and [0162] b) an auxiliary
layer; and [0163] c) an absorbent material provided between said
carrier layer and said auxiliary layer wherein a plurality of
smaller sized pockets release extra volume so as to form relative
fewer bigger sized compartments as a result of exposing said
absorbent structure to liquid wherein at least some primary and/or
secondary attachments join said carrier layer and said auxiliary
layer together to form pockets characterized in that when the
secondary attachments are loosened as a result of exposing said
absorbent structure to liquid the absorbent structure swells
in-homogenously so as to form liquid management surface
structure.
[0164] In a preferred embodiment the following is provided: A
substantially cellulose free absorbent structure comprising a
carrier layer, an auxiliary layer and an absorbent particulate
polymer material there between, the carrier layer and auxiliary
layer being at least partially joined together by attachment
regions made up of substantially permanent primary attachment grids
having relative higher bonding strength and/or substantially
temporary secondary attachment patterns having relative lower
bonding strength, so as to form a sandwich-like composite structure
containing clustered absorbent particulate polymer materials
provided in at least some of the unattached regions between the
carrier layer and auxiliary layer thereby forming an absorbent
polymer material area, the plurality of smaller-sized pockets of
substantially equal thickness made up by at least substantially
temporary secondary attachments define spaces which immobilize the
available dry volume absorbent polymer material, the substantially
temporary secondary attachment being gradually releasable as a
result of exposing the peripheral absorbent polymer material to
liquid so as phase in an intermediate volume increase to fewer
medium-sized compartments immobilising the partially wetted
absorbent polymer material, subsequently resulting in still fewer
maximum-sized compartments immobilising the wetted absorbent
polymer material. Preferably it shows non-homogenous swelling due
to non-homogeneous swelling of the absorbent polymer materials
and/or releasing of the secondary attachments so as to from liquid
management structures.
[0165] Prior art absorbent structures swell substantially
homogeneous and continuous until the available liquid uptake
capacity of the absorbent material is reached and/or the available
free volume and space within the various absorbent structure
boundaries is taken up by the swollen and volume-expanded absorbent
materials. The placing of too much absorbent polymer material in
smaller and confined pockets which do not have the volume expanding
capacities according to the present invention thus lead to
underused absorbent material capacities, while the overfilled
pockets often result in undesirable lumpy pocket feelings for the
handler and user and in extreme cases may cause the pockets to
unintentionally rupture thereby expelling the swollen absorbent
materials into contact with the user which is to be avoided.
[0166] Other absorbent structures foresee in dry state the
necessary swelling volume for their subsequent wetted and swollen
absorbent polymer material by providing larger and spacious pockets
prior to use. However, especially in substantially cellulose free
absorbent structure, the required volume leads to the absorbent
material not being sufficiently immobilized resulting in free
migration, moving and clustering together leading to extremely poor
fluid and liquid management. Furthermore the clustering together of
absorbent material in too large pockets in dry state causes severe
gel-blocking when wetted and more over decreases the overall fit,
comfort and discreetness due to the fact these large pockets cause
the absorbent polymer material to form significant volumes in parts
of the large pockets during usage which are felt by the user in
use, which is highly undesirable. The apparent gel-blocking leads
to very poor usage of the expensive absorbent polymer
materials.
[0167] Nevertheless it has been found when absorbent polymer
material absorbs liquid and swells it actually performs much more
rapidly, effectively and efficiently when it has been disposed in
pockets or arrangements. These predefined locations together with
the meticulous dosing of absorbent polymer material can thus help
to obtain optimal absorbency, fit and/or comfort. It is desirable
for absorbent polymer material to remain in its intended location,
while unwanted migration and uncontrolled movement thereof within
the absorbent structure should be avoided. However the absorbent
material is very desirably also immobilized and/or restrained via
an absorbent structure in such a way that the absorbent particulate
polymer material performs both in partially liquid loaded as well
as in fully liquid loaded condition taking in mind required volume
expansion for material and structural performance.
[0168] The absorbent structure according to present invention is
therefore distinguished by its capability to firmly pocket,
immobilize and/or restrain absorbent material within the dry state
while allowing additional, predetermined, phased and controlled
expansion from a multitude of smaller-sized pockets to fewer but
bigger-sized unleashed compartments during the wetting of the
absorbent structure, thus creating additional (yet unavailable)
space, volume and surface area in light of optimal expansion,
swelling and/or loading of the absorbent material. While the
substantially permanent primary attachment grids will essentially
help to safeguard the structural integrity of the absorbent
structure since they are substantially resistant to the forces
exerted upon them during the wetting and using of the absorbent
article, the substantially temporary secondary attachment patterns
will allow the rise of unprecedented functionalities, while
nevertheless securely encapsulating the absorbent material during
gradual phased expansion and swelling.
[0169] The absorbent structure attachment grid and pattern is
preferably in line with the to be exerted forces generated by the
user and by the available and usable absorbent material when being
loaded from substantially dry to a partially loaded up to fully
liquid loaded state. The primary attachments in essence retain more
integrity during and after absorbent structure absorption than the
secondary attachments. The difference in bonding strength between
the primary attachments and the secondary attachments allows the
carrier layer and auxiliary layer to separate between the multiple
primary attachment regions, respectively at the secondary
attachment regions, thus releasing additional space and volume to
allow further and free expansion of the absorbent material in the
partially or fully liquid loaded state as opposed to the dry state.
This release is brought in line with the volume swelling.
[0170] The unlocking of the extra volumes and space during usage
only, leads to several manufacturing, storage and transport
advantages, since the absorbent materials can now be positioned,
clustered and immobilized more accurately and effectively, as the
removal of initial restraining means during use allows for deferred
fluid and liquid management systems leading to excellent
performance and significant raw material savings. Better and
controlled liquid wicking and dispersion thus leads to improved
fluid communication from less absorbent (e.g. saturated) to the
more absorbent area's (e.g. unsaturated).
[0171] For reasons of further improved absorbency, fluid
distribution, transport, retention and lower amount of leakages and
rewet-values, it is preferably desirable for these absorbent
structures to have outspoken macroscopic liquid management surface
structures such as heights and elevations and/or depressions and
valleys which can act as channels, canals and/or embankments to
guide the liquid in a desired manner. The absorbent structure
comprises a carrier layer, an auxiliary layer and an absorbent
material sandwiched there between wherein primary attachments and
secondary attachments bond said carrier layer and said auxiliary
layer together characterized in that the absorbent structure
non-homogeneously swells to form a superficial liquid-managing
surface structure as a result of exposing the absorbent structure
to liquid.
[0172] For reasons of optimal flexibility, fit, comfort,
discreetness, transportation and storage efficiency, it is
desirable for such three-dimensional macroscopic surface structures
to appear and function only when needed, i.e. when the product is
partially and/or fully wetted by liquid, and are thus preferably
not yet present prior to the usage of the absorbent structure. The
invention allows for indirect functionalities, whereby `hidden`
features in dry state are essentially `unleashed` by wetting,
thereby `revealing` essentially the three-dimensional structures
with higher) elevated and/or low(er) depressed functional and
structural parts of the absorbent structure. The three-dimensional
swelling of the absorbent structure can be caused by differential
swelling of the absorbent polymer material or by the differential
grid and pattern of bonding and debonding attachments, or by a
combination thereof. In a preferred embodiment, the absorbent
structure comprises absorbent materials different in volume
absorption capacity, by at least 25%, preferably at least 50%, most
preferably at least 100%. By way of example an originally flat cuff
being for instance attached between two areas of high absorption
would be freed and erect itself when these areas take up liquid and
swell.
[0173] The inventor has found that the ability to create
macroscopic surface structures with internal, incorporated and
superficial liquid management systems allow unseen fluid management
by enabling liquid guidance towards desired locations with
additional uptake, distribution, transport and containment
opportunities as effect and thus ensuring a significant increase in
efficiency and effectiveness of raw material usage while limiting
gel blocking, reducing rewet, minimizes leakage and failure.
Preferably the liquid is guided towards the entire surface of the
absorbent structure with the exception of the side edges to
minimize leakages and product failures.
[0174] Ideally the liquid taken up by the absorbent structure and
the swelling and volume increase resulting therefrom is in line
with the respective spaces and volumes created by the incremental
debonding and loosing process of the attachment patterns. While the
dry immobilisation of the lower volume absorbent material is
secured in the small(ler) pockets formed by the combination of the
primary and secondary attachments, the wet immobilisation of the
wetted higher volume absorbent material is continuously ensured by
the expanding big(ger) compartments defined by intact primary
attachments after partial or full release of the secondary
attachment patterns under the influence of liquid, vapour and/or
moisture. As the absorbent material gains significant volume it is
thus important to restrain the absorbent material continuously.
Well-designed phased absorbent structures allow gradual expansion
of the absorbent material without too little or too excessive
restraining and too late or too early detachment of the secondary
attachments during the gradual wetting and swelling process. The
bonding strength should suffice the parameters of the absorbent
structure and will depend on the article, its product size and
shape and the required duration of the usage and performance.
[0175] It is noted that when stated primary attachments remain
substantially intact under influence of liquid, reference is
preferably being made to characteristics under relatively normal
wearing/usage conditions, typical usage timing, average liquid
amounts and intervals at room or body temperatures without taking
into account exaggerated, severe and/or extreme conditions such as
for example abnormal large amounts of litres of liquid during
multiple days of intense contact. In such case, although not
preferred, the initially wet-resistant primary attachments might
become loosened, detached or broken up after all. It would be clear
from the above that such primary attachments eventually turning
into secondary attachments after being exposed to prolonged and/or
more intense usage conditions than normal are also envisaged under
this invention.
[0176] Unlike previously existing absorbent articles and methods
from the prior art limited by permanent or fully releasable
immobilization and/or restraining means leading to unsatisfactory
absorbency, distribution and retention parameters combined with
limited flexibility, fit and wearing comfort, the present invention
overcomes various problems relating thereto and deriving therefrom
by having absorbent material containing pockets and compartments
with pre-defined and well-managed permanent grids and temporary
patterns leading to gradual volume expansion. The present invention
furthermore overcomes various problems by having wetted absorbent
material forming obstacles and liquid guides thereby providing
physical and chemical barriers and blockages preventing leakage
and/or providing extra fluid distribution and transport. More
specifically the invention allows increased absorbent material
expansion and swelling within the unleashed compartments, while
additional distribution and transport arises within and in between
the absorbent polymer material clusters which have until now been
underused and unappreciated.
[0177] The present invention thereby does not only provide for an
efficacious compartmentalization and restraining of absorbent
materials in dry, partially and fully liquid loaded stated, it also
allows a significant increase in efficiency and effectiveness of
raw materials available in the absorbent structure within partially
and fully liquid load state, increases overall absorbency and
retention capacities and limits gel blocking, reduces rewet and
minimizes leakage.
[0178] In a second aspect, the present invention provides an
absorbent article comprising, at least in the front half of the
absorbent article, an absorbent structure according to an
embodiment of the invention. In a preferred embodiment, the
absorbent article comprises an absorbent structure comprising a
carrier layer and auxiliary layer, whereby the upper surface of the
carrier layer is facing the wearer's skin and a lower surface of
the auxiliary layer is facing the garment of the wearer. The
absorbent material is preferably in direct contact with the lower
surface of the auxiliary layer and the upper surface of the carrier
layer, however additional fabric, non-woven, woven, tissue and/or
paper layer can be provided to accommodate further fluid management
and integrity.
[0179] It is known that for most absorbent articles, for instance
for articles such as feminine hygiene garments, baby diapers, baby
pants and adult incontinence products, that liquid discharge occurs
predominantly in the front half. It is therefore advantageous to
provide an improved absorbent article with an absorbent structure
according to an embodiment of the invention in that area where
fluid loading and uptake requirement is highest. Obviously, an
absorbent article comprising an absorbent structure according to an
embodiment of the invention which is entirely or partially located
in either the front, crotch and/or back region of the absorbent
article, such as for instance a baby diaper, is also covered under
this invention. Any combinations thereof are hereby also
encompassed.
[0180] In the hygiene industry, absorbent articles are specifically
designed to absorb, distribute and retain bodily exudates. Apart
from taking up liquid and retaining it within the absorbent
structure of the absorbent article, the absorbent articles are also
intended to satisfactory prevent bodily exudates from soiling,
wetting, or otherwise contaminating clothing or other articles,
such as bedding, that may possibly or come in contact with the
wearer. A disposable absorbent article, such as a disposable
diaper, may be worn for several hours in a dry state and/or in
liquid loaded state. Accordingly multiple attempts have been made
toward improving the fit and wearing comfort of the absorbent
article, both when the article is dry and when the absorbent
article is fully or partially loaded with bodily exudates, while
enhancing the absorption, distribution and retention functions of
the absorbent article. Flexible, thin, light-weight and discreet
absorbent articles are also here greatly preferred.
[0181] A typical absorbent article has a crotch width of about 100
mm and an average core length of about 500 mm. An absorbent article
with a crotch width of this dimension provides improved consumer
comfort. An absorbent structure according to the present invention
achieves a crotch width of preferably less than 85 mm, 80 mm, 75
mm, 70 mm, 65 mm, 60 mm, 55 mm or 50 mm and a core length of
preferably less than 500 mm, 450 mm, 400 mm, 350 mm or 300 mm.
Hence, preferably an absorbent structure according to the present
invention has a crotch width and a core length in line with the
above dimensions.
[0182] In a third aspect, a method and apparatus to produce an
absorbent structure according to an embodiment of the invention
used as absorbent core in a feminine hygiene garment, baby diaper,
baby pants or adult incontinence garment product. While particular
embodiments of the present invention are illustrated and described,
it would be obvious those skilled in the art that various other
changes and modifications can be made without departing from the
spirit and scope of the invention.
[0183] Method and apparatus for the manufacturing of an absorbent
structure for use in an absorbent article comprising the steps of:
[0184] providing a carrier layer; [0185] covering the carrier layer
with an absorbent material wherein said absorbent material
comprises [0186] i) an absorbent polymer material, and [0187] ii)
from zero to an amount less than about 40 weight percent absorbent
fibrous material, based on the weight of absorbent polymer
material; [0188] covering the absorbent material with an auxiliary
layer which is joinable to the carrier layer; and [0189] joining
the auxiliary layer to the carrier layer thereby forming primary
attachments and secondary attachments that define pockets there
between wherein the absorbent material is held in at least one of
the pockets, characterized in that, the secondary attachments are
loosened, preferably to form larger compartments, as a result of
exposing the absorbent structure to a liquid whereas the primary
attachments remain substantially intact.
[0190] Examples are used below for further non-limitative
illustration of the invention.
[0191] With reference to FIGS. 1 A-D, 2 and 3, the absorbent
structure 14 includes at least one carrier layer 101 and at least
one auxiliary layer 102, and absorbent material 110. The carrier
layer 101 and auxiliary layer 102 are joined via secondary
attachments 115, optionally via a secondary attachment media such a
for instance glue or hot-melt, and preferably also joined together
via primary attachments 111, optionally via primary attachment
media such as for instance an adhesive or binder.
[0192] It should be noted although absorbent structures using
secondary attachments 115 as well as primary attachments 111 are
very much preferred, absorbent structures 14 only using secondary
attachments 115 without the use of primary attachments 111 are also
covered by this invention. One might for instance think about a
combination of several pieces of absorbent segments combined to
form an absorbent structure 14 which is only using secondary
attachments 115 within the absorbent segments so upon wetting to
come from a multitude of dry segments with smaller pockets 130 to a
multitude of wetted segments with larger compartments. Various
combinations, shapes and sizes are of course possible and are
hereby encompassed by the present invention.
[0193] Referring to FIG. 1B, a carrier layer 101 and an auxiliary
layer 102 is provided. The carrier layer 101 is covered on one side
by discrete amounts of absorbent material 110. The absorbent
material 110 is covered by an auxiliary layer 102. The auxiliary
layer 102 lies on top of the absorbent material 110 and is joined
at regular intervals a distribution layer 100a or wicking layer
100b thereby providing pockets 130 holding the absorbent material
110. The absorbent material 110 preferably comprises absorbent
particulate polymer particles, but in addition absorbent fibrous
materials can be used. Preferably the amount of absorbent fibrous
material used is less than 10 weight percent based on the total
weight of absorbent polymer material.
[0194] Referring to FIG. 1C, it has been found that absorbent
structures 14 can be formed by combining two layers of absorbent
material 110. The absorbent structure 14 as shown comprises one
carrier layer 101, two layers of absorbent material 110 and two
auxiliary layers 102. When two discontinuous layers of an absorbent
material 110 are used, being one on the wearer facing surface and
one on the garment facing surface, they would be typically arranged
in such a way that the compartments 130 containing the absorbent
material 110 from one storage layer are aligned with the
compartments 130 containing the absorbent material 110 from the
other storage layer in order to have the attachments from both
layers adjacent to one another. In another alternative embodiment,
however, the compartments 130 and the respective attachments are
offset one another.
[0195] Referring to FIG. 1D, it has also been found that absorbent
structures 14 can be formed by combining two or more layers of
absorbent material 110. The absorbent structure 14 as shown
comprises two layer of absorbent material 110, two carrier layers
101, and two auxiliary layers 102. When two discontinuous layers of
an absorbent material 110 are used, they would typically be
arranged in such a way that the pockets 130 containing the
absorbent material 110 of one storage layer faces the pockets 130
containing the absorbent material 110 of the other storage layer.
In an alternative preferred embodiment, however, the attachments
are offset and do not face each other. Hence preferably, when two
storage layers are joined, this is done such that the first carrier
layer 101 of the first storage layer faces the auxiliary layer 102
of the second storage layer, while the auxiliary layer 102 from
upper storage layer is situated on the wearer facing surface and
the carrier layer 102 from lower storage layer is situated on the
garment facing surface of the sandwiched structures.
[0196] Typical examples of methods used to join material and layers
to each other are by way of example, but are not limited to, the
use of an adhesive such as for instance pressure sensitive
adhesive, curing, chemical links such as for instance hydrogen and
covalent bonds or via the use of ultrasonic and/or other thermal,
mechanical or thermo-mechanical attachment techniques such as for
instance heat sealing, needling, air, entanglement, resistance and
water jet pressure, and the like.
[0197] However, if the carrier layer 101 and the auxiliary layer
102 are solely attached to one another for example via an area of
mechanical resistance or entanglement, or via an area on which the
layers are fused together; without the need of any additional
bonding or joining agent, no attachment media is provided. In a
preferred embodiment, the primary attachments 111 and secondary
attachments 115 are solely made up by ultrasonic thermo-sealing,
which are preferably water-insensitive. Typically thermo-sealing
areas of the primary attachments 111 are relatively large(r) in
surface, tenacity and/or integrity (than the thermo-sealing area's
of the secondary attachments 115), resulting in an absolute or
relative high(er) separation force. In general, the attachments can
come in various sizes and shapes, such as round, elliptic,
rectangular or square shapes but it is preferred to provide them
with rounded edges to inhibit the carrier layer 101 and auxiliary
layer 102 from tearing apart during use. Preferably primary
attachments 111 are arranged in a pattern consisting of rounded
elements of which around 50% are oriented along an X-axis, and the
remainder along a Y-axis. Combinations of elliptical-like shapes,
such as uni-dimensional and bi-dimensional shapes serve as
excellent primary attachments 111.
[0198] It is also preferred to design the attachments so that they
have an average surface size of at least about 0.5 mm.sup.2,
preferably at least about 1.0 mm.sup.2, 2 mm.sup.2 or 3 mm.sup.2,
more preferably at least about 16 mm.sup.2. Also the density of the
attachments can vary, depending on the surface size of the
individual attachments and desired separation forces. For
attachments with a surface area smaller than 1 cm.sup.2 for
instance, it is recommended to use a density of at least about 100
per m.sup.2. In another embodiment of this invention, the primary
attachments 111 are arranged in a primary attachment grid composed
of continuous lines so as to allow for additional liquid
distribution and transport, for a high separation force and high
resistance against the propagation of an eventual cracks or
fissures in the pockets 130. The primary attachment pattern is
carefully designed so that in a wetted state, the swollen material
remains stabilized around the locations where it was restrained
and/or immobilized in dry state. Failure to do so would result in
breaking-up and/or displacement of the wet absorbent material,
resulting in defective fluid management and to loss of performance,
reduced fit and comfort, even full failure. The primary attachment
pattern also accommodates the liquid management surface
structures.
[0199] Apart from the primary attachments 111 and secondary
attachments 115, there are also unattached regions 119, where there
is substantially no attachment, bond and/or joint between the
carrier layer 101 and auxiliary layer 102, thereby providing
pockets 130 in which the absorbent material 110 can be located to
form well-designed clusters. The primary attachments 111 correspond
with a primary attachment grid, whereas the secondary attachments
115 correspond with a secondary attachment pattern. As the
secondary attachment pattern will release under the swelling force
of the absorbent materials and/or under the influence of water, the
secondary attachment 115 should have a relative low separation
force is use. Preferably the separation force necessary to break
the attachment will be lower than about 5.0 N/cm, more preferably
lower than about 2.5, 2.0 or 1.0 N/cm, even more preferably lower
than about 0.75, 0.5 or 0.25 N/cm and most preferably lower than
about 0.20 or 0.10 N/cm in use.
[0200] The bonding strength, such as for example the dry strength,
wet burst strength and/or wet strength, should suffice all required
parameters of the absorbent structure and will amongst others
depend on the absorbent article, its product size and shape and the
required duration of the usage and performance. The specific
structural and functional strength of the attachments in between
the auxiliary layer and the carrier layer and/or the different wet
strengths in between the attachments of the primary attachment
regions and the secondary attachment regions allows for more
efficient design and usage of the absorbent structures leading to
more, faster and enhanced absorption, distribution and retention of
liquids, such as bodily exudates. Moreover it also allows for
better and controlled liquid wicking and dispersion within said
absorbent storage layer, leading to more efficient and effective
fluid communication or transport from the less absorbent area's
(e.g. saturated) to the more absorbent area's (e.g.
unsaturated).
[0201] In one embodiment of this invention, a specific
hydro-soluble or water-sensitive secondary attachment is used, for
instance in the form of an adhesive as secondary attachment medium.
In a more preferred embodiment however, both layers are
thermo-sealed together, most preferably by wet-insensitive
ultrasonic bonding, without any synthetic attachment admixtures.
The thermo-sealing areas of the secondary attachments 115 being
relatively small(er) in surface, tenacity or integrity (than the
primary attachments 115) resulting in an absolute or relative
low(er) separation force. The thermo-sealing areas can come in
various sizes and shapes, but it is preferred to provide at least
one sharp edge to facilitate the carrier layer 101 and auxiliary
layer 102 to tear apart. Combinations of circle-like shapes, such
as round and dot shapes are also preferred as secondary attachments
115. Elimination of attachment media leads to lower raw material
and production costs and environmental/sustainable absorbent
structures. It is furthermore advantageous to use thermo-sealing as
attachment means, rather than using adhesive, as the production
cost is then usually substantially lower and one can claim to be
`adhesive-free`, a claim which is important to
environment-conscious consumers.
[0202] As carrier layer 101 and/or auxiliary layer 102, having a
typical basis weight in the range of 3-400 gsm, more preferably
5-75 gsm, one can choose from a variety of materials such as but
not limited to high-lofts, airlaids, rigid, stretchable or elastic
non-wovens or a woven fabric, wetlaid material such as cellulose
tissue, paper, film, tissue, perforated films, foam material,
thermoplastic material, layers of adhesive or whatever material
suitable within the absorbent structure 14. The sandwich layers can
be made out of the same or different materials having different
compositions, weights and/or structures. In a preferred embodiment,
at least one of the layers is liquid permeable over at least part
of its surface so that liquids can be taken up in the Z-direction.
In another embodiment both the carrier layer 101 and the auxiliary
layer 102 are liquid permeable. In yet another preferred
embodiment, one of the layers is a liquid permeable non-woven
material and the other layer is a substantially liquid-impervious
and possibly breathable polyethylene (PE) film, whereby the
non-woven is positioned at the expected liquid flow such as the
wearer-facing side of the absorbent structure 14 in case of an
absorbent article such as a diaper, and the PE film is positioned
away from the expected liquid flow such as the garment-facing side
of the absorbent structure in case of an absorbent article such as
a baby diaper. In this case, one could for instance select 22 gsm
polypropylene non-woven material from Albis and 20 .mu.m breathable
polyethylene film from Nuova Pansa. The use of the terminology
`carrier layer` by no means implies that the fabric should be
strong enough to support the structure or should be situated at the
lower region of the absorbent structure 14. Nor does `auxiliary
layer` imply that this layer should have a lesser function or
should by analogy be situated at the upper region of the absorbent
structure 14.
[0203] In an alternative embodiment the carrier layer 101 and/or
auxiliary layer 102 can be an adhesive in combination with other
immobilisation diluents such as tackifying resins, plasticizers and
additives such as antioxidants, but could well be any other
composition able to substantially immobilise absorbent polymer
material 110 within the absorbent structure 14 according to the
invention. Some immobilisation materials are thermoplastic others
are not, while some initially thermoplastic materials may lose
their thermoplastic behaviour 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
cross-linked network of covalent bonds. The adhesive and binders
are preferably applied by a nozzle system. Preferably, a nozzle
system is utilised which can provide a relatively thin but wide
curtain of binder. This glue curtain can be continuous or
discontinuous, so as to be applied in a homogeneous or
heterogeneous surface or can be applied in various combinations of
lines, grids, spirals, figures, spots, dots, etc. either in a
determined or undetermined location of the target surface and/or
any combination thereof. Those materials having lost their initial
thermoplastic behaviour are herein also understood as
immobilisation materials. It has been found that compositions most
useful for immobilizing absorbent polymer materials are those which
combine controlled cohesion and adhesion behaviour. Adhesion is
preferred to ensure that the layer maintains sufficient contact
with the absorbent polymer material 110. Cohesion ensures that the
attachment does not unintentionally detach or keeps attached, in
particular in response to external forces, and namely in response
to strain. The attachments are subject to external forces during
usage and when the absorbent structure swells due to the acquired
liquid.
[0204] In an alternative embodiment of the present invention the
absorbent structure 14 comprises an additional distribution layer
100a which helps to additionally absorb, distribute and transport
liquids and having a capability to disperse the liquid permeating
within said distribution layer 100a from the less absorbent area's
(e.g. saturated) to the more absorbent area's (e.g.
unsaturated).
[0205] In an alternative embodiment of the present invention the
absorbent structure 14 comprises an additional liquid-impermeable,
either hydrophilic or hydrophobic, wicking layer 100b which helps
to wick and transport liquids and having a capability to disperse
the liquid over the surface of said wicking layer 100b from the
less absorbent area's (e.g. saturated) to the more absorbent area's
(e.g. unsaturated).
[0206] In an alternative embodiment of the present invention the
absorbent structure comprises an additional thermoplastic
immobilisation layer such as thermoplastic adhesive or binder (e.g.
hot-melt) which helps to immobilize the absorbent materials 110
within the absorbent structure 14.
[0207] However it should be understood that in the alternative
embodiments hereof, the carrier layer 101 and/or auxiliary 102 can
have the same or similar properties as the distribution layer 100a
and/or wicking layer 100b and thus be uniform therewith to form the
actual absorbent structure 14. For reasons of clarity the
embodiments down below will be explained so as the distribution
layer 100a and wicking layer 100b are complementary to the carrier
layer 101 and the auxiliary layer 102 within the absorbent
structure 14. Although such distribution layer 100a or wicking
layer 100b is preferably located at the garment facing side of the
absorbent polymer material area, it is understood that the
orientation of the absorbent structure 14, although not preferred,
can also be re-orientated so as to locate the distribution layer
100 or (for instance perforated) wicking layer 100b at the wearer
facing side of the absorbent polymer material area, while various
combinations and variations are of course also possible. The
distribution layer 100a and/or wicking layer 100b can for instance
also have access means, such as perforations, holes, channels,
openings, fixed or releasable pockets and the like.
[0208] Due to the specific absorbent capacity of the distribution
layer 100a, the liquid around the attachments in between the
pockets 130 will be drawn up into the distribution layer 100a and
will spread out throughout the rest of the distribution layer 100a.
In a preferred embodiment of the invention, the liquid wetting of
the distribution layer 100a will therefore also contact the lower
side of the absorbent polymer material area possibly fully or
partially closed off by the upper gel-formation and/or -blocking.
The absorbent material held in the compartments 130 will thus
advantageously also be contacted from the lower side by redirecting
the liquid from the upper side through the distribution layer 100b
into the absorbent material 110, such as absorbent particulate
polymer material.
[0209] Due to the specific distribution capacity of the wicking
layer 100b, the liquid which comes in contact with the
substantially liquid-impermeable wicking layer 100b will readily
spread out over said surface to also contact the absorbent
materials 110 located at the adjacent and/or lower surface of the
absorbent polymer material area, being the side opposite the major
surface side where the liquid was first deposited. The
distribution, transport and absorption of the liquid is thus
greatly improved and this speedy distribution will help to avoid
large amounts of unbound quantities of liquid within helping to
prevent absorbent article failure and high rewet values. Providing
an additional and more direct co-extensive wicking, dispersion and
transportation of liquid to the still more absorbent underused
pockets and compartments of the absorbent structure increases
effectiveness and efficiency of the available absorbent materials
110. The presence of unbound liquid droplets leading to leakages,
high rewet values and discomfort are thereby minimized.
[0210] This distribution layer 100a has preferably an absorbing
capacity of at least about 1, 2, 3, 4 or 5 g/m.sup.2, preferably
about 10 g/m.sup.2, more preferably about 20 g/m.sup.2, more
preferably at least about 35 g/m.sup.2, most preferably at least
about 50 g/m.sup.2, or 100 g/m.sup.2. Preferably the distribution
layer 100b is presented in the form of a substantially continuous
sheet of cellulosic fibers, such as a nonwoven or a sheet of paper
or tissue. In a preferred embodiment, it has a basis weight range
where the low limit of the range is about 1, 2, 3, 4, 5, 6, 7, 8,
9, 10 g/m.sup.2 per ply, about 13 g/m.sup.2 per ply, or about 15
g/m.sup.2 per ply. The high limit of the basis weight range is
about 150 g/m.sup.2 per ply, 100 g/m.sup.2 per ply, about 40
g/m.sup.2 per ply, or about 25 g/m.sup.2 per ply. Suitable wicking
layer 100b are for instance coated polyethylene or polypropylene
films, with a total thickness of such film is usually in the range
from 5 to 1500 .mu.m, preferably from 10 to 500 .mu.m, for instance
a being corona-treated, hydrophilic, micro-embossed PE film in the
15-22 .mu.m thickness range.
[0211] The substantially liquid-impermeable wicking layer 100b is
for instance provided by a substantially continuous layer of foil,
film, closed foam, plastic or similar substantially
liquid-impermeable materials, media and/or layers. The effect of
providing the substantially liquid-impermeable wicking layer 100b
in the form of a substantially continuous layer of film or foil is
that a substantially impervious barrier is provided. The provision
of a film or foil is advantageous compared to the use of a pervious
layer, such as for instance a non-woven material, as in contrast to
such non-woven material the film or foil is not comprised of
fibers. Hence, it is not possible that fibers are torn upon
exertion of a force onto the film or foil, for instance during
movement and/or liquid uptake process (e.g. swelling and expansion
of the absorbent material such as super absorbent polymers).
Opposed to non-woven materials, such wicking layer 100b does not
contain unintentional open spaces and cavities in which unbound
quantities of liquid may be stored, thus not leading to an
increased risks of leakages and augmented rewet with reduced
comfort and fit.
[0212] In a preferred embodiment the carrier layer 101, auxiliary
layer 102, distribution layer 100a and/or wicking layer 100b can be
fully or partially hydrophilic or hydrophobic. In a more preferred
embodiment, they are provided with a hydrophilic or hydrophobic
coating. Combinations thereof are hereby also encompassed. The
effect of providing such layers with coatings is that the
properties of the layer can be modified according to the intended
use. For instance, synthetic materials that are inherently
hydrophobic such as polyethylene (PE) or polypropylene (PP) can for
instance be provided with a coating layer such that the resulting
material has a contact angle of less than 50.degree., preferably
less than 35.degree., more preferably less than 25.degree., still
more preferably less than 20.degree., most preferably less than
15.degree., for a water droplet lying thereon. For instance,
materials that are inherently hydrophilic can be provided with a
hydrophobic coating layer such that the resulting material shows
hydrophobic properties. This may be advantage in the fact that a
cheap base layer, itself not displaying the desired property can be
adjusted on at least one of its sides to display the desired
property, thereby providing cost savings. The coating can be
applied by a commonly used suitable process, for example with a
slot coater, or by a spray process. It is particularly preferable
to apply the coating by the reverse gravure-roll process, which can
apply an extremely homogeneous coating with application weights of
from 0.5 to 5.0 g/m.sup.2. The thickness of the coating on the
finished film is preferably from 3 to 1000 nm, in particular from
30 to 200 nm. Obviously such coating can also be applied
continuously, substantially continuously, partially or at discreet
locations possibly showing multiple flow enhancing patterns and/or
shapes depending on the desired end product and features.
[0213] The distribution layer 100a and/or wicking layer 100b used
may differ in basis weight, thickness, composition or other
properties. If provided as multiple plies, they can be passively
bound or joined, or a certain amount of adhesive or other
attachment means could be added to provide additional adhesion to
portions of the component plies. For example, needling, embossing,
or other thermal or mechanical bonding means could also be used to
actively bond the substantially continuous layer near some or all
of the edges of the sheet, thereby providing increased resistance
to undesired delaminating of the component plies. Joining may also
be done by ultrasonic bonding or autogenous bonding, or other
bonding methods known in the art. For example, if the edges of the
ply or layers are coextensive with the edges of the outer plies,
adhesive bonding and heat sealing adhesive may not provide active
bonding, depending on the adhesive used and the surface energy
characteristics of the ply. In this case, mechanical bonding may be
more desirable, for example by mechanical bonding at a mechanical
bonding station after formation of the multiple plies. Depending on
the structural and functional requirements the bonding parameters
may be adjusted so as to obtain the most suitable dry and wet
strength values. If desired, multiple plies of the substantially
continuous layer may be joined and embossed. If desired, the plies
may be joined together using knob-to-knob or know-to-flat surface
embossing as is known in the art. Alternatively, the multiple plies
may be embossed using nested embossing. The substantially
continuous layer may manifest various physical characteristics.
[0214] The distribution layer 100a preferably has an absorbency
ranging from about 0.1 g to 3 g water per g of distribution layer,
preferably from about 3 to 7 g, more preferably from about 7 to 10
g and preferably the absorbency is higher than about 10 g water per
g of distribution layer 100a. The distribution layer 100a typically
has an absorbent capacity of at least about 5-10 g/m.sup.2,
preferably at least about 30 g/m.sup.2, more preferably at least
about 50 g/m.sup.2, more preferably at least about 75 g/cm.sup.2,
preferably at least about 100 g/cm.sup.2 or 150 g/cm.sup.2.
Preferably distribution layer 100a is presented in the form of a
substantially continuous sheet of cellulosic fiber, such as a sheet
of paper, tissue or a drylaid, airlaid or wetiaid material.
[0215] Despite the high absorbency and distribution capacities of
the substantially continuous layer, the bulkiness of said layer is
absolutely and relatively limited, for instance in comparison with
absorbent articles and absorbent structures from the art allowing
the envisaged thinner, more flexible and comfortable
structures.
[0216] For the present invention, the substantially continuous
layers can have a basis weight ranging from about 5 g/m.sup.2 to
about 150 g/m.sup.2. Preferably, the substantially continuous layer
can have a basis weight ranging from about 13 g/m.sup.2 to about 23
g/m.sup.2. More preferably, the substantially continuous layer can
have a basis weight of about 16-18 g/m.sup.2. The substantially
continuous layers preferably have sufficient strength to perform
their intended tasks. Preferably, the substantially continuous
layer maintains its integrity when partially or fully wetted, so
that the distribution of liquids to and the immobilization of the
absorbent materials may be accomplished. The distribution layer
preferably has a wet burst strength ranging from a lower limit of
about 50-75 g and preferably about 200 g, to an upper limit of
about 800 g, more preferably about 600 g, and most preferably about
400 g. This is advantageous as it provides the layer with a good
combination of absorbency and wet strength. The substantially
continuous layer can be creped, uncreped, or wet micro-contracted
tissue webs. The substantially continuous layer may be nonwoven,
paper or tissue consisting essentially of cellulosic papermaking
fibers. Optionally, the substantially continuous layer may be
foreshortened, and/or contain synthetic fibers. In a preferred
embodiment of the absorbent article according to the invention, the
bonds, joints and connections from the distribution layer 100a are
not permanent so that the bonds may partially break, detach and/or
disintegrate during wetting.
[0217] In a preferred embodiment of the invention, portions of the
carrier layer 101 and/or auxiliary layer 102 bond or join to
portions of the distribution layer 100a; the distribution layer
100a together with one or more layers from the absorbent structure
14 cavities for the immobilization of the absorbent material,
preferably absorbent particulate polymer material. The bonding
strength should suffice the required parameters of the absorbent
structure and will amongst others depend on the product size,
shape, category and required duration of the usage and
performance.
[0218] The pockets 130 can have a regular shape, irregular shape or
combination thereof. Preferred shapes of the pockets 130 are
circular, elliptic or square with a diameter, radius or side larger
than about 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, more preferably
larger than about 0.75 mm and smaller than about 60 mm, more
preferably larger than about 1.0 mm and smaller than about 40 mm,
more preferably lager than about 2.0 mm and smaller than about 20
mm and most preferably larger than about 3.0 mm and smaller than
about 15 mm. The absorbent material 110 does not necessarily fill
the pockets 130 entirely as it might be advantageous to leave some
void space adjacent the absorbent material 110 in the pockets 130
or leave some pockets 130 partially or completely empty. The
inventor has found that in particular rectangular shaped pockets
130 with a side of about 10 mm are particularly advantageous to be
used as building blocks for the final compartment sizes within the
wetted and released absorbent structure 14, as they are easier to
manufacture at high production speed while still allowing
meticulous controlling of the prescribed bonding strength of the
primary and secondary attachments.
[0219] Preferably the distribution of absorbent polymer material is
profiled and most preferably profiled in the longitudinal
direction. Hence, along the longitudinal axis of the absorbent
structure, which is normally coincident with the longitudinal axis
of the absorbent article, for example of the baby diaper, the basis
weight of the absorbent polymer material will change. Preferably
the basis weight of absorbent polymer material in at least one
freely selected first square measuring 1 cm.times.1 cm is at least
about 10%, or 20%, or 30%, 40%, 50% up to more than 100% higher
than the basis weight of absorbent polymer material in at least one
freely selected second square measuring 1 cm.times.1 cm. Preferably
the criterion is met if the first and the second square are centred
about the longitudinal axis.
[0220] The primary attachments 111 have to substantially resist the
frictions and strain during normal use of the absorbent structure
14 and the forces resulting from the expanding and swelling
absorbent material 110 caused by the liquid uptake. Since the
bonding strength of water-sensitive attachment means would be very
hard to control during usage conditions, they are preferably not
used within an absorbent structure 14 according to the present
invention. Preferably the dry and/or wet separation force necessary
to release the primary attachment grids in between the carrier
layer 101 and auxiliary layer 102 will be higher than about 0.05
N/cm or about 0.75 N/cm, more preferably higher than about 0.1,
N/cm, 0.2 N/cm or 0.3 N/cm, even more preferably higher than about
1.0 N/cm, 1.5 N/cm, 2.5 N/cm and most preferably higher than about
3-5 N/cm. The attachment grids and patterns can consist of various
sub-regions, corresponding to different separation forces.
[0221] As can be seen from FIGS. 4 and 5, the absorbent material
pattern formed in between attachments can be random or regular,
substantially continuously connected or isolated, fully-covering or
partially covering and/or any other suitable combination.
Preferably the absorbent material regions consists of several
clusters of absorbent material 110, surrounded by areas where
substantially no absorbent material 110 is present, which can act
as additional distribution and transport channels facilitating the
flow of liquid away from the point of insult and towards available
clusters of absorbent material 110. Weight distribution of
absorbent material 110 over the absorbent structure 14 can be
regular across the major surface or can profiled, i.e. the basis
weight of the absorbent material 110 may change depending on its
position in the absorbent structure 14, for instance very desirable
for use in diaper and pants cores where one would like to
concentrate absolute and/or relative more absorbent material 110
near the point of liquid insult. Suitable materials such as for
instance highly permeable SAP are offered by Evonik, BASF and
Nippon Shokubai. Although preferably the absorbent polymer material
form up to 100% of the absorbent material 110 it can also be used
in combination with other materials such as for instance cellulose
fibres or fluff pulp, however preferably the amount of fibrous
materials would not make up more than about zero to 40 weight
percent. Fully cellulose free structures benefit maximal of this
invention.
[0222] The total absorbency and swelling capacity of an absorbent
polymer materials are controlled by the type and degree of
cross-linkers used to make the hydrogel. Low density cross-linked
SAP generally has a higher absorbent capacity and thus typically is
able to swell to a relatively larger degree. These types of SAP
also have a softer and more sticky gel formation. High density
cross-linked SAP generally exhibits lower absorbent capacity and
swell to a relative lower degree, but the gel's strength is firmer
and can maintain particle shape even under modest pressure.
Absorbent polymer material are commonly made from the
polymerization of acrylic acid blended with sodium hydroxide in the
presence of an initiator to form a poly-acrylic acid sodium salt
(sometimes referred to as sodium polyacrylate). This polymer is the
most common type of SAP made in the world today. Other materials
are also used to make a SAP, such as polyacrylamide copolymer,
ethylene maleic anhydride copolymer, cross-linked
carboxymethylcellulose, polyvinyl alcohol copolymers, cross-linked
polyethylene oxide, and starch grafted copolymer of
polyacrylonitrile to name a few. The latter is one of the older SAP
forms created.
[0223] All these SAP technologies have been common in the absorbent
structure industries for many years and are well-known by the
persons skilled in the art. Generally, SAP manufacturers can vary
several process parameters and finishing specifications such as
cross-linking level and particle size and offer the absorbent
article designers a wide choice of absorbent polymer material
products ranging from SAP with low swelling capacity to high
swelling capacity, and from slow swelling behavior to fast swelling
behavior. By making the appropriate choice, one can design
absorbent structures with a combination of such different SAP
concepts, where preferably the fast swelling SAP and/or SAP with
high swelling capacity would be used in the areas which would have
to act as heights or embankments, while preferably the slow
swelling SAP and/or SAP with low swelling capacity would be used in
the areas which would have to act as depressions or canals.
[0224] In an alternative embodiment of this invention, one can use
higher amounts of SAP in certain areas, while other areas would be
free from SAP or have relative limited amounts of SAP so that, when
wetted, the areas with relative higher amounts of SAP would swell
to form heights while those without or with relatively limited
amounts of SAP would form the depressions.
[0225] The breaking of the secondary attachments 115 allows the
carrier layer 101 and/or auxiliary layer 102 to deform, stretch and
change shape. As a result, the minimal volume pockets 130 are able
to expand to an intermediate volumes and finally to maximum volume
compartments so as to accommodate the extra volume resulting from
the highly expandable absorbent material 110. Thus, as seen in FIG.
6, an absorbent structure 14 with expandable pockets 130 with
additional activated free swell volume is created, allowing the
absorbent material 110 to be more effectively and efficiently used
and reducing the risk of bursting of one or more sandwiching
layers. The extra volume created by the expanding pockets can for
instance be about 1% to 5% of the original volume. Preferably it is
higher than about 5% to 25%, more preferably higher than about 25%
to 50%, most preferably higher than about 50% or 100% of the
original volume. In an alternative embodiment, the absorbent
structure 14 consists of multilayered sandwich structures where on
the first sandwich structure of carrier layer 101--absorbent
material 110--auxiliary layer 102, additional layers of absorbent
material and/or complementary layers can be added. Such structures
can provide good liquid absorption whilst retaining product
integrity, in dry and wet state.
[0226] FIGS. 7, 8 and 9 show embodiments according to the invention
where secondary attachment 115 consist of weaker secondary
attachments 115' and stronger secondary attachments 115'' where
weaker secondary attachments 115' loosen faster than the stronger
secondary attachments 115''. The different functionalities in
between the primary attachments 111 and secondary attachments 115
in combination with the bonding strength differentiation in between
weaker secondary attachments 115' and stronger secondary
attachments 115'' allows the design of an absorbent structure 14
with a predetermined, controlled and/or phased volume-expansion of
the absorbent structure for ultimate fluid management.
[0227] In a more preferred embodiment, the absorbent structure 14
consists of weaker secondary attachments 115' at the periphery of
the absorbent structure 14 allowing for primary and easy expansion
of the absorbent material 110 adjacent the longitudinal and/or end
edges of the absorbent structure 14, thereby creating containment
or anti-leakage barriers within the absorbent structure 14. Such a
particular internal incorporated barrier construction has great
pre-usage, usage and post-usage advantages for the construction of
disposable absorbent hygiene articles such as garments, diapers or
pants. As shown in FIGS. 7, 8 and 9, the weaker secondary
attachment 115' loosen to form first barriers or embankments 150,
whereas the stronger secondary attachments 115'' form the only
later arising secondary barriers or embankments 151. The
substantially wet-resistant permanent primary grids form canals 152
in between the first embankments 150 and/or the secondary
embankments 151. Due to the time difference between the formation
of the first embankments 150 and the respective secondary
embankments 151, the first embankments 150 will contain the liquid
inside the product, where it can be distributed via the canals 152
and it will further be stored in and contained by secondary
embankments 151. Obviously combinations and variants are
possible.
[0228] In a preferred embodiment, one can for instance create
embankments in such a way to obtain a pocket being an elongated or
rounded depression, substantially surrounded by embankments. Such
embankments can be lowered or interrupted to create one or more in-
or outlets. The void space inside the pocket can especially be used
to store liquids, solids and/or liquids of high viscosity. In baby
diaper or adult incontinence products, such additional embankments
can act as a cushion, providing comfort, keeping skin away from
stool and preventing stool to be pushed out of the absorbent
article when the wearer exerts pressure, e.g. by sitting, on the
product. Various shapes, sizes, locations and combinations can be
envisaged. In a more preferred embodiment of this invention, one
can create a stool containing pocket since it is known that infant
stool can be very `liquid-like`.
[0229] Human feces (or human faeces), also known as stools, is the
waste product of the human digestive system and varies
significantly in appearance, depending on the state of the whole
digestive system, influenced and found by diet and health. Normally
stools are semisolid, with a mucus coating. The Bristol Stool Chart
or Bristol Stool Scale is a medical aid designed to classify the
form of human feces into seven categories. Sometimes referred to in
the UK as the "Meyers Scale," it was developed by K. W. Heaton at
the University of Bristol and was first published in the
Scandinavian Journal of Gastroenterology in 1997. The form of the
stool depends on the time it spends in the colon.
[0230] The seven types of stool are:
1. Separate hard lumps, like nuts (hard to pass). 2. Sausage-shaped
but lumpy. 3. Like a sausage but with cracks on its surface. 4.
Like a sausage or snake, smooth and soft. 5. Soft blobs with clear
cut edges (passed easily). 6. Fluffy pieces with ragged edges, a
mushy stool. 7. Watery stool, entirely liquid.
[0231] Types 1 and 2 indicate constipation, with 3 and 4 being the
"ideal stools" especially the latter, as they are the easiest to
pass, and 5-7 being further tending towards diarrhea or urgency.
Stool from small children, and especially younger babies, can often
be classified in type 5, 6 or 7 and may be referred to as `liquid
stool`.
[0232] Due to its high viscosity, the liquid stool does not
significantly get absorbed through the topsheet of the absorbent
article, and often gives rise to a leakage. Leakage of stool from
an absorption article is even less appreciated than urine leakage,
as the former provides even more inconvenience to the wearer and
caretaker, and provides more problems for health and hygiene. By
creating the superficial liquid management system such as for
instance a stool pocket, one can create a void space which can be
filled with stool. Contained by the embankments, the stool will
substantially remain in place. In order for a stool pocket to
perform optimally, the depressions should be at least 5%,
preferably 10%, more preferably 15% or most preferably at least 20%
lower than the heights in the rear section of the product.
[0233] In alternative embodiment, at least one of the carrier
layers 101 or auxiliary layer 102 is made out of an elastic or
stretchable material, allowing for at least a first volume
expansion before the gradually increasing expansion force of the
wetting and swelling absorbent materials 110 accommodates the
eventual breaking of the wet secondary attachments 118.
[0234] With reference to FIG. 10 A-B the primary attachments 111
from the absorbent structure 14 correspond with a predefined
primary bonding grids 113, whereas the secondary attachments 115
from the absorbent structure 14 correspond with a secondary bonding
pattern 117. These grid and pattern shapes are developed in light
of the desired structural and functional features. Obviously these
grids and patterns merely act as illustrations and examples as
various combinations, shapes and sizes are of course possible in
relation to desirable absorbent structures. Referring to FIG. 10A,
the lines of these patterns may be disposed regular or irregular,
continuous or discontinuous, coextensive with the entire surface of
the absorbent structure or only part thereof and any combination
and/or derivations thereof. These lines may be aligned with the
longitudinal, transversal or diagonal axis of the absorbent
structure 14 or alternatively any angle in respect of such axis. It
has been found that, that a continuous disposition of these lines
throughout the absorbent structure 14 creates additional channels
and ducts which help the fluid transport from the point of liquid
contact to the rest of the absorbent structure via mass flow
allowing better and more spread out immediate liquid management via
capillary flow locally. Care however should be taken not to allow
channelling of liquid to the very side of the absorbent structures
to avoid leakages upon time of insult, preferably they will thus
guide the liquid to the entire surface of the absorbent structure
with the exception of the outer edges thereof. Another preferred
pattern for grids and patterns comprises polygons, for example
pentagons and sexangles or a combination thereof. Also irregular
patterns are possible. In essence those grids and patterns are
preferred which allow optimal packaging of absorbent particulate
material in dry smaller pockets 130 while allowing ideal and
maximum volume expansion to bigger compartment in wet state taking
in mind the thin and flexible absorbent structures are envisaged.
Too much loss of pocket and/or compartment volume in light of
primary and secondary attachment grids and patterns in respective
dry and wet stat is preferably avoided.
[0235] Referring to FIG. 10B, exemplary absorbent structures are
shown with intact primary bonding grids 113 and released secondary
pattern 117 leading to the bigger and fewer compartments as opposed
to the plurality of smaller pockets 130 formed by the intact
primary attachments 111 and secondary attachments 115 (FIG.
10A).
[0236] The invention provides use of an absorbent structure
according to an embodiment of the invention in an absorbent
product, selected from the list of coffee pads, disposable body
warmers, sheet formed detergent article, filter material,
insulation material, make-up pads, anti-septic wads, feminine
hygiene garments, baby diapers, baby pants, adult incontinence
garments, preferably said absorbent article is a feminine hygiene
garment, baby diaper, baby pants or adult incontinence garment. The
construction of such commercially available products is well-know
from the art.
[0237] The absorbent structure claimed according to the present
invention is thin and flexible, and thus has a low
flexure-resistance. The flexure-resistance of the absorbent
structures is measured by the Peak Bending Stiffness as determined
by the test which is modelled after the ASTM D 4032-82 Circular
Bend Procedure, the procedure being considerably modified and
performed as described in EP0336578B1. In a preferred embodiment of
the absorbent article of the invention, the absorbent structure has
a flexure-resistance of less than 500.0 grams, more preferably less
than about 250.0-350.0 grams, and still more preferably less than
about 175.0 grams and most preferably less than about 130.0 or
100.0 grams. Thus, the absorbent structure of the present invention
is highly flexible and conforms very well to the various shapes of
the urogenital region. Use of an absorbent structure with this low
a flexure-resistance has for effect that an easily flexible
absorbent articles can be provided. This feature is advantageous as
such a structure will easily ply and allow the structure to follow
a body shape, and thus wearer fit and comfort.
[0238] The absorbent structure claimed according to the present
invention has superior immobilisation characteristic in dry and wet
state and the minimum wet immobilisation values as measured by the
shaker test weight retention as determined by the Wet
Immobilisation test as described in US Patent Application
20070167928 are very favourable. In a preferred embodiment of the
absorbent structure of the invention, the absorbent structure has a
wet immobilization of more than 60 wt %, preferably more than 70 wt
%, more preferably more than 80 wt %, and most preferably more than
90 wt %. Such absorbent structure has an increased loading capacity
and an improved absorption capacity.
[0239] With reference to FIG. 11, a method and apparatus is
illustrated for forming a composite structure 700 according to the
present invention, having a plurality of discrete particulate
material clusters 703 which are preferably discretely distributed
and deposited on a carrier layer 101 and contain selected
quantities of particulate material 703. The representatively shown
apparatus includes a particulate material supplying means 200 for
providing absorbent materials 110 towards carrier layer 101. A web
supplying means 400 and web transport means 402 provides a carrier
layer 101 and a support means 600 via guiding means 601 and 602
moves the carrier layer 101 adjacent a depositing means, preferably
provided in the form of a substantially endless rotating drum 100.
A material supply means 200 direct absorbent material 110 by way of
a dosing system 204 and a feeding tube 205 towards the a proximal
opening 206. Optional brushing means 208 help to `right-fill` the
clustering means 250. The depositing means 206 preferably having
clustering means 250 with a pattern of perforations arranged to
form and provide a desired depositing pattern of particulate
material clusters 703 onto the carrier layer 101. The support means
600 is preferably in substantial contact with the support surface
412 of the carrier layer 101. The support means 600 preferably
ensures a close enough connection in between the deposit surface
411 of the carrier layer 101 and clustering means 250 to prevent
unwanted migration of the particulate materials 110 from the
carrier deposit zones to the carrier inter-deposit zones.
Preferably also a position means is provide which can be unitary
with the support means 600, and which stabilizes, positions and/or
repositions any blurring in the printing pattern of particulate
material clusters 703 towards an exact pocketing pattern prior to
immobilisation. A covering means 500 and web transporting 502
provides an auxiliary layer 102, such as for instance a
liquid-permeable fibrous web such as a non-woven, paper, tissue,
woven, fabric, web, perforated film or foil. Alternatively the
auxiliary layer 101 can also represent a homogenous and/or
heterogeneous layer of glue, adhesive, binders, resins,
thermoplastic material and the like, capable of sandwiching the
particulate materials clusters 703 between the carrier layer and
auxiliary layer to form a composite structure 700, such as for
instance an absorbent structure 14. This relative expensive,
technically challenging and environmentally burdensome alternative
embodiment according to the invention is however not preferred
above the non-woven, paper or tissue like layer for instance. A
much preferred attachment process according to a preferred
embodiment of the present invention comprises an airflow generated
by blowing zones having an overpressure in comparison to standard
process pressure and/or by suction zones having an under-pressure
in comparison to standard process pressure. Alternatively, a
combination of blowing and/or suction holes is used for airflow.
Ultrasonic means 800 and adhesive applicator means 900 and/or 901
may also be provided.
[0240] An exemplary absorbent article is disposable baby
diaper.
[0241] FIG. 12 is a top plan view of a diaper 10 as a preferred
embodiment of an absorbent article including an absorbent structure
according to the present invention. It should be understood,
however, that the present invention is also applicable to other
absorbent articles such as feminine hygiene garments, baby pants,
adult incontinent garments and the like.
[0242] The absorbent article is shown in its flat out,
un-contracted state with the wearer side facing the viewer.
Portions of the absorbent article are cut away to more clearly show
the underlying structure of the diaper 10 including the absorbent
elements and absorbent components. The chassis 12 of the diaper 10
in FIG. 12 comprises the main body of the diaper 10. The chassis 12
comprises an outer covering including a liquid pervious top sheet
18 and/or a liquid impervious back sheet 20. The chassis 12 may
include a portion of an absorbent structure 14 encased between the
top sheet 18 and the back sheet 20. The chassis 12 may also include
most or all of the absorbent structure 14 encased between the top
sheet 18 and the back sheet 20. The chassis 12 preferably further
includes side panels or ears 22, elasticized leg cuffs 24 and
elastic waist features 26, the leg cuffs 24 and the elastic waist
feature 26 each typically comprise elastic members 28. One end
portion of the diaper 10 is configured as a front waist region 30
of the diaper 10. The opposite end portion is configured as a back
waist region 32 of the diaper 10. An intermediate portion of the
diaper 10 is configured as a crotch region 34, which extends
longitudinally between the first and second waist regions 30 and
32. The waist regions 30 and 32 may include elastic elements such
that they gather about the waist of the wearer to provide improved
fit and containment (e.g. elastic waist feature 26). The crotch
region 34 is that portion of the diaper 10 which, when the diaper
10 is worn, is generally positioned between the wearer's legs. The
diaper 10 is depicted with its longitudinal axis 36 and its
transverse axis 38. The periphery of the diaper 10 is defined by
the outer edges of the diaper 10 in which the longitudinal edges 42
run generally parallel to the longitudinal axis 36 of the diaper 10
and the end edges 44 run between the longitudinal edges 42
generally parallel to the transverse axis 38 of the diaper. The
chassis 12 also comprises a fastening system, which may include at
least one fastening or securing member 46 and at least one landing
zone 48. The various components within the diaper 10 may be bound,
joined or secured by any method know in the art, for example by
adhesives in uniform continuous layers, patterned layers or arrays
of separate lines, spirals or spots. The top sheet 18, the back
sheet 20, the absorbent structure 14 and other components may be
assembled in a variety of well-known configurations and are well
known in the art.
[0243] The back sheet 20 covers the absorbent structure 14 and
preferably extends beyond the absorbent structure 14 toward the
longitudinal edges 42 and end edges 44 of the diaper 10 and may be
joined with the top sheet 18. The back sheet 20 prevents the bodily
exudates absorbed by the absorbent structure 14 and contained
within the diaper 10 from soiling other external articles that may
contact the wearer, such as bed sheets and undergarments. In
preferred embodiments, the back sheet 20 is substantially
impervious to bodily exudates and comprises a laminate of a
nonwoven and a thin plastic film such as a thermoplastic film. The
back sheet 20 may comprise breathable materials that permit vapour
to escape from the diaper 10 while still preventing bodily exudates
from passing through the back sheet 20. It may be semi-rigid,
non-elastic and can be made fully or partially elasticized and
include backing. The back sheets 20 may be assembled in a variety
of well-known configurations and are well known in the art.
[0244] The diaper 10 comprises a top sheet 18 that is preferably
soft, compliant, exhibits good strikethroughs and has a reduced
tendency to rewet from the liquid absorbent material. The top sheet
18 is placed in close proximity to the skin of the wearer when the
diaper 10 is worn. In this way, such top sheet 18 permits bodily
exudates to rapidly penetrate it so as to flow toward the absorbent
structure 14 more quickly, but preferably not allowing such bodily
exudates to flow back through the top sheet 18. The top sheet 18
may be constructed from any one of a wide range of liquid and
vapour permeable, preferably hydrophilic, materials. The upper and
lower surface of the top sheet 18 may be treated differently and
may for instance include a surfactant on the upper surface so as to
facilitate liquid transfer there through, especially at a central
zone or area of the top sheet 18 located over the absorbent
structure 10, and for instance include a hydrophobic agent on the
lower surface to minimize the liquid contained within the absorbent
core from contact wetting the top sheet 18 thereby reducing rewet
values. The top sheet 18 may also be coated with a substance having
rash preventing or rash reducing properties (e.g. aloe vera). The
top sheet 18 covers substantially the entire wearer facing area of
the diaper 10, including substantially all of the front waist
region 30, back waist region 32, and crotch region 34. Further, the
side panels 22 and/or waist feature layers of the inner region may
be formed from the same single top sheet material and, thus, may be
referred to as being unitary with the top sheet 18 in forming
longitudinal and lateral extensions of the top sheet 18 material.
Alternatively, the top sheet 18 may be formed from multiple
different materials which vary across the width of the top sheet
18. Such a multiple piece design allows for creation of preferred
properties and different zones of the top sheet 18. The top sheet
18 be semi-rigid, non-elastic and can be made fully or partially
elasticized. The top sheet 18 may be assembled in a variety of
well-known configurations and are well known in the art.
[0245] The absorbent structure 14 in FIG. 12 generally is disposed
between the top sheet 18 and the back sheet 20. The absorbent
structure 14 may comprise any absorbent material 110 that is
generally compressible, conformable, non-irritating to the wearer's
skin, and capable of absorbing and retaining bodily exudates. The
absorbent structure 14 may comprise a wide variety of liquid
absorbent materials 110 commonly used in absorbent articles such as
fluff pulp, which is generally referred to as airlaid. Examples of
other suitable absorbent materials include creped cellulose
wadding; melt blown polymers; chemically stiffened, modified or
cross-linked cellulosic fibres; tissue, including tissue wraps and
tissue laminates; absorbent foams; absorbent sponges; absorbent
polymer materials; absorbent gelling materials; or any other known
absorbent materials or combinations of materials. The absorbent
structure 14 may further comprise minor amounts (typically less
than 10%) of non-liquid absorbent materials, such as adhesives,
binders, plastics, waxes, oils and the like. The absorbent
structure 14 according to various embodiments of the invention may
be configured to extend substantially the full length and/or width
of the diaper 10. However, alternatively the absorbent structure 14
according to the invention is not coextensive with the entire
diaper 10 and is limited to certain regions of the diaper 10 such
as for instance the crotch region 34. In various embodiments, the
absorbent structure 14 extends to the edges of the diaper 10 and
the absorbent material 110 is concentrated in the crotch region 34
or another target zone of the diaper 10. In still another
embodiment, the particles can be a combination of absorbent
material 110, preferably comprising absorbent polymer material, and
skin care particles such as ion exchange resins, deodorant,
anti-microbial agents, binder particles, or other beneficial
particles.
[0246] The diaper 10 may also utilize a pair of containment walls
or cuffs 24. Each cuff 24 is a longitudinally extending wall
structure preferably positioned on each side of the absorbent
structure 14 and spaced laterally from the longitudinal axis 36.
The longitudinal ends of the cuffs 24 may be attached or joined,
for example, to the top sheet 18 in the front and rear waist
regions 30 and 32. Preferably, the ends of the cuffs 24 are tacked
down inwardly and attached, for example, by adhesive or sonic
bonding to the lower structure. Such a construction effectively
biases the cuffs 24 inwardly and is generally considered to cause
the cuffs 24 to exhibit improved leakage prevention properties.
Preferably, the cuffs 24 are equipped with elastic members 28,
which extend along a substantial length of the cuffs 24. In a
common application, the elastic members 28 are placed within the
cuffs 24, preferably at the top of the cuff 24 while in a stretched
condition and then glued or sonic bonded to the cuff 24 at least at
their ends. When released or otherwise allowed relaxing, the
elastic members 28 retract inwardly. When the diaper 10 is worn,
the elastic members 28 function to contract the cuffs 24 about the
buttocks and the thighs of the wearer in a manner, which forms a
seals between the diaper 10, the buttocks and the thighs. The cuffs
24 may be assembled in a variety of well-known configurations and
are well known in the art.
[0247] The diaper 10 may also employ additional layers known in the
art including an acquisition layer or surge layer, preferably
situated between the top sheet and the absorbent core and highloft
and/or coverstock layers. This serves to slow down the flow so that
the liquid has adequate time to be absorbed by the absorbent
core.
[0248] In order to keep the diaper 10 in place about the wearer,
preferably at least a portion of the back waist region 32 is
attached by fastening or securing members 46 to at least a portion
of the front waist region 30, preferably to form leg openings and
an absorbent article waist. Fastening or securing members 46 carry
the tensile load around the absorbent article waist and compliment
the elastic members 28 by providing a quasi-seal between the
wearer, the elastic waist feature 26 and cuffs 24, so that bodily
exudates are contained within the diaper 10 which are then
absorbed.
[0249] In other words, so that it does not leak through gaps
between the wearer and the edge of the diaper 10. The fastening or
securing members 46 may for instance be adhesive, mechanical
fasteners, hook and loop features, conceivable strings and/or
combinations thereof, i.e., anything that will secure one end of
the diaper 10 to the longitudinally opposite end of the diaper 10.
The fastening or securing members 46 may also be co-adhesive such
that they adhere to each other but not other materials. The
fastening or securing members 46 and any component thereof may
include any material suitable for such a use, including but not
limited to plastics, films, foams, non-woven webs, woven webs,
paper, laminates, fibre reinforced plastics and the like, or
combinations thereof. It may be preferable that the materials
making up the fastening or securing members 46 are flexible,
extensible and/or elastic, allowing them to better conform to the
shape and movements of the body and thus, reduces the likelihood
that the fastening system will irritate or injure the wearer's
skin. Preferably, the diaper 10 is affixed to the wearer by tape
fasteners which are permanently affixed to the back sheet 20. Tape
fasteners are contacted with the transversely opposite side panel
or ears 22 attached or joined and extending from the back sheet 20,
where they remain affixed due to the binding compound applied to
the fasteners. Alternatively, the absorbent article may be pants
and the like. In this configuration, the absorbent article may or
may not have tape fasteners. Specific disposability tapes may
however also be provided on such absorbent articles. All fastening
and securing elements 46 may be assembled in a variety of
well-known configurations and are well known in the art.
[0250] The waist regions 30 and 32 each comprise a central region
and a pair of side panels or ears 22 which typically comprise the
outer lateral portions of the waist regions. These side panels 22
may be unitary with the chassis 12 and/or back sheet 20 or may be
attached or joined thereto by any means know in the art. In a
preferred embodiment of the present invention, the side panels 22
positioned in the back waist region 32 are flexible, extensible
and/or elastic in at least the lateral direction (i.e., elasticized
side panels), in another embodiment the side panels 22 are
non-elastic, semi-rigid, rigid and/or stiff. These variety of side
panels 22 are known in the art.
[0251] Furthermore waistbands 26 employing elastic members can be
positioned along the transverse portion of the diaper 10 so that
when worn, the waistbands 26 are positioned along the waist of the
wearer. Generally, the waistband 26 preferably creates a seal
against the waist so that bodily exudates do not leak from the
regions between the elastic waistband 26 and the waist of the
wearer. Although the bodily exudates are primarily absorbed by the
absorbent materials within the diaper 10, the seal is important
considering the assault of liquid by the wearer may overwhelm the
absorption rate capacity of the absorbent structure 14. Hence, the
waistbands 26 contain the liquid while it is being absorbed, they
are well known in the art.
[0252] The absorbent article such as a diaper 10 may also include
such other features, components and elements as are known in the
art including front and rear ear panels, waist cap features,
elastics and the like to provide better fit, containment and
aesthetic characteristics. These features may be assembled in a
variety of well-known configurations and are well known in the
art.
[0253] The process for producing preferred absorbent structures in
accordance with the present invention comprises the following
steps: A carrier layer 101 is provided onto which absorbent
material 110 is disposed by methods known in the art. To deposit
the absorbent material 110, vacuum, gravity or other forces can be
used. Then an auxiliary layer 102 is provided, covering the
absorbent material 110, and primary bonding regions 111 and
secondary bonding regions 115 are being provided. In case one would
like to use adhesives or chemical binders, then it might be useful
to attach these to the carrier layer 101 and/or auxiliary layer 102
layer prior to bringing the sandwich structure together. In case
one opts for thermo-sealed bonding areas, then the thermo-sealing
can be applied after the sandwich structure components have been
brought together. It is of course also possible to combine both
techniques in the same absorbent structure.
[0254] The process for producing preferred absorbent structures 14
in accordance with the present invention comprises the following
steps: A carrier layer 101 is provided onto which absorbent
material 110 is disposed by methods known in the art. To deposit
the absorbent material 110, vacuum, gravity or other forces can be
used. Then an auxiliary layer 102 is provided, covering the
absorbent material 110, and primary attachments 111 and secondary
attachments 115 are being provided, preferably via sonic bonding.
In case one would like to use adhesives or chemical binders, then
it might be useful to attach these to the carrier layer 101 and/or
auxiliary layer 102 layer prior to bringing the sandwich structure
together. In case one opts for thermo-sealed or sonic bonding
areas, then the thermo-sealing can be applied after the sandwich
structure components have been brought together. It is of course
also possible to combine both techniques in the same absorbent
structure.
* * * * *