U.S. patent application number 12/657982 was filed with the patent office on 2011-07-28 for flexible, highly absorbent material.
This patent application is currently assigned to Glatfelter Falkenhagen GmbH. Invention is credited to Ralf Ehmke, Stefanie Lutter, Henning Rottger.
Application Number | 20110184365 12/657982 |
Document ID | / |
Family ID | 44309500 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110184365 |
Kind Code |
A1 |
Rottger; Henning ; et
al. |
July 28, 2011 |
Flexible, highly absorbent material
Abstract
An absorbing structure has a sequence of layers, including at
least first and second outer layers with at least a liquid storage
layer disposed therebetween. The layers are disposed on top of one
another and form a layered structure. At least the liquid storage
layer has a cellulose material, preferably cellulose fibers, and a
super absorbing polymer SAP, preferably SAP particles and/or SAP
fibers. The liquid storage layer uses at least less binder material
than the other liquid storing plies of the absorbing structure. The
liquid storing plies are adjacent to the liquid storage layer.
Preferably, the liquid storage layer does not have binder
material.
Inventors: |
Rottger; Henning;
(Kaltenkirchen, DE) ; Lutter; Stefanie;
(Wittstock, DE) ; Ehmke; Ralf; (Meyenburg,
DE) |
Assignee: |
Glatfelter Falkenhagen GmbH
|
Family ID: |
44309500 |
Appl. No.: |
12/657982 |
Filed: |
January 28, 2010 |
Current U.S.
Class: |
604/372 ;
264/173.1; 425/102; 442/389; 604/374 |
Current CPC
Class: |
A61F 13/15747 20130101;
A61L 15/28 20130101; B32B 2555/02 20130101; Y10T 442/668 20150401;
A61F 2013/15878 20130101; A61F 13/539 20130101; A61F 13/15658
20130101; A61F 2013/530131 20130101; B32B 2255/26 20130101; B32B
2262/062 20130101; B32B 2264/02 20130101; B32B 2255/02 20130101;
B32B 5/26 20130101; B32B 2262/12 20130101; A61F 2013/530481
20130101; A61F 13/537 20130101; A61F 13/15707 20130101; A61L 15/60
20130101; B32B 33/00 20130101; B32B 2250/20 20130101; B32B 2262/14
20130101; A61F 13/53743 20130101; A61F 13/5116 20130101; A61L 15/28
20130101; A61F 2013/15821 20130101; A61F 13/15764 20130101; B32B
2307/726 20130101; B32B 2262/02 20130101; C08L 1/02 20130101; A61F
13/534 20130101 |
Class at
Publication: |
604/372 ;
604/374; 264/173.1; 425/102; 442/389 |
International
Class: |
A61F 13/53 20060101
A61F013/53; A61L 15/22 20060101 A61L015/22; B29C 63/48 20060101
B29C063/48; B32B 5/26 20060101 B32B005/26 |
Claims
1-10. (canceled)
11. An absorbing structure with a sequence of layers comprising at
least a first and a second outer layer and at least a liquid
storage layer disposed therebetween, wherein the layers are
disposed on top of one another and form a layered structure,
wherein at least the liquid storage layer comprises a cellulose
material and a super absorbing polymer and wherein the liquid
storage layer comprises at least less binder material than liquid
storing layers of the absorbing structure, which are adjacent to
the liquid storage layer.
12. The absorbing structure according to claim 11, wherein the
cellulose material is made of cellulose fibers.
13. The absorbing structure according to claim 12, wherein the
super absorbing polymer is super absorbing polymer particles or
super absorbing polymer fibers.
14. The absorbing structure according to claim 13, wherein the
liquid storage layer has no binder material.
15. The absorbing structure according to claim 13, wherein the
super absorbing polymer particles or super absorbing polymer fibers
are disposed moveable relative to one another in the liquid storage
layer when liquid is absorbed and/or pressure is introduced.
16. The absorbing structure according to claim 11, wherein the
super absorbing polymer is super absorbing polymer particles or
super absorbing polymer fibers.
17. The absorbing structure according to claim 16, wherein the
liquid storage layer has no binder material.
18. The absorbing structure according to claim 11, wherein the
liquid storage layer comprises no binder material.
19. The absorbing structure according to claim 11, wherein at least
a substantial portion of the liquid storage layer is made of
treated and/or non treated cellulose material.
20. The absorbing structure according to claim 19, wherein the
layered structure comprises a first outer surface and a second
outer surface, wherein at least the first outer surface has a
binder material layer.
21. The absorbing structure according to claim 20, wherein the
binder layer is a latex based binder material layer.
22. An absorbing structure comprising a paper tissue ply as a first
ply, a second ply with fluff pulp, bonding fibers and super
absorber, a third ply with fluff pulp and with super absorber, and
a fourth ply with fluff pulp and bonding fibers, wherein the third
ply comprises at least less bonding fibers than the respective
second ply and the respective fourth ply.
23. The absorbing structure according to claim 22, wherein the
third ply has no bonding fibers.
24. The absorbing structure according to claim 22, wherein the
third ply facilitates a relative moveability between the second ply
and the fourth ply in a longitudinal direction of the absorbing
structure during a wet state of the absorbing structure.
25. A method for producing an absorbing structure, comprising at
least the following steps: providing a support layer as a first
ply; laying fluff pulp, super absorbing polymer and a binder
material as a second ply on the support layer; laying a third ply
made of fluff pulp and super absorbing polymer on the second ply;
laying a fourth ply made of fluff pulp and binder material on the
third ply; applying the binder material on at least one outer
surface of the plies; supplying the plies to a calender which
comprises a calender nip; and compressing the plies in the calender
nip.
26. The method according to claim 25, wherein the binder material
is a latex based binder material.
27. A device for producing an absorbing structure, comprising at
least: a sieve conveyor belt for laying plies for forming a layered
structure; a first forming device through which at least cellulose
fibers, super absorbing polymer and a binder material can be
applied to the sieve conveyor belt; a second forming device,
through which cellulose fibers and super absorbing polymer can be
applied to the sieve conveyor belt for forming an additional ply; a
third forming device, through which a binder material and cellulose
fibers can be applied to the sieve conveyor belt as an additional
ply; at least one application station through which a binder
material can be applied at least on an outer surface of the layered
structure; and a compression station through which the layered
structure can be compressed.
28. The device according to claim 27, wherein the binder material
is a latex based binder material.
29. The device according to claim 28, wherein the compression
station includes a calender.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The invention relates to a multilayer absorbing structure
including at least one liquid storage layer, preferably with a
liquid acquisition layer, a liquid storage layer and a liquid
distribution layer using cellulose fibers and a super absorbing
polymer. The invention also relates to a method and an apparatus
for producing the structure.
[0003] 2. Description of the Background Art
[0004] Multilayer absorbing structures using cellulose and super
absorbing polymers abbreviated as SAP, e.g. in the form of SAP
particles or SAP fibers have been known for many years and are
being used as a layer material in disposable products, e.g. in
hygiene products, medical products and industrial products.
[0005] Fiber layers with absorbent layer in which binder materials
are being used for stabilizing the absorbent layer and for avoiding
abrasion of the fibers are known. The layers of such layer material
include binder materials, e.g. in the form of fibers, powder, hot
melt glues, solvent-binder mixes for application in liquid form or
similar.
[0006] For example, EP 1721 036 describes producing a fiber web
made of cellulose fibers with absorbing properties through an
airlaid method. The fiber web includes several layers. An inner
absorbent layer includes a point bonded cellulose material with a
super absorber. In order to prevent creating dust from the fibers,
called "linting", which is generated through abrasion or fuzzing of
cellulose fibers, the fibers, in particular in the outer portions
of the center fiber web, are impregnated with water-latex mix.
[0007] When an absorbing structure which includes, e.g., a liquid
acquisition layer, a liquid storage layer and a liquid distribution
layer is wetted, e.g. by a liquid, the liquid moves from the liquid
acquisition layer to the liquid storage layer through capillary
action. Superfluous liquid can enter from the liquid storage layer
into the liquid distribution layer and can be distributed by the
liquid distribution layer through pore structure selected
accordingly and can be fed back into the storage layer if
necessary. This prevents undesirable back wetting effects which can
occur through a run out of liquid from a liquid acquisition layer
into a liquid distribution layer and beyond, e.g. onto the skin of
a bearer of a hygiene product. However, such products tend to have
considerable deficiencies with respect to wearing comfort. Thus,
e.g. a liquid storage layer wetted and compressed through liquid
absorption and subsequent deformation, this means through regular
use, does not tend to go back into its original position after it
is unloaded. For example, when SAP particles are loaded with
moisture and deformed, a gluing effect between the particles can be
created. For known relatively compact liquid storage layers thus
the capacity for absorbing additional liquid is substantially
reduced which impairs wearing comfort.
SUMMARY OF THE INVENTION
[0008] Thus it is desirable to have a product available which helps
to avoid such impairments of wearing comfort during use.
[0009] Thus, it is the object of the present invention to provide a
product, a method and an apparatus for producing an absorbing
product which facilitates better properties during use, in
particular increased flexibility.
[0010] This object is accomplished through an absorbing structure,
a method for producing an absorbing structure and an apparatus
according to the independent claims. Preferred embodiments are
further defined in the dependent claims. The features included
therein, however, can also be combined in further embodiments with
other features from the subsequent description and they are not
limited to the embodiments respectively claimed. The respective
proposed features, in particular also of the respective independent
claims only serve as a first proposal for a solution, wherein one
or plural of the features included in the independent claims can
also be supplemented and/or replaced by the subsequent
features.
[0011] Thus, an absorbing structure with a sequence of layers is
proposed which includes at least first and second outer layers with
at least one liquid storage layer disposed therebetween. The layers
are disposed on top of one another and form a layered structure. At
least the liquid storage layer has a cellulose material preferably
cellulose fibers and a super absorbing polymer SAP, preferably SAP
particles and/or SAP fibers. The liquid storage layer uses at least
less binder material than liquid storage plies of the absorbing
structure adjacent to the liquid storage layer. Preferably, the
liquid storage layer includes no binder material. The adjacent
liquid storage plies according to one embodiment can at least
include one of the plies, which form the first and the second outer
layer of the absorbing structure.
[0012] In a preferred embodiment, the absorbing structure includes
at least one liquid acquisition layer, at least one subsequent
liquid storage layer and at least one subsequent liquid
distribution layer, wherein the layers are connected and form a
layered structure. The liquid acquisition layer and/or the liquid
storage layer include a cellulose material, preferably cellulose
fibers and a super absorbing polymer SAP, preferably SAP particles
and/or SAP fibers. The liquid acquisition layer and/or the liquid
distribution layer include a binder material. Contrary to the
cellulose fibers of the liquid acquisition layer and of the liquid
distribution layer, the cellulose fibers of the liquid storage
layer according to a preferred embodiment are not impregnated with
a binder material, or they do not include binder material. Another
embodiment provides that a binder material is provided in a low
concentration, this means only with a low adhesion within the
liquid storage layer. This concentration is e.g. adjusted, so that
the adhering connections in the liquid storage layer immediately
tear open when a force is introduced, e.g. a shear force and/or
when a force is introduced through swelling of SAP, wherein the
tearing open of the adhering connections facilitate a degree of
freedom of movement. Such a concentration of binder material can
e.g. be used to fixate a local disposition of SAP in the liquid
storage ply for producing the absorbing structure at least at one
point in time. However, when liquid is absorbed the adhering
connections can disengage and facilitate moveability within the
liquid storage ply. For example, a usable binder material can lose
its bond when wetted by a liquid. A shear force can also occur when
an absorbing structure is being used, which shear force then
disengages the adhering connection and establishes the moveability
in the liquid storage ply.
[0013] Preferably, the layered structure according to an embodiment
includes at least the following assembly: [0014] a first layer,
comprising at least a treated fluff pulp, multi component fibers,
preferably PE/PETbi-component fibers and a super absorber; [0015] a
second layer, comprising at least a treated and/or non treated
fluff pulp and a super absorber; and [0016] a third layer,
comprising at least a non treated fluff pulp and multi component
fibers, preferably PE/PET bi-component fibers.
[0017] In order to support the first ply, its outer surface can
additionally be provided with a paper-tissue ply. In one
embodiment, this layered structure comprises a loose compression
through a calendering step, preferably through a smooth calender
roller, whereby a first thickness, e.g. a final thickness of the
ply material can be adjusted.
[0018] Furthermore, a latex binder, e.g. an EVA-dispersion binder
can be applied to one or both outer surfaces of the layer
structure, wherein the binder is subsequently dried and hardened.
Contrary to conventional materials, the suggested configuration of
the layered structure facilitates that the super absorber can
expand freely in the center layer after liquid is introduced, which
center layer is preferably formed by the liquid storage layer or at
least co-formed by the liquid storage layer, since the super
absorber is not impeded by the bonding fibers. This expansion
process is e.g. not impeded by a pulp-bico-ply which is stiffened
by an EVA dispersion binder, but otherwise open.
[0019] Preferably this provides an elastic ply structure which
comprises solid outer layers and at least one loose, hardly
compacted inner ply.
[0020] The layered structure can also be produced without a tissue
ply and/or with other support plies, e.g. spunbond layers or
fleeces produced in any manner.
[0021] The ply material according to one embodiment has a
substantially constant thickness which is in an order of magnitude
of approximately 0.1 g/ccm. It can also be in a range of 0.08 to
0.15 g/ccm. According to another embodiment, the layer material in
dry state at a thickness of approximately 5 mm can have a surface
weight of approximately 460 g/m.sup.2 and for a thickness of
approximately 6 mm it can have a basis weight of approximately 600
g/m.sup.2. A basis weight in a range between 440 g/m.sup.2 and up
to 680 g/m.sup.2 is desirable. A thickness between 4.7 mm and 6.7
mm of the absorbing structure is also desirable. This is a
manufactured layer thickness of the layered structure which the
layered structure can have in a dry state. Besides these preferred
layer thicknesses, layer thicknesses between 3 mm and 15 mm,
preferably between 4 mm and 8 mm are conceivable for the layered
structure according to the invention as a function of the
respective use of the layered structure and the liquid volume
associated therewith or as a function of the frequency of the
liquid provision within a short time interval. When wetting the
layered structure, this means in wet condition, the layer thickness
will change much less due to the enormous receiving capability of
the liquid acquisition layer and due to the relative moveability of
the adjacent layers, than this is known for conventional products.
The increase in layer thickness as a function of the degree of
saturation is in a range of 50-150% with reference to the initial
thickness of the layer structure.
[0022] Surprisingly, it has become evident that the ply material
has substantial advantages over the known fluff pulp SAP layered
structures or layered structures with homogenously thermally bonded
layers, in which all layers are provided with binder materials,
e.g. bi-component fibers. The proposed layer structure has proven
advantageous in used condition, thus in wet condition.
[0023] Thus, it has become evident that the absorbing structure has
the advantage that the liquid storage layer during use of the
absorbing structure can substantially revert back to its original
state in spite of multiple liquid absorptions and pressure
loadings. Since no bonding fibers are provided, the super absorbing
material is not prevented from free swelling. Thus, e.g. the
desired parameter of the free swelling capacity, the so called free
swell capacity, which is preferably in the range of 20 g/g, can be
achieved with comparatively lower SAP percentages and lower surface
weights than this is provided for conventional layered structures.
This helps reduce the cost for raw materials. According to an
embodiment, the free swelling capacity is in a range between 17 g/g
and 24 g/g.
[0024] Additionally, it was observed for known layered structures
that the super absorber acts like glue after liquid is introduced
and fixates the layer in the formed shape. When the loose material
is deformed and fixated in this form, it has no more propensity to
assume its original shape. Supported by gravity, it forms lumps,
the so called sagging which degrades wearing comfort and absorption
performance, since the super absorber is not distributed in the
liquid storage layer in an optimum manner any more. The proposed
layer structure overcomes these disadvantages, so that a material
with reduced wet stiffness, this means greater moveability and a
high wearing comfort is provided compared to the respective
identical material which includes a binder material within the
liquid storage layer.
[0025] It has furthermore proven advantageous that the SAP material
which is already disposed in the liquid acquisition layer
immediately absorbs incoming liquid and thus facilitates a quicker
transportation of the liquid from its location of introduction to
the core of an absorber product. This helps to avoid back wetting
effects, e.g. through run out of excess liquid for a high liquid
volume towards the wearer of absorbing product. Furthermore, an
improvement of the re-wetting capability of the absorbing structure
is facilitated.
[0026] An improvement of the invention provides that the absorbing
structure includes at least 3 plies, wherein a center ply comprises
at least less, preferably no binder material.
[0027] It is also provided that all layers of the layer structure
respectively comprise at least one air laid material preferably as
a main component of the layer, wherein the respective layers
themselves can be configured in multiple plies. For example, the
liquid acquisition layer, the liquid storage layer and/or the
liquid distribution layer can include one or several functional
layers besides the air laid layer, which improve the desired effect
of each of these layers. Preferably, the particular layers of a ply
can be'arranged, so that a property gradient can be generated from
an outer surface of the ply to another outer surface. On the other
hand, the layers of a ply can be configured, so that an optimum for
the desired property is generated within a ply.
[0028] Another embodiment of the invention provides that the center
ply is at least made with less binder material, preferably made
without binder material, and that it is at least substantially made
of treated and/or untreated cellulose material.
[0029] According to an embodiment, the binder material of the
liquid acquisition layer and/or of the liquid distribution layer is
configured as thermal plastic fibers, preferably multi component
fibers, particularly preferably bi-component fibers.
[0030] According to another embodiment of the invention, SAP
particles and/or SAP fibers are disposed moveable relative to one
another in the liquid storage layer when liquid is absorbed and/or
under pressure.
[0031] In an embodiment of the invention, the layered structure has
a first and a second surface, wherein the first and/or the second
surface respectively comprises a binder material layer which is
preferably latex based.
[0032] According to a preferred embodiment, the absorbing structure
comprises a paper tissue layer, a second layer with fluff pulp,
bonding fibers and super absorber, a third layer with fluff pulp
with at least less bonding fibers than the respective second layer
and the respective fourth layer, preferably without bonding fibers
and with super absorber and a fourth layer with fluff pulp and
bonding fibers.
[0033] According to the embodiment of the invention, the liquid
acquisition layer includes a large volume fleece made of treated
and/or untreated cellulose material.
[0034] Particular plies of the absorbing structure can include:
[0035] respectively the same type of cellulose fibers; [0036]
respectively different types of cellulose fibers; [0037] mixtures
thereof; [0038] chemically or physically treated cellulose fibers;
[0039] non treated cellulose fibers; [0040] mixtures of treated and
non treated cellulose fibers; [0041] synthetic fibers by themselves
or mixed with cellulose fibers in treated or non treated form; and
[0042] mineral fibers by themselves or mixed with synthetic and/or
cellulose fibers.
[0043] Particular layers can also exclusively include cellulose
fibers.
[0044] The term "cellulose fibers" in the context of this
disclosure is not interpreted in a restrictive manner. All natural
fibers can be used which are capable or made capable through
chemical or physical treatment to receive liquids and preferably
also to bind liquids. Synthetic fibers and mineral fibers can also
be processed through the same treatment.
[0045] As a matter of principle all layers of the layered structure
can include treated and/or non treated cellulose fibers. However,
it has proven useful that the liquid acquisition layer includes an
air laid layer which includes essentially chemically and/or
physically non treated cellulose fibers. According to another
embodiment, the cellulose fibers of the liquid distribution layer
are chemically and/or physically treated.
[0046] Chemical treatments are e.g. the following: [0047] washing
processes, extraction processes; [0048] bleaching processes; [0049]
dying processes; [0050] fibrillation processes using solvents;
[0051] surface treatment preferably for hydrophilization, increase
of strength or elasticity, e.g. through spraying, dipping,
drenching, washing and similar.
[0052] A physical treatment can be performed through: [0053]
comminution and fibrillation, e.g. cutting, milling, defibration,
[0054] classification, e.g. air classification.
[0055] Depending on the decomposition process and the bleaching
process of the fibers, defined property combinations can be
achieved in the cellulose fibers.
[0056] For example, preferably untreated fibers are used in the
liquid storage layer. This has various reasons. By adding treatment
materials, in particular surface treatment materials, the pulp
loses absorption capability. In order to assure the best possible
absorption in a liquid storage layer, preferably a non-treated pulp
type is being used. It can be compressed best in the process, since
the non-treated fibers adhere together well.
[0057] In the layer structure according to the invention, the
following components can be advantageously disposed, respectively
with reference to the total weight of the layer structure: [0058]
2-10% by weight of a tissue, preferably 3-4% by weight; [0059]
20-60% by weight cellulose fibers in treated form or in non-treated
form, preferably [0060] 35-45% by weight, particularly preferably
respectively 15-25% by weight, treated or untreated cellulose,
[0061] 30-50% by weight superabsorber material, preferably 40-45%
by weight, [0062] 1-5% by weight of a first binder material,
preferably 3-4% by weight, wherein the first binder material
preferably comprises a polymer dispersion, a latex binder is
particularly preferred, [0063] 3-10% by weight of a second binder
material, preferably 5-7% by weight, wherein the second binder
material includes multi-component fibers, preferably bi-component
fibers on the basis of polyethylene and polyethylene terephthalate
(PET), wherein the cited ranges of the components can be
distributed in portions over the particular plies of the structure,
or one or several components can be omitted in a particular
ply.
[0064] When the absorbing structure absorbs liquid and/or is
exposed to a slight pressure, at least the SAP particles and/or the
SAP fibers of the liquid storage layer are capable during liquid
absorption and/or under slight pressure to substantially retain
their external shape. This loading causes a swelling of the SAP
particles and/or the SAP fibers and possibly a deformation. After
unloading, the SAP material is configured to substantially revert
back to its original shape.
[0065] An embodiment of the absorbing structure provides that the
absorbing structure includes a paper tissue ply as a first ply, a
second ply with fluff pulp, bonding fibers and super absorber, a
third ply with fluff pulp and with super absorber, and a fourth
layer with fluff pulp and bonding fibers, wherein the third ply
includes at least less bonding fibers than the respective second
and fourth plies, preferably it is without bonding fibers.
According to an embodiment, it is provided that the third ply
facilitates relative movability between the second and the fourth
ply in a longitudinal direction of the absorbing structure in a wet
state of the absorbing structure.
[0066] The super absorbing material e.g. provided as SAP particles
and/or SAP fibers recited supra is capable of swelling and
typically transitions into a gel type condition. Thus, they cannot
only store water. Rather, the SAP particles are capable for a
disposition in the layered structure as described supra to generate
a suction flow, thus functioning e.g. as a drainage material for
the liquid distribution layer.
[0067] From a chemical point of view, SAP can be copolymers, which
include acrylic acid and sodium acrylate, wherein the ratio of the
two monomers relative to one another can vary. Additionally, e.g.
crosslinking materials are added for polymerization, which link the
formed long chain polymer in particular locations through chemical
bridges. The properties of the polymer can be adjusted as a
function of the degree of crosslinking. For example, SAP materials
can be used as they are shown in EP 08 10 886, in particular also
shown in the art cited therein, which is incorporated into the
disclosure by reference in its entirety. An embodiment provides
e.g. that SAP particles include a coating. The coating can e.g.
dissolve when it comes in contact with a liquid, in order to enable
the absorption of the liquid through the SAP particle in the first
place. Furthermore, SAP material can be used as respectively
evident from DE 10 2004 015 686 A1, DE 698 217 94 and/or DE 10 2004
005 417 A1 respectively, in particular with reference to the
structure, the geometry of the super absorbing polymer and also the
materials and methods employed in its production. These documents
are incorporated into the disclosure in an exemplary manner.
Another embodiment provides that the SAP particles can be granular,
or they can also have a different geometry. They can e.g. be
fibrous, round or shaped differently. Fibers with a super absorber
content can be derived e.g. from DE 102 32 078 A1 and also DE 102
51 137 A1. These are also incorporated in the instant disclosure by
reference.
[0068] The respective layers thus can include identical or
different types of cellulose fibers and/or SAP particles and/or SAP
fibers. This way, the absorption properties of the layer structure
for liquids can be adjusted in a defined manner.
[0069] For example, highly permeable SAP particles and/or SAP
fibers can be used in one ply, which cause a two-stage absorption
and storage effect together with SAP particles and/or SAP fibers in
another ply. For example, SAP particles and/or SAP fibers with high
absorption capability can be provided in a ply that faces the
liquid acquisition layer, and semi-permeable SAP particles and/or
SAP fibers can be provided in another ply. This can provide a
buffer function in the additional ply, which is advantageous in
particular when liquid is introduced several times.
[0070] In a preferred embodiment of the invention, the SAP
particles and/or SAP fibers remain disposed movable relative to one
another in the liquid storage layer for liquid acquisition and/or
slight pressure. This is facilitated by not providing binder
material in the liquid storage layer, e.g. in the form of
thermoplastic fibers like e.g. multi-component fibers. Thus, the
SAP particles and/or SAP fibers can move in the liquid storage
layer, expand well, since there is sufficient space for swelling,
which improves the absorption properties of the layer structure,
and they can simultaneously generate free spaces again, in which a
liquid can be stored for another liquid introduction. Thus, such a
product can comply with the requirements for incontinence products.
Furthermore, the ply can contribute to an improvement of the
straining properties of the layered structure, e.g. also with
respect to an elastic property. Since the cellulose fibers in the
layer structure are not glued together or brought in contact
through a binder material, these fibers and/or the SAP material are
disposed movable relative to one another. Even in used condition,
the so-called wet condition, there is no impairment or only minor
impairment of the components of this layer. Furthermore, the SAP
material in particular the SAP particles act after swelling, which
occurs with a crosslinking or post-linking on the surface of the
particles, like a "lubricant", or the liquid storage layer in its
entirety acts overall like a "sliding layer" between the liquid
acquisition layer and the liquid distribution layer. Preferably,
the SAP particles in dry state already have mostly arc shaped
sections at their surfaces, so that preferably spherical particles
are created in swelled condition, which only introduces
insubstantial changes for the external configuration of the
particles, when transitioning from dry state into wet state.
[0071] The substantially spherical particles provide movability
within the liquid storage layer, and between the liquid storage
layer and the particular layers of the layer structure, when using
the absorbing structure, wherein the movability yields improved
wearing comfort for a disposable product made from the layered
structure. The movability of the SAP particles or SAP fibers in the
liquid storage layer means that the particles in humidified and
swelled condition, this means in wet condition, are still capable
of moving and sliding on one another under load. In unloaded
condition, even a partial rolling movement can occur, which has the
effect that an inner layer configured as a liquid storage layer can
substantially return to its original condition after unloading. In
wet state, the outer layers of the layer structure decouple and the
SAP enlarged to form a solid gel forms a movable sliding
intermediary layer, in which the gel easily facilitates the lateral
relative movement in the X-Y surface like a ball bearing. This
provides wearing comfort without sacrificing material integrity.
The outer layers bonded by a moisture resistant dispersion binder
maintain their desired textile properties with reset forces, so
that the material overall retains the capability to follow a
predetermined shape. Also, when changing shape, the material does
not act in a plastic manner like conventional wet layers made of
fluff pulp and SAP. The movability of the layer structure and a
textile property proximal to the surface are thus maintained.
[0072] Thus, e.g. acting compression-, shearing- or tension forces,
which can be imparted upon the layer structure from the outside by
using an absorber product, can be compensated by the movability of
the liquid acquisition, liquid storage and liquid distribution
layer relative to one another, so that a permanent deformation or
even a delaminating of the layers during use of the absorber
structure is prevented.
[0073] Thus, it is not excluded that sporadic components of the
binder material of the liquid acquisition layer and/or of the
liquid distribution layer can protrude into the liquid storage
layer, and even entirely or partially envelope the cellulose fibers
and/or particular SAP particles or fibers. This creates increased
strength for the interconnection, wherein in particular the outer
surfaces of the liquid storage layer are stabilized in the
transition portions towards the respective liquid distribution
layer, however, the movability of the layers relative to one
another and of the liquid storage layer itself required to obtain
good wearing comfort is being maintained.
[0074] Thus, e.g. another embodiment for an absorbing structure
provides that at least a portion of the binder material, preferably
of the bi-component fibers of the liquid distribution layer and/or
the liquid acquisition layer, is mixed with the cellulose material
of the liquid storage layer in a transition portion towards the
liquid storage layer respectively disposed therebetween.
[0075] In a preferred embodiment of the invention, the binder
material includes thermoplastic fibers in the form of bi-component
fibers. For example, bi-component fibers in particular core-sheath
fibers can be used, in which the sheath has a lower melting point
than the core. It is also provided that the bi-component fibers
include at least a PET. Preferably, the bi-component fibers include
at least a polyethylene, preferably a LDPE or a LLDPE. In a
bi-component fiber with a core-sheath structure, a PET or a polymer
including polypropylene is provided in the core and a polymer
including polyethylene is provided in the sheath. The bi-component
fibers are at least softened far enough through heating, so that
they form a sticky surface, at which cellulose fibers and also
other components of the layer and also components of adjacent
layers are attached when a cooling occurs. According to an
embodiment, cellulose bonding fibers can be used as they can be
derived from DE 69 80 80 61, which is incorporated by
reference.
[0076] Furthermore, the layers of the liquid distribution layer
and/or the liquid storage layer and/or the liquid acquisition layer
can at least partially transition within one another within the
respective transition portion.
[0077] Thus, it is assured that the layers of the ply
interconnection of the absorbing structure have very good cohesion
in comparison to conventional products, not only in dry state but
also in wet state, while still being movable relative to one
another, which facilitates sufficient wet tear resistance, while
maintaining good wear comfort. The tear resistance of the layered
structure according to the invention in dry state is in a range
between 15 to 27 N, and in wet state between 4 to 7 N, wherein the
bending stiffness of the layered structure, which determines the
wear comfort, only has approximately 3 to 8% of the stiffness in
wet condition that it has in dry condition.
[0078] Another embodiment of the invention provides that the liquid
acquisition layer and/or the liquid distribution layer are
compressed more than the liquid storage layer. The absorbing
structure can be configured, so that the liquid distribution layer
has a first and a second surface, wherein the first surface is in
contact with the liquid storage layer, and wherein the liquid
distribution layer is compressed more on its second surface than on
its first surface.
[0079] The liquid storage layer is preferably configured as a
voluminous fleece, and is mostly comprised of cellulose fibers.
These can be treated or untreated like in the liquid acquisition
layer or the liquid distribution layer.
[0080] Though the particular layers of the ply material are mostly
comprised of cellulose fibers, and sporadically comprised of
bonding fibers, preferably thermal plastic bonding fibers, it is
not excluded that also additional fibers of a natural or synthetic
type, e.g. thermoplastic fibers, preferably spunbond fibers, melt
blown fibers, staple fibers and similar, are disposed in the
layers. Through the selection of the disposition and/or preparation
of these fibers, a property gradient can also be generated within a
layer of the ply material, or over one or more plies. In order to
produce these synthetic fibers, polymers are preferred, which
mostly comprise polypropylene, polyethylene, polyester and
polyamide.
[0081] By using thermoplastic fibers, e.g. in the liquid
acquisition layer, repeated wetting with liquid and transferring
this liquid into the liquid storage ply can be improved. For this
purpose, the fibers of the liquid acquisition layer can be
configured accordingly and adapted for a particular application,
e.g. through hydrophobic configuration, wherein incoming liquid
immediately flows in the direction of hydrophilic fibers, or
hydrophilic configuration, wherein capillary paths are created in a
directed manner, which facilitate a quicker liquid transport.
[0082] In an embodiment of the invention, the liquid acquisition
layer, the liquid storage layer and/or the liquid distribution
layer include air laid plies or are made of air laid plies.
[0083] Furthermore, the absorbing structure can include a support
layer, preferably a tissue layer. Thus, the support layer can be
disposed at an outside of the liquid distribution layer.
[0084] Furthermore, the absorbing layer can include an additional
binder layer, e.g. a latex layer, which is disposed on the liquid
distribution layer and/or the liquid acquisition layer.
[0085] Accordingly, an embodiment of the invention includes a
layered structure with first and second surfaces, wherein the first
and/or the second surface include a binder material layer, which is
preferably latex based. A non-treated cellulose pulp type is
preferably used in the outer liquid acquisition layer of the
absorbing structure in order to generate more volume with longer
fibers.
[0086] The first and/or the second surface of a layer structure can
e.g. be an outer surface of a liquid acquisition layer or of a
liquid distribution layer or of a support layer, preferably of a
tissue layer. The absorbing structure can have a gradient with
respect to a pore structure which supports a flow from the liquid
acquisition layer to the liquid distribution layer. The gradient
structure can extend within one layer and also over several layers.
The gradient can preferably cause an increase of the capillary
force. A gradient can e.g. be adjusted through the type of
deposition for the cellulose fibers, through additional compression
and/or through reduction of the number of pores through additional
means, e.g. supplying liquid or binder material, which makes the
pores smaller or partially plugs them. This is possible e.g.
through latex wetting.
[0087] The invention provides a method for producing an absorbing
structure, which includes at least the following steps: [0088]
laying fluff pulp, SAP and a binder material as a second ply on a
support layer; [0089] laying fluff pulp and SAP on the second ply
as a third ply; [0090] laying a fourth ply made of fluff pulp and
binder on the third ply; [0091] preferably applying a binder
material, preferably a latex based binder material on at least one
ply, preferably on the layered structure thus obtained, in
particular on an outer ply of the layered structure; [0092]
supplying the layered structure to a calender which includes a
calender nip; and [0093] compression of the layered structure in
the calender nip.
[0094] The fourth ply functions according to an embodiment as a
liquid acquisition ply, the third and second plys function as a
liquid storage ply and the first ply functions as a liquid
distribution ply. Therefore, preferably the respective plies are
made of the listed respective components without an additional
component being additionally present in the respective plies, or
being fed into the respective plies. Thus, a respective device
according to an embodiment only comprises a supply for the
respective components, or it is configured according to another
embodiment, so that only the components in the respective ply are
supplied and other components in the respective ply, which can be
supplied in an alternative or supplemental manner, can be blocked
and are also blocked.
[0095] An embodiment of the invention provides a method for
producing an absorbing structure which includes at least the
following steps: [0096] laying at least a first layer, preferably
an air laid layer, comprising at least a cellulose material, a
binder material, preferably multi-component fibers, for configuring
a liquid acquisition layer; [0097] laying a ply, preferably an air
laid ply, for configuring a liquid storage layer, which comprises
at least a cellulose material, preferably cellulose fibers and a
super absorbing polymer, preferably SAP particles and/or SAP fibers
and no binder material; [0098] laying a third ply, preferably an
air laid ply, for configuring a liquid distribution layer, which
comprises at least a cellulose material and a binder material,
preferably multi-component fibers; [0099] preferably applying a
binder material layer, preferably latex based, onto a ply,
preferably onto the ply structure thus obtained; [0100] preferably
passing the ply structure through a heating device in order to bond
the ply structure; [0101] supplying at least one ply preferably
from the ply structure to a calender, comprising at least one
smooth roller and an opposite roller forming a calender nip; [0102]
loose compression of the at least one ply preferably of the ply
structure in the calender nip.
[0103] The invention furthermore provides a device for producing an
absorbing structure comprising at least: [0104] a sieve conveyor
belt for laying plies for forming a ply structure; [0105] a first
forming device through which at least cellulose fibers, SAP and
binder materials can be extracted; [0106] a second forming device
through which cellulose fibers and SAP can be extracted, for
forming an additional layer; [0107] a third forming device through
which a binder material and cellulose fibers can be extracted as
another layer; [0108] an application station through which a binder
material, preferably a latex layer, can be applied at least on an
outer surface of the absorbing structure; [0109] a compression
station, preferably a calender, through which the ply structure can
be compressed.
[0110] An apparatus for producing an absorbing structure, in
particular the absorbing structure recited supra, is also proposed,
comprising at least: [0111] a sieve conveyor belt for laying plies
for forming a ply structure; [0112] a first forming device, through
which at least cellulose fibers and a binder material can be
applied to the sieve conveyor belt; [0113] a second forming device,
through which the cellulose fibers and SAP can be applied to the
sifting band for forming another ply; [0114] a third forming
device, through which a super absorbing polymer SAP, a binder
material and cellulose fibers can be applied as another ply on the
sifting band; [0115] at least one application station, through
which a binder material, preferably a latex based binder material,
can be applied on the outer surface of the ply structure; [0116] a
compression station, preferably a calender, through which the ply
structure can be compressed.
[0117] The second forming apparatus is preferably configured, so
that no binder material is supplied or can be supplied through it.
For example, the required connections can be lacking at a binder
material application component or at a binder material supply
component. A connection to a binder material reservoir can also be
interrupted.
[0118] When a binder material is supplied in the second forming
device anyhow, the feeding of binder material, however, is
adjusted, so that less binder material is supplied than in the
first or third forming apparatus. Less binder material means in
this context the absolute supply of binder material per second.
[0119] According to another embodiment of the invention, an
apparatus for producing an absorbing structure is proposed, which
includes at least the following components: [0120] a sifting band
for laying plies, preferably air laid plies for forming a ply
structure; [0121] a first forming apparatus, preferably an air laid
forming apparatus, through which at least one cellulose material,
preferably cellulose fibers, can be extracted; [0122] a second
forming device, through which a binder material, preferably
multi-component fibers can be extracted in order to form a first
layer together with the cellulose fibers; [0123] a third forming
apparatus, through which a super absorbing polymer SAP, preferably
SAP particles and/or SAP fibers, can be laid on the first ply;
[0124] a fourth forming device, through which at least cellulose
fibers and a super absorbing polymer SAP, preferably SAP particles
and/or SAP fibers, can be laid on the first ply and preferably form
a second ply; [0125] a laying device for a third ply including a
cellulose material and a binder material, preferably
multi-component fibers; [0126] preferably an application device
through which a binder material, preferably a latex layer, can be
applied; [0127] a heating apparatus, in which bi-component fibers
and/or the binding material can be activated; [0128] a roller
assembly, preferably a calender through which the layer structure
can be loosely compressed.
[0129] A dosing of the SAP particles and/or SAP fibers can vary
over a width of the material. Also, there is the possibility to
dispose different SAP materials over the width of the material at
various locations and also at identical locations, in particular to
lay them. An embodiment provides that SAP particles are disposed
differently in a layer over a thickness of the material. A position
control is performed e.g. through an oriented alignment of the SAP
supply. There is also the possibility to perform this position
control automatically, e.g. through sensors, image analyzing
processing or similar. Also, there is the possibility to test the
position of the SAP particles and/or the SAP fibers in the layer
automatically, e.g. through detecting the SAP particles and/or SAP
fibers. Thus, SAP particles and/or SAP fibers can include e.g. a
detectable identifier, e.g. a particular material, a color or
another identifier. This facilitates e.g. a correction while the
production process is running.
[0130] The further processing of the absorbing structures can be
performed directly subsequent to the production of the plies. The
absorbing structures, however, can also be rolled up while still
coherent, or they can be made transportable through a festooning
unit. A further processing can then be performed at another
location. A further processing can include e.g. a coating, another
lamination process with one or more other layers, a cutting in
longitudinal and/or transversal direction, another compressing
and/or bonding, a stretching or another process step.
[0131] Components of an air laid production apparatus and its
respective use can be derived e.g. from DE 10 2004 009 556 A1
relating to the production of a fiber web made of cellulose fibers,
DE 10 2004 024 551 B4 relating to a forming head, and also a method
for producing an air laid layer, from DE 10 2004 056 154 A1
relating to a transport device. Furthermore, a method for producing
a fiber fleece according to an air laid method and a fiber suitable
for the method can be derived from DE 103 270 26 A1. Furthermore,
an air laid method and an air laid ply can be derived from DE 199
183 43 A1, in which a bonding fiber is also being used. From WO
2005/080655 A1, in turn, the configuration of an air laid
production plant with various additional components and its
assembly arrangement and purpose can be derived. A detection of SAP
and its controlled dispensing and possible correction and the
production of absorbing structures separated from one another can
be derived e.g. from WO 03/034963 A2.
[0132] The documents recited supra and also the documents recited
therein state additional options, as to how the device can be
configured. In the context of the disclosure of the invention,
these printed documents and also the art recited therein are
incorporated by reference in their entirety.
[0133] The absorbing structure can be used e.g. in a disposable
product for hygiene applications. The absorbing structure can also
be the disposable article itself.
[0134] Preferably, these disposable products are used for baby
diapers, female hygiene and incontinence products.
[0135] Furthermore, such disposable products can be used in the
field of: [0136] medical products, like e.g. absorber materials and
absorber mats; or [0137] industrial products, like e.g. absorbing
materials for receiving liquids.
[0138] Thus, the absorbing structure itself can form at least one
outer surface, preferably both outer surfaces of a product. The
absorbing structure, however, can be at least covered with an
additional ply at least on one side, e.g. also on all sides,
preferably it can be connected to the ply.
[0139] Further advantageous configurations and improvements of the
present invention are described with reference to the following
embodiments with reference to the appended drawings. Thus, the
recited features are not limited to the particular embodiments, but
can be linked with one another and also with the features of
further improvements recited supra, which are not described herein
in every detail.
BRIEF DESCRIPTION OF THE DRAWINGS
[0140] FIG. 1 and
[0141] FIG. 2 illustrate schematic views of cross sections of
various bonded absorbing structures;
[0142] FIG. 3 illustrates a schematic view of a configuration of a
production apparatus;
[0143] FIG. 4 is a schematic view of a cross-section of another
embodiment of the absorbing structure of the present invention;
and
[0144] FIG. 5 illustrates a schematic view of another embodiment of
a production apparatus.
DETAILED DESCRIPTION OF THE INVENTION
[0145] The absorbing ply structure 1 illustrated in FIG. 1 includes
the following layers: [0146] a support layer 2 which includes a
tissue and forms the first ply of the ply structure; [0147] a
second ply 6 made of cellulose fluff pulp 3, SAP particles 4 and
bonding fibers 5, e.g. bi-component fibers; [0148] a third ply 8
made of cellulose pulp 7 and cellulose fluff pulp 3; [0149] a
fourth ply 9 made of cellulose pulp 7, preferably SAP particles 4,
which, however, can also be omitted, and bonding fibers 5; and
[0150] a layer made of a binding material 10, e.g. a latex
binder.
[0151] The plies of the ply structure are disposed on top of one
another and connected with one another in a subsequent calendering
process using heat and pressure. Thus, the outer plies of the
structure are compressed more than the center plies. The ply
material 1 can also be configured without the support layer 2. The
second ply 6 alone or in combination with the support layer 2
assumes the function of a liquid acquisition layer in the layered
structure. Due to the SAP particles 4 provided in the ply 6, this
ply also has a storage function that is reinforced by the ply 8.
The ply 8 includes fluff pulp 3 and cellulose pulp 7. It is only
slightly compressed and includes a high volume of voids. The ply 9
includes cellulose pulp 7, bonding fibers 5 and SAP particles 4,
and can act as a liquid distribution layer. An outer layer made of
binder material 10, e.g. a latex binder, is disposed on the layer
9.
[0152] As a function of the selection of the laying and binding
process, which is an inline process in this case, the particular
layers can have different compression, which is advantageously
higher at both outer surfaces of the layer structure than in its
inner portion. As described with reference to FIG. 1, the function
of the particular layers can also be reversed. Thus, the fourth ply
9 is provided as an acquisition ply for liquid, wherein then no SAP
is provided in the fourth ply, whereas the support layer 2
configured as a tissue forms a barrier layer, since it has the
tightest pores of all plies, and thus the greatest resistance with
respect to liquid passage in this case.
[0153] The absorbing ply structure 1 illustrated in FIG. 2 has the
following layers: [0154] a support layer 2 which includes a tissue
and forms the first ply of the ply structure; [0155] a second ply 6
made of cellulose fluff pulp 3, SAP particles 4 and bonding fibers
5, e.g. bi-component fibers; [0156] a third ply 8' made of
cellulose pulp 7, cellulose fluff pulp 3 and SAP particles 4;
[0157] a fourth ply 9' made of cellulose pulp 7 and bonding fibers
5; and [0158] an outer ply made of a latex binder 10.
[0159] The ply 8', based on its composition, preferably includes
the cellulose fluff pulp and a very slight compression compared to
the adjacent layers. Thus, the SAP particles 4 provided in the ply
8' have high movability in case of a loading through liquid
application or shear loading, e.g. by the user. This movability
within the ply 8' facilitates decoupling the plies adjacent
thereto, so that the plies of the structure are thus movable
relative to one another. The SAP particles 4 which are swelled in
used condition can slide on one another based on the low
compression of the ply 8', thus forming the prerequisite for the
sliding effect observed in the ply 8', which prevents a tearing or
delamination of the ply structure under load.
[0160] FIG. 3 illustrates a schematic depiction of a possible
embodiment for a device 11 for producing an absorbing ply structure
1. An inline process is illustrated with an unwinding apparatus for
providing an air laid material 2, which is laid on a sifting band
2a with drive rollers 2b, a first forming apparatus 13 for
providing fluff pulp 3, a forming device 14 for providing an
absorber, e.g. SAP particles 4, an additional forming device 15,
15' for providing bonding fibers 5, and possibly additional bonding
fibers 5a for forming a first ply 6, which is laid on the support
layer 2. Fluff pulp 3 and pulp 7 are provided through the forming
apparatuses 16 and 16' in order to form a third ply 8, which is
laid on the second ply 6. A forming apparatus 16'' for providing
pulp 7 and forming devices 14 or 15 for providing SAP particles 4
or binding fibers 5 are used for configuring a fourth ply 9, which
is laid on the third ply. A binder material 10 e.g. a latex binder
is applied to the ply 9 through an apparatus 17, e.g. through
application spraying or blade coating. The ply structure can be
activated through heat (not shown) after the binder material is
applied, and subsequently passes through an apparatus 12 for
compressing the ply structure. The apparatus 12 is e.g. a calender
with an assembly of smooth rollers, but an infrared heater, an oven
section or another heater for activating the bonding fibers can
also be provided, which bonds the layers including binder material
with one another, but also respectively to one another.
[0161] FIG. 4 illustrates another preferred embodiment of an
absorbing structure 20 in a schematic view. A second ply 22 is
disposed on a paper tissue 21 configured as a first ply. The second
ply 22 includes pulp, preferably treated pulp, SAP and a binder
material, preferably gluing fibers, e.g. provided in the form of
bi-component fibers. The SAP can e.g. also be provided as a
particle and/or also as a fiber. The second ply 22 is used as a
backup accumulator and can also be used for distributing liquid,
which passes through a liquid accumulator disposed thereabove. The
second ply 22 can e.g. facilitate such function e.g. through
distribution of the SAP, through adjusting the pore size and/or
other means. The paper tissue 21 is preferably compressed far
enough, so that it acts as a barrier for the liquid included in the
second ply and flowing through. Another third ply 23 is disposed on
the second ply 22, which third ply is preferably made of pulp,
preferably from untreated pulp and/or treated pulp and SAP.
Preferably, no binder material is included therein. The third ply
23 is a liquid storage ply. A fourth ply 24 is disposed on the
third ply 23. The fourth ply preferably includes pulp, preferably
untreated pulp, and a binder material, preferably gluing fibers,
e.g. bi-component fibers. Preferably, the fourth ply 24 is made
from these materials. Furthermore, the fourth ply 24 acts as an
acquisition ply, this means it is the first ply to come in contact
with the liquid introduced and conducts the liquid to the
subsequent plies. The first ply and also the fourth ply 24 are
furthermore preferably loaded respectively with additional binder
material, e.g. through impregnation, application through a printing
(coating) method or through a spraying method or in another manner.
Preferably, a latex application is performed respectively. The
binder material that is respectively applied to the first ply and
to the fourth ply from the outside is preferably the same binder
material, in particular the same latex application. An embodiment
provides that the binder materials applied to the respective
outsides differ from one another. The binder material according to
an embodiment is applied in a dosage, so that it only penetrates
the first or fourth ply. Another embodiment provides, that it at
least essentially only remains at the surface of the first or
fourth ply. Another embodiment provides in turn that the binder
material penetrates from the first ply 21 into the second ply 22
adjacent thereto, but not into the third ply 23.
[0162] FIG. 5 illustrates a schematic depiction of another possible
embodiment for a device 11 for producing an absorbing layered
structure 1. An inline process is illustrated with an unwinding
apparatus for providing a support layer as a first ply as an air
laid material 2, which is laid on a sieve conveyor belt 2a with
drive rollers 2b, a first forming apparatus 13 for providing fluff
pulp 3, a forming device 14 for providing an absorber, e.g. SAP
particles 4, an additional forming device 15 for providing bonding
fibers 5, for forming a second ply 6, which is laid on the support
layer 2. Fluff pulp 3 and absorber 4 are provided through the
forming apparatuses 16 and 14' in order to form a third ply 8,
which is laid on the second ply 6. A forming apparatus 16' for
providing fluff pulp 3 and an apparatus 17 for providing a binder
material 10 are used for configuring a fourth ply 9, which is laid
on the third ply. A binder material 10 e.g. a latex binder is
applied to the ply 9 through the apparatus 17, e.g. through
application spraying or blade coating, on at least one outer
surface of the plies. The layered structure can be activated
through heat (not shown) after the binder material is applied, and
subsequently passes through an apparatus 12, e.g. a calender which
comprises a calender nip for compressing the layered structure in
the calender nip. The apparatus 12 is e.g. a calender with an
assembly of smooth rollers, but an infrared heater, an oven section
or another heater for activating the bonding fibers can also be
provided, which bonds the layers including binder material with one
another, but also respectively to one another.
Preferred Embodiments
[0163] In the subsequent embodiments, the ply structure and its
production according to the present invention are described in more
detail. As will be described infra, samples according to the
invention and reference samples were produced, and subsequently,
measurements for determining their thickness, bending length,
bending stiffness, tear strength, bonding strength, the liquid
absorption capacity and regarding their shear strength were
performed.
[0164] Two materials A and B were produced using air laid layers
according to a proposal for a new absorbing structure. Both
materials include three layers, which have been laid on a support
layer made from a tissue. After forming this ply structure, a
spraying of the two outer surfaces of the ply structure is
performed with a dispersion binder material made from a water-based
EVA-latex mixture.
[0165] The material A (VH460.103) has a weight per area of 460
g/m.sup.2 at a thickness of 5 mm (at 0.5 kPa) and a density of
0.092 g/ccm after a calendering step, while material B (VH600.101)
has a weight per area of 600 g/m.sup.2 at a thickness of 6 mm and a
density of 0.100 g/ccm for an analogous production process. Thus, a
first air laid layer is made of a treated fluff pulp, e.g. Biofluff
TDR made by Ternbec Tartas, thermoplastic bi-components fibers,
e.g. HC255 by Trevira or Al-Bounce-Adhesion by FiberVisions, and a
SAP with natural extracts developed in particular for urine odor
control. A second air laid layer is laid on the top side of the
first layer, which air laid layer includes treated fluff pulp, e.g.
Tartas TDR, and non-treated fluff pulp, e.g. GP4881 by Georgia
Pacific, and the SAP recited supra for urine odor control. On the
topside of the second air laid layer, a third layer made of
non-treated fluff pulp, e.g. GP4881, and thermoplastic bi-component
fibers has been laid.
[0166] The layer structures of the samples A and B can include the
subsequent typical portions with respect to the composition of the
layers:
[0167] The tissue portion in the sample A is 3.9% by weight with
reference to the total weight of the layer structure. Layer 1
includes 42.9% by weight pulp, 7.1% by weight bi-component fibers
and 50% by weight SAP, respectively with reference to the total
weight of the layer. The second layer includes 39.3% by weight pulp
and 61.7% by weight SAP, respectively with reference to the total
weight of the layer, and the third layer includes 82.1% by weight
pulp and 17.9% by weight bi-component fibers, also with reference
to the total weight of the respective layer.
[0168] Accordingly, the configuration of the ply structure B with
the particular portions of the respective layers, which refer in
turn to the entire weight of the particular layer, is as follows:
[0169] tissue: 3.0% by weight; [0170] layer 1 with 42.8% by weight
pulp, 7.2% by weight bi-component fibers and 50% by weight SAP;
[0171] layer 2 with 43.1% by weight pulp and 56.9% by weight SAP;
[0172] layer 3 with 75.7% by weight pulp and 24.3% by weight
bi-component fibers.
[0173] The bi-component fibers include a titer of e.g. 2.2 dtex and
fiber lengths of approximately 3 mm. The core includes PET, while
the sheath includes a co-polyolefin or polyethylene. Favor Z 3269
by Stockhausen Inc. was used as a super absorber. Ethylene-vinyl
acetate (EVA)-Latex, e.g. Airflex.RTM.192, with the designation
Vinnapas.RTM.192 by Wacker Chemie AG, with .about.1.3% dry residue
after hardening, the water latex dispersion is used as a latex
binder material on the surfaces of the ply structure. An overview
of the raw materials used for producing the samples
VH460.103/sample A and VH600.101/sample B and their compositions
are provided in tables 1 and 2.
[0174] The production of the ply structures A and B was performed
in the subsequent steps:
[0175] The air laid plies were laid as three subsequent layers on
the wet laid tissue, which is used as a support material, and an
endless fleece was formed. Subsequently, the layer structure was
compressed in a roller nip, which was formed by heated smooth
rollers. Subsequently, the layer structure was sprayed on both
sides with a dispersion binder, the water was extracted, the latex
was cross-linked and the melting of the low temperature melting
sheath of the bi-component fibers was performed in a multistage
drying system. After heating and consolidating the ply structure,
the adjustment of the required thickness was performed in a nip of
a smooth roller calendar.
[0176] The measurement results determined for the samples A,
VH460.103 and B, VH600.101 as well as the reference samples
MT410.104 and VT500.200 are listed in table 3 for the thickness and
in table 4 for the mechanical properties.
Determination of Thickness:
[0177] The thickness is determined according to the standard test
method WSP120.6 (05) for the samples A, VH460.103 and B, VH600.101
and for the reference samples MT410.104 and VT500.200 at ten
respective particular samples with a size of 7 cm.times.7 cm
respectively. Thus, respectively samples in dry condition, in
drenched condition with 10 g of liquid per gram of sample and in
saturated condition were measured. The measured values in table 3
prove that e.g. the material VH600.101 according to the invention
with a density of approximately 0.1 g/ccm is configured very
loosely in dry condition, which provides more free volume for
liquid absorption, and thus its thickness in wet condition does not
increase as much as the thickness of the reference material
VE500.200, which is more compressed in dry condition than the
material VH600.101. Thus, the thickness of the proposed layer
structure during liquid absorption is rather constant, which can be
considered a comfort feature for use.
Determination of Bending Length and Bending Stiffness:
[0178] In order to determine the bending stiffness, the standard
test method WSP90.5 (05) was used. Herein, the samples were cut
into rectangular strips, whose bending length was measured at the
four sides of the strips, and its mean was formed. In order to
determine the bending stiffness in mN.times.cm, the determined
bending length in centimeters was multiplied with the respective
area weight of the sample and divided by 1000. It can be derived
from table 4 that the values for the bending length of the samples
in wet state only include approximately 30% to 35% of the values
for the dry state for the samples. The stiffness for the samples in
wet state, however, only comprises approximately 5% of the
stiffness in dry state. The reference samples MT410.104 and
VE500.200 illustrate a similar tendency with respect to that
property.
Determination of Tear Resistance:
[0179] The tear resistance was determined according to the standard
test procedure WSP110.4 (05) option B, using a Zwick test apparatus
with a clamp distance of 200 mm and a feed of 100 mm/min. According
to table 4, the tear resistance of the samples in wet condition
decreases to approximately 25% of the value, which was determined
for the sample in dry condition (VH600.101), and to approximately
20% of the value for the sample VH460.103. The reference samples
MT410.104 and VE500.200 illustrate a lower decrease of the tear
resistance from the dry state to the wet state of the samples.
Furthermore, the tear resistance values for the sample VH600.101
can be derived from table 4, which were measured for the complete
sample, the tissue and the upper side of the sample, which forms
the liquid acquisition layer. Thus, the complete sample has higher
tear resistance values than the reference samples. This yields an
indication that the outer layers yield the major portion of the
tear resistance.
Determination of Bonding Strength:
[0180] In order to determine the bonding strength according to
WSP401.0, this means the force that is required for tearing the
layers apart, samples with a width of 25 mm were provided, and torn
up at one side for approximately 3 cm. Subsequently, the clamps
have been mounted at their outer plies. Herein, samples were
drenched with 10 g of liquid per gram of sample. Samples with a
weight of approximately 3 g were evenly drenched with 30 ml of 0.9%
NaCl solution, and samples with a weight of approximately 4 g were
evenly drenched with 40 ml of 0.9% NaCl solution, and subsequently
measured quickly, so that the measurement of the samples was
performed in humid state. The side of the samples, which was not
yet torn open, was held for support, this means the material was
always supported by hand at half the elevation of the clamp
distance, so that the high weight of the sample did not falsify the
measurement. Table 4 illustrates that the measured values hardly
change from dry state to wet state. Contrary thereto, the reference
samples MT410.104 and VE500.200 have substantially lower bonding
strength in wet condition than in dry condition.
[0181] It is being assumed that the sliding effect of the liquid
storage layer, which causes a decoupling of the layers of the layer
structure, is capable to absorb a certain amount of shear forces
and pull forces, thus being able to counteract a tearing or
delamination of the sample.
Determination of Liquid Absorption Capability:
[0182] The liquid absorption capability was determined according to
the standard test method WSP10.1 (05) position 7.2. Thus, five
particular samples were used respectively with a size of 10
cm.times.10 cm. Accordingly, particular samples were made from
approximately 6 g of the sample VH600.101. The samples were
pretreated by placing them into 0.9% NaCl solution for
approximately 1 minute and by having them subsequently drip off for
2 minutes vertically suspended.
[0183] In parallel thereto, a method for SAP containing materials
developed by the Concert Corp. was used, "CG Test 4 Rev.5 Test
Procedure for Absorption Capacity", dated Mar. 2, 2009. This yields
different values compared to the values that have been determined
according to the standard test method WSP10.1 (05). For the method
developed by Concert, the samples are submerged for 10 min, and
drip off vertically for 10 seconds. Using the Concert-method leads
to higher values for the liquid absorption capacity of the samples
which can be in the range of over 20 g/g, than this is provided for
the standard test method recited supra, since the super absorber is
configured to bind liquid quickly, but cannot develop its entire
absorption capability within one minute. Table 4 lists the
determined masses for the respective samples and their calculated
mean values.
[0184] The values determined according to the comparison method by
Concert are higher than the values for the standard test
method.
[0185] The liquid absorption capacity LAC in % is determined
according to the standard test method WSP 10.1(05) according to the
subsequent formula:
LAC % = M n - M k M k .times. 100 % ##EQU00001##
wherein M.sub.K is the mass of the dry sample and M.sub.n is the
mass of the wet sample.
[0186] Accordingly, the sample VH600.101 has a liquid absorption
capacity of approximately 1763% or 17.63 g/g. It becomes evident
that the materials according to the invention have a higher liquid
absorption capacity than MT410.104 or VE500.200. This effect is
explained with a larger moveability of the SAP particles or SAP
fibers and the cellulose fibers of the liquid absorption layer,
which provides more free volume for liquid during liquid absorption
and the associated swelling processes through the existing
moveability of the particles.
Determination of the Shear Resistance
[0187] The measurements for determining shear resistance were
preformed according to the measurement method for the tear
resistance. Thus, shearing is interpreted as a type of deformation
of a body under the effect of a force, wherein the force acts
opposite parallel to parallel inner or outer surfaces of an object.
Thus, the surfaces are moved relative to one another. For measuring
the shear resistance respective 25 mm wide strips have been cut out
of the previously recited samples according to the invention and
out of the reference samples, which strips have a length of over 20
cm, typically 26 cm. Thus, all materials were respectively cut to
length in machine direction. Subsequently, the samples were grabbed
at the outer surfaces of the plies and torn open for approximately
3 cm. This was performed at both ends of the strips.
[0188] Initially, the samples were clamped respectively without
using a tape, so that the one opened outer layer, e.g. the material
upper side was clamped in the upper clamp and the other outer
layer, this means the material bottom side remained loose under the
upper engagement clamp. Subsequently, the opened outer layer of the
side opposite to the upper end, thus the material bottom side was
clamped into the lower clamp and the other outer layer, thus the
material upper side remained loose above the lower engagement
clamp.
[0189] As expected, the coherence of the samples VH460.103 and
VH600.101 in the inner layer made of pulp and SAP was not as high
as the tear resistance of the outer layers, this means of the
tissue supported pulp--SAP bi-component bottom side reinforced with
hardened latex binder. For the sample VH600.101, tear resistance on
the side where the tissue is disposed is approximately 3/4 of the
measured tear resistance and the tear resistance of the upper side
of the ply structure which includes a bi-component layer with
hardened latex binder provides approximately 1/4 of the total tear
resistance, while the inner layer, which does not include binding
fibers, thus hardly contributes to the tear resistance. There were
hardly any differences found between measurements with and without
tape.
[0190] In order to be able to also measure the reference materials,
applying tapes was necessary, since the opened outer layers of
these samples prematurely tore off during clamping and starting of
the movement according to the method recited supra. By applying
tape to the upper and under side of the samples the premature
tearing of the outer layers was prevented, since the tear
resistance of the tape at 45 N/cm is above the shear fracture force
of the materials and the outer layers have thus been effectively
fixated against tear off.
[0191] Gluing Tesapack.RTM. 4024 PP, brown variant, onto the
samples was performed in the subsequent steps:
First the samples in a typical A4-hand sample size were glued in
longitudinal direction with a 5 cm wide tape, so that the tape
entered on adhesion bond with the surface of the sample.
Subsequently, the 25 mm wide strips were cut analogously to the
previously recited mechanical standard measuring methods for tear
resistance, bending stiffness and bonding strength with a standard
cutting apparatus to a length of typically 26 cm. Subsequently, the
samples glued with tape on both sides were opened in the center and
torn open for approximately 3 cm, as provided for measuring the
bonding strength according to WSP401.0, however, the tearing open
is performed on both ends of the strip. Like previously for the
tests without using tapes, the clamping was performed in an
alternating manner at the opposite ends, while the one end remained
loose within the clamp distance, so that it does not contribute to
shear resistance and only the shear force in the center layer is
determined.
[0192] High and unfavorable values for the shear fracture force
were observed for the reference materials. Thus, the value for MT
410.104 was at 37 N, which is presumed to be a consequence of the
thermal bonding of the pulp and the bi-component fibers in
combination with the SAP particles of the inner layer. A shear
force of 44 N was determined for the reference material VE 500.200
which is caused by a high density and strength, in particular also
in the interior of the ply structure. Contrary thereto, 5-6 N were
determined for the sample VH 600.101 according to the invention and
4 N were determined for the sample VH 460.103. The measurements
show that the samples according to the invention can be moved more
easily relative to one another even in dry state and thus provide
the advantage of the moveability of pure pulp-SAP-materials in the
interior of the ply structure, wherein, however, the strength in
the outer layers provides the desired comfortable textile
properties.
[0193] A combination of free absorption and mechanical surface
strength in wet condition sets the layer structure according to the
invention apart from the purely mechanically compressed
cellulose-SAP-airlaids as they are known e.g. from McAirlaid's and
Rayonier's EAM. These layer materials do not have sufficient wet
integrity and thus are similar to the properties of so called
"airfelt pads".
[0194] Compared to homogenously thermally bonded airlaid materials
like e.g. the reference material MT 410.104, the deformation of the
ply material according to the invention in wet condition is
reversible which causes reduced stiffness of the ply structure.
Furthermore, the material has sufficient flexibility also in dry
condition through large pores in the center of the ply structure,
this means that the cantilever bending stiffness for this material
also in dry condition is lower than for thermally bonded products
with a stiff matrix.
TABLE-US-00001 TABLE 1 Raw Materials and Composition of Sample A
(VH460.103) TRADE DESCRIPTION CHEMICAL % BY CAS COMPONENT NAME USE
NAME WEIGHT REGISTRY # SUPPLIER 1 GP 4881 or pulp, fibers cellulose
22 65996-61-4 Georgia Pacific NB 416 Weyerhaeuser 2 Biofluff TDR
pulp, fibers cellulose 21 65996-61-4 Tembec Tartas 3 Favor Z 3269
superabsorber poly acrylic acid, partly neutralised 45 9003-04-7
Evonik 4 Vinnapas 192 or polymer dispersion ethylene vinyl acetate
copolymer 3 24937-78-8 Wacker Polymers Elite Ultra soft Celanese 5
T 255 bicomponent fibers polyethylene 5 26221-73-8 Trevira
polyethylene terephthalate 25038-59-9 6 3008 or cellulose tissue
cellulose 4 65996-61-4 Cellu Tissue KB 1800 Swedish Tissue 7 8 9
10
TABLE-US-00002 TABLE 2 Raw Materials and Composition of Sample B
(VH600.101) TRADE DESCRIPTION CHEMICAL % BY CAS COMPONENT NAME USE
NAME WEIGHT REGISTRY # SUPPLIER 1 GP 4881 or pulp, fibers cellulose
24 65996-61-4 Georgia Pacific NB 416 Weyerhaeuser 2 Biofluff TDR
pulp, fibers cellulose 20 65996-61-4 Tembec Tartas 3 Favor Z 3269
superabsorber poly acrylic acid, partly neutralised 45 9003-04-7
Evonik 4 Vinnapas 192 or polymer dispersion ethylene vinyl acetate
copolymer 3 24937-78-8 Wacker Polymers Elite Ultra soft Celanese 5
T 255 bicomponent fibers polyethylene 5 26221-73-8 Trevira
polyethylene terephthalate 25038-59-9 6 3008 or cellulose tissue
cellulose 3 65996-61-4 Cellu Tissue KB 1800 Swedish Tissue 7 8 9
10
TABLE-US-00003 TABLE 3 Measurement of Layer Thickness Thickness0.5
kPa Ratio GSM Thickness 0.5 kPa 10 g/g 0.9% NaCl Thickness 0.5 kPa
moist/dry Product Code Position g/m.sup.2 dry Solution free
Absorption 1 min/2 min drip off VH600.101 A4 631.01 7.55 7 cm
.times. 7 cm sample 1 5.93 9.25 2 6.10 8.16 *measured with Steel
Ruler, since does not fit under Thickness Measuring Device 3 5.85
8.13 4 6.12 8.46 5 5.76 8.27 6 5.75 11 7 7.29 11 8 7.45 12 9 7.59
12 10 7.69 12 avg 6.55 8.45 11.6 VH460.103 A4 468.18 5.09 7 cm
.times. 7 cm sample 1 5.06 6.20 2 4.85 6.03 3 4.93 5.80 4 4.85 5.48
5 4.90 5.64 6 5.05 9.79 7 5.13 9.69 8 5.07 9.81 9 5.14 10.20 10
5.06 10.18 avg 5.00 5.83 9.93 MT410.104 A4 420.01 5.48 7 cm .times.
7 cm sample 1 5.30 5.61 2 5.40 5.56 3 5.28 5.55 4 5.34 5.52 5 5.47
5.54 6 5.41 7.00 7 5.50 7.17 8 5.50 6.97 9 5.43 7.08 10 5.42 7.20
avg 5.41 5.56 7.08 VE500.200 A4 473.84 1.59 7 cm .times. 7 cm
sample 1 1.67 4.67 2 1.64 4.38 3 1.58 4.51 4 1.58 3.66 5 1.59 4.85
6 1.60 7.34 7 1.60 7.24 8 1.56 7.52 9 1.59 6.93 10 1.55 6.60 avg
1.60 4.41 7.13
TABLE-US-00004 TABLE 4 Mechanical Properties of Layer Structure
Bending Bending GSM Length *Stiffness Length *Stiffness RF N*
Bonding N* Product Code Position g/m.sup.2 dry dry wet wet dry wet
dry wet VH600.101 1 622.68 10.15 651.12 3.61 29.29 21.99 6.10 0.213
0.128 2 646.35 10.13 671.89 3.65 31.43 25.40 6.57 0.142 0.148 3
611.18 9.45 515.78 3.58 28.04 24.59 6.16 0.139 0.122 VH460.103 1
477.34 8.58 301.50 2.99 12.76 23.69 4.37 0.143 0.145 2 477.18 7.98
242.49 2.79 10.36 23.45 4.00 0.109 0.109 3 491.84 8.13 264.30 2.94
12.50 22.13 4.70 0.114 0.114 MT410.104 1 432.84 11.68 689.69 3.55
19.36 20.92 8.54 0.799 0.344 2 424.18 11.58 658.68 3.31 15.38 17.35
8.14 0.565 0.342 3 446.68 11.53 684.67 3.39 17.40 23.15 9.85 0.426
0.453 VE500.200 1 484.01 7.15 176.92 2.91 11.93 13.54 2.82 0.460
0.034 2 452.84 6.49 123.79 2.98 11.98 10.48 2.36 0.553 0.056 3
436.01 6.86 140.76 2.96 11.31 11.60 2.48 0.486 0.077 Method Concert
Position 10 Min. submersion/ Product Code 1 2 3 4 5 Mean 10 Sec.
dripping VH600.101 17.75 17.35 17.36 18.06 17.63 17.63 25.98
VH460.103 17.23 18.11 17.29 17.51 17.74 17.58 27.20 MT410.104 15.44
14.97 15.75 15.33 14.83 15.26 18.75 VE500.200 12.37 12.97 12.68
12.98 11.37 12.47 18.94 Tear Resistance VH600.101 complete 16.93
19.87 16.69 VH600.101 Tissue 15.02 14.89 13.65 VH600.101 upper side
5.05 5.63 4.71 4.64 *narrow Strips (1 inch) Absorption: 0.9% NACL
Solution 1 Min. Submersion 2 Min. Suspension
* * * * *