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.

Description

BACKGROUND OF THE INVENTION

1. Technical Field

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.

2. Description of the Background Art

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.

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.

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.

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

Thus it is desirable to have a product available which helps to avoid such impairments of wearing comfort during use.

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.

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.

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.

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.

Preferably, the layered structure according to an embodiment includes at least the following assembly:

• • a first layer, comprising at least a treated fluff pulp, multi component fibers, preferably PE/PETbi-component fibers and a super absorber;
  • a second layer, comprising at least a treated and/or non treated fluff pulp and a super absorber; and
  • a third layer, comprising at least a non treated fluff pulp and multi component fibers, preferably PE/PET bi-component fibers.

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.

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.

Preferably this provides an elastic ply structure which comprises solid outer layers and at least one loose, hardly compacted inner ply.

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.

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/m² and for a thickness of approximately 6 mm it can have a basis weight of approximately 600 g/m². A basis weight in a range between 440 g/m² and up to 680 g/m² 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

According to the embodiment of the invention, the liquid acquisition layer includes a large volume fleece made of treated and/or untreated cellulose material.

Particular plies of the absorbing structure can include:

• • respectively the same type of cellulose fibers;
  • respectively different types of cellulose fibers;
  • mixtures thereof;
  • chemically or physically treated cellulose fibers;
  • non treated cellulose fibers;
  • mixtures of treated and non treated cellulose fibers;
  • synthetic fibers by themselves or mixed with cellulose fibers in treated or non treated form; and
  • mineral fibers by themselves or mixed with synthetic and/or cellulose fibers.

Particular layers can also exclusively include cellulose fibers.

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.

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.

Chemical treatments are e.g. the following:

• • washing processes, extraction processes;
  • bleaching processes;
  • dying processes;
  • fibrillation processes using solvents;
  • surface treatment preferably for hydrophilization, increase of strength or elasticity, e.g. through spraying, dipping, drenching, washing and similar.

A physical treatment can be performed through:

• • comminution and fibrillation, e.g. cutting, milling, defibration,
  • classification, e.g. air classification.

Depending on the decomposition process and the bleaching process of the fibers, defined property combinations can be achieved in the cellulose fibers.

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.

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:

• • 2-10% by weight of a tissue, preferably 3-4% by weight;
  • 20-60% by weight cellulose fibers in treated form or in non-treated form, preferably
  • 35-45% by weight, particularly preferably respectively 15-25% by weight, treated or untreated cellulose,
  • 30-50% by weight superabsorber material, preferably 40-45% by weight,
  • 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,
  • 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The invention provides a method for producing an absorbing structure, which includes at least the following steps:

• • laying fluff pulp, SAP and a binder material as a second ply on a support layer;
  • laying fluff pulp and SAP on the second ply as a third ply;
  • laying a fourth ply made of fluff pulp and binder on the third ply;
  • 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;
  • supplying the layered structure to a calender which includes a calender nip; and
  • compression of the layered structure in the calender nip.

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.

An embodiment of the invention provides a method for producing an absorbing structure which includes at least the following steps:

• • 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;
  • 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;
  • 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;
  • preferably applying a binder material layer, preferably latex based, onto a ply, preferably onto the ply structure thus obtained;
  • preferably passing the ply structure through a heating device in order to bond the ply structure;
  • 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;
  • loose compression of the at least one ply preferably of the ply structure in the calender nip.

The invention furthermore provides a device for producing an absorbing structure comprising at least:

• • a sieve conveyor belt for laying plies for forming a ply structure;
  • a first forming device through which at least cellulose fibers, SAP and binder materials can be extracted;
  • a second forming device through which cellulose fibers and SAP can be extracted, for forming an additional layer;
  • a third forming device through which a binder material and cellulose fibers can be extracted as another layer;
  • 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;
  • a compression station, preferably a calender, through which the ply structure can be compressed.

An apparatus for producing an absorbing structure, in particular the absorbing structure recited supra, is also proposed, comprising at least:

• • a sieve conveyor belt for laying plies for forming a ply structure;
  • a first forming device, through which at least cellulose fibers and a binder material can be applied to the sieve conveyor belt;
  • a second forming device, through which the cellulose fibers and SAP can be applied to the sifting band for forming another ply;
  • 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;
  • 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;
  • a compression station, preferably a calender, through which the ply structure can be compressed.

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.

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.

According to another embodiment of the invention, an apparatus for producing an absorbing structure is proposed, which includes at least the following components:

• • a sifting band for laying plies, preferably air laid plies for forming a ply structure;
  • a first forming apparatus, preferably an air laid forming apparatus, through which at least one cellulose material, preferably cellulose fibers, can be extracted;
  • 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;
  • 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;
  • 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;
  • a laying device for a third ply including a cellulose material and a binder material, preferably multi-component fibers;
  • preferably an application device through which a binder material, preferably a latex layer, can be applied;
  • a heating apparatus, in which bi-component fibers and/or the binding material can be activated;
  • a roller assembly, preferably a calender through which the layer structure can be loosely compressed.

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.

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.

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.

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.

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.

Preferably, these disposable products are used for baby diapers, female hygiene and incontinence products.

Furthermore, such disposable products can be used in the field of:

• • medical products, like e.g. absorber materials and absorber mats; or
  • industrial products, like e.g. absorbing materials for receiving liquids.

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.

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

FIG. 1 and

FIG. 2 illustrate schematic views of cross sections of various bonded absorbing structures;

FIG. 3 illustrates a schematic view of a configuration of a production apparatus;

FIG. 4 is a schematic view of a cross-section of another embodiment of the absorbing structure of the present invention; and

FIG. 5 illustrates a schematic view of another embodiment of a production apparatus.

DETAILED DESCRIPTION OF THE INVENTION

The absorbing ply structure 1 illustrated in FIG. 1 includes the following layers:

• • a support layer 2 which includes a tissue and forms the first ply of the ply structure;
  • a second ply 6 made of cellulose fluff pulp 3, SAP particles 4 and bonding fibers 5, e.g. bi-component fibers;
  • a third ply 8 made of cellulose pulp 7 and cellulose fluff pulp 3;
  • a fourth ply 9 made of cellulose pulp 7, preferably SAP particles 4, which, however, can also be omitted, and bonding fibers 5; and
  • a layer made of a binding material 10, e.g. a latex binder.

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.

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.

The absorbing ply structure 1 illustrated in FIG. 2 has the following layers:

• • a support layer 2 which includes a tissue and forms the first ply of the ply structure;
  • a second ply 6 made of cellulose fluff pulp 3, SAP particles 4 and bonding fibers 5, e.g. bi-component fibers;
  • a third ply 8′ made of cellulose pulp 7, cellulose fluff pulp 3 and SAP particles 4;
  • a fourth ply 9′ made of cellulose pulp 7 and bonding fibers 5; and
  • an outer ply made of a latex binder 10.

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.

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.

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.

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

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.

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.

The material A (VH460.103) has a weight per area of 460 g/m² 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/m² 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.

The layer structures of the samples A and B can include the subsequent typical portions with respect to the composition of the layers:

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.

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:

• • tissue: 3.0% by weight;
  • layer 1 with 42.8% by weight pulp, 7.2% by weight bi-component fibers and 50% by weight SAP;
  • layer 2 with 43.1% by weight pulp and 56.9% by weight SAP;
  • layer 3 with 75.7% by weight pulp and 24.3% by weight bi-component fibers.

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®192, with the designation Vinnapas®192 by Wacker Chemie AG, with ˜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.

The production of the ply structures A and B was performed in the subsequent steps:

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.

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:

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×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:

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×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:

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:

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.

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:

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×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.

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.

The values determined according to the comparison method by Concert are higher than the values for the standard test method.

The liquid absorption capacity LAC in % is determined according to the standard test method WSP 10.1(05) according to the subsequent formula:

$\mathrm{LAC}\%=\frac{M_n-M_k}{M_k}\times 100\%$

wherein M_K is the mass of the dry sample and M_n is the mass of the wet sample.

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

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.

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.

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 ¾ 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 ¼ 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.

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.

Gluing Tesapack® 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.

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.

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”.

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 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 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 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/m2	dry	Solution	free Absorption 1 min/2 min drip off
VH600.101	A4	631.01	7.55
7 cm × 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 × 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 × 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 × 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 4
Mechanical Properties of Layer Structure
			Bending		Bending
		GSM	Length	*Stiffness	Length	*Stiffness	RF N*	Bonding N*
Product Code	Position	g/m2	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

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.