Inventors: Reno Volkmer, Bernd Seger, Thomas Tischer, Jorg Kiihn, Dijana Ladanji

FIELD

[0001] The present disclosure relates to absorbent nonwoven materials and absorbent products such as disposable absorbent articles, diapers, feminine hygiene articles, incontinence devices, food pads, bed pads, pet pads, wound care products, and the like, and to the manufacture of such nonwoven materials and products. The present disclosure is particularly applicable to air laid nonwoven materials.

BACKGROUND OF THE DISCLOSURE

[0002] Nonwoven fabric structures are known for applications in absorbent articles, such as baby or adult incontinence products, feminine hygiene products, food pads, bed pads, pet pads, wound care products, and the like. In particular, air laid nonwoven materials have been used in such applications. In addition to effectively and efficiently satisfying the primary liquid handling functionality of acquisition, distribution and storage of the exudates, nonwoven fabric structures require the perception and acceptance by the user or wearer, such as with regard to wearing comfort, also have desirable aspects.

[0003] Such materials have generally included multilayer absorbing structures using cellulose and super absorbing polymers (“SAP”) in the form of SAP particles and/or SAP fibers. The materials can further include binder materials used for stabilizing the absorbent layer. By stabilizing, it is meant that the binder materials provide added rigidity. The binder materials can be in the form of fibers, powders, hot melt glues, and/or solvent-binder mixes for application in liquid or similar form. Such materials are described for example in U.S. Patent 10,512,567, filed January 12, 2015, entitled SOFT ABSORBENT SANDWICH WEB COMPRISING HIGH CONCENTRATIONS OF SUPERABSORBENT MATERIAL, CELLULOSIC FIBERS AND SURFACE APPLIED BINDER, which is incorporated herein in its entirety.

[0004] Nonwoven materials can include, among others, air laid nonwoven fabrics and non-air laid nonwoven fabrics. An objective of this disclosure is to achieve better flexibility, resilience, cushion, and comfort than found in the presently available air laid nonwoven based products and non-air laid nonwoven based products. [0005] For instance, U.S. Patent 6,261,679 describes a process by which a nonwoven containing a foam is created from a removable gas phase. Gas is injected under pressure into the binder or formed through the addition of gas generating chemistries, and the foamed nonwoven is created through releasing the gas. However, the degasification of the binder creates undesirable holes in the fibrous structure due to the arrangement of fibers. Thus, an additional step of reorienting the fibers is required to close the holes.

[0006] U.S. Patent Application Publication 2015/0335498 describes discrete portions of foam integrated or embedded into a heterogenous mass. However, based upon the process, the entire nonwoven volume cannot be embedded in a single and continuous homogenous mass of foam. Further, the foaming chemistry described therein is an emulsion of one liquid in another that requires polymerization after foaming.

[0007] International Patent Publication WO 2021/018544 describes a product consisting of a layer of textile material discrete from and laminated to a foam layer. Thus, it similarly fails to describe a homogenous configuration of fiber and foam that would allow for adequate comfort and resilience.

[0008] U.S. Patent Application Publication 2011/0155338 describes and air laid substrate that can have increased thickness through the addition of thermally expandable microspheres into the substrate. However, the microspheres are not embedded into the foam matrix, because the intent of this publication is to expand the thickness of an air laid product, and hence does not describe microspheres embedded in a foam matrix. Thus, the disclosure cannot achieve improved resilience and comfort from a continuous matrix of a foamed binder material together with a nonwoven. In addition, the final product does not achieve a microsphere closed cells within the foamed matrix.

[0009] U.S. Patent 8,034,847 describes a composition containing expandable microspheres having an ionic component through treatment with an ionic chemistry. The microspheres are intended to expand the thickness of a fibrous web and are not embedded in a foamed matrix. [0010] U.S. Patent 8,382,945 describes the use of expandable microspheres in papermaking processes to increase the paper bulk. As a result of the disclosure, the microspheres are not embedded in a foamed matrix in the final product. Nor do the expandable microspheres form closed cells in a homogenous matrix of a nonwoven material. [0011] As can be seen, there is a need to achieve a nonwoven product wherein the entire or substantially the entire nonwoven volume is embedded in a single and continuous homogenous mass of foam.

[0012] Thus, new products and methods of manufacture are needed to provide improved nonwoven fabric structures and associated absorbent products that have improved comfort, flexibility, resilience, cushion, and comfort as a less expensive alternative to the non-air laid based products. In addition, improvements are needed to non-air laid nonwoven materials to provide the same improved functionality at a lower cost.

[0013] In addition, in certain applications thermal and acoustic insulation is further desired. Such improved nonwoven fabric structures and materials should provide significant thermal and acoustic insulation.

[0014] Further, it would be preferable if such nonwoven fabric materials and products were made from sustainable foam composites and were readily adaptable for use in outdoor durable applications, such as for athletic shoes soles and the like.

[0015] The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.

SUMMARY OF THE DISCLOSURE

[0016] It is desirable to have a product available which helps to provide wearing comfort during use.

[0017] Thus, the present disclosure provides products and methods for producing and using an absorbing product which facilitates better properties during use, in particular, increased flexibility and resilience.

[0018] Through the structures and methods described herein, it is possible to achieve a nonwoven absorbent material that is cushiony and resilient for use, for example, in feminine hygiene and adult incontinence absorbent cores, and wound care products having good adhesive release characteristics. This disclosure is particularly suitable for use in air laid nonwoven materials.

[0019] It is further achievable to obtain nonwoven absorbent structures having good acoustic and thermal insulation. [0020] In addition, sustainable foam composites described herein can be used in outdoor durable applications, such as, for example, athletic shoe soles and the like.

BRIEF DESCRIPTION OF THE DRAWINGS [0021] Fig. 1 shows the top surface of a foam on a nonwoven material.

[0022] Fig. 2 shows the top surface of a foam on a nonwoven material.

[0023] Fig. 3 is a micrograph of a foam on a nonwoven material.

[0024] Fig. 4 is a micrograph of a cross-section of a foam on a nonwoven material.

[0025] Fig. 5 is a micrograph of a foam on a nonwoven material.

[0026] Fig. 6 is a micrograph of a cross-section of a foam on a nonwoven material.

[0027] Fig. 7 shows the top surface of a nonwoven material containing expanded expandable microspheres.

[0028] Fig. 8 shows the top surface of a nonwoven material containing expanded expandable microspheres.

[0029] Fig. 9 is a micrograph of a nonwoven material containing expanded expandable microspheres.

[0030] Fig. 10 is a micrograph of a cross-section of a nonwoven material containing expanded expandable microspheres.

[0031] Fig. 11 is a micrograph of a nonwoven material containing expanded expandable microspheres.

[0032] Fig. 12 is a micrograph of a cross-section of a nonwoven material containing expanded expandable microspheres.

PET ATT ED DESCRIPTION OF THE DISCLOSURE [0033] Absorbent nonwoven structures of the present disclosure can comprise cellulose and super absorbent polymers (SAP) arranged together in either single layers or multiple layers, for example, an absorbent structure may comprise one, two, or three or more plies, each representing a layer. The layers can contain cellulose and/or SAP m the same or different concentrations.

The cellulose and/or SAP form the function of liquid acquisition and distribution. This has been described in, for example, U.S. Patent 10,512,567. [0034] “Absorbent structures” in the context of this disclosure is not to be interpreted in a restrictive manner or limiting. Instead, absorbent structures include all forms of absorbent structures containing cellulose and/or SAP, including, for example, nonwoven materials.

Further, in particular embodiments, the absorbent structures comprising cellulose and/or SAP can be prepared through known air laid processes. Cellulosic absorbent material can also be provided in the form of man-made fibers, for example, Viscose or Tencel®. In addition, the absorbent structures discussed herein are not limited in any manner as to the size and/or shape of the absorbent structures but applies to all nonwoven absorbent structures and/or materials.

[0035] “Cellulose” in the context of this disclosure is not to be interpreted in a restrictive manner. For example, the cellulose used in the present disclosure can include cellulose fibers and or cellulose particles. All fibers can be used which are capable or made capable through chemical or physical treatment to receive liquids and preferably also to bind liquids, including, but not limited to, natural, synthetic, and/or mineral fibers.

[0036] “SAP” in the context of the present disclosure can be any super absorbing polymer suitable for use in nonwoven absorbent materials, and particularly, air laid nonwoven absorbent materials. One suitable SAP material can be a copolymer of acrylic acid and sodium acrylate, wherein the ratio of the two monomers relative to each other can vary. Additionally, crosslinking materials can be added for polymerization, which link the formed long chain polymers through chemical bridges. The properties of the polymer can be adjusted as a function of the degree of crosslinking. The SAP can preferably be in the form of SAP particles and/or SAP fibers.

[0037] In absorbent structures comprising multiple layers, each layer can include identical or different types of cellulose fibers and/or SAP particles and/or SAP fibers. In addition, each layer can include identical or different concentrations of the cellulose fibers and/or SAP particles and/or SAP fibers. For example, in one layer the concentration of cellulose fibers may be greater than the concentration of SAP particles and/or SAP fibers, while in another layer, the concentration may be similar.

[0038] Absorbent structures having multiple layers can include a sequence of two layers including at least one liquid absorbent layer, a subsequent liquid storage layer with SAP, preferably configured in the form of SAP particles and/or SAP fibers and a subsequent liquid distribution layer, wherein the layers are connected and form a layer structure. Thus, at least the liquid storage layer and the liquid distribution layer at least respectively include a nonwoven material as main component, preferably an air laid layer, which includes cellulose fibers. At least the storage layer includes SAP particles. The super absorbent polymer of the liquid storage layer, preferably provided in the form of SAP particles and/or SAP fibers, extends partially into the liquid distribution layer and thus comes into direct contact with the liquid which is distributed in the liquid distribution layer of the product. The SAP causes a back suction effect for the liquid which has entered through the liquid absorption layer and the liquid storage layer into the liquid distribution layer.

[0039] A liquid absorption layer can include a nonwoven material, and preferably an air laid nonwoven material. Preferably this layer at least to a major portion is made from cellulose fiber. It can furthermore be provided that the liquid absorption layer includes thermoplastic fibers. These fibers can be for example gluing fibers. For example, bico fibers, in particular core- jacket-fibers can be used in which the jacket has a lower melting point than the core. Alternatively, a liquid absorption layer can include a voluminous fleece made from thermoplastic fibers. The voluminous fleece can be a carded fleece. The voluminous fleece can be a hot air solidified fleece made from thermoplastic fibers. The voluminous fleece can include fibers made from polyester, polypropylene, viscous and/or polyethylene. The voluminous fleece can have a weight per unit area of 5 to 90 g/m ² . An embodiment for a usable material is Paratherm Loft 142/25 made by TWB Corporation.

[0040] Layers of an absorbent structure can be produced in an in-line process. Optionally, at least one layer of the absorbent structure can be prefabricated and supplied to the manufacturing process as an intermediary product. The intermediary product can be rolled onto a winder and subsequently rolled-off again at the production line and supplied to the process. A layer can be provided that is to be used as a liquid absorption layer in the subsequent absorbent structure. Alternatively, a prefabricated layer can be provided which functions as a liquid distribution layer in a subsequently finished absorbent structure. Furthermore, at least one layer can be configured with multiples layers, for example, the liquid distribution layer can be connected with another layer, preferably with a smaller pore size than the fiber layer provided with the liquid distribution layer, for example, a tissue layer. The tissue layer can be arranged directly adjacent to an air laid layer and connected with an air laid layer which forms the distribution layer. The tissue can support liquid distribution through having a smaller pore size than the air laid layer, which causes a higher capillary force. The tissue, for example, can form an outside of the absorbent structure. A voluminous fleece made from thermoplastic fibers, preferably staple fibers can for example form the other outside of the absorbent structure.

[0041] The SAP material, for example, provided in the form of the SAP particles and/or SAP fibers described supra is swell-capable and typically transitions into a gel type condition. Thus, the fibers cannot only store water. Rather, the SAP particles and/or fibers in an arrangement as described supra in the layer structure are capable of generating a suction flow and thus can be used for example as drainage material for the liquid distribution layer.

[0042] Chemically speaking, SAP can be co-polymers which include, for example, acrylic acid and sodium acrylate monomers, wherein the ratio of the two monomers relative to one another can vary. Additional, for example, cross linkers can be added during polymerization, wherein the cross linkers connect the formed long chain polymers at some locations with one another through chemical bridges. The properties of the polymer can be adjusted as a function of the degree of cross linking. For example, two different SAP materials, for example, two different SAP particles, two different SAP fibers and/or SAP particles and SAP fibers that differ from one another and have properties that different from one another can be used. Thus, the difference can be in the liquid absorption capability, the speed of liquid absorption, the swelling itself during liquid adsorption, a time delay until the liquid absorption starts, a liquid absorption rate or another parameter. Various SAP materials can be arranged in a mixed manner and also separate from one another in various portions. The different portions cannot only be arranged in machine-direction and cross-direction of a processing with respect to an air laid production device. Rather also an arrangement along a thickness of the material can differ, thus, in particular, different portions can be configured.

[0043] Based upon the function of the respective layer, different concentrations of SAP and cellulose may be contained therein. For example, in a first layer, the cellulose fibers can be between 60% by weight to 70% by weight and a second fiber between 30% by weight and 40% by weight with reference to the total weight of the layer. In another layer including cellulose fibers and SAP particles and/or SAP fibers can contain the SAP fibers and/or SAP fibers in a range between 15% by weight to 35% by weight with reference to the total weight of the layer.

In other layers, for example, there can be essentially 100% cellulose. Alternately, the product can be entirely free of SAP. [0044] A non-woven absorbent structure, including an air laid nonwoven absorbent structure, can further include binder materials. Based upon the purpose of the specific layer the amount of binder materials included in the absorbent structure can be adjusted. For example, a liquid storage layer can include less binder material than a liquid storage layer adjacent to the liquid storage layer. Alternatively, or in addition, a first liquid storage layer can include binder material and the second liquid storage layer can include no binder material or binder material at a concentration lower than the first liquid storage layer.

[0045] An embodiment of a nonwoven structure can comprise the following components, respectively with reference to the total weight of the layer structure: 20-60% by weight cellulose fibers, preferably 35-45% by weight, particularly preferably 15-25% by weight; 30-50% by weight SAP, preferably 40-45% by weight; 4-15% by weight binder material, preferably 8-11 % by weight.

[0046] The binder material of the present disclosure may be latex binders. A single binder material can be included in the absorbent structure or more than one binder material can be included. The binder can be, for example, a polymer dispersion, and preferably a latex binder. [0047] For example, in certain embodiments, the binder can be a self-crosshnkmg latex binder. A preferably self-crosslinkmg binder is a vinyl-acetate-ethylene copolymer. The binder can optionally be polymerized prior to addition to the nonwoven material such that, for example, a self-crosslinked polymer can be added to the nonwoven material. The absorbent structure can include from about 1-5 % binder, and preferably from 2-4 % binder based on the weight of the absorbent structure.

[0048] In a first embodiment, a nonwoven structure can have binder materials incorporated into its structure to form a stable foam nonwoven material. By stable foam, it is herein meant, a foam structure that keeps its integrity during the application and drying step. Alternatively, a nonwoven structure can have a meta-stable foam and result in a meta-stable nonwoven material. By meta-stable foam, it is herein meant that the initially applied wet foam layer, which is put on the air laid and/or nonwoven surface keeps its integrity until it is subjected to a drying at elevated temperature. Flere the foam is slowly transformed to a homogenous layered structure. The binder materials can be applied to the surface of the air laid material to form a layer of foam adjacent to the surface of the nonwoven structure. Alternatively, the foam can penetrate into the nonwoven structure to impregnate the nonwoven structure and form a single and continuous homogenous mass of foam. In forming the mass of foam, the foaming binder material can remain in the nonwoven structure containing the single and homogenous mass of foam. The foam can be a polymer dispersion attached to the surface of the nonwoven air laid material. Suitable polymers for the foam are the binders recited herein for example, but not limited to, copolymers of vinyl acetate and ethylene. In certain applications the foam can be crosslinked. VINNAPAS® 192 and VINNAPAS® AN214 manufactured by Wacker have been found to be particularly suitable to form the foam component of the present disclosure.

[0049] This results in a nonwoven absorbent structure have resilient partially open-celled foam integrated on and/or into the structure in a continuous and homogenous mass of foam containing the nonwoven structure. Such a structure can result in a nonwoven product having sufficient cushion. Depending on various end use applications, the foam can be applied entirely on the surface of the nonwoven structure, it can partially embed inside the nonwoven structure, and or it can entirely embed inside the nonwoven structure. By resilient partially open-celled foam integrated on and into the nonwoven structure, it is meant a continuous gaseous phase may exist between the respective cells.

[0050] In addition, in certain embodiments, the absorbent structure can further incorporate fibers into the foam. The suitable fibers for the presently described absorbent structure can be short or long fibers. It has been determined that short fibers are particularly suitable, for example, fibers that are <lmm. Suitable fibers can be pulp fibers from, for example, eucalyptus species, such as eucalyptus soft wood pulp fibers, micro fibrillated cellulose, and synthetic hollow short fibers. A particular suitable synthetic hollow short fiber is cellulose acetate fibers. As used herein, micro fibrillated cellulose is a natural material comprising cellulose fibrils that have been separated from a source, for example, wood pulp. Through a fibrillation process, the cellulose fibers are separated into a three-dimensional network of microfibrils having a larger surface area. The foam can contain any proportion of the above-referenced fibers, for example, in some embodiments, the foam can contain 50 % eucalyptus pulp fibers and 50 % cellulose acetate hollow fibers.

[0051] In some embodiments, it was determined that short staple fibers could be particularly suitable to incorporate into the open-celled foam of the present disclosure. Such short staple fibers result in an absorbent structure having increased absorbency, in other words, faster fluid acquisition into the absorbent structure than open-celled foam absorbent structure without the short fibers contained in the open-celled foam structures. In particular, short fibers having a length of from 0 5-4 mm were found to be particularly suitable and resulting in improved absorbency. In particular embodiments, eucalyptus soft wood pulp fibers having a fiber length of from 0 8 0.9 mm can be used. In other embodiments, cellulose acetate hollow fibers can be included having a length of less than 3 mm.

[0052] The nonwoven structure can further include a foam forming agent. The foam forming agent can be utilized to prepare the latex binder prior to or after application the nonwoven material. The foam forming agent can be a cationic, anionic, non-ionic, amphoteric surfactant or a combination thereof. For instance, the foam forming agent can be a blend of cationic and anionic compounds. The surfactant can be chosen, but is not limited to, from the groups of sulfates, sulfonates, ethoxylated fatty acid esters, quaternary ammonium compounds, betaines, or amino acid derivates.

[0053] The nonwoven absorbent of the present embodiment includes a foam structure having at least partially open-celled foam. As an example, an open celled foam phase of the present disclosure can have a preferable pore size in the range of 1-500 pm, more preferably in the range of 10-300 pm and even more preferably of 20-200 pm. The pore distribution is preferably in the range of 100-100.000 pores /cm ³

[0054] Such nonwoven absorbent structures can further provide improved acoustic and thermal insulation as compared to nonwoven absorbent structures without the foam. Due to the open- celled foam phase, these nonwoven absorbent structures achieve improved acoustic and thermal insulation.

[0055] The teachings of the present disclosure apply to nonwoven absorbent structures of any thickness. For example, the thickness of the combined foam and nonwoven structure can be from 0,1-10 mm, more preferably 1-5 mm and even more preferably 2-3 mm.

[0056] Instead of thickness, in certain aspects of the present disclosure, the relative quantity of foam to nonwoven absorbent structure can provide improved results. The foam phase of the nonwoven absorbent structure can be from 0 01 0.8 g/cm ³ more preferably 0.03 0.5 g/cm ³ and even more preferably 0 05 0.25 g/cm ³ .

[0057] In particular embodiments of the presently disclosed absorbent structure, the pore size distribution across the absorbent structure can vary. For example, the pore size of the open- celled foam can be larger on one side of the absorbent structure and smaller on the other side of the absorbent structure. In certain circumstances, the size of the pores can form a gradient in the absorbent structure. In one embodiment, the pore size on one side of the absorbent structure can be larger than the pore size on the other side of the absorbent structure. In such an embodiment, the pore size can gradually reduce from the large pore size to the smaller pore size as it traverses the absorbent structure. As an example, the average pore size of the open-celled foam of the larger pore size can have a range of from 120 - 200 pm, and in particular approximately 160 pm and the average pore size of the smaller pore size side of the absorbent structure can have an average pore size from 70 - 100 pm, and in particular 80 pm. In preparing the absorbent structure, alternating settings of the foam generator can vary the pore size distribution for the foams. For instance, varying temperature, viscosity, and/or plasticizer can influence pore size during the manufacture of the absorbent structures.

[0058] The binder add on was monitored by weighing the substrate prior and after the addition of the wet foam on the substrate. Calculation of binder add on can be conducted employing the known solid content of the wet foam. The added foam content can be in the range of 10-150 g/m ² .

[0059] Absorbent structures of the present disclosure can be improved through the incorporation of a foam integrated into or on nonwoven absorbent materials. The foam can be formed through multiple processes, such as the processes described herein. The incorporation of foam to make a continuous homogenous mass of foam containing a nonwoven structure, as described herein, allows for a more flexible, comfortable, resilient, and stable air laid product in the applications described herein.

[0060] The absorbent structures described herein can further include a moisturizer. A person of ordinary skill in the art would recognize suitable moisturizers for use in connection with the presently described absorbent structure. A particular suitable moisturizer is Plastilys moisturizer, manufactured by the Roquette company. The moisturizers of the present disclosure are liquid products that keep moisture in the absorbent structure.

[0061] Methods of manufacturing nonwoven absorbent structures are known. For example, such methods have been described in U S. Patent 10,512,567. Nonwoven absorbent structures of the present disclosure can be produced in either a discrete structure or as part of continuous web manufacturing process. [0062] To a nonwoven absorbent structure, a binder material, with or without the foam mixture can be applied to the surface. The foam mixture is the composition that is added to the non woven material to generate the open-celled foam portion of the non-woven material. Various different binder materials are suitable for use herein. Based upon the composition and structure of the binder material, the binder material can be applied in a variety of manners. For instance, if the binder material is in the form of a latex emulsion, the binder material can be applied on the surface of the air laid structure using a foam foulard applicator. In some embodiments, the binder material can be a polymer prior to addition to the nonwoven material. Alternatively, the binder material can be prefoamed and applied using a knife applicator. In order to prefoam the binder, in one embodiment, vigorous stirring with the aim to incorporate air, can be applied to the foaming mixture. In addition, it is also feasible to generate gas bubbles employing pressured air or any other gas, which is guided through or generated via chemical reactions in the mixture. When adding the binder material, the binder materials can be applied while having a 40-50% solid content with the remaining amount being water. A person skilled in the art would recognize that different solids contents can be utilized depending on the density of the open- celled foam desired in the absorbent structure.

[0063] In an embodiment, vinyl acetate-ethylene (“VAE”) copolymers can be used alone or together with polyurethane, polyester, or a polyurethane/polyester combination to make the foam of the present disclosure. In another embodiment, polyurethane, polyester, or a polyurethane/polyester combination can be used to make the foam of the present disclosure. Suitable VAE copolymers are manufactured as VINNAPAS ^® from Wacker Chemie AG.

Suitable polyurethane/polyester compositions are manufactured as EPOTAL ^® Eco, available from BASF Corporation. It has been determined that, for example, a mixture including VAE copolymers, polyester, and polyurethane, can strengthen foam stability and resiliency in the absorbent structure.

[0064] In certain embodiments requiring additional stabilization of the absorbent structure, stabilizing compounds can be added to the nonwoven absorbent structure. Suitable stabilizing compounds are Ammonium Stearate, Sodium Stearate, and combinations thereof. The quantity of added stabilizing compounds can vary depending on desired final product applications. The chemical compound selected as a stabilizing compound can similarly depend on final applications and final properties of the nonwoven absorbent structure. [0065] Excess liquid should be removed from the nonwoven absorbent structure during manufacture. In order to remove the excess liquid, for example, the additional water added to the nonwoven absorbent structure during formation, heat is applied to the nonwoven absorbent material. The heat can be provided by placing the nonwoven absorbent material in an oven. The heat can also be provided by passing the nonwoven absorbent structure through an oven.

[0066] Through the process described herein, after passing the nonwoven absorbent structure through the oven, a nonwoven structure is acquired having a stable foam or meta-stable foam integrated within or adjacent to the nonwoven material.

[0067] In another embodiment, a nonwoven material can be made via foam impregnation through the inclusion of thermoplastic expandable microspheres inside the structure. Such thermoplastic expandable microspheres can be incorporated into the nonwoven material during manufacture of the nonwoven absorbent structure. The thermoplastic expandable microspheres are impregnated into the nonwoven material during formation of the foamed nonwoven structure. The thermoplastic expandable microspheres contain a shell encapsulating a gas or liquid. This can be hollow polymeric spheres each of which includes a thermoplastic shell encapsulating, for example, liquid hydrocarbon or an expandable gas. Under the application of heat at a sufficient temperature, the shell softens and the increased pressure from the hydrocarbon liquid expanding or the gas expanding causes the microsphere to expand, increasing the sphere volume by a significant factor. For example, the sphere volume can increase by 80 to 100 times its original volume. The density of the microsphere after expansion is significantly lower than pre expansion and can be lower than 30 kg/m ³ . On cooling down, the shell of the microsphere remains in an expanded state. The expanded state in the air laid nonwoven absorbent structure provides a stable resilient structure. Suitable microspheres for this application are available from Crerax, under the expandable microsphere product line, or Nouryon, under the Expancel product line.

[0068] The concentration of the thermoplastic expandable microspheres contained in the nonwoven air laid absorbent structure depends on the desired properties of the final product. However, suitable concentrations of up to 50% by wt.%. of the nonwoven absorbent structure have been found to result in a suitable product having beneficial properties. The result of the expansion of the thermoplastic expandable microspheres results in a foamed nonwoven material having closed-celled spheres contained therein. [0069] To prepare a foam impregnated nonwoven in accordance with this embodiment, a nonwoven absorbent structure is provided, for example, as a discrete structure or as part of manufacturing web. To the nonwoven absorbent structure, thermoplastic expandable microspheres are added. The thermoplastic expandable microspheres can be embedded in dry form into the nonwoven absorbent structure or can be blended into an aqueous spray that is applied to the nonwoven absorbent structure. Similar to the other embodiments described herein, binder materials and/or stabilizer compounds can further be added to the nonwoven absorbent structure.

[0070] Heat can then be applied to the nonwoven absorbent structure. Any source of heat can be used, but it has been found preferable to apply heat by placing or passing through the nonwoven absorbent structure in an oven. The oven can either be a discrete oven if the material is a discrete portion, or it can be an oven that is suitable for a continuous web of nonwoven material. The application of the heat allows the thermoplastic expandable microsphere to expand in volume significantly. Suitable temperature ranges for the oven are from 100-180 °C]. A suitable duration for the application of heat is 10-120 min for a discrete portion, for a continuous web the drying temperature can be higher (120-200 °C) with a simultaneous reduced dwell time (0.3-2 min). After the application of heat, the nonwoven absorbent structure is allowed to cool, resulting in a stable resilient absorbent structure.

[0071] The present disclosure provides nonwoven absorbent structures having an open-celled foam integrated into the air laid structure. The methods and structures described herein can result in the foam either being applied entirely on the surface of the structure, partially embedded inside the nonwoven structure, or entirely embedded inside and/or throughout the structure.

Based upon the application of the nonwoven absorbent structure, the chemical properties of the continuous foam can be altered such that the foam has either a hydrophobic or a hydrophilic property. The chemistry can be altered by wetting agents, for example, ethoxylated unsaturated carbohydrates (Surfynol range manufactured from Evomk or Plastilys manufactured from Roquette), which can improve the water absorption of the substrate. Contrariwise the generation of hydrophobic foams can be achieved by employing silane or oligomeric siloxane-based agents.

EXAMPLES

Example 1: [0072] Two different types of foams were investigated: the meta-stable and stable foams of VINNAPAS ^® 192 manufactured by Wacker.

[0073] An air laid nonwoven structure with a grammage of 100 g/m ² was chosen as a coating substrate. The foam can be generated via vigorously mixing Subsequently, the mixture can be applied via rod or knife edge coating on the air laid nonwoven structure to achieve coatings with different thicknesses. The combined material is then dried by elevated temperature, preferably below 100°C, more preferably below 70°C. For the meta-stable foam (Sample 1), VINNAPAS ^® 192 was mixed with a surfactant, e.g., RUCO ^® -COAT FO 4010 manufactured by Rudolf Group, preferably at a concentration of 1% or higher (Sample 1).

[0074] To fixate the foam to form a stable variant, a stabilizer, e g., RUCO ^® -COAT FO 2000 manufactured by Rudolf Group can be additionally added, preferably with concentration of 5% or higher (Sample 2) prior to foam generation.

[0075] Figure 1 and Figure 2 show the top surfaces of Sample 1 and Sample 2, respectively. As it is obvious, the meta stable foam on Sample 1 shows an increased pore size compared to Sample 2. Figure 3-6 show additional micrographs of the aforementioned samples and depict the porous nature of the foam surface (Figure 3 and Figure 5) as well as a cross-section of the samples (Figure 4 and Figure 6). There was good top surface coverable of the absorbent structure. No binder strike through could be observed on any of the samples. By binder strike through, it is herein meant, a visible binder content on the opposite side of the nonwoven material to the application. Table 1 describes the properties the air laid nonwoven absorbent structure after the application of a meta stable and stable foam of VINNAPAS ^® 192.

Table 1

Example 2:

[0076] Two different types of foams were investigated: the meta-stable and stable foams of VINNAPAS ^® 192 manufactured by Wacker. [0077] An air laid nonwoven structure with a grammage of 100 g/m ² was chosen as a coating substrate. The foam can be generated via vigorously mixing. Subsequently, the mixture can be applied via rod or knife edge coating on the air laid nonwoven structure to achieve coatings with different thicknesses. The combined material is then dried by elevated temperature, preferably above 100 °C, ore preferably above 110 °C. For the meta-stable foam (Sample 1), VTNNAPAS ^® 192 was mixed with a surfactant, e.g., RUCO ^® -COAT FO 4010 manufactured by Rudolf Group, preferably at a concentration of 1% or higher.

[0078] To fixate the foam to form a stable variant, a stabilizer, e g., RUCO ^® -COAT FO 2000 manufactured by Rudolf Group can be added, preferably with concentration of 5% or higher. To increase the bulkiness of the foam layer, thermo expandable microspheres can be added, e.g., Expancel manufactured by Nouryon, with a preferable concentration of 10% or higher, based on the binder content. To activate the microspheres’ expansion the elevated temperature compared to Example 1 is crucial.

[0079] Figure 7 and Figure 8 show the results of Sample 3 and Sample 4, respectively. Sample 3 and Sample 4 exhibit the expanded microspheres incorporated in the foam, rendering the foam with a higher dry coating thickness (compared to Sample 1 and 2 from Example 1). This can be observed in addition in Figure 9-12, which exhibit detailed micrographs of Sample 3 and 4 including cross section views (Figure 10 and Figure 12). There was good top surface coverable of the absorbent structure. No binder strike through could be observed on any of the samples. Table 2 describes the properties of the air laid nonwoven absorbent structure after the application of a meta-stable and stable foam of VTNNAPAS ^® 192.

Table 2

Example 3:

[0080] Nonwoven materials of the present disclosure were prepared. In order to test absorbency, a solution of 15g carboxymethylcellulose / NA salt, 1 Og sodium chloride, 4g sodium bicarbonate, 80g glycerol, and 89 lg de-ionized water was added to the nonwoven material. The test was intended to simulate the absorption, distribution, and storage of the nonwoven absorbent articles described herein.

[0081] The nonwoven materials of the present example included a first material without additional fibers in the open-celled foam (Sample 5), a second nonwoven material comprising 10% Navia eucalyptus pulp fibers (Sample 6), and a third containing 2.5% cellulose acetate pulp fibers and 2.5% Navia eucalyptus pulp fibers (Sample 7). The respective percentages are percentages of the fibers against the weight of the whole foam.

[0082] It was found that the inclusion of short fibers into the open-celled foam lowered the acquisition/absorption time of the liquid into an acceptable range of less than 20 seconds for Sample 6 Sample 7 resulted in a performance of less than 20 seconds for absorption. Sample 5, without the additional short fibers, resulted in an unacceptable >30 second absorption time.

[0083] Sample 6 was the best result with less than 10 seconds until the fluid fully penetrated into the upper surface of the absorbent structure.

Example 4:

[0084] A nonwoven material of the present disclosure was prepared having a gradient in the open-celled foam pore size. The pore size differed from the top of the absorbent structure to the bottom. In this scenario, the top side had a small average pore size of the foam, and the bottom side had a larger average pore size of the foam. The top had an open-cell foam pore size of approximately 80 pm and the bottom had an average poor size of approximately 160 pm. The absorbent structure of this example contained 10% short fibers.

[0085] It was determined that there was a significant correlation between absorbency, e.g., fluid acquisition, and fiber content. In particular, it was determined that more short fiber included in the absorbent structure, the better the absorbency of the absorbent structure.

Example 5:

[0086] Additional foam recipes were also identified.

[0087] A foam recipe containing 500 g Vinnapas 192 (VAE) dispersion, 50 g Plastilys (moisturizer), 25 g RucoCoat 2000 (ammonium stearate), 5 g RucoCoat 4010, 24 g eucalyptus fibers, cellulose acetate hollow fibers, or a 50:50 mixture of the two can be utilized to prepare the open-celled foam absorbent structure. This would result in a VAE foam with approximately 10% short fiber content, related to the whole weight of the foam.

[0088] A mixture of VAE copolymers, polyester, and polyurethane can be utilized to make the foam of the present disclosure. The recipe can include 350g Vinnapas 192 (VAE) dispersion, 150 g Epotal Eco (polyester/polyurethane) dispersion, 4.5 g Basonat, 50 g Plastilys (moisturizer), 25 g RucoCoat 2000 (ammonium stearate), 5 g RucoCoat 4010, and 24 g eucalyptus fibers, softwood fibers, or 50:50 mixture. To produce such a mixture, the short fibers were dispersed in water prior to the addition and pressed. This step added additional 160-250 g water to the foam mixture. [0089] Absorbent structures having open-celled foam pores were produced utilizing these foam mixtures. The foam was incorporated into the absorbent structure utilizing a foam generator, for example, a PICO-Mix from Hansa Mixer, having mix head speeds of 1400 rpm, a volume speed of 5L/h, and a wet foam density of 100-300 g/L.

Example 6:

[0090] An air laid nonwoven structure with a grammage of 70 g/m ² was chosen as a coating substrate. The coating substrate was an air laid nonwoven without super absorbent polymer as a base material. The foam can be generated via vigorously mixing. Subsequently, the mixture can be applied via rod or knife edge coating on the air laid nonwoven structure to achieve coatings with different thicknesses. The combined material is then dried. There was good top surface coverable of the absorbent structure. The applied foam added onto the substrate was 70 g/m ² . *

[0091] The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter.

[0092] In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.