WO2001085083A1 - Composite absorbant reticule - Google Patents

Composite absorbant reticule Download PDF

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Publication number
WO2001085083A1
WO2001085083A1 PCT/US2001/015271 US0115271W WO0185083A1 WO 2001085083 A1 WO2001085083 A1 WO 2001085083A1 US 0115271 W US0115271 W US 0115271W WO 0185083 A1 WO0185083 A1 WO 0185083A1
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WO
WIPO (PCT)
Prior art keywords
composite
fibers
absorbent
fibrous
weight
Prior art date
Application number
PCT/US2001/015271
Other languages
English (en)
Inventor
Peter A. Graef
Original Assignee
Weyerhaeuser Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Weyerhaeuser Company filed Critical Weyerhaeuser Company
Priority to MXPA02011106A priority Critical patent/MXPA02011106A/es
Priority to AU2001261452A priority patent/AU2001261452A1/en
Priority to CA002406501A priority patent/CA2406501A1/fr
Priority to JP2001581738A priority patent/JP2003532496A/ja
Priority to EP01935349A priority patent/EP1289467A1/fr
Publication of WO2001085083A1 publication Critical patent/WO2001085083A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F13/534—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having an inhomogeneous composition through the thickness of the pad
    • A61F13/535—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having an inhomogeneous composition through the thickness of the pad inhomogeneous in the plane of the pad, e.g. core absorbent layers being of different sizes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F13/00—Bandages or dressings; Absorbent pads
    • A61F13/15—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators
    • A61F13/53—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium
    • A61F13/534—Absorbent pads, e.g. sanitary towels, swabs or tampons for external or internal application to the body; Supporting or fastening means therefor; Tampon applicators characterised by the absorbing medium having an inhomogeneous composition through the thickness of the pad

Definitions

  • the present invention relates to an absorbent composite and more particularly, to a reticulated absorbent composite that includes superabsorbent material in a fibrous matrix.
  • Cellulose fibers derived from wood pulp are used in a variety of absorbent articles, for example, diapers, incontinence products, and feminine hygiene products. It is desirable for the absorbent articles to have a high absorbent capacity for liquid as well as to have good dry and wet strength characteristics for durability in use and effective fluid management.
  • the absorbent capacity of articles made from cellulose fibers is often enhanced by the addition of superabsorbent materials, such as superabsorbent polymers.
  • superabsorbent polymers known in the art have the capability to absorb liquids in quantities from 5 to 100 times or more their weight. Thus, the presence of superabsorbent polymers greatly increases the liquid holding capacity of absorbent articles made from cellulose.
  • superabsorbent polymers absorb liquid and swell upon contact with liquid
  • superabsorbent polymers have heretofore been incorporated primarily in cellulose mats that are produced by the conventional dry, air-laid methods. Wetlaid processes for forming cellulose mats have not been used commercially because superabsorbent polymers tend to absorb liquid and swell during formation of the absorbent mats, thus requiring significant energy for their complete drying.
  • Cellulose structures formed by the wetlaid process typically exhibit certain properties that are superior to those of an air-laid structure.
  • the integrity, fluid distribution, and the wicking characteristics of wetlaid cellulosic structures are superior to those of air-laid structures.
  • Attempts to combine the advantages of wetlaid composites with the high absorbent capacity of superabsorbent materials has led to the formation of various wetlaid absorbent composites that include superabsorbent materials.
  • these structures include superabsorbent materials distributed as a layer within a multilayered composite. In these structures the superabsorbent polymer is relatively localized and not uniformly distributed throughout the absorbent structure and thus renders these composites susceptible to gel blocking.
  • an absorbent composite that includes superabsorbent material and that effectively acquires and wicks liquid throughout the composite and distributes the acquired liquid to absorbent material where the liquid is efficiently absorbed and retained without gel blocking.
  • a need also exists for an absorbent composite that continues to acquire and distribute liquid throughout the composite on successive liquid insults.
  • an absorbent composition containing superabsorbent materials that exhibits the advantages associated with wetlaid composites including wet strength, absorbent capacity and acquisition, liquid distribution, softness, and resilience. The present invention seeks to fulfill these needs and provides further related advantages.
  • the present invention relates to a reticulated fibrous absorbent composite containing absorbent material.
  • the absorbent composite is a fibrous matrix that includes absorbent material and a three-dimensional network of channels or capillaries.
  • the composite's reticulated nature enhances liquid distribution, acquisition, and wicking, while the absorbent material provides high absorbent capacity.
  • Wet strength agents can be incorporated into the composite to provide wet integrity and also to assist in securing the absorbent material in the composite.
  • the absorbent composite formed in accordance with the present invention includes a stable three-dimensional network of fibers and channels that afford rapid acquisition and wicking of liquid.
  • the fibers and channels distribute the acquired liquid throughout the composite and direct liquid to absorbent material present in the composite where the liquid is ultimately absorbed.
  • the composite maintains its integrity before, during, and after liquid is introduced.
  • the composite is a densif ⁇ ed composite that can recover its original volume on wetting.
  • the present invention provides an absorbent composite having a fibrous matrix that includes absorbent material.
  • the fibrous matrix defines voids and passages between the voids, which are distributed throughout the composite.
  • Absorbent material is located within some of the voids. The absorbent material located in these voids is expandable into the void.
  • the reticulated absorbent composite includes at least one fibrous stratum.
  • the composite includes a core and a fibrous stratum adjacent and coextensive with a surface of the core.
  • the composite includes strata on opposing surfaces of the core.
  • the composite's strata can be composed of any suitable fiber or combination of fibers and can be formed from fibers that are the same as or different from the fibers used for forming the reticulated core.
  • methods for forming the composite and absorbent articles that include the composite are provided.
  • the absorbent articles include consumer absorbent products such as diapers, feminine care products, and adult incontinence products.
  • FIGURE 1 is a cross-sectional view of a portion of a reticulated absorbent composite formed in accordance with the present invention
  • FIGURE 2 is a photomicrograph of a cross section of a representative reticulated absorbent composite formed by a wetlaid method in accordance with the present invention at 12 times magnification;
  • FIGURE 3 is a photomicrograph of the wetlaid composite of FIGURE 2 at 40 times magnification
  • FIGURE 4 is a photomicrograph of a cross section of a representative reticulated absorbent composite formed by a foam method in accordance with the present invention at 12 times magnification;
  • FIGURE 5 is a photomicrograph of the foam-formed composite of FIGURE 4 at 40 times magnification
  • FIGURE 6 is a photomicrograph of a cross section of a representative reticulated absorbent composite formed by a wetlaid method in accordance with the present invention in a wetted state at 8 times magnification;
  • FIGURE 7 is a photomicrograph of the wetlaid composite of FIGURE 6 at 12 times magnification
  • FIGURE 9 is a photomicrograph of the foam-formed composite of FIGURE 8 at 12 times magnification
  • FIGURE 11 is a cross-sectional view of a portion of another absorbent construct incorporating a reticulated absorbent composite formed in accordance with the present invention.
  • FIGURE 14 is a cross-sectional view of a portion of another absorbent article incorporating a reticulated absorbent composite formed in accordance with the present invention.
  • FIGURE 18 is a cross-sectional view of a portion of an absorbent article incorporating a reticulated absorbent composite formed in accordance with the present invention.
  • FIGURE 20 is a cross-sectional view of a portion of another absorbent article incorporating a reticulated absorbent composite formed in accordance with the present invention
  • FIGURES 21 A and B are cross-sectional views of portions of reticulated absorbent composites formed in accordance with the present invention
  • FIGURE 22 is a diagrammatic view illustrating a twin-wire device and method for forming the composite of the present invention
  • FIGURE 23 is a diagrammatic view illustrating a representative headbox assembly and method for forming the composite of the present invention
  • FIGURE 24 are cross-sectional views of portions of absorbent constructs incorporating an acquisition layer and a reticulated absorbent composite formed in accordance with the present invention
  • FIGURE 26 are cross-sectional views of portions of absorbent articles incorporating a reticulated absorbent composite formed in accordance with the present invention
  • FIGURE 27 are cross-sectional views of portions of absorbent articles incorporating an acquisition layer and a reticulated absorbent composite formed in accordance with the present invention
  • FIGURE 30 is a graph illustrating the correlation between composite edgewise compression and percentage matrix fiber in the composite.
  • the absorbent composite formed in accordance with the present invention is a reticulated fibrous composite that includes absorbent material.
  • the absorbent material is distributed substantially throughout the fibrous composite and serves to absorb and retain liquid acquired by the composite.
  • the absorbent material is a superabsorbent material.
  • the composite's fibers provide a stable three-dimensional network of channels or capillaries that serve to acquire liquid contacting the composite and to distribute the acquired liquid to the absorbent material.
  • the composite optionally includes a wet strength agent that further increases tensile strength and structural integrity to the composite.
  • the composite is a fibrous matrix that includes absorbent material. The fibrous matrix defines voids and passages between the voids, which are distributed throughout the composite.
  • FIGURES 6-9 Photomicrographs of the representative composites shown in FIGURES 2-5 in a wetted state are illustrated in FIGURES 6-9, respectively. These photomicrographs were obtained by sectioning freeze-dried composites that had acquired synthetic urine under free swell conditions.
  • FIGURES 6 and 7 are photomicrographs of the wetted wetlaid composite at 8 x and 12 x magnification, respectively.
  • FIGURES 8 and 9 are photomicrographs of the wetted foam-formed composite at 8 x and 12 x magnification, respectively.
  • absorbent material in the wetted composite has swollen and increased in size to more fully occupy voids that the absorbent material previously occupied in the dry composite.
  • the composite's fibrous matrix is composed primarily of fibers.
  • fibers are present in the composite in an amount from about 20 to about 90 weight percent, preferably from about 50 to about 70 weight percent, based on the total weight of the composite.
  • Fibers suitable for use in the present invention are known to those skilled in the art and include any fiber from which a wet composite can be formed.
  • the composite includes resilient fibers.
  • resilient fiber refers to a fiber present in the composite that imparts reticulation to the composite.
  • resilient fibers provide the composite with bulk and resiliency.
  • the incorporation of resilient fibers into the composite allows the composite to expand on absorption of liquid without structural integrity loss.
  • Resilient fibers also impart softness to the composite.
  • resilient fibers offer advantages in the composite's formation processes. Because of the porous and open structure resulting from wet composites that include resilient fibers, these composites drain water relatively easily and are therefore dewatered and dried more readily than wet composites that do not include resilient fibers.
  • the composite includes resilient fibers in an amount from about 5 to about 60 percent by weight, preferably from about 10 to 40 percent by weight, based on the total weight of the composite.
  • Resilient fibers include cellulosic and synthetic fibers.
  • Resilient fibers include chemically stiffened fibers, anfractuous fibers, chemithermomechanical pulp (CTMP), and prehydrolyzed kraft pulp (PHKP).
  • CTMP chemithermomechanical pulp
  • PKP prehydrolyzed kraft pulp
  • the term "chemically stiffened fiber” refers to a fiber that has been stiffened by chemical means to increase fiber stiffness under dry and wet conditions. Fibers can be stiffened by the addition of chemical stiffening agents that can coat and/or impregnate the fibers. Stiffening agents include the polymeric wet strength agents including resinous agents such as, for example, polyamide-epichlorohydrin and polyacrylamide resins described below. Fibers can also be stiffened by modifying fiber structure by, for example, chemical crosslinking. In one embodiment, the chemically stiffened fibers are intrafiber crosslinked cellulosic fibers.
  • the composite includes matrix fibers in an amount from about 10 to about 60 percent by weight, preferably from about 20 to about 50 percent by weight, based on the total weight of the composite.
  • the composite can include a combination of resilient and matrix fibers.
  • the composite includes resilient fibers in an amount from about 5 to about 20 percent by weight and matrix fibers in an amount from about 20 to about 60 percent by weight based on the total weight of the composite.
  • the composite includes from about 10 to about 15 percent by weight resilient fibers, preferably crosslinked cellulosic fibers, and from about 40 to about 50 percent by weight matrix fibers, preferably wood pulp fibers, based on the total weight of the composite.
  • Fibers are commercially available from a number of companies, including Weyerhaeuser Company, the assignee of the present invention.
  • suitable cellulose fibers produced from southern pine that are usable with the present invention are available from Weyerhaeuser Company under the designations CF416, NF405, PL416, FR516, and NB416.
  • the wood pulp fibers can also be pretreated prior to use with the present invention.
  • This pretreatment may include physical treatment, such as subjecting the fibers to steam, or chemical treatment, for example, crosslinking the cellulose fibers using any one of a variety of crosslinking agents.
  • Crosslinking increases fiber bulk and resiliency, and thereby can improve the fibers' absorbency.
  • crosslinked fibers are twisted or crimped.
  • the use of crosslinked fibers allows the composite to be more resilient, softer, bulkier, have better wicking, and be easier to density than a composite that does not include crosslinked fibers.
  • Suitable crosslinked cellulose fibers produced from southern pine are available from Weyerhaeuser Company under the designation NHB416.
  • Crosslinked cellulose fibers and methods for their preparation are disclosed in U.S. Patents Nos. 5,437,418 and 5,225,047 issued to Graef et al., expressly incorporated herein by reference.
  • Suitable urea-based crosslinking agents include methylolated ureas, methylolated cyclic ureas, methylolated lower alkyl cyclic ureas, methylolated dihydroxy cyclic ureas, dihydroxy cyclic ureas, and lower alkyl substituted cyclic ureas.
  • urea-based crosslinking agents include dimethyldihydroxyethylene urea (DMeDHEU, l,3-dimethyl-4,5-dihydroxy-2- imidazolidinone), dimethyloldihydroxy ethylene urea (DMDHEU, 1,3- dihydroxymethyl-4,5-dihydroxy-2-imidazolidinone), dimethylol urea (DMU, bis[N- hydroxymethyl]urea), dihydroxyethylene urea (DHEU, 4,5-dihydroxy-2- imidazolidinone), and dimethylolethylene urea (DMEU, l,3-dihydroxymethyl-2- imidazolidinone).
  • DMeDHEU dimethyldihydroxyethylene urea
  • DMDHEU dimethyloldihydroxy ethylene urea
  • DMU dimethylol urea
  • DMU bis[N- hydroxymethyl]urea
  • DHEU dihydroxyethylene urea
  • DHEU 4,5-dihydroxy-2- imidazolidinone
  • DMEU
  • Suitable polycarboxylic acid crosslinking agents include citric acid, tartaric acid, malic acid, succinic acid, glutaric acid, citraconic acid, itaconic acid, tartrate monosuccinic acid, and maleic acid.
  • Other polycarboxylic acid crosslinking agents include polymeric polycarboxylic acids such as poly(acrylic acid), poly(methacrylic acid), poly(maleic acid), poly(methylvinylether-co-maleate) copolymer, poly(methylvinylether-co-itaconate) copolymer, copolymers of acrylic acid, and copolymers of maleic acid.
  • polymeric polycarboxylic acid crosslinking agents such as polyacrylic acid polymers, polymaleic acid polymers, copolymers of acrylic acid, and copolymers of maleic acid is described in U.S. patent application Serial No. 08/989,697, filed December 12, 1997, and assigned to Weyerhaeuser Company. Mixtures or blends of crosslinking agents can also be used.
  • the crosslinking agent can include a catalyst to accelerate the bonding reaction between the crosslinking agent and cellulose fiber. Suitable catalysts include acidic salts, such as ammonium chloride, ammonium sulfate, aluminum chloride, magnesium chloride, and alkali metal salts of phosphorous-containing acids.
  • pretreating fibers include the application of surfactants or other liquids that modify the surface chemistry of the fibers.
  • Other pretreatments include incorporation of antimicrobials, pigments, dyes and densification or softening agents.
  • Cellulosic fibers treated with particle binders and/or densification/softness aids known in the art can also be employed in accordance with the present invention.
  • the particle binders serve to attach other materials, such as cellulosic fiber superabsorbent polymers, as well as others, to the cellulosic fibers.
  • Cellulosic fibers treated with suitable particle binders and/or densification/softness aids and the process for combining them with cellulose fibers are disclosed in the following U.S. patents:
  • Patent No. 5,543,215 entitled “Polymeric Binders for Binding Particles to Fibers”
  • Patent No. 5,538,783 entitled “Non-Polymeric Organic Binders for Binding Particles to Fibers”
  • Patent No. 5,300,192 entitled “Wet Laid Fiber Sheet
  • Patent No. 5,352,480 entitled “Method for Binding Particles to Fibers Using Reactivatable Binders”
  • Patent No. 5,308,896 entitled “Particle Binders for High- Bulk Fibers”
  • Patent No. 5,589,256 entitled “Particle Binders that Enhance Fiber Densification”
  • Patent No. 5,607,759 entitled “Particle Binding to Fibers”
  • Patent No. 10 Patent No.
  • synthetic fibers including polymeric fibers, such as polyolefin, polyamide, polyester, polyvinyl alcohol, and polyvinyl acetate fibers may also be used in the absorbent composite.
  • Suitable polyolefin fibers include polyethylene and polypropylene fibers.
  • Suitable polyester fibers include polyethylene terephthalate fibers.
  • Other suitable synthetic fibers include, for example, nylon fibers.
  • the absorbent composite can include combinations of natural and synthetic fibers.
  • the absorbent composite includes a combination of wood pulp fibers (e.g., Weyerhaeuser designation NB416) and crosslinked cellulosic fibers (e.g., Weyerhaeuser designation NHB416). Wood pulp fibers are present in such a combination in an amount from about 10 to about 85 weight percent by weight based on the total weight of fibers.
  • the reticulated absorbent composite When incorporated into an absorbent article, the reticulated absorbent composite can serve as a storage layer for acquired liquids.
  • the absorbent composite includes absorbent material.
  • the term "absorbent material” refers to a material that absorbs liquid and that generally has an absorbent capacity greater than the cellulosic fibrous component of the composite.
  • the absorbent material is a water-swellable, generally water-insoluble polymeric material capable of absorbing at least about 5, desirably about 20, and preferably about 100 times or more its weight in saline (e.g., 0.9 percent saline).
  • the absorbent material can be swellable in the dispersion medium utilized in the method for forming the composite.
  • the absorbent material is untreated and swellable in the dispersion medium.
  • the absorbent material is a coated absorbent material that is resistant to absorbing water during the composite formation process.
  • the amount of absorbent material present in the composite can vary greatly depending on the composite's intended use.
  • the amount of absorbent material present in an absorbent article, such as an absorbent core for an infant's diaper, is suitably present in the composite in an amount from about 2 to about 80 weight percent, preferably from about 30 to about 60 weight percent, based on the total weight of the composite.
  • the absorbent material may include natural materials such as agar, pectin, and guar gum, and synthetic materials, such as synthetic hydrogel polymers.
  • Synthetic hydrogel polymers include, for example, carboxymethyl cellulose, alkaline metal salts of polyacrylic acid, polyacrylamides, polyvinyl alcohol, ethylene maleic anhydride copolymers, polyvinyl ethers, hydroxypropyl cellulose, polyvinyl morpholinone, polymers and copolymers of vinyl sulphonic acid, polyacrylates, polyacrylamides, and polyvinyl pyridine among others.
  • the absorbent material is a superabsorbent material.
  • a "superabsorbent material” refers to a polymeric material that is capable of absorbing large quantities of fluid by swelling and forming a hydrated gel (i.e., a hydrogel). In addition to absorbing large quantities of fluids, superabsorbent materials can also retain significant amounts of bodily fluids under moderate pressure.
  • Superabsorbent materials are available commercially, for example, polyacrylates from Clariant of Portsmouth, Virginia. These superabsorbent polymers come in a variety of sizes, morphologies, and absorbent properties (available from Clariant under trade designations such as IM 3500 and IM 3900). Other superabsorbent materials are marketed under the trademarks SANWET (supplied by Sanyo Kasei Kogyo Kabushiki Kaisha), and SXM77 (supplied by Stockhausen of Greensboro, North Carolina). Other superabsorbent materials are described in U.S. Patent No. 4,160,059; U.S. Patent No. 4,676,784; U.S. Patent No. 4,673,402; U.S. Patent No.
  • Suitable superabsorbent materials useful in the absorbent composite include superabsorbent particles and superabsorbent fibers.
  • the absorbent composite includes a superabsorbent material that swells relatively slowly for the purposes of composite manufacturing and yet swells at an acceptable rate so as not to adversely affect the absorbent characteristics of the composite or any construct containing the composite.
  • a superabsorbent material that swells relatively slowly for the purposes of composite manufacturing and yet swells at an acceptable rate so as not to adversely affect the absorbent characteristics of the composite or any construct containing the composite.
  • the smaller the absorbent material the more rapidly the material absorbs liquid.
  • the absorbent composite can optionally include a wet strength agent.
  • the wet strength agent provides increased strength to the absorbent composite and enhances the composite's wet integrity.
  • the wet strength agent can assist in binding the absorbent material, for example, superabsorbent material, in the composite's fibrous matrix.
  • the wet strength agent is present in the composition in an amount from about 0.01 to about 2 weight percent, preferably from about 0.1 to about 1 weight percent, and more preferably from about 0.3 to about 0.7 weight percent, based on the total weight of the composite.
  • the wet strength agent useful in forming the composite is a polyamide-epichlorohydrin resin commercially available from Hercules, Inc. under the designation KYMENE.
  • the wet and dry tensile strengths of an absorbent composite formed in accordance with the present invention will generally increase with an increasing the amount of wet strength agent.
  • the tensile strength of a representative composite is described in Example 7.
  • the absorbent material is incorporated into the composite during the formation of the composite.
  • the methods for forming the reticulated absorbent composite include combining the components of the composite in a dispersion medium (e.g., an aqueous medium) to form a slurry and then depositing the slurry onto a foraminous support (e.g., a forming wire) and dewatering to form a wet composite. Drying the wet composite provides the reticulated composite.
  • a dispersion medium e.g., an aqueous medium
  • a foraminous support e.g., a forming wire
  • drying the wet composite provides the reticulated composite.
  • the reticulated composite is prepared from a combination of fibers, absorbent material, and optionally a wet strength agent in a dispersion medium.
  • a slurry is formed by directly combining fibers, absorbent material, and wet strength agent in a dispersion medium.
  • the slurry is prepared by first combining fibers and the wet strength agent in a dispersion medium to provide a fibrous slurry to which is then added absorbent material in a second step.
  • a fibrous slurry is combined with a second slurry containing absorbent material, the combined slurry then being deposited onto the support.
  • individual slurries for example, a fibrous slurry and a slurry containing absorbent material
  • a divided headbox for example, a twin slice headbox that deposits two slurries onto a support simultaneously.
  • the slurry or slurries containing the composite's components in a dispersion medium are deposited onto a foraminous support. Once deposited onto the support the dispersion medium begins to drain from the deposited fibrous slurry. Removal of the dispersion medium (e.g., dewatering) from the deposited fibrous slurry continues through, for example, the application of heat, pressure, vacuum, and combinations thereof, and results in the formation of a wet composite.
  • dispersion medium e.g., dewatering
  • the reticulated absorbent composite can be ultimately produced by drying the wet composite. Drying removes the remaining dispersion medium and provides an absorbent composite having the desired moisture content. Generally, the composite has a moisture content less than about 20 percent and, in one embodiment, has a moisture content in the range from about 6 to about 10 percent by weight based on the total weight of the composite.
  • Suitable composite drying methods include, for example, the use of drying cans, air floats, and through air dryers. Other drying methods and apparatus known in the pulp and paper industry may also be used. Drying temperatures, pressures, and times are typical for the equipment and methods used, and are known to those of ordinary skill in the art in the pulp and paper industry.
  • Example 1 A representative wetlaid method for forming a reticulated absorbent composite is described in Example 1.
  • the fibrous slurry is a foam dispersion that further includes a surfactant.
  • Suitable surfactants include ionic, nonionic, and amphoteric surfactants known in the art.
  • a representative foam method for forming a reticulated absorbent composite is described in Example 2.
  • the wet composite containing the water-swollen absorbent material is distributed onto a support from which water (i.e., the dispersion medium) can be withdrawn and the wet composite dried. Drying causes the water-swollen absorbent material to dehydrate and decrease in size, thereby creating voids in the composite surrounding the absorbent material.
  • the absorbent material preferably absorbs less than about 20 times its weight in the dispersion medium, more preferably less than about 10 times, and even more preferably less than about 5 times its weight in the dispersion medium.
  • Foam methods are advantageous for forming the absorbent composite for several reasons. Generally, foam methods provide fibrous webs that possess both relatively low density and relatively high tensile strength. For webs composed of substantially the same components, foam-formed webs generally have densities greater than air-laid webs and lower than wetlaid webs. Similarly, the tensile strength of foam-formed webs is substantially greater than for air-laid webs and approach the strength of wetlaid webs.
  • foam forming technology allows better control of pore and void size, void size to be maximized, the orientation and uniform distribution of fibers, and the incorporation of a wide range of materials (e.g., long and synthetic fibers that cannot be readily incorporated into wetlaid processes) into the composite.
  • the reticulated absorbent composite can be formed by a foam process, preferably a process by Ahlstrom Company (Helsinki, Finland).
  • the process encompasses desirable manufacturing efficiencies while producing a product with desirable performance characteristics.
  • the formation of a reticulated absorbent composite by representative wetlaid and foam processes is described in Examples 1 and 2, respectively.
  • Absorbent properties i.e., rewet, acquisition time, liquid distribution, dry strength, and resilience
  • Wicking and liquid distribution for a representative absorbent composite are described in Examples 5 and 6, respectively.
  • the tensile strength of representative composites formed in accordance with the present invention is described in Example 7.
  • the softness (i.e., Taber stiffness) of representative wetlaid and foam-formed composites is described in Example 8.
  • the methods allow for control and variation of absorbent material swelling.
  • Absorbent material swelling generally depends on the degree of its crosslinking (e.g., surface and internal crosslinking) and the amount of water absorbed by the absorbent material.
  • the extent of swelling depends on a number of factors, including the type of absorbent material, the concentration of absorbent material in an aqueous environment (e.g., the dispersion medium and the wet composite), and the period of time that the absorbent material remains in contact with such an environment.
  • Absorbent material swelling can be minimized by dispensing the absorbent in chilled water (e.g., 34- 40°F).
  • the residence time i.e., time from absorbent material addition to dispersion medium to wet composite introduction to dryer
  • absorbent material in the forming process is preferably less than about 30 seconds.
  • the greater the initial swelling of the absorbent material the greater the void volume and, consequently, the lower the density of the resulting absorbent composite.
  • the greater the void volume of a composite the greater its liquid acquisition rate and, generally, the greater the composite's absorbent capacity.
  • the composite's voids are formed by the hydration and swelling of absorbent material (i.e., during wet composite formation) and the subsequent dehydration and decrease in size of the absorbent material (i.e., during wet composite drying).
  • the density of the composite depends on the extent to which the absorbent material absorbs liquid and swells during the formation of the wet composite, and the conditions and extent to which the wet composite incorporating the swollen absorbent material is dried. Water absorbed by the absorbent material during wet composite formation is removed from the absorbent material, decreasing its size, on drying the wet composite. The dehydration of the swollen absorbent material defines some of the voids in the fibrous composite.
  • the reticulated absorbent composite can be incorporated as an absorbent core or storage layer in an absorbent article including, for example, a diaper or feminine care product.
  • the absorbent composite can be used alone or, as illustrated in FIGURES 10 and 11, can be used in combination with one or more other layers.
  • absorbent composite 10 is employed as a storage layer in combination with upper acquisition layer 20.
  • a third layer 30 e.g., distribution layer
  • absorbent composite 10 and acquisition layer 20 can also be employed, if desired, with absorbent composite 10 and acquisition layer 20.
  • a variety of suitable absorbent articles can be produced from the absorbent composite. The most common include absorptive consumer products, such as diapers, feminine hygiene products such as feminine napkins, and adult incontinence products.
  • absorbent article 38 comprises composite 10, liquid pervious facing sheet 22 and liquid impervious backing sheet 24.
  • absorbent article 40 comprises absorbent composite 10 and overlying acquisition layer 20.
  • a liquid pervious facing sheet 22 overlies acquisition composite 20
  • a liquid impervious backing sheet 24 underlies absorbent composite 10.
  • the absorbent composite will provide advantageous liquid absorption performance for use in, for example, diapers.
  • the reticulated structure of the absorbent composite will aid in fluid transport and absorption in multiple wettings.
  • the articles can further include leg gathers.
  • FIGURES 12A and 12B are shown for purposes of exemplifying a typical absorbent article, such as a diaper or feminine napkin.
  • a typical construction of an adult incontinence absorbent structure is shown in FIGURE 13.
  • the article 50 comprises a facing sheet 22, acquisition layer 20, absorbent composite 10, and a backing sheet 24.
  • the facing sheet 22 is pervious to liquid while the backing sheet 24 is impervious to liquid.
  • a liquid pervious tissue 26 composed of a polar, fibrous material is positioned between absorbent composite 10 and acquisition layer 20.
  • another absorbent article includes a facing sheet 22, an acquisition layer 20, an intermediate layer 28, absorbent composite 10, and a backing sheet 24.
  • the intermediate layer 28 contains, for example, a densified fibrous material such as a combination of cellulose acetate and triacetin, which are combined prior to forming the article.
  • the intermediate layer 28 can thus bond to both absorbent composite 10 and acquisition layer 20 to form an absorbent article having significantly more integrity than one in which the absorbent composite and acquisition layer are not bonded to each other.
  • the hydrophilicity of layer 28 can be adjusted in such a way as to create a hydrophilicity gradient among layers 10, 28, and 20.
  • the reticulated absorbent composite can also be incorporated as a liquid management layer in an absorbent article such as a diaper.
  • the composite can be used in combination with a storage core or layer.
  • the liquid management layer can have a top surface area that is smaller, the same size, or greater than the top surface area of the storage layer.
  • Representative absorbent constructs that incorporate the reticulated absorbent composite in combination with a storage layer are shown in FIGURE 15.
  • absorbent construct 70 includes reticulated composite 10 and storage layer 72.
  • Storage layer 72 is preferably a fibrous layer that includes absorbent material.
  • the storage layer can be formed by any method, including airlaid, wetlaid, and foam- forming methods.
  • the storage layer can be a reticulated composite.
  • FIGURE 16 illustrates absorbent construct 80 having acquisition layer 20 overlying composite 10 and storage layer 72.
  • Construct 80 can further include intermediate layer 74 to provide construct 90 shown in FIGURE 17.
  • Intermediate layer 74 can be, for example, a tissue layer, a nonwoven layer, an airlaid or wetlaid pad, or a reticulated composite.
  • Constructs 70, 80, and 90 can be incorporated into absorbent articles.
  • absorbent articles 100, 110, and 120 shown in FIGURES 18-20, respectively, include a liquid pervious facing sheet 22, a liquid impervious backing sheet 24, and constructs 70, 80, and 90, respectively.
  • the facing sheet is joined to the backing sheet.
  • the reticulated absorbent composite formed in accordance with the present invention further includes a fibrous stratum.
  • the composite includes a reticulated core and a fibrous stratum adjacent an outward facing surface of the core.
  • the fibrous stratum is integrally formed with the reticulated core to provide a unitary absorbent composite.
  • integrally formed refers to a composite having more than one strata produced in a formation process that provides the composite as a unitary structure.
  • the stratum is coextensive with an outward facing surface (i.e., an upper and/or lower surface) of the composite.
  • the composite includes first and second strata adjacent each of the core's outward facing surfaces (i.e., the strata are coextensive with opposing surfaces of the core).
  • a representative absorbent composite having a fibrous stratum is shown in FIGURE 21 A and a representative composite having fibrous strata is shown in FIGURE 21B.
  • absorbent composite 130 includes reticulated core 10 and stratum 132 and, as shown in FIGURE 21B, composite 140 includes reticulated core 10 intermediate strata 132 and 134.
  • core 10 is a fibrous matrix that includes fibrous regions 12 defining voids 14, some of which include absorbent material 18.
  • the present invention provides an absorbent composite that is a unitary structure that includes two or more strata.
  • unitary refers to the composite's structure in which adjacent strata are integrally connected through a transition zone to provide a structure with adjacent strata in intimate fluid communication.
  • surface stratum 132 is integrally connected to core stratum 10 through a transition zone.
  • strata 132 and 134 are each integrally connected to core stratum 10 through a transition zone.
  • transition zones separate the composite's strata.
  • the nature of the transition zone can vary from composite-to-composite and from stratum-to- stratum within a composite.
  • the transition zone can be designed to satisfy the performance requirements of a particular composite.
  • the transition zone integrally connects adjacent strata and provides for intimate liquid communication between strata.
  • the transition zone includes fibers from one stratum extending into the adjacent stratum.
  • the transition zone includes fibers from the first stratum extending into the second stratum and fibers from the second stratum extending into the first stratum.
  • Transition zone thickness within a composite can be widely varied depending on the composite.
  • Absorbent composites of the present invention can include a transition zone that is relatively thin. Absorbent composites that include such thin transition zones have fairly abrupt transitions in material composition between strata. Alternatively, the composite can include a transition zone that is gradual such that the transition from one zone to the next occurs over a relatively greater thickness of the composite. In such a composite, the material compositions of each zone are intermixed to a significant extent resulting in rather extended composition gradients.
  • Unitary composites having multiple strata and methods for their formation are described in international patent application Serial No. PCT/US97/22342, Unitary Stratified Composite, and U.S. patent application Serial No. 09/326,213, Unitary Absorbent System, each incorporated herein by reference in its entirety.
  • the stratum or strata of the composite are fibrous and can be composed of any suitable fiber or combination of fibers noted above.
  • the stratum's fibrous composition can be widely varied.
  • the stratum can be formed from fibers that are the same as or different from the fibers used for forming the reticulated core.
  • the stratum can be formed from resilient fibers, matrix fibers, or combinations of resilient and matrix fibers.
  • the stratum can optionally include a wet or dry strength agent.
  • Suitable strata can be formed from a single fiber type, for example, a stratum composed of 100 percent wood pulp fibers (e.g., southern pine fibers).
  • the stratum can be formed from fibrous blends, such as an 80:20 blend of wood pulp fibers and crosslinked fibers, and synthetic blends, and blends of synthetic and cellulosic fibers.
  • the stratum composition can be varied to provide a composite having desired characteristics.
  • the stratum preferably has a relatively high wood pulp fiber content.
  • the stratum is preferably composed of wood pulp fibers such as southern pine fibers.
  • the stratum has a lower liquid acquisition rate compared to a similarly constituted stratum containing relatively less wood pulp fiber and, for example, greater amounts of crosslinked fibers.
  • the stratum preferably has a relatively high crosslinked or synthetic fiber content.
  • a stratum provides less liquid distribution than a comparable stratum that includes relatively less crosslinked fiber.
  • first and second strata can be selectively and independently controlled and varied.
  • the compositions of the first and second strata need not be the same.
  • the strata can be formed from the same or different fiber furnishes.
  • stratum basis weight can also be independently controlled and varied.
  • Stratum basis weight can also be varied with respect to the core's basis weight. In a foam method, basis weight can be varied by adjusting the rate at which the fibrous furnish is supplied to and deposited on the forming support.
  • a representative method for forming a fibrous web having an intermediate stratum generally includes the following steps: (a) forming a first fibrous slurry comprising fibers in an aqueous dispersion medium;
  • the means for withdrawing liquid/foam from the first and second slurries through the foraminous elements to form a web on the foraminous elements are also included in the headbox assembly.
  • the means for withdrawing liquid/foam can include any conventional means for that purpose, such as suction rollers, pressing rollers, or other conventional structures.
  • first and second suction box assemblies are provided and mounted on the opposite sides of the interior structure from the foraminous elements (see boxes 206 and 208 in FIGURES 22 and 23).
  • Composite flexibility and softness are factors for determining the suitability of composites for incorporation into personal care absorbent products.
  • Composite flexibility can be indicated by composite edgewise ring crush, which is a measure of the force required to compress the composite as described below.
  • the composite includes from about 40 to about 70 percent and, preferably, about 60 percent by weight superabsorbent material based on the total weight of the composite; from about 20 to about 50 percent and, preferably, about 30 percent by weight crosslinked fiber; and from about 5 to about 20 percent and, preferably, about 10 percent by weight matrix fiber based on the total weight of the composite.
  • the ratio of crosslinked fibers:matrix fibers can be at least 1 : 1 and, preferably, about 2:1.
  • the composites of the invention exhibit advantageous fluidic properties.
  • the properties can be indicated by various measures including liquid acquisition rate, wicking, and rewet. Acquisition rate and rewet, unrestrained vertical wicking height, and saddle acquisition rate, distribution, and wicking height for representative composites is described in Examples 22 and 25.
  • the composites' components, composition, and formation methods exhibit advantageous fluidic properties including high liquid absorbent capacity and high liquid wicking.
  • Liquid absorbent capacity can be indicated by an absorbency under load measure (e.g., Gravimetric Absorbency Test, or Demand Absorbency as described in U.S. Patent No. 4,357,827).
  • the composite exhibits a demand absorbency of from about 15 to about 35 mL/g.
  • Absorbent composites having a variety of basis weights can be prepared from the composite formed as described above by pre- or post-drying densification methods known to those in the art.
  • the sheet is then dried in a drying oven to remove the moisture.
  • the aqueous solution used in the tests is a synthetic urine available from National Scientific under the trade name RICCA.
  • the synthetic urine is a saline solution containing 135 meq./L sodium, 8.6 meq./L calcium, 7.7 meq./L magnesium, 1.94% urea by weight (based on total weight), plus other ingredients.
  • a sample of the absorbent structure was prepared for the test by determining the center of the structure's core, measuring 1 inch to the front for liquid application location, and marking the location with an "X".
  • the test was conducted by first placing the sample on a plastic base (43/4 inch x 19 1/4 inch) and then placing a funnel acquisition plate (4 inch x 4 inch plastic plate) on top of the sample with the plate's hole positioned over the "X”.
  • a donut weight (1400 g) was then placed on top of the funnel acquisition plate to which was then attached a funnel (4 inch diameter).
  • Liquid acquisition was then determined by pouring 100 mL synthetic urine into the funnel and measuring the time from when liquid was first introduced into the funnel to the time that liquid disappeared from the bottom of the funnel into the sample.
  • the aqueous solution used in the tests was a synthetic urine available from National Scientific under the trade name RICCA, and as described above in Example 1.
  • sample composites (10 cm x 22 cm) were cut and marked with consecutive lines 1 cm, 11 cm, 16 cm, and 21 cm from one of the strip's edges.
  • samples were preconditioned for 12 hours at 50 percent relative humidity and 23°C and then stored in sample bags until testing.
  • the sample composite was oriented lengthwise vertically and clamped from its top edge at the 1 cm mark, allowing its bottom edge to contact a bath containing synthetic urine. Timing was commenced once the strip was contacted with the liquid. The time required for 5 percent of the wicking front to reach 5 cm, 10 cm, 15 cm, and 20 cm was then recorded.
  • the vertical wicking results are summarized in Table 4.
  • the wet tensile strength, N/m is converted to tensile index, Nm/g, by dividing the tensile strength by the basis weight g/m .
  • Nm/g tensile index
  • increasing the amount of KYMENE from 2 to 100 pounds per ton of fiber may increase the dry tensile strength from about 0.15 Nm g to 0.66 Nm/g and the wet tensile from about 1.5 Nm/g to about 2.4 Nm g.
  • Sample size may be shorter than 10.2 cm as long as the sample is securely held by the end clamps.
  • the stiffness of representative reticulated absorbent composites formed in accordance with the present invention was determined by the Taber Stiffness method. Representative composites were formed by wetlaid and foam methods. These composites included matrix fibers (48 percent by weight, southern pine commercially available from Weyerhaeuser Co. under the designation NB416), resilient fibers (12 percent by weight, polymaleic acid crosslinked fibers), and absorbent material (40 percent by weight, superabsorbent material commercially available from Stockhausen). One of the wetlaid and one of the foam-formed composites further included a wet strength agent (about 0.5 percent by weight, polyamide- epichlorohydrin resin commercially available from Hercules under the designation KYMENE.
  • a wet strength agent about 0.5 percent by weight, polyamide- epichlorohydrin resin commercially available from Hercules under the designation KYMENE.
  • the stiffness of the foam-formed composites was significantly lower than the similarly constituted wetlaid composites.
  • the results also indicate that, for the wetlaid composites, the inclusion of a wet strength agent increases the composite's stiffness.
  • This example illustrates a representative wetlaid method for forming a reticulated composite using a Rotoformer papermaking machine.
  • slurries of absorbent material and fibers in water were introduced into the Rotoformer's headbox.
  • the fibrous slurry was introduced to the headbox in the conventional manner.
  • the absorbent slurry was introduced through the use of a dispersion unit consisting of a set of spargers.
  • the spargers were fed from a header fed by the absorbent slurry supply.
  • the dispersion unit is mounted on the Rotoformer headbox with the spargers inserted into the headbox fiber stock such that the flow of the absorbent slurry is against the fiber stock flow.
  • Such a reversed flow for the absorbent slurry is believed to provide more effective mixing of the absorbent material and the fibers than would occur for absorbent material flow in the same direction as the fiber stock.
  • Absorbent material is introduced into the Rotoformer headbox as a slurry in water.
  • One method that provides suitable results for introducing absorbent material into the headbox is a mixing system that includes a funnel attached directly to the inlet of a pump into which chilled water is fed at a controlled rate.
  • the funnel receives water and dry absorbent material delivered from absorbent material supply by auger metering and forms a pond that contains absorbent material and water.
  • the absorbent slurry is preferably pumped from the funnel to the headbox at approximately the same rate as water is delivered to the funnel. Such a system minimizes the exposure of the absorbent to the water.
  • the absorbent slurry is delivered from the mixing system to the headbox through a 10 to 50 foot conduit in less than about 10 seconds.
  • the target fiber basis weight was about 370 gsm (g/m 2 ) and the production speed was about lO fjpm (ft/min).
  • the relatively slow production speed was a consequence of the relatively limited drying capability of the machine's flat-bed dryer.
  • the headbox contents including fibers and absorbent were deposited on a forming wire and dewatered to provide a wet composite.
  • the wet composite was then dried to a moisture content of from about 9 to about 15 weight percent based on total composite weight to form a representative reticulated absorbent composite.
  • Absorbent composites having a variety of basis weights can be prepared from the composite formed as described above by pre- or post-drying densification methods known to those in the art.
  • Examples 10-15 illustrate the formation of representative reticulated absorbent composites using the method described above.
  • a representative composite was formed as described in Example 9.
  • the composite included about 60% by weight fibers and about 40% by weight absorbent material based on the total weight of composite.
  • the fiber stock was a mixture of 80% by weight standard wood pulp fibers (once-dried southern pine commercially available from Weyerhaeuser Company under the designation FR416) and 20% by weight crosslinked pulp fibers.
  • the absorbent material was a crosslinked polyacrylate commercially available from Stockhausen under the designation SXM 77, which was screened using 300 micron mesh to eliminate fines prior to use.
  • the composite also included about 25 pounds wet strength agent (a polyacrylamide-epichlorohydrin resin commercially available from Hercules under the designation KYMENE 557LX) per ton of fibers.
  • a representative composite was formed as described in Example 10 except that the composite was calendered at 25 fpm.
  • a representative composite was formed as described in Example 11 except that the amount of wet strength agent in the composite was reduced to 12.5 pounds per ton fiber and the standard wood pulp fibers were never-dried FR416 fibers.
  • Example 13 A representative composite was formed as described in Example 12 except that the composite was not densified.
  • a representative composite was formed as described in Example 12 except that the wood pulp fibers were once-dried FR416 fibers.
  • a representative composite was formed as described in Example 12 except that the amount of fibers in the composite was increased to about 80% by weight and the amount of absorbent present in the composite was decreased to about 20% by weight of the total composite.
  • the absorbent capacity of several of the representative composites is summarized in Table 6.
  • portions of the representative composites i.e., 10 cm squares
  • the samples were allowed to absorb liquid and swell for 10 minutes.
  • the difference in the weight of the composite before and after the 10 minute swell is the capacity that is reported as cc/g.
  • Example 17 The Flexibility and Softness of Representative Reticulated Absorbent Composites:
  • the flexibility and softness of representative reticulated absorbent composites formed by wetlaid and foam-forming methods in accordance with the present invention were determined by measuring composite edgewise ring crush and edgewise compression.
  • the flexibility and softness of representative composites was determined by an edgewise ring crush method.
  • a length of the composite typically about 12 inches
  • Edgewise ring crush is measured by adding mass to the top of the composite ring sufficient to reduce the composite cylinder's height by one-half. The more flexible the composite, the less weight required to reduce the height in the measurement.
  • the edgewise ring crush is measured and reported as a mass (g).
  • Edgewise compression (EC) is the ring crush reported in units of g/gsm in the tables below. The following is a description of the ring crush method. Samples: 6.35 cm (2.5 in) X 30.5 cm (12 in)
  • Composite 8-2 A wetlaid composite composed of 40 percent by weight superabsorbent material (small screened SXM-77, 0.208-0.355), 30 percent by weight matrix fibers, and 30 percent by weight crosslinked fibers.
  • Composite 8-3 A wetlaid composite composed of 40 percent by weight superabsorbent material (unscreened SXM-77), 30 percent by weight matrix fibers, and 30 percent by weight crosslinked fibers.
  • Composite 16 A wetlaid composite composed of 40 percent by weight superabsorbent material, 30 percent by weight matrix fibers, and 30 percent by weight crosslinked fibers.
  • Surfactant QS-15 (Union Carbide Corporation) was included in the formation process.
  • Replacing the crosslinked fiber in the composite with other materials such as CTMP (Composite 4) or HPZ (Composite 5) results in increased ring crush values and reduced flexibility and softness.
  • Replacing the composite's crosslinked fiber with additional superabsorbent material (Composite 6) also decreases flexibility and softness.
  • increasing the amount of superabsorbent material and maintaining a relatively high proportion (about 50 percent by weight based on total weight of fibers) of crosslinked fiber provides a composite (Composite 7) having increased flexibility and softness compared a representative wetlaid composite (Composite 2).
  • the flexibility and softness of the composites of the invention can be dramatically increased by increasing the amount of superabsorbent material and crosslinked fiber in the composite.
  • the flexibility and softness of representative composites composed of superabsorbent (40, 50 and 60 percent by weight), crosslinked fiber (10, 15, 25, 30, and 45 percent by weight), and matrix fiber (10, 15, 25, 30, and 45 percent by weight) is summarized in Table 9.
  • superabsorbent A refers to a superabsorbent obtained from Stockhausen
  • superabsorbent B refers to a superabsorbent obtained from Stockhausen under the designation SXM-77.
  • Both composites included a wet strength agent (polyamide-epichlorohydrin resin, 10 lb/ton fiber) and had surface strata composed of matrix fibers (NB416, 40 percent by weight) and crosslinked fibers (60 percent by weight).
  • the first composites had an average edgewise compression value of about 2.9 g/gsm and the second composites had an average edgewise compression value of about 1.1 g/gsm.
  • the Softness and Wet Integrity of Representative Reticulated Absorbent Composites was determined by the edgewise compression and wet modified circular bend methods. Edgewise compression is discussed in The Handbook of Physical and Mechanical Testing of Paper and Paperboard, Richard E. Mark, Dekker 1983 (Vol. 1). Modified circular bend can be determined by ASTM D4032-82 Circular Bend Procedure. As noted above, edgewise compression (EC) is an indication of the softness of a dried absorbent composite. Modified circular bend (MCB) is a measure of the composite's wet integrity. Suitably, the composite has a wet MCB value greater than about 0.3 g/gsm, preferably greater than about 0.4 g/gsm, and more preferably greater than about 0.5 g/gsm.
  • superabsorbent polymer particle size on the flexibility and softness of representative composites of the invention is described.
  • Representative composites were formed as described above using a foam-forming twin-wire method.
  • the composites included 60% by weight superabsorbent particles, 20% by weight matrix fibers (southern pine, NB416), and 20% crosslinked fiber.
  • the composites also included a wet strength agent (polyamide-epichlorohydrin resin, 10 lb/ton fiber).
  • the superabsorbent polymer particles incorporated into the representative composites included lightly crosslinked polyacrylates: (1) superabsorbent A obtained from Stockhausen; (2) SXM77; and (3) screened SXM77 having particle diameter in the range of from about 0.5 to about 1.0 mm.
  • the measured ring crush, saturation capacity (measured by immersing a weighed portion of a composite in saline for a period of time, placing the wetted composite on a screen and covering the composite with a rubber dam, applying a specified vacuum to the assembly, and then reweighing the composite) tensile strength, wicking, and basis weights for the representative composites 44-46 are summarized in Table 11.
  • Composite 44-46 included the components described above and superabsorbent polymer particles A, SXM77, and screened SXM77, respectively.
  • Example 21 The Tensile Strength of Representative Reticulated Absorbent Composites: Wetlaid
  • Control composite is composed of superabsorbent particles (40% by weight) and matrix fibers (60%) by weight, southern pine)
  • Composite 2 is composed of superabsorbent particles (40% by weight), matrix fibers (30% by weight, southern pine), and crosslinked fibers (30% by weight).
  • FIGURE 29 The correlation between composite edgewise compression and dry tensile is presented graphically in FIGURE 29.
  • edgewise compression increases dramatically as dry tensile increases.
  • composite flexibility and softness decreases.
  • composite density decreases.
  • Representative composites were prepared by foam-forming methods in accordance with the methods described above.
  • the composites included absorbent material (SAP, from about 35 to about 45 percent by weight superabsorbent particles based on the total weight of the composite), crosslinked cellulosic fiber OIL), and matrix fibers (weight ratio of crosslinked fibers to matrix fibers, 1:1).
  • SAP absorbent material
  • OIL crosslinked cellulosic fiber
  • matrix fibers weight ratio of crosslinked fibers to matrix fibers, 1:1.
  • Unrestrained Vertical Wicking Height The unrestrained vertical wicking height at 15 minutes was measured for the above-identified composites (i.e., unsoftened Composites 43-45) and the corresponding calendered composites as described below.
  • Material Synthetic urine for wicking - "Blood Bank” 0.9% Saline Solution
  • the acquisition rate and rewet of the representative composites was determined by the methods described above in Example 4. In addition to measuring the acquisition rate for three liquid insults and rewet for Composite 48, the acquisition rate and rewet for Composites 47 and 48 combined with a pledget was also determined. For these constructs, the pledget acts as an acquisition/distribution layer. The results are summarized in Table 15.
  • compositions of representative composites of the invention are summarized in Table 19 below.
  • the amount of matrix fibers e.g., southern pine
  • crosslinked cellulosic fibers e.g., crosslinked cellulosic fibers
  • superabsorbent material e.g., glycerol, glycerol, glycerol, glycerol, glycerol, glycerol, glycerol, polyamide-epichlorohydrin adduct
  • the representative compositions have basis weights ranging from about 161 to about 900 g/m 2 .
  • the representative composites include composites having matrix fibers in an amount from about 8 to about 72 percent by weight, crosslinked fibers in an amount from about 5 to about 64 percent by weight, and superabsorbent material in an amount from about 10 to about 60 percent by weight based on the total weight of the composite.
  • the optional wet strength agent can be present in an amount up to about 25 pounds per ton fiber.

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Abstract

La présente invention concerne un composite réticulé absorbant comportant une couche centrale réticulée et une couche intermédiaire fibreuse. La couche centrale et la couche intermédiaire sont formés solidaires et la couche intermédiaire est accolée à une surface de la couche centrale. Dans un premier mode de réalisation, le composite comprend des couches intermédiaires sur les surfaces opposées de la couche centrale. La couche centrale comprend une matrice fibreuse et une matière absorbante. La matrice fibreuse définit des vides et des passages entre les vides, lesquels sont répartis dans tout le composite. Une matière absorbante est située à l'intérieur de certains des vides. Lors d'une humidification, la matière absorbante située dans ces vides s'étend à l'intérieur du vide. L'invention concerne également des procédés de formation du composite et d'articles absorbants contenant ce composite.
PCT/US2001/015271 2000-05-11 2001-05-10 Composite absorbant reticule WO2001085083A1 (fr)

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MXPA02011106A MXPA02011106A (es) 2000-05-11 2001-05-10 Material mixto absorbente reticulado.
AU2001261452A AU2001261452A1 (en) 2000-05-11 2001-05-10 Reticulated absorbent composite
CA002406501A CA2406501A1 (fr) 2000-05-11 2001-05-10 Composite absorbant reticule
JP2001581738A JP2003532496A (ja) 2000-05-11 2001-05-10 網目状吸収性複合体
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US9498384B2 (en) * 2011-12-01 2016-11-22 Leigh E. Wood Assembled intermediate comprising staple fiber nonwoven web and articles
WO2014145668A1 (fr) * 2013-03-15 2014-09-18 Dsg Technology Holdings Ltd Article absorbant comprenant noyau élastique
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US9439815B2 (en) 2011-04-26 2016-09-13 The Procter & Gamble Company Absorbent members having skewed density profile
US9452093B2 (en) 2011-04-26 2016-09-27 The Procter & Gamble Company Absorbent members having density profile
US9452089B2 (en) 2011-04-26 2016-09-27 The Procter & Gamble Company Methods of making absorbent members having density profile
US9452094B2 (en) 2011-04-26 2016-09-27 The Procter & Gamble Company Absorbent members having density profile
US9534325B2 (en) 2011-04-26 2017-01-03 The Procter & Gamble Company Methods of making absorbent members having skewed density profile
US10011953B2 (en) 2011-04-26 2018-07-03 The Procter & Gamble Company Bulked absorbent members
US10195251B2 (en) 2011-06-09 2019-02-05 University Of Miami Methods of treatment for retinal diseases using MANF and CNDF
US11744747B2 (en) 2011-11-09 2023-09-05 The Procter And Gamble Company Absorbent article with dual core
US10519606B2 (en) 2016-12-22 2019-12-31 Kimberly-Clark Wordlwide, Inc. Process and system for reorienting fibers in a foam forming process

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EP1289467A1 (fr) 2003-03-12
MXPA02011106A (es) 2004-08-19
AU2001261452A1 (en) 2001-11-20
KR20030004396A (ko) 2003-01-14
CN1427705A (zh) 2003-07-02
WO2001070158A1 (fr) 2001-09-27
JP2003532496A (ja) 2003-11-05
CA2406501A1 (fr) 2001-11-15

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