MXPA02003144A

MXPA02003144A - Absorbent composite having fibrous bands.

Info

Publication number: MXPA02003144A
Application number: MXPA02003144A
Authority: MX
Inventors: G Marsh David
Original assignee: Weyerhaeuser Co
Priority date: 1999-09-21
Filing date: 2000-09-21
Publication date: 2002-09-30
Also published as: EP1274889A1; AU7708100A; KR20020040812A; JP2003510470A; EP1274889A4; CA2384376A1; WO2001021873A1

Abstract

An absorbent composite having fibrous bands is described. The composite (300) includes one or more fibrous bands (320) in a fibrous base (310). The base includes a fibrous matrix and absorbent material. The fibrous bands are substantially free of absorbent material. Absorbent articles that include the composite and methods for forming the composite are also disclosed.

Description

MIXED ABSORBENT MATERIAL THAT HAS FIBROUS BANDS CROSS REFERENCE TO RELATED REQUEST This application claims the benefit of the priority of the filing date of the E.U.A. Copending No. 50 / 155,464, filed September 21, 1999, which is expressly incorporated herein by reference in its entirety.

FIELD OF THE INVENTION The present invention relates to a mixed absorbent material and very particularly to a mixed absorbent material including superabsorbent material and fibrous webs.

BACKGROUND OF THE INVENTION 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 that the absorbent articles have a high absorbent capacity for liquids as well as characteristics of resistance to dryness and moisture for durability during effective use and fluid handling. The absorbent capacity of articles made of cellulose fibers is often increased by the addition of superabsorbent materials, such as superabsorbent polymers. The superabsorbent polymers known in the art have the ability to absorb liquids in amounts of 5 to 100 times or more their weight. Therefore, the presence of superabsorbent polymers greatly increases the liquid holding capacity of absorbent articles made of cellulose. Because superabsorbent polymers absorb liquid and swell upon contact with liquid, superabsorbent polymers have hitherto been incorporated mainly into cellulose mats that are produced by conventional dry air-laying methods. Wet laying processes that form cellulose mats have not been used commercially because the superabsorbent polymers tend to absorb liquids and swell during the formation of the absorbent mats, thus requiring significant energy for complete drying. The cellulose structures formed by wet laying processes typically exhibit certain properties that are superior to those of the air laid structure. The integrity, fluid distribution and capillary absorption characteristics of wet-laid cellulosic structures are superior to those of air-laid structures. Attempts to combine the advantages of wet-laid mixed materials with the high absorbent capacity of superabsorbent materials led to the formation of several mixed absorbent materials laid on • r & * »& & j i * > tJ humid including superabsorbent materials. In general, these structures include superabsorbent materials distributed as a layer within a mixed multilayer material. In these structures, the superabsorbent material is relatively located and not uniformly distributed throughout the absorbent structure and therefore makes these mixed materials susceptible to gel blocking. By absorbing liquid, the superabsorbent materials tend to coalesce and form a gelatinous mass that prevents capillary absorption of liquid into unmoistened portions of the mixed material. By preventing the distribution of liquid acquired from unmoistened portions of the mixed material, gel blocking prevents the effective and efficient use of superabsorbent materials in fibrous mixed materials. The decreased capacity of said mixed fibrous materials results from the narrowing of the capillary acquisition and distribution channels that accompany the swelling of the superabsorbent material. The decrease in the absorbent capacity and the percomponent loss of capillary distribution channels for conventional absorbent centers including superabsorbent material is manifested by the decreased liquid acquisition rates and the ideal liquid distribution in successive liquid dischargesTherefore, there is a need for a mixed absorbent material that includes superabsorbent material and that effectively acquires and that capillary absorbs liquid through mixed material and distributes the acquired liquid to an absorbent material where the liquid is efficiently absorbed and retained without blocking of gel. There is also a need for a mixed absorbent material that continues to acquire and distribute liquid throughout the mixed material in successive liquid discharges. In addition, there is a need for a mixed absorbent material containing superabsorbent materials having the advantages associated with wet laid mixed materials including moisture resistance, absorbent capacity and acquisition, liquid distribution, softness and elasticity. The present invention seeks to satisfy these needs and provides other related advantages.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to a cross-linked fibrous absorbent composite material containing absorbent material. The mixed absorbent material is a fibrous matrix that includes absorbent material and a three-dimensional network of channels or capillaries. The reticulated nature of mixed material increases the distribution, acquisition and capillary absorption of liquid, while the absorbent material provides high absorbent capacity. Moisture resistance agents can be incorporated into the mixed material to provide moisture integrity and also help secure the absorbent material in the mixed material. The mixed absorbent material formed in accordance with the present invention includes a stable three dimensional network of fibers and channels that give a rapid acquisition and capillary absorption of liquid. The fibers and channels distribute the acquired liquid through the mixed material and direct the liquid to absorbent material present in the mixed material, where the liquid is finally absorbed. The mixed material maintains its integrity before, during and after the liquid is introduced. In one embodiment, the mixed material is a densified mixed material that can coat its original wet volume. In one aspect, the present invention provides a mixed absorbent material having a fibrous matrix that includes absorbent material. The fibrous matrix defines gaps and passages between the gaps, which are distributed throughout the mixed material. The absorbent material is located inside some of the holes. The absorbent material located in these holes is expandable in the hole. In one embodiment, the cross-linked absorbent mixed material includes at least one fibrous stratum. For such modality, the mixed material includes a cross-linked center and an adjacent fibrous stratum coextensive with a surface facing away from the center. In another embodiment, the mixed material includes strata on surfaces facing away from the center. The layers of the mixed material 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 to form the crosslinked center. In another embodiment, the mixed material includes fibrous webs.

In another aspect of the invention, absorbent articles are provided that include cross-linked mixed material. Absorbent articles include consumer absorbent products such as diapers, feminine care products and adult incontinence products.

BRIEF DESCRIPTION OF THE DRAWINGS The above aspects and many of the advantages of this invention will be more readily appreciated by reference to the following detailed description when taken in conjunction with the accompanying drawings in which: Figure 1 is a cross-sectional view of a portion of a mixed absorbent material formed in accordance with the present invention; Figure 2 is a photomicrograph of a cross section of a cross-linked absorbent composite material formed by a wet laying method according to the present invention at a 12-fold amplification; Figure 3 is a photomicrograph of the mixed wet laid material of Figure 2 at a 40-fold amplification; Figure 4 is a photomicrograph of a cross-section of a representative cross-linked absorbent composite material formed by a foam method according to the present invention at a 12-fold amplification; Figure 5 is a photomicrograph of a mixed material formed with foam of Figure 4 at a 40-fold amplification; Fig. 6 is a photomicrograph of a cross section of a representative cross-linked absorbent composite material formed by a wet laying method according to the present invention in a wet state at an 8-fold amplification; Figure 7 is a photomicrograph of a mixed material stretched from Figure 6 at a 12-fold amplification; Figure 8 is a photomicrograph of a cross section of a representative cross-linked absorbent composite material formed by a foam method in accordance with the present invention in a wet state at an 8-fold amplification; Figure 9 is a photomicrograph of the mixed material formed with foam of Figure 8 at a 12-fold amplification; Figure 10 is a cross-sectional view of a portion of an absorbent construction incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 11 is a cross-sectional view of a portion of another absorbent construction incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 12 is a cross-sectional view of a portion of an absorbent article incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 13 is a cross-sectional view of a portion of another absorbent article incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 14 is a cross-sectional view of a portion of another absorbent article incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 15 is a cross-sectional view of a portion of an absorbent construction incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 16 is a cross-sectional view of a portion of another absorbent construction incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 17 is a cross-sectional view of a portion of another absorbent article incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 18 is a cross-sectional view of a portion of an absorbent article incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 19 is a cross-sectional view of a portion of another absorbent article incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figure 20 is a cross-sectional view of a portion of another absorbent article incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figures 21 A and B are cross-sectional views of portions of cross-linked absorbent composite materials formed in accordance with the present invention; Fig. 22 is a diagrammatic view illustrating a double wire device and method for forming the mixed material of the present invention; Figure 23 is a diagrammatic view illustrating a representative headbox assembly and method for forming the same material of the present invention; Figure 24 is a diagrammatic view illustrating a representative headbox assembly and method for forming the mixed material of the present invention; Figure 25 is a view illustrating representative ducts for introducing absorbent material into a fibrous web in accordance with the present invention; Figures 26 A-C are cross-sectional views of portions of absorbent constructions incorporating an acquisition layer and a cross-linked absorbent composite material formed in accordance with the present invention; Figures 27 A-C are cross-sectional views of portions of absorbent constructions incorporating an acquisition layer, an intermediate layer and a crosslinked absorbent composite material formed in accordance with the present invention; Figures 28 A-C are cross-sectional views of portions of absorbent articles incorporating a cross-linked absorbent composite material formed in accordance with the present invention; Figs. 29A-C are cross-sectional views of portions of absorbent articles incorporating an acquisition layer and a cross-linked absorbent composite material formed in accordance with the present invention; Figures 30A-C are cross-sectional views of portions of absorbent articles incorporating an acquisition layer, intermediate layer and a cross-linked absorbent composite material formed in accordance with the present invention; Figure 31 is a schematic figure of a representative mixed material having fibrous webs formed in accordance with the present invention; Figure 32 is a graph comparing the capillary absorption height in 15 minutes, capacity at 15 cm, and wetted zone capacity for representative mixed materials formed in accordance with the present invention; - i a -lAJ-Jif '- Figure 33 is a graph that correlates the crushing strength and the ring tension of mixed material for representative mixed materials formed in accordance with the present invention; Figure 34 is a non-restricted capillary vertical saturation and saturation capacity of mixed material for representative mixed materials formed in accordance with the present invention; Figure 35 is a graph correlating the crushing strength and the ring tension of mixed material for representative mixed materials formed in accordance with the present invention; and Figure 36 is a non-restricted capillary vertical saturation and saturation capacity of mixed material for representative mixed materials formed in accordance with the present invention; DETAILED DESCRIPTION OF THE PREFERRED MODALITY The mixed material formed in accordance with the present invention is a cross-linked fibrous composite material that includes absorbent material. The absorbent material is substantially distributed through the mixed fibrous material and serves to absorb and retain the liquid required by the mixed material. In a preferred embodiment, the mixed material is a superabsorbent material. In addition to forming a matrix for the absorbent material, the fibers of the mixed material provide a stable three-dimensional network of channels or capillaries which serve to acquire liquid by contacting the mixed material and distribute the acquired liquid to the absorbent material. The mixed material optionally includes a moisture resistance agent that increases more to tensile strength and structural integrity to the mixed material. The mixed material is a fibrous matrix that includes absorbent material. The fibrous matrix defines gaps and passages between the gaps, which are distributed throughout the mixed material. The absorbent material is located inside some of the holes. The absorbent material located in these holes is expandable within the gap. The mixed absorbent material can advantageously be incorporated into a variety of absorbent articles such as diapers and training pants; feminine care products including sanitary pads, tampons and pantiliners; incontinence products in adults; towels; surgical and dental sponges; bandages; pads for food trays; and similar. Because the mixed material is highly absorbent having a high liquid storage capacity, the mixed material can be incorporated into an absorbent article as a liquid storage center. In such construction the mixed material can be combined with one or more other mixed materials or layers including, for example, an acquisition and / or distribution layer. In a preferred embodiment, the absorbent article, such as a diaper, includes an acquisition layer that overlaps a cross-linked storage center and has a liquid-permeable front sheet and a liquid-impermeable backsheet. Due to the ability of the mixed material to rapidly acquire and distribute the liquid, the mixed material can serve as a liquid handling layer and acquire and transfer a portion of the acquired liquid to an underlying storage layer. Therefore, in another embodiment, the mixed absorbent material can be combined with a storage layer to provide an absorbent center that is useful in absorbent articles. The mixed absorbent material formed according to the present invention is a cross-linked absorbent mixed material. As used herein, the term "cross-linked" refers to the open and porous nature of the mixed material characterized as having a stable three-dimensional fiber network (ie, fibrous matrix) that creates channels or capillaries that serve to rapidly acquire and distribute the liquid in all the mixed material, finally supplying acquired liquid to the absorbent material that is distributed in all the mixed material. The crosslinked mixed material is an open and stable structure. The open and stable structure of the mixed fibrous material includes a network of capillaries or channels that are effective in acquiring and distributing liquid throughout the mixed material. In the mixed material, the fibers of relatively dense packets direct fluid throughout the mixed material and towards absorbent material distributed throughout the mixed material. The moisture resistance agent of the mixed material serves to stabilize the fibrous structure by providing bonding between fibers. The union between fibers helps to provide a mixed material that has a stable structure in which the capillaries or channels of the mixed material remain open before, during and after discharge of liquid. The stable structure of the mixed material provides capillaries that remain open after the initial liquid discharge and that are available to acquire and distribute liquid in subsequent discharges. Referring to Figure 1 a representative cross-linked absorbent composite material generally indicated by the reference numeral 10 formed in accordance with the present invention is a fibrous matrix that includes fibrous regions 12 substantially composed of fibers 16 and defining gaps 14. Some gaps include absorbent material 18. Holes 14 are distributed throughout the mixed material 10. Representative cross-linked composite materials formed in accordance with the present invention are shown in Figures 2-9. These mixed materials include 48% by weight of matrix fibers (ie, southern pine commercially available from Weyerhaeuser Co. under the designation NB416), 12% by weight of elastic fibers (i.e., entangled polymaleic acid fibers), 40% by weight of absorbent material (i.e., superabsorbent material commercially available from Stockhausen ), and about 0.5% by weight of moisture resistant agent (ie, polyamide-epichlorohydrin resin commercially available from Hercules under the designation Kymene®). Figure 2 is a photomicrograph of a cross section of a representative mixed material formed by a wet-run procedure at a 12-fold amplification. Figure 3 is a photomicrograph of the same cross section at a 40-fold amplification. Figure 4 is a photomicrograph of a cross section of a representative mixed material formed by a foam procedure at a 12-fold amplification. Figure 5 is a photomicrograph of the same cross section at a 40-fold amplification. The reticulated nature of the mixed materials is shown in these figures. Referring to Figure 3, the fibrous regions extend throughout the mixed material creating a network of channels. The hollow regions, including those that include absorbent material, appear throughout the mixed material and are in fluid communication with the fibrous region of the mixed material. The absorbent material appears in the voids of the mixed material, generally surrounded by packages of dense fibers. Photomicrographs of the representative mixed materials shown in Figures 2-5 in a wetted state are illustrated in Figures 6-9, respectively. These photomicrographs are obtained by sectioning freeze-dried mixed materials that had acquired synthetic urine under free swelling conditions. Figures 6 and 7 are photomicrographs of mixed material wet laid at an amplification of 8 times and 12 times respectively. Figures 8 and 9 are photomicrographs of mixed material formed with foam moistened at an amplification of 8 times and 12 times respectively. Referring to Figure 6, the absorbent material in the moistened mixed material has swelled and increased in size to more fully occupy the voids than the absorbent material previously occupied in the dry mixed material. The fibrous matrix of the mixed material is composed mainly of fibers. Generally, the fibers are present in the mixed material in an amount of from about 20 to about 90% by weight, preferably from about 50 to about 70% by weight, based on the total weight of the mixed material. Suitable fibers for use in the present invention are known to those skilled in the art and include any fiber from which the wet mixed material can be formed. The mixed material includes elastic fibers. As used herein, the term "elastic fiber" refers to a fiber present in the mixed material that imparts crosslinking to the mixed material. Generally, elastic fibers provide the mixed material with volume and elasticity. The incorporation of elastic fibers in the mixed material allows the mixed material to expand when absorbing liquid without loss of structural integrity. The elastic fibers also impart softness to the mixed material, in addition, the elastic fibers offer advantages in the process of forming the mixed material. Due to the porous and open structure resulting from wet mixed materials including elastic fibers, these mixed materials drain water relatively easily and are therefore dehydrated and dried more quickly than wet mixed materials that do not include elastic fibers. Preferably, the mixed material includes elastic fibers in an amount of from about 5 to about 60% by weight, most preferably from about 10 to 40% by weight, based on the total weight of mixed material. The elastic fibers include cellulosic and synthetic fibers. Preferred elastic fibers include chemically stiffened fibers, fibers anfractuosas, quimiotermomecánica pulp (CTMP), and prehydrolized kraft pulp (PHKP). The term "chemically stiffened fiber" refers to a fiber that has been stiffened by chemical means to increase its fiber stiffness under dry and wet conditions. The fibers can be stiffened by the addition of chemical stiffening agents which can coat and / or impregnate the fibers. Stiffening agents include polymeric moisture resistant agents including resinous agents such as, for example, polyamide-epichlorohydrin and polyacrylamide resins which are described below. The fibers can also be stiffened by modifying the structure of the fiber, for example, by chemical entanglement. Preferably, the chemically stiffened fibers are intrafiber interlaced cellulosic fibers. The elastic fibers may include non-cellulosic fibers including, for example, synthetic fibers such as polyolefin, pliamide and polyester. In a preferred embodiment, the elastic fibers include interwoven cellulosic fibers.

As used herein, the term "anfractuous fiber" refers to a cellulosic fiber that has been chemically treated. Fracture fibers include, for example, fibers that have been treated with ammonia. In addition to the elastic fibers, the mixed material includes matrix fibers. As used herein, the term "matrix fiber" refers to a fiber that is capable of forming hydrogen bonds with other fibers. The matrix fibers are included in the mixed material to impart strength to the mixed material. The matrix fibers include cellulosic fibers such as wood pulp fibers, highly refined cellulosic fibers and high surface area fibers such as expanded cellulose fibers. The cellulose fibers include cotton fluff, cotton fibers and hemp fibers among others. Mixtures of fibers can also be used. Preferably, the mixed material includes matrix fibers in an amount of from about 10 to about 60% by weight, most preferably from about 20 to about 50% by weight, based on the total weight of the mixed material. The mixed material preferably includes a combination of elastic and matrix fibers. In a preferred embodiment, the mixed material includes elastic fibers in an amount of about 5 to about 20% by weight and matrix fibers in an amount of from about 20 to about 60% by weight based on the total weight of the mixed material. In a preferred embodiment, the mixed material includes from about 10 to about 15% by weight of elastic fibers, preferably entangled cellulosic fibers and from about 40 to about 50% by weight of matrix fibers, preferably wood pulp fibers, based on the total weight of the mixed material. The cellulosic fibers are a basic component of the mixed absorbent material. Although available from other sources, cellulosic fibers are mainly derived from wood pulp. Wood pulp fibers suitable for use with the invention can be obtained from well-known chemical methods such as kraft and sulphite processes, with or without subsequent bleaching. The pulp fibers can also be processed by thermomechanical and chemimetromechanical methods or combinations thereof. The preferred pulp fiber is produced by chemical methods. Fibers from milled wood, recycled or secondary wood pulp fibers, and bleached and unbleached wood pulp fibers can be used. Soft woods and hard woods can be used. The details of the selection of wood pulp fibers are well known to those skilled in the art. These fibers are commercially available from a number of companies including Weyerhaeuser Company, the assignee of the present invention. For example, suitable cellulose fibers produced from southern pine that are useful with the present invention are available from Weyerhaeuser Company under the designations CF16, NF405, PL416, FR516 and NB416. The wood pulp fibers can also be pretreated before being used with the present invention. The pretreatment may include physical treatment, such as subjecting the fibers to steam or chemical treatment, for example, by interlacing the cellulose fibers using any of a variety of crosslinking agents. The entanglement includes the volume and elasticity of the fiber, and in this way can improve the absorbency of the fibers. Generally, the interlaced fibers are twisted or curled. The use of interlaced fibers allows the mixed material to be more elastic, softer, more bulky, have better capillary absorption and be easier to densify than a mixed material that does not include interlaced fibers. Suitable interlaced cellulose fibers produced from southern pine are available from Weyerhaeuser Company under the designation NHB416. Interlaced cellulose fibers and methods for their preparation are described in the U.S. Patents. Nos. 5,437,418 and 5,225,047, issued to Graef et al., Expressly incorporated herein by reference. The intrafiber interlaced cellulosic fibers are prepared by treating cellulose fibers with an interlacing agent. Suitable cellulose crosslinking agents include aldehyde and formaldehyde addition products based on urea. See, for example, the patents of E.U.A. Nos. 3,224,926; 3,241, 533; 3,932,209; 4,035,147; 3,756,913; 4,689,913; 4,689,118; 4,822,453; patent of E.U.A. No. 3,440,135, issued to Chung; patent of E.U.A. No. 4,935,022, issued to Lash et al .; patent of E.U.A. No. 4,889,595, issued to Herrón et al .; patent of E.U.A. No. 3,819,470, issued to Shaw et al .; patent of E.U.A. No. 3,658,613, issued to Steijer et al .; and U.S. Patent No. 4,853,086, issued to Graef et al., all of which are hereby expressly incorporated by reference in their entirety. The cellulose fibers have also been intertwined by carboxylic acid crosslinking agents including polycarboxylic acids. The patents of E.U.A. Nos. 5,137,537; 5,183,707; and 5,190,563, describe the use of C2-Cg polycarboxylic acids containing at least three carboxyl groups (eg, citric acid and oxydisuccinic acid) as crosslinking agents. Suitable urea based crosslinking agents include methylolated ureas, cyclic methylolated ureas, cyclic lower alkyl methylolated ureas, methylolated hydroxylic cyclic ureas, cyclic dihydroxy ureas and cyclic ureas substituted with lower alkyl. Preferred specific urea based crosslinking agents include dimethyldihydroxyethyleneurea (DMeDHEU, 1,3-dimethyl-4,5-dihydroxy-2-imidazolidinone), dimethyloldihydroxyethylene urea (DMDHEU, 1,3-dihydroxymethyl-4,5-dihydroxy-2-) imidazolidinone), dimethylolurea (DMU, bis [N-hydroxymethyl] urea), dihydroxyethyleneurea (DHEU, 4,5-dihydroxy-2-imidazolidinone), and dimethylolethyleneurea (DMEU, 1,3-dihydroxymethyl-2-imidazolidinone). Suitable polycarboxylic 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 crosslinking agents include polymeric polycarboxylic acids such as poly (acrylic) acid, poly (methacrylic) acid, poly (maleic) acid, poly (methyl vinyl ether-co-maleate) copolymer, poly (methyl vinyl ether-co-methyl ether) copolymer. itaconate), copolymers of acrylic acid and maleic acid copolymers. The use of polymeric polycarboxylic acid crosslinking agents such as polyacrylic acid polymers, polymaleic acid polymers, acrylic acid copolymers and maleic acid copolymers are described in the patent application of E.U.A. series No. 08/989/697, filed on December 12, 1997 and assigned to Weyerhaeuser Company. Mixtures or combinations of crosslinking agents can also be used. The interlacing agent may include a catalyst to accelerate the binding reaction between the crosslinking agent and the cellulose fiber. Suitable catalysts include acid salts, such as ammonium chloride, ammonium sulfate, aluminum chloride, magnesium chloride and alkali metal salts of phosphorus-containing acids. Although not to be considered as a limitation, examples of fiber pretreatment include the application of surfactants or other liquids that modify the surface chemistry of the fibers. Other treatments include the incorporation of antimicrobials, pigments, dyes and densifying agents or softeners. Fibers pretreated with other chemical compounds, such as thermoplastic and thermosetting resins can also be used. Pretreatment combinations can also be used. Similar treatments can also be applied after the formation of mixed material in post-treatment procedures.

The cellulose fibers treated with particle binders and / or densification / softness aids known in the art can also be used in accordance with the present invention.The particle binders serve to fix other materials, such as cellulosic fiber superabsorbent polymers. , as well as others, to the cellulosic fibers The cellulosic fibers treated with suitable particle binders and / or densification / softness aids and the processes for combining them with cellulose fibers are described in the following US patents: (1) Patent No 5,543,215, entitled "Polymeric Binders for Binding Particles to Fibers"; (2) Patent No. 5,538,783, entitled "Non-Polymeric Organic Binders of Binding Particles to Fibers"; (3) Patent No. 5,300,192, entitled "Wet Laid Fiber Sheet Manufacturing With Reactivatable Binders for Binding Particles to Binders "; (4) Patent No. 5,352,480, entitled" Method for Binding Particles to Fibe rs Using Reactivatable Binders "; (5) Patent No. 5,308,896, entitled "Particle Binders for High-Bulk Fibers"; (6) Patent No. 5,589,256, entitled "Particle Binders that Enhance Fiber Densification"; (7) Patent No. 5,672,418, entitled "Particle Binders"; (8) Patent No. 5,607,759, entitled "Particle Binding to Fibers"; (9) Patent No. 5,693,411, entitled "Binders for Binding Water Soluble Particle to Fibers"; (10) Patent No. 5,547,745, entitled "Particle Binders"; (11) Patent No. 5,641, 561, entitled "Particle Binding to Fibers"; (12) Patent No. 5,308,896, entitled "Particle Binders for High-Bulk Fibers"; (13) Patent No. 5,498,478, entitled "Polyethylene Glycol as a Binder Material for Fibers"; (14) Patent No. 5,609,727, entitled "Fibrous Product for Binding Particles"; (15) Patent No. 5,571, 618, entitled "Reactivatable Binders for Binding Particles to Fibers"; (16) Patent No. 5,447,977, entitled "Particle Binders for High Bulk Fibers"; (17) Patent No. 5,614,570, entitled "Absorbent Articles Containing Binder Carrying High Bulk Fibers; (18) Patent No. 5,789,326, entitled" Binder Treated Fibers "; and (19) Patent No. 5,611, 885, entitled" Particle Binders " , all specifically incorporated herein by reference.In addition to natural fibers, synthetic fibers include polymeric fibers, such as polyolefin fibers, polyamide, polyester, polyvinyl alcohol and polyvinyl acetate may also be used in the mixed absorbent material. suitable polyolefins include polyethylene and polypropylene fibers Suitable polyester fibers include polyethylene terephthalate fibers Other suitable synthetic fibers include, for example, nylon fibers The mixed absorbent material can include combinations of natural and synthetic fibers. preferred embodiment, the mixed absorbent material includes a combination of wood pulp fibers (for example, Weyerhaeuser, NB416) and interwoven cellulosic fibers (for example, Weyerhaeuser, designation NHB416). The wood pulp fibers are present in said combination in an amount of from about 10 to about 85% by weight based on the total weight of the fibers. When incorporated into an absorbent article, the crosslinked absorbent mixed material can serve as a storage layer for purchased liquids. To effectively retain acquired liquids, the mixed material absorbed includes absorbent material. As used herein, the term "absorbent material" refers to a material that absorbs liquid and that generally has a greater absorbent capacity than the cellulosic fiber component of the mixed material. Preferably, the absorbent material is water-swellable polymeric material, generally insoluble in water capable of absorbing at least about 5, conveniently about 20 and preferably about 100 times or more its weight in saline solution (eg, 0.9 percent saline solution). ). The absorbent material may be inflatable in a dispersion medium used in the method to form the mixed material. In a modality, the absorbent material is untreated and is inflatable in the dispersion medium. In another embodiment, the absorbent material is a coated absorbent material that is resistant to absorb water during the mixed material formation process. The amount of absorbent material present in the mixed material can vary greatly depending on the intended use of the mixed material. The amount of absorbent material present in an absorbent article, such as an absorbent center for a baby diaper, is suitably present in the mixed material in an amount of from about 5 to about 60 weight percent, preferably from about 30 to 50 weight percent. about 50 weight percent, based on the total weight of the mixed material.

The absorbent material can include natural materials such as agar, pectin and guar gum, and synthetic materials such as synthetic hydrogel polymers. Synthetic hydrogel polymers include, for example, carboxymethylcellulose, alkali metal salts of polyacrylic acid, polyacrylamides, polyvinyl alcohol, ethylene-maleic anhydride copolymers, polyvinyl ethers, hydroxypropylcellulose, polyvinylmorpholinone, sulfonic acid polymers and copolymers, polyacrylates, polyacrylamides and polyvinylpyrine among others. In a preferred embodiment, the absorbent material is a superabsorbent material. As used herein, an "absorbent material" refers to a polymeric material that is capable of absorbing large amounts of fluid by swelling and forming a hydrated gel (i.e., a hydrogel). In addition to absorbing large amounts of fluid, superabsorbent materials can also retain significant amounts of body fluids under moderate pressure. The superabsorbent materials generally fall into three classes: starch graft polymers, crosslinked carboxymethyl cellulose derivatives and modified hydrophilic polyacrylates. Examples of such absorbent polymers include graft copolymers of hydrolyzed starch-acrylonitrile, graft copolymers of neutralized starch-acrylic acid, copolymers of saponified acrylic acid ester-vinyl acetate, hydrolyzed acrylonitrile copolymers or acrylamide copolymers, modified crosslinked polyvinyl alcohol , neutralized self-interlacing polyacrylic acids, cross-linked polyacrylate salts, carboxylated cellulose and neutralized crosslinked isobutylene-maleate anhydride copolymers. The superabsorbent materials are, for example, polyacrylates commercially available from Clariant of Portsmouth, Virginia. These superabsorbent polymers are provided in a variety of sizes, morphologies and absorbent properties (available from Clariant under brand designations such as IM 3500 and IM 3900). Other superabsorbent materials are marketed under the trade names SANWET (supplied by Sanyo Kasei Kogyo Kabushiki Kaisha), and SXM77 (supplied by Stockhausen of Greensboro, North Carolina). Other superabsorbent materials are described in the U.S.A. No. 4,160,059; Patent of E.U.A. No. 4,676,784; Patent of E.U.A. No. 4,673,402; Patent of E.U.A. No. 5,02,814; Patent of E.U.A. No. 5,057,166; Patent of E.U.A. No. 4,102,340; and Patent of E.U.A. No. 4,848,598, all expressly incorporated herein by reference. Products such as diapers incorporating superabsorbent materials are described in the U.S. Patent. No. 3,699,103 and the U.S. Patent. No. 3,670,731. Suitable superabsorbent materials useful in the mixed absorbent material include superabsorbent particles and superabsorbent fibers. In a preferred embodiment, the mixed absorbent material includes a superabsorbent material that swells relatively slowly for the purposes of manufacturing mixed material and yet swells at an acceptable rate so as not to adversely affect the absorbent characteristics of the mixed material or any construction that contain the mixed material. Generally, the smaller the absorbent material, the faster the material absorbs liquid. The mixed absorbent material may optionally include a moisture resistance agent. The moisture resistance agent provides increased resistance to the mixed absorbent material and increases the moisture integrity of the mixed material. In addition to increasing the moisture resistance of the mixed material, the moisture resistance agent can assist in the bonding of the absorbent material, eg, superabsorbent material, to the fibrous matrix of the mixed material. Suitable moisture-resisting agents include cationic modified starch having hydrogen-containing groups (e.g., amino groups) such as those commercially available from National Starch and Chemical Corp., Bridgewater, NJ; latex; moisture resistant resins such as polyamide-epichlorohydrin resin (e.g., Kymene® 557LX, Hercules, Inc., Wilmington, DE), polyacrylamide resin (described, for example, in U.S. Patent No. 3,556,932 issued 19 Jan. 1971 to Coscia et al., also, for example, commercially available polyacrylamide marketed by American Cyanamid Co., Stanfor, CT, under the tradename Parez ™ 631 NC); urea formaldehyde and melamine formaldehyde resins, and polyethyleneimine resins. A general discussion on resins resistant to humidity .,. In the field of paper and generally applicable in the present invention, they can be found in the monograph of TAPPI series No. 29, "Wet Stength in Paper and Paperboard," Technical Association of the Pulp and Paper. Industry (New York, 1965). In general, the moisture resistance agent is present in the composition in an amount of from about 0.01 to about 2 weight percent, preferably from about 0.1 to about 1 weight percent, and most preferably about 0.3. to about 0.7 weight percent, based on the total weight of the mixed material. In a preferred embodiment, the moisture resistance agent useful in the formation of the mixed material is a polyamide-epichlorohydrin resin commercially available from Hercules, Inc. under the designation Kymene®. The wet and dry tensile strengths of a mixed absorbent material formed in accordance with the present invention will generally increase with an increase in the amount of moisture resistance agent. The tensile strength of a representative mixed material is described in Example 7. The mixed absorbent material generally has a basis weight of from about 50 to about 1000 g / m2, preferably from about 200 to about 800 g / m2. In a more preferred embodiment, the mixed absorbent material has a basis weight of from about 300 to about 600 g / m2. The mixed absorbent material generally has a density of about 0.02 to about 0.7 g / cm3, preferably about 0.04 to about 0.3 g / cm3. In a more preferred embodiment, the mixed absorbent material has a density of about 0.15 g / cm3. In one embodiment, the mixed absorbent material is a densified mixed material. Densification methods useful in the production of densified mixed materials are well known to those skilled in the art. See, for example, U.S. Patent. No. 5,547,541 and serial patent application No. 08 / 859,743, filed May 21, 1997, entitled "Softened Fibers and Methods of Softening Fibers", assigned to Weyerhaeuser Company, both expressly incorporated herein by reference. The mixed dense absorbent crosslinked storage storage materials after the dryer generally have a density of about 0.1 to about 0.5 g / cm3, and preferably about 0.15 g / cm3. Denser densification can also be used. Preferably, the mixed absorbent material is densified either by a heated calendering roller method or at room temperature. See, for example, US patents. Nos. 5,252,275 and 5,324,575, both expressly incorporated herein by reference. The composition of the cross-linked absorbent mixed material can be varied to suit the needs of the desired final product in which it can be incorporated. In a preferred embodiment, the mixed absorbent material includes about 60% by weight of cellulosic fibers (about 48 percent by weight of wood pulp fibers and about 12% by weight of interwoven cellulosic fibers), about 40 percent by weight of material absorbent (e.g., superabsorbent particles) and about 0.5 percent by weight of moisture-resisting agent (e.g., polyamide-epichlorohydrin resin, Kymene®, approximately 4.54 kg of resin per tonne of fiber), based on total weight of the mixed material. The crosslinked absorbent mixed material can be formed by wet laying and foam processes known to those skilled in the pulp processing art. A representative example of a wet laying process is described in the U.S. Patent. No. 5,300,192, issued April 5, 1994, entitled "Wet-laid Fiber Sheet Manufacturing with Reactivatable Binders for Binding Particles to Fibers", expressly incorporated herein by reference. Wet laying procedures are also described in standard texts, such as Casey, PULP AND PAPER, 2a. edition, 1960, volume II, chapter Vlll-Sheet Formation. Representative foam procedures useful in the formation of mixed material are known in the art and include those described in US Patents. Nos. 3,716,449; 3,839,142; 3,871, 952; 3,937,273; 3,938,782; 3,947,315; 4,166,090; 4,257,754; and 5,215,627, assigned to Wiggins Teape and related to the formation of fibrous materials from suspensions of foamed aqueous fiber, and "The use of an Aqueous Foam as a Fiber-Suspending Medium in Quality Papermaking," Foams, Proceedings of «^ 1x > * É Symposium organized by the Society of Chemical Industry, Colloid and Surface Chemistry Group, R.J. Akers, Ed., Academic Press, 1976, which describes the Radfoam procedure, all expressly incorporated herein by reference. In the methods, the absorbent material is incorporated into the mixed material during the formation of the mixed material. Generally, methods for forming the crosslinked absorbent composite material include combining the components of the mixed material in a dispersion medium, (for example, an aqueous medium to form a suspension and then depositing the suspension on a foraminous support (for example, a wire of formation) and dehydrate to form a wet mixed material The drying of the mixed wet material provides the cross-linked mixed material As indicated above, the cross-linked mixed material is prepared from a combination of fibers, absorbent material and optionally an agent of Moisture resistance in a dispersion medium In one embodiment of the method, a suspension is formed by directly combining fibers, absorbent material and moisture resistance agent in a dispersion medium In another embodiment, the suspension is prepared by first combining fibers and the moisture resistance agent in a dispersion medium to provide a suspension f and then absorbent material is added in a second step. In another embodiment, a fibrous suspension is combined with a second suspension containing absorbent material, the combined suspension being after "4 i i deposited on the support. Alternatively, individual suspensions, for example, a fibrous suspension and a suspension containing absorbent material can be deposited in the foraminous support by the use of a split head box, for example a double-sliced headbox that deposits two suspensions in a Support simultaneously. In one embodiment, the suspension or suspensions containing the components of the mixed material in a dispersion medium are deposited on a foraminous support. Once deposited on the support, the dispersion medium begins to drain from the deposited fibrous suspension. The removal of the dispersion medium (eg, by dehydrating) from the deposited fibrous suspension continues, for example, by the application of heat, pressure, vapor and combinations thereof and results in the formation of a wet mixed material. The crosslinked absorbent mixed material is finally produced by drying the wet mixed material. The drying removes the remaining dispersion medium and provides a mixed absorbent material having the desired moisture content. Generally, the mixed material has a moisture content of less than about 20 percent and preferably has a moisture content in the range of about 6 to about 10 weight percent based on the total weight of the mixed material. Suitable methods of drying the mixed material include, for example, the use of drying cans, air floats and through air dryers. Other drying methods and drying apparatuses known in the pulp and paper industry can also be used. The temperatures, pressures and drying times are typical for the equipment and methods used and are known to those skilled in the art in the pulp and paper industry. A representative wet laying method for forming a cross-linked absorbent mixed material is described in Example 1. For foaming methods, the fibrous suspension is a foam dispersion that also includes a surfactant. Suitable surfactants include ionic, nonionic and amphoteric agents known in the art. A representative foam method for forming a cross-linked absorbent mixed material is described in Example 2. The deposition of the components of the absorbent mixed material on the foraminous support, followed by dehydration, results in the formation of a wet mixed material that includes absorbent material that may have water absorbed, and as a result may be swollen in size. The mixed wet material containing the absorbent material swollen with water is distributed on a support from which the water, (i.e., the dispersion medium) can be extracted and the mixed material dried. Drying causes the absorbent material swollen with water to dehydrate and reduce in size, thus creating gaps in the mixed material surrounding the absorbent material. In the methods, the absorbent material preferably absorbs less than about 20 times its weight in the dispersion medium, . . . It is most preferably less than about 10 times and even more preferably less than about 5 times its weight in the dispersion medium. Foaming methods are advantageous for forming the mixed absorbent material for several reasons. In general, foaming methods provide fibrous meshes having relatively low density and relatively high tensile strength. For meshes composed substantially of the same components, the meshes formed with foam generally have densities greater than meshes stretched in air and smaller than meshes stretched in wet. Similarly, the tensile strength of the meshes formed with foam is substantially greater than for meshes stretched in air and reaches the strength of the wet laid meshes. Also, the use of foam forming technology allows better control of pore size and voids, size of hole to be maximized, orientation and uniform distribution of fibers, and the incorporation of a wide range of materials ( for example, long and synthetic fibers that can not be easily incorporated in wet laying procedures) in mixed material. For manufacturing, the cross-linked absorbent mixed material can be formed by a foam process, preferably a process from Ahlstrom Company (Helsinki, Finland). The process comprises desirable manufacturing efficiencies while producing a product with desirable performance characteristics. The formation of crosslinked absorbent composite material by representative wet and foam laying procedures is described in Examples 1 and 2 respectively. The absorbent properties (ie rewetting, acquisition time, liquid distribution, drying resistance and elasticity) for representative crosslinked absorbent mixed materials are described in Examples 3 and 4. The capillary absorption and liquid distribution for a mixed absorbent material representative are described in examples 5 and 6 respectively. The tensile strength of representative mixed materials formed in accordance with the present invention is described in Example 7. The softness (i.e. Taber stiffness) of representative wet and foam-formed mixed materials is described in Example 8 A variable that affects the performance characteristics of mixed absorbent material including, for example, the acquisition of liquid and the speed of liquid distribution and absorbent capacity, is the degree of swelling of the absorbent material in the mixed material. The methods allow the control and variation of swelling of the absorbent material. The swelling of the absorbent material generally depends on the degree of entanglement (eg, interlacing of surface and internal) and on the amount of water absorbed by the absorbent material. The degree of swelling depends on a number of factors including the type of absorbent material, the concentration of absorbent material in an aqueous environment (for example, the dispersion medium and the wet mixed material), and the period that the absorbent material remains in. contact with said environment. In general, the lower the concentration of the absorbent material in an aqueous medium and the longer the contact time, the greater the swelling of an absorbent material. The swelling of absorbent material can be minimized by supplying the absorbent in chilled water. In general, the greater the initial swelling of the absorbent material, the greater the void volume and consequently the lower the density of the resulting absorbent mixed material. The greater the void volume of the mixed material, the higher the liquid acquisition speed and the greater the absorbent capacity of the mixed material. As stated above, hollows of the mixed material are formed by hydration and by the swelling of the absorbent material (i.e., during the formation of the wet mixed material) and the subsequent dehydration and reduction in size of the absorbent material (i.e., during drying of the material) mixed wet). Finally, the density of the mixed material depends on the degree to which the absorbent material absorbs liquid and swells during the formation of the wet mixed material and the conditions and degree to which the wet mixed material incorporating the swollen absorbent material is dried. The water absorbed by the absorbent material k-é., during the formation of the mixed wet material is removed from the absorbent material, reducing its size, when drying the mixed wet material. The dehydration of the swollen absorbent material defines some of the gaps in the fibrous mixed material. The crosslinked absorbent composite material can be incorporated as an absorbent center or storage layer in an absorbent article including, for example, a diaper or feminine care product. The mixed absorbent material can be used alone or, as illustrated in Figures 10 and 11, can be used in combination with one or more capable. In Figure 10, the absorbent mixed material 10 is used as a storage layer in combination with an upper acquisition layer 20. As illustrated in Figure 11, a third layer 30 (eg, distribution layer) can also be used. employ, if desired, with mixed absorbent material 10 and acquisition layer 20. A variety of suitable absorbent articles can be produced from the mixed absorbent material. The most common include absorbent consumer products, such as diapers, feminine hygiene products such as sanitary napkins and adult incontinence products. For example, referring to Figure 12, the absorbent article 40 comprises an absorbent mixed material 10 and an overlying acquisition layer 20. A liquid-permeable front sheet 22 is superimposed on a mixed absorbent material 20 and a waterproof backsheet 20. liquids 24 is underlying the absorbent mixed material 10.

The mixed absorbent material will provide advantageous liquid absorption performance for use for example in diapers. The cross-linked structure of the mixed absorbent material will aid in the transport and absorption of fluid in multiple wettings. For absorbent articles that incorporate the mixed material and that are suitable for use as diapers or as incontinence products, the articles may further include shirring at the leg portion. The construction in Figure 12 is shown for illustration purposes of a typical absorbent article, such as a female diaper or towel. A person skilled in the art will be able to make a variety of different constructions using the concepts taught herein. The example, a typical construction of an absorbent structure for incontinence in adults is shown in Figure 13. The article 50 comprises a front sheet 22, an acquisition layer 20, a mixed absorbent material 10 and a back sheet 24. The front sheet 22 is permeable to liquids while the backsheet 24 is impervious to liquids. In this construction, the liquid permeable fabric 26 composed of a polar fibrous material is located between the absorbent mixed material 10 and the acquisition layer 20. Referring to Figure 14, another absorbent article includes a front sheet 22, a layer acquisition 20, an intermediate layer 28, a mixed absorbent material 10 and a backsheet 24. The intermediate layer 28 contains for example a densified fibrous material such as a combination of cellulose acetate and triacetin which are combined before forming the article. The intermediate layer 28 can therefore be bonded to the absorbent blended material 10 and the acquisition layer 20 to form an absorbent article having significantly more integrity than one in which the absorbent blended material and the acquisition layer do not merge with one another. other. The hydrophilic nature of the layer 28 can be adjusted in such a way as to create a hydrophilic character gradient between the layers 10, 28 and 20. The crosslinked absorbent mixed material can also be incorporated as a liquid handling layer in an absorbent article such like a diaper. In said article, the liquid material can be used in combination with a storage or storage layer. In the combination, the liquid handling layer may have a higher surface area that is less than the same size as or greater than the upper surface area of the storage layer. The representative absorbent construction incorporating the cross-linked absorbent mixed material in combination with the storage layer is shown in Figure 15. Referring to Figure 15, the absorbent construction 70 includes cross-linked mixed material 10 and a storage layer 72. The storage layer 72 is preferably a fibrous layer including absorbent marial. The storage layer can be formed by any method, including laying in air, wet laying and foaming. The storage layer can be a crosslinked mixed material. An acquisition layer can be combined with the crosslinked mixed material and the storage layer. Figure 16 illustrates the absorbent construction 80 having an acquisition layer 20 overlying the mixed material 10 and a storage layer 72. The construction 80 may further include an intermediate layer 74 that provides the construction 90 shown in Figure 17. The intermediate layer 74 can be, for example, a fabric layer, a non-woven layer, a cushion laid in air or wet laid, or a cross-linked mixed material. The constructions 70, 80 and 90 can be incorporated in absorbent articles. In general, the absorbent articles 100, 110 and 120 shown in Figures 18-20, respectively, include a liquid permeable front sheet 22, a liquid impermeable backsheet 24 and constructions 70, 80 and 90 respectively. In said absorbent articles, the front sheet is attached to the back sheet. In another embodiment, the crosslinked absorbent composite material formed in accordance with the present invention further includes a fibrous stratum. In this embodiment, the mixed material includes a cross-linked center and a fibrous stratum adjacent to a surface facing away from the center. The fibrous stratum is formed integrally with the cross-linked center to provide a unitary, absorbent mixed material. Generally, the stratum is coextensive with an outward facing surface (i.e., an upper and / or lower surface) of the mixed material. Preferably, the mixed material includes first and second strata adjacent each of the surfaces facing outward from the center (ie, the strata are coextensive with opposite surfaces of the center). A representative absorbent blended material having a fibrous stratum is shown in Figure 21 A and a representative mixed material having fibrous layers is shown in Figure 21 B. Referring to Figure 21 A, the absorbent mixed material 130 includes a center lattice 10 and a stratum 132 and, as shown in Fig. 21 B, the mixed material 140 includes a cross-linked center 10 intermediate between the strata 132 and 134. As indicated above, the center 10 is a fibrous matrix that includes fibrous regions 12 defining gaps 14, some of which include absorbent material 18. The stratum or strata of the mixed material are fibrous and may be composed of any suitable fiber or combination of fibers indicated above. The fibrous composition of the stratum can be varied widely. The stratum can be formed from fibers that are the same as or different from the fibers used to form the crosslinked center. The stratum can be formed from elastic fibers, matrix fibers or combinations of elastic and matrix fibers. The layer may optionally include a moisture or dryness resistance agent. Suitable layers can be formed from a single type of fiber, for example, a layer composed of 100 percent wood pulp fibers (eg, southern pine fibers). Alternatively, the stratum can be formed from fibrous mixtures, such as a 80:20 mixture of wood pulp fibers and interlaced fibers, and synthetic blends, and blends of synthetic and cellulosic fibers. ...to. 4"-, ..» < The stratum composition can be varied to provide a mixed material having desired characteristics. For example, to provide a stratum having high capillary liquid absorption capacity, the stratum preferably has a relatively high fiber content of wood pulp. Therefore, for liquid distribution, the stratum is preferably composed of wood pulp fiber such as southern pine fibers. However, said stratum has a lower liquid acquisition rate compared to a similarly constituted stratum which contains relatively smaller wood pulp fiber and, for example, higher amounts of entangled fibers. On the contrary, to provide a stratum having a high liquid acquisition rate, the stratum preferably has a relatively high interlaced or synthetic fiber content. However, as a consequence of its high interlaced fiber content, said stratum provides less liquid distribution than a comparable stratum that includes relatively less interlaced fiber. For liquid acquisition, the stratum is preferably a mixture of interlaced fibers and pulp fibers, for example, the stratum can include from about 30 to about 50 weight percent of interlaced fibers and from about 50 to about 70 percent. in weight of pulp fibers. Alternatively, strata having high liquid acquisition rates may also include, in combination with cellulosic fibers, a relatively high synthetic fiber content (e.g.

* * * "-« - * • - * * - PET fibers or a mixture of PET or thermo-compatible fibers.) Optionally, one or both layers may include synthetic fibers, because the layer of the mixed material is formed with the cross-linked center to provide an integrated unitary structure, the global characteristics of the mixed material can be optimized by the appropriate selection of the individual center and stratum components.To further optimize the performance of the mixed material, the nature of the first and second strata can be controlled and varying in a selective and independent manner The compositions of the first and second strata do not need to be the same.The strata can be formed from the same or different fiber materials.For compositions formed by foaming methods, the weight of The base of the stratum can also be controlled and varied independently.The base weight of the stratum can be varied with respect to the base weight of the stratum. In a foam method, the basis weight can be varied by adjusting the speed at which the fibrous material is supplied to and deposited on the forming support. For example, varying the pumping speed for a specific material effectively controls the base weight of that portion of the mixed material. Accordingly, in one embodiment, the mixed absorbent material includes an intermediate cross-linked center between the first and second layers, each stratum having different base weight. The base weights of the strata can also be varied for mixed absorbent materials formed by wet laying methods.

The stratum can be formed integrally with the cross-linked center by the wet laying and foam methods. Generally, the mixed material including the crosslinked center and the strata can be formed by depositing substantially simultaneously fibrous suspensions including the center and stratum components. The deposition of more than a single fibrous suspension on a forming support can be achieved by standard devices known in the art including, for example, divided and / or multi-head split boxes. Representative absorbent composite materials can be formed using conventional papermaking machines including, for example, Rotoformer, Fourdrinier, and two wire machines. Mixed absorbent materials having a single layer can be formed with Rotoformer and Fourdrinier machines and mixed materials including two layers can be formed by two wire machines. A representative method for forming the absorbent blended material using a Rotoformer machine is described in Example 9. The performance characteristics of the representative absorbent blended materials formed by the method are described in Examples 10-15. The mixed absorbent materials formed using the Rotoformer machine include a fibrous strand of wire side. The thickness of the stratum and the structure of the mixed material can be controlled by the position of the sprinklers of the head box, which supply absorbent material to and mix the material with the fiber supply material. Generally, the more deeply the sprinkler introduces the absorbent material into the fiber supply material in the thinner drum Rotoformer will be the resulting stratum. Conversely, a relatively thicker layer can be formed by introducing absorbent material into the fiber supply material at a greater distance from the drum. The mixed absorbent material can be formed by devices and methods that include a twin wire configuration (ie, twin forming wires). A representative twin-wire machine for forming mixed materials is shown in Fig. 22. Referring to Fig. 22, the machine 200 includes twin forming wires 202 and 204 over which components of the mixed material are deposited. Basically, the fibrous suspension 124 is inserted into the head box 212 and deposited on forming wires 202 and 204 at the outlet of the headbox. Vacuum elements 206 and 208 dehydrate the fibrous suspensions deposited on the wires 202 and 204 respectively to provide partially dewatered fabrics that exit the twin wire portion of the machine as a partially dewatered fabric 126. The fabric 126 continues to travel along the length of the fabric. wire 202 and continues to be dewatered by additional vacuum elements 210 to provide a wet mixed material 120 which is then dried in drying means 216 to provide the mixed material 10. Absorbent material can be introduced into the fibrous web in any of the various positions in the wire procedure 'ZSm & ^ ifa twins depending on the desired product configuration. Referring to Figure 22, the absorbent material 122 can be injected into the partially dehydrated fabric in positions 2, 3 or 4, or other positions along the wires 202 and 204 where the fabric has been at least partially dehydrated. An absorbent material can be introduced into the partially dehydrated fabric formed and traveling along the wire 202 and / or 204. The absorbent material can be injected into the partially dehydrated fibrous webs by laterally spaced nozzles across the width of the fabric. The nozzles are connected to a supply of absorbent material. The nozzles can be placed in several positions (for example, positions 1, 2 or 3 in figure 22). As described above. For example, referring to Fig. 22 the nozzles can be located in positions 2 to inject absorbent material into partially dewatered fabrics on wires 202 and 204. Depending on the position of the introduction of absorbent material, the twin wire method to form the mixed material I could provide a mixed material that has a fibrous stratum. The mixed material may include integrated phases having fibrous or extensive layers with the outer surfaces of the mixed material. These fibrous composite materials can be formed from twin-layer, multi-layer shaped formers and split-head boxes. These methods can provide mixed stratified and phased materials having strata or phases having specific properties designed and containing components to achieve mixed materials having desired properties. Basically, the position of the absorbent material in the z-direction of the mixed material effectively defines the fibrous stratum covering the band. For a forming method that includes a single fiber material, the position of the band can be adjusted by placing the injection system of absorbent material (eg, nozzle assembly) in relation to the forming wire. For methods involving multiple materials, the upper and lower layers should be composed of the same or different components and can be inserted into a sectioned headbox. Referring to Figure 22, mixed material 10 having strata 11 can be formed by machine 200. For mixed materials in which strata 11 comprise the same components, a single fiber material 124 is inserted into the headbox 212. For forming mixed materials having layers 11 comprising different components, the head box 212 includes one or more baffle 214 for introducing fiber materials (eg, 124a, 124b, and 124c) having different compositions. In said method, the upper and lower layers can be formed to include different components and have different base weights and properties. Preferably, the crosslinked mixed material is formed by a foaming method using the components described above. In the foaming method, fibrous fabrics having multiple layers and including absorbent material can be formed from multiple fibrous suspensions. In a preferred embodiment, the foaming method is implemented in a double wire former. The method can provide a variety of mixed multi-layer materials including, for example, mixed materials having three layers. A representative mixed material having three strata includes a first stratum formed of fibers (for example, cellulose and / or alginate synthetic fibers); an intermediate layer formed of fibers and / or other aborbent material such as superabsorbent material; and a third stratum formed of fibers. The method of the invention is versatile in that said mixed material can have relatively distinct and discrete strata or alternatively has gradual transition zones from one stratum to another. A representative method for forming a fibrous web having an intermediate layer generally includes the following steps: a) forming a first fibrous suspension comprising fibers and a surfactant in an aqueous dispersion medium; b) forming a second fibrous suspension comprising fibers and a surfactant in an aqueous dispersion medium; c) moving a first foraminous element (e.g., a forming wire) in a first path; d) moving a second foraminous element in a second path; . - * ^ «- * -t« •! e) passing the first suspension in contact with the first foraminous element moving in a first path; f) passing the second suspension in contact with the second foraminous element moving in the second path; g) passing a third material between the first and second suspensions in such a way that it makes contact with the first or second foraminous elements; and h) forming a fibrous web from the first and second suspensions and a third material by withdrawing liquid from the suspensions through the first and second foraminous elements. As indicated above, the method is suitably carried out in a twin wire former, preferably a vertical former, and most preferably a twin vertical downstream wire former. In the vertical trainer the trajectories for the foraminous elements are substantially vertical. A representative vertical downlink and twin wire former useful in the practice of the method of the invention is illustrated in FIG. 23. Referring to FIG. 23, the former includes a vertical head box assembly having a former with a first closed end (top), closed first and second sides and an interior volume. A second (lower) end of the former is defined by moving the first and second foraminous members 202 and 204 and forming a grip 213. The interior volume defined by the first closed end of the former, first and second closed sides and first and second foraminous elements includes an interior structure 230 extending from the first end of the former and towards the second end. The lower structure defines a first volume 232 on one side thereof and a second volume 234 on the other side thereof. The former further includes a supply 242 and means 243 for introducing a first fiber suspension in the first volume, a supply 244 and means 245 for introducing a second fiber suspension in the second volume and a supply 246 and means 247 for introducing a third. material in the interior structure. Means for removing liquids (and / or foam) (e.g., suction boxes 206 and 208) from the first and second suspensions through the foraminous elements to form a fabric are also included in the headbox assembly. In the method, the twin wire former includes a means for introducing at least one third material through the inner structure. Preferably, the introduction means includes at least a first plurality of conduits having a first effective length. A second plurality of conduits having a second effective length different from the first length can also be used. You can also use more than two duct assemblies. Another representative vertical downlink twin wire former useful in the practice of the forming method is illustrated in FIG. 24. Referring to FIG. 24, the former includes a vertical head box assembly having an interior volume defined by the first extreme Zf? - closed of the former, first and second closed sides, and first and second foraminous elements, 202 and 204, and includes a lower structure 230 extending from the first end of the former and towards the second end. In this embodiment, the lower structure 230 includes a plurality of 5 ducts 235 and 236 and optional divider walls 214. The interior structure defines a first volume 232 on one side thereof and a second volume 234 on the other side thereof. The former further includes a supply 242 and a means 243 for introducing a first fiber suspension in the first volume, a supply 244 and a means 245 for introducing a second fiber suspension in the second volume, a supply 246 and a medium 247. to introduce a third material in the plurality of conduits 236, a supply 248 and a means 249 for introducing a third material into the plurality of conduits 235, and a supply 250 and a means 251 for introducing another material, such as a foam suspension, into the volume defined by the walls 214. A plurality of conduits 235 may have an effective length different from a plurality of conduits 236. The third material may be introduced through conduits 235 and 236 or alternatively a third material may be introduced through conduits 235 and a fourth 20. material can be introduced through ducts 236. Preferably, the ends of ducts 235 and 236 terminate at a position beyond where the suction boxes begin to extract foam from the suspensions in contact with the foraminous elements (i.e. beyond ry p.lÍftM¿S •. ,. ! ,,. *,. * "< u > ».. .. - '.. - »- ~ -. - í * -, * ÍMá from the point where the formation of the fabric begins). A plurality of conduits 235 and / or 236 are suitable for introducing strips or bands of a third material into fibrous fabrics formed in accordance with the present invention. A plurality of ducts 235 and 236 can be moved in a first dimension towards and away from the grip 213 and also in a second dimension substantially perpendicular to the first, closer to one forming wire or the other. A representa plurality of conduits 235 and 236 are illustrated in Fig. 25. In general, the interior structure of the former (ie, the structure 230 in Figs. 23 and 24) are located with respect to the foraminous elements in such a way that the material introduced through the interior structure will not directly contact the first and second foraminous elements. Accordingly, the material is introduced through the interior structure between the first and second suspensions after the suspensions have made contact with foraminous elements and the extraction of foam and liquid from those suspensions has begun. Said configuration is particularly advantageous for introducing superabsorbent materials and for forming layered structures in which the third material is a suspension / fiber depending on the nature of the mixed material to be formed, the first and second fiber suspensions can be the same , or different, one from another and from the third material. In a preferred embodiment, the method includes introducing the third material into a plurality of different points. The positions of , ». < - fc - lfllt-. Do not some of the plurality of different points for introducing the third material into the box head can be adjusted when desired to adjust the insertion point in a first dimension towards and away from the output from the box head (i.e., grip 213 in Figures 23 and 24), and to adjust at least some of a plurality of points in a second dimension substantially perpendicular to the first dimension, closer to a forming wire or the other. The method also includes the use of a plurality of different conduits, the conduits being of at least two different lengths, for introducing the third material into the headbox. The method can also be used in headboxes having dividing walls that extend part of the length of the ducts towards the outlet of the headbox. Said head boxes are illustrated in Figures 22 and 24. The means for introducing first and second suspensions in the first and second volumes may include any conventional type of duct, nozzle, orifice, head or the like. Typically, these means include a plurality of provided conduits disposed at the first end of the former and facing the second end. Means for extracting liquid and foam from the first and second suspensions through the foraminous elements to form a fabric on the foraminous elements are also included in the headbox assembly. The means for extracting liquid and foam may include any conventional means for that purpose, such as rollers ... of suction, pressure rollers or other conventional structures. In a preferred embodiment, the first and second suction box assemblies are provided and mounted on opposite sides of the interior structure from the foraminous elements (see boxes 206 and 208 in Figures 22, 23 and 24). In another embodiment, the mixed material of the invention includes one or more fibrous webs in a fibrous base. The base includes a fibrous matrix and absorbent material. Suitable fibrous bases are as described above. The fibrous webs are substantially free of absorbent material. In one embodiment the fibrous web or fibrous webs extend along the machine direction of the mixed material. The number of bands in a particular mixed material is not particularly critical and will depend on the nature and the absorbent article in which the mixed material is incorporated. In a modality, the mixed material includes two fibrous webs and in other embodiments, the mixed material includes more than two webs, for example, three to about six webs. A representative mixed material of the invention having two fibrous webs is illustrated schematically in Fig. 31. Referring to Fig. 31, the mixed material 300 includes a base matrix 310 and fibrous webs 320. For embodiments of the mixed material in which the base matrix includes an absorbent material, the fibrous webs conduct fluid along the length of the mixed material by distributing the fluid throughout the mixed material and to the absorbent material in the base matrix where the fluid is finally stored. In Figure 31, the movement of fluid is indicated by the arrows. Representative mixed materials having fibrous webs and their performance characteristics are described in examples 18, 19 and 21. A representative mixed material having two fibrous webs is described in example 19. For this mixed material, the capillary absorption height in 15 minutes, 15 cm capacity, and wetted area capacity for representative mixed materials are presented graphically in Figure 32. Representative mixed foam-formed materials having two fibrous webs are described in Example 21. For these mixed materials, the Ring crushing and tensile strength are correlated graphically in figure 33; the unrestricted vertical capillary absorption height and saturation capacity are correlated graphically in Figure 34; ring crushing and tensile strength are compared graphically in Figure 35; and the unrestricted vertical capillary absorption height and saturation capacity are graphically correlated in Figure 36. The fibrous webs can include any of the fibrous materials described above including blends of fibers. For example, the fibrous web may include matrix fibers, elastic fibers and mixtures of matrix and elastic fibers. In some embodiments, the fibrous web includes interlaced cellulosic fibers and / or matrix fibers. The fibrous web may include interlaced fibers in an amount of about 15% to about 90% by weight based on the total weight of the fibers in the web. In one embodiment, the fibrous web includes interlaced fibers in an amount of from about 20% to about 80% by weight based on the total weight of the fibers in the web. In another embodiment, the fibrous web includes interlaced fibers in an amount of about 40% to about 60% by weight based on the total weight of the fibers in the web. The fibrous web may include matrix fibers in an amount of from about 10% to about 85% by weight based on the total weight of the fibers in the web. In one embodiment, the fibrous web includes matrix fibers in an amount of from about 20% to about 80% by weight based on the total fiber weight in the web. In another embodiment, the fibrous web includes matrix fibers in an amount of from about 40% to about 60% by weight based on the total weight in the web. As indicated above, in one embodiment, the fibrous web includes a mixture of interwoven and matrix fibers. In one embodiment, the weight ratio of matrix fibers to interwoven cellulosic fibers is about 1: 1, in another embodiment, the ratio is about 1: 4, and in another embodiment the ratio is about 4: 1. The mixed absorbent material having fibrous webs offers advantages over other mixed materials that lack fibrous webs, among other advantages, the fibrous web or the fibrous webs act as trajectories or channels for distribution of liquid within the fibrous matrix of the fibrous web.

-J - r mixed material that includes absorbent material. In this way, the liquid acquired by the mixed material is rapidly distributed along the fibrous web and is absorbed out of these bands and makes the surrounding fibrous matrix where the liquid is finally absorbed and stopped by the absorbent material. Mixed materials including fibrous webs offer advantages associated with capillary absorption of liquid, total liquid absorbed, the rate of liquid absorption and liquid flow, among other advantageous properties. For example, as described below, a representative absorbent mixed material having fibrous webs has a The capillary absorption height is not restricted to 30 minutes of at least about 10 cm and preferably at least about 12 cm. The mixed material also has an absorbed value of total unrestricted vertical capillary absorption fluid at 30 minutes of at least about 30 g and, preferably, at least about 40 g. 15 g The mixed material also has a vertical capillary action absorption rate not restricted to 12 cm of at least about 1.0 g / g / min and preferably, at least about 2.0 g / g / min. The mixed material also has a vertical capillary absorption flow not restricted to 12 cm of at least about 2.0 / g / cm2 / min and preferably so 20 less 3.0 g / cm2 / min. Mixed material that has fibrous webs also provides strength and softness advantages. The fibrous bands that run throughout of a mixed material generally increase the smoothness of the mixed material across its width. Fibrous webs also offer advantages related to processing of mixed material. For example, the relatively porous fibrous web increases the drying efficiency of the mixed material. Also, the fibrous webs can impart transpiration capability to the mixed material when used in an absorbent article. Although the mixed material has been described as obtaining strips of fibrous material, it can be appreciated that other configurations of only fiber regions are within the scope of the invention. scope of the invention. Representative configurations include circular, annular, ring, star, cross and rectangular shapes, among others. The width of the band or other configuration can also be varied to suit a particular need. Broad bands have a greater capacity than thin bands. The band or other configuration can also be tapered to facilitate, for example, the movement of fluid. In addition to having a tapered length or width, the band or other configuration may also have tapered or shifting thickness (ie, in the thickness direction of the mixed material). The fibrous web can also be located in the fibrous base in various positions (eg, variation in length, width and thickness of the mixed material), to provide mixed materials having a variety of fluid movement properties.

: The mixed absorbent material having fibrous webs can be formed by wet laying and foaming methods described above. The fibrous webs can be incorporated into the fibrous matrix to provide the mixed material by the methods described above. The fibrous webs can be formed by introducing fibers as the third (or fourth) material in the method described above. Mixtures of fibers can also be introduced as the third material. In such forming methods, the absorbent material can be introduced into the mixed material through other conduits, for example, as the fourth (or third) material, as described above. The mixed absorbent material formed in accordance with the present invention can be incorporated as an absorbent center or storage layer in an absorbent article such as a diaper. The mixed material can be used alone or combined with one or more layers, such as acquisition and / or distribution layers, to provide useful absorbent constructions as described herein. In the figures that illustrate article constructions, the reference number 10 refers to all the modalities of the mixed materials of the invention. Representative absorbent constructions incorporating the mixed absorbent material having a cross-linked center and fibrous strata are shown in Figures 26 A-C and 27 A-C. Referring to Figure 26A, the construction 150 includes the material 130 (i.e., the cross-linked center 10 and the stratum 132) employed as a storage layer in combination with an upper acquisition layer 20. Figure 26B illustrates the construction 160, which includes the mixed material 130 and the acquisition layer 20 with the stratum 132 to the acquisition layer 20. The construction 170, which includes the acquisition layer 20 and the mixed material 140, is illustrated in Figure 26C. In addition to the aforementioned constructions including the combination of absorbent mixed material and acquisition layer, the additional constructions may include an intermediate distribution layer between the acquisition layer and the mixed material. Figure 27A illustrates the construction 180 having an intermediate layer 30 (eg, distribution layer) interposed between the acquisition layer 20 and the mixed material 130. Similarly, Figures 27B and 23C illustrate constructions 190 and 200 having a layer 30 intermediate between the acquisition layer 20 and the mixed materials 130 and 140, respectively. The mixed materials 130 and 140 and the constructions 150, 160, 170, 180, 190 and 200 can be incorporated in absorbent articles. Generally, absorbent articles 210, 220 and 230 shown in Figures 28 A-C, respectively; absorbent articles 240, 250 and 260 shown in Figures 29 A-C, respectively; and absorbent articles 270, 280 and 290 shown in Figures 30 AC respectively, include a liquid permeable front sheet 22, a liquid permeable back sheet 24, and mixed materials 130, 140, and constructions 150, 160, 170, 180 190 and 200, respectively. In said absorbent articles, the front sheet is attached to the back sheet. The following examples are provided for purposes of illustration and not limitation.

EXAMPLES EXAMPLE 1 Formation of cross-linked absorbent mixed material: representative air-laying method This example illustrates a method of laying in air to form a representative absorbent mixed material. A mixed wet laid material formed in accordance with the present invention is prepared using a standard wet laid apparatus known to those skilled in the art. A suspension of a mixture of standard wood pulp fibers and interlaced pulp fibers (48 and 12 weight percent respectively based on the total weight of the dry mixed material) in water having a consistency of about 0.25 to 3 percent it forms. The consistency is defined as the weight percent of fibers present in the suspension, based on the total weight of the suspension. A moisture resistance agent such as Kymene® (0.5 weight percent based on the total weight of the mixed material) is then added to the fibrous mixture. Finally, the absorbent material (40 weight percent based on the total weight of the dry mixed material) is added to the suspension, the suspension is uniformly mixed, and then distributed over a wire mesh to form a wet mixed material. The wet mixed material is dried to a moisture content of 9 to about 15 weight percent based on the weight of the total mixed material to form a cross-linked absorbent mixed material. Mixed absorbent materials having a variety of base weights can be prepared from the mixed material formed as described above by pre-drying or post-drying densification methods known in the art.

EXAMPLES 2 Formation of crosslinked absorbent mixed material: representative foam method This example illustrates a foam method for forming a representative absorbent mixed material. A laboratory-sized Waring blender is filled with 4 I of water and pulp fibers are added. The mixture is allowed to mix for a short time. The interlaced cellulose fibers are then added to the pulp fibers and allowed to mix for at least one minute to open the interlaced fibers and effect mixing of the two fibers. The resulting mixture may contain 0.07 to 12 weight percent solids. The mixture is placed in a container and mixed for a few seconds with an air entrapment blade. A surfactant (Incronan 30, Croda, Inc.) is added to the mixture already mixed. Approximately 1 g of surfactant solids per gram of fiber is added. The mixture is allowed to mix while raising the height of the mixing blade of the rising foam slowly. After about one minute, the mixture is finished and superabsorbent is added, and the mixing is resumed for a further half minute at a constant mixing blade height. The resulting foam fiber mixture will have a volume of about three times the volume of the original mixture. The mixture is quickly emptied into a sheet mold having an inclined diffusion plate. After being added to the mixture, the plate is removed from the mold and a strong vacuum is applied to reduce the height of the foam fiber, after most of the visible foam disappears, the vacuum is discontinued and the resulting sheet is removed. removes from the mold and is passed, along with a forming wire, on a slotted platform to remove excess foam and water. The sheet is then dried in a drying oven to remove moisture.

EXAMPLE 3 Acquisition times for a mixed reticulated material In this example, the acquisition time for a representative cross-linked absorbent material 5 formed in accordance with the present invention (mixed material A) is compared with a commercially disposable diaper (diaper A, Kimberly-Clark). The tests were conducted on commercially disposable diapers (Kimberly-Clark) from which the center and cushion layer 10 were removed and the surrounding material was used. The test diapers were prepared by inserting the mixed absorbent material into the diaper. The aqueous solution used in the tests is a synthetic urine available from National Scientific under the trade name of RICA. Synthetic urine is a saline solution that contains 135 meq./l of sodium, 8.6 meq./l 15 of calcium, 7.7 meq./l of magnesium, 1.94% of 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 center of the structure, measuring 2.54 cm to the front for location of the liquid application, and marking the location 20 with an "X". Once the sample was prepared, the test was conducted by first placing the sample on a plastic base (12.06 cm x 48.85 cm) and then placing the funnel acquisition plate (10.16 cm and 10.16 cm plastic plate) over the top of the mixture with in hole of the plate located on the "X". A donut-shaped weight (1400 g) was then placed on the top of the funnel acquisition plate to which a funnel was then fixed (10.16 cm in diameter). The fluid acquisition was then determined by emptying 100 ml of synthetic urine in the funnel and measuring the time from when the liquid was first introduced into the funnel until the time when the liquid disappeared from the bottom of the funnel into the sample. The time measured is the acquisition time for the first liquid discharge. After waiting for one minute, a second 100 ml portion was added to the funnel and the acquisition time for the second discharge was measured. After waiting an additional minute, the acquisition was repeated a third time to provide an acquisition time for the third download. The acquisition times reported in seconds for each of the three successive 100 ml liquid discharges for a diaper A and a mixed material A are summarized in block 1. - »i».

TABLE 1 Comparison of acquisition time 10 As shown in Table 1, the liquid is more readily acquired by the mixed absorbent material than for the commercially available diaper which contains a storage center lying in air. The results show that the center lying in air does not acquire liquid almost as 15 quickly as the mixed reticulated material. The commercial diaper also showed characteristic decrease of acquisition speed in successive liquid discharges. On the contrary, the mixed material formed according to the invention maintained a relatively constant acquisition time as the mixed material continued to absorb liquid in a discharge 20 successive. Significantly, the mixed absorbent material has an acquisition time for the third discharge that is substantially less (approximately 4 times) than that of the diaper commercially available for initial discharge. The results reflect the greater absorption capacity '- «*« - »a-kfci" ~ - - * capillary and capillary network for mixed material wet laid compared to a storage center laid in conventional air in general, and the increased prmance of the crosslinked absorbent mixed material in particular.

EXAMPLE 4 Acquisition and rewet speed for representative cross-linked absorbent materials In this example, the acquisition and rewet time of representative cross-linked absorbent materials according to the present invention (mixed materials A1-A4 designated) compared to a commercially available diaper (diaper A, Kimberly-Clark). The mixed materials A1-A4 differ by the method by which the mixed materials were dried. Certain properties of the mixed materials tested, including the amount of superabsorbent material (percent by weight SAP) in the mixed material and base weight for each of the mixed materials, are summarized in Table 2. The tests were conducted on diapers commercially available (Kimberly-Clark) from which the centers were removed and used as wrappings. The test diapers were prepared by inserting the tested mixed materials into the diapers.

The acquisition and rewet time are determined according to the multiple dose rewet test described below. In short, the multiple dose rewet test measures the amount of synthetic urine released from an absorbent structure after each of three liquid applications, and the time required for each of these three doses of liquid to be absorbed by capillary action in the product. The aqueous solution used in the tests was a synthetic urine available from National Scientific under the trade name RICCA, as described in example 1. A previously weighed sample of the absorbent structure was prepared for the test by determining the core of the structure core , measuring 2.54 cm from the front for the liquid application location, and marking the location with an "X". A liquid application funnel (minimum capacity of 100 ml, flow rate of 5-7 ml / sec) was placed 10.16 cm above the surface of the sample on the "X". Once the sample was prepared, the test was conducted as follows. The sample was flattened, on the non-woven side up, on a surface of a table under the liquid application funnel. The funnel was filled with a dose (100 ml) of synthetic urine. A dosing ring (0.39 cm stainless steel, 5.08 cm ID x 7.62 cm height) was placed on the "X" marked on the samples. A first dose of synthetic urine was applied inside the dosing ring. Using a stopwatch, the liquid acquisition time was recorded in seconds from the time the funnel valve was opened until the liquid was absorbed by capillarity in the product from the bottom of the dosing ring. After a waiting period of twenty minutes, rewetting was determined. During the twenty minute waiting period after the first dose was applied, a stack of filter papers (19-22 g, Whatman # 3, 11.0 cm or equivalent, which had been exposed to ambient humidity for a minimum of 2 hours) was weighed. Before the test). The pile of pre-weighed filter papers was placed on the center of the moistened area. A cylindrical weight (of 8.9 cm in diameter, 4.45 Kg.) Was placed on these filter pads. After two minutes in which the weight had been removed, the filter papers were weighed and the weight change recorded. The procedure was repeated twice more. A second dose of synthetic urine was added to the diaper, and the acquisition time was determined, the filter pads were placed on the sample for two minutes and the weight change was determined. For the second dose, the weight of the dry filter papers was 29-32 g, and for the third dose, the weight of the filter papers was 39-42 g. The dried papers of the previous dose were supplemented with additional dry filter papers. The liquid acquisition time is reported as the length of time (seconds) necessary for the liquid to be absorbed in the product for each of the three doses. The results are summarized in table 2. »- < »M * MIÍH < 1lif- Rewetting is reported as the amount of liquid (grams) absorbed back into the filter papers after each liquid dose (ie, the difference between the weight of wet filter papers and the weight of dry filter papers). The results are also summarized in table 2.

TABLE 2 Comparison of acquisition and rewet time As indicated in Table 2, the acquisition times for representative mixed materials formed according to the invention (mixed materials A1-A4) was significantly lower than for the commercially available center. ÉA *, .i The rewetting of representative mixed materials (mixed materials A1-A4) is significantly less than for the other centers. Although the mixed materials initially showed relatively low rewetting, after the third discharge the commercially available center showed substantial rewetting. On the contrary, the mixed materials A continued to show low rewetting.

EXAMPLE 5 10 Horizontal and vertical capillary absorption for a representative crosslinked absorbent composite material In this example, the capillary absorption characteristics of a representative cross-linked absorbent mixed material (mixed material A) is 15 compare with commercially available diaper storage centers (B diaper, Procter &Gamble). The horizontal capillary absorption test measures the time required for the liquid to be capillarity absorption horizontally at preselected distances. The test was performed by placing a mixed material 20 of sample on a horizontal surface with one end in contact with a liquid bath and measuring the time required for the liquid to be absorbed by capillarity at preselected distances. In brief, a strip of mixed sample material (40 cm x 10 cm) was cut from a pulp sheet or , c. .A?? T? .. to t ^ another source. If the sheet has a machine direction, the cut is made in such a way that the length of 40 cm of the strip is parallel to the machine direction. Starting at one end of the 10 cm width of the strip, a first line was marked 4.5 cm from the edge of the strip and then 5 consecutive lines at 5 cm intervals were marked along the entire length of the strip (ie, 0 cm, 5 cm, 150 cm, 15 cm, 20 cm, 25 cm, 30 cm and 35 cm). A horizontal capillary absorption apparatus having a central depression with level horizontal wings extending away from opposite sides of the depression was prepared. The unsupported edge of each wing is 10 placed so that it was flush with the inner center of the depression. At the end of each wing, a plastic extension was placed to support each wing at a level and horizontal position. The depression was then filled with synthetic urine. The strip of mixed sample material was gently bent at the 4.5 cm mark to form an approximately 45 ° angle on the strip. The The strip was then placed on the wing in such a way that the strip was laid horizontally and the folded end of the strip extended inwardly and in contact with the liquid in the depression. The capillary absorption of the liquid was time-controlled starting from when the liquid reached the first line marked on the mixed material 5 cm from the 4.5 cm fold. The time of Capillary absorption was then recorded at 5 cm intervals when 50 percent of the liquid front reached the marked range (e.g., 5 cm, 10 cm). The liquid level in the depression remained at a level i? .í ? rf.T 'Érii. ! r? ,? I relatively constant throughout the test filling with additional synthetic urine. The results of horizontal absorption are summarized in table 3.

TABLE 3 Comparison of horizontal capillary absorption The above tabulated results indicate that the horizontal capillary absorption is increased for the mixed absorbent material formed according to the invention as compared to a center laid in conventional air. The capillary absorption time for the mixed material A is approximately 50 percent that of the center of the conventional diaper. Therefore, the horizontal capillary absorption for the mixed material A is i * • - - < ? ea * au approximately 1.5 to approximately 3 times that of the commercially available storage center. The vertical capillary absorption test measures the time required for the liquid to vertically absorb pre-selected distances by capillarity. The test was performed by vertically suspending a mixed sample material with one end of the mixed material in contact with a liquid bath and measuring the time required for the liquid to be absorbed at preselected distances. Before the test, mixed sample materials (10 cm x 22 cm) were cut and marked with successive lines at 1 cm, 11 cm, 16 cm and 21 cm from one of the edges of the strip. Preferably, the samples were preconditioned for 12 hours at a relative humidity of 50 percent and at 23 ° C and then stored in sample bags until the test was performed. The mixed sample material was oriented vertically and was held from its upper edge at the 1 cm mark, allowing its lower edge to make contact with a bath containing synthetic urine. The time measurement was started once the strip got in contact with the liquid. The time required for 5 percent of the capillary absorption front to reach 5 cm, 10 cm, 15 cm and 20 cm was recorded afterwards. The results of vertical capillary absorption are summarized in table 4.

TABLE 4 Comparison of vertical capillary absorption As with the results of horizontal capillary absorption, the mixed material A had significantly higher vertical capillary absorption compared to the commercial center. The results also show that the mixed material formed according to the invention has a significantly higher wet tensile strength compared to the mixed material laid in conventional air.

EXAMPLE 6 Liquid distribution for a representative cross-linked absorbent mixed material In this example, the distribution of liquid in a crosslinked absorbent mixed material (mixed material A) is compared to that of two diapers I? ^, Í? -Í 4 it- rM. you. .l-? commercially available (diapers A and B above). The test measures the capacity of a diaper core to distribute the acquired liquid. The perfect distribution would have 0% deviation from the average. The ideal liquid distribution would result in an equal distribution of the liquid applied in each of the distribution zones (ie, approximately 25% liquid in each zone). The liquid distribution is determined by different zones of a sample that has been subjected to the multiple dose rewet test described above in example 4. Basically, after the last rewet, the diaper wings were removed and then cut into four zones of equal length distribution. Each zone is then weighed to determine the weight of liquid contained in each zone. The liquid distribution results for a representative cross-linked absorbent material approximate the ideal. The results indicate that although the representative commercial storage cores accumulate liquid almost at the discharge site, the liquid is distributed efficiently and effectively throughout the reticulated absorbent storage core.

EXAMPLE 7 Wet and dry tensile strength for a cross-linked absorbent mixed material In this example, the measurement of the wet and dry tensile strength of a representative absorbent blended material is described. A dry pad tension integrity test is performed on a 10.16 cm by 10.16 cm square test pad by holding a dry test pad along two opposite sides. 10 Approximately 7.62 cm of pad length is visible between the clamps. The sample is pulled vertically on an Instron test machine and the measured tensile strength is reported in N / m. The tensile strength is converted to a tension index, Nm / g, by dividing the tensile strength by the basis weight g / m2. 15 A wet tension integrity test was performed by taking a mixed sample material that has been immersed in synthetic urine for 10 minutes and then allowed to drain for 5 minutes and placing the sample on a horizontal platform. Opposite ends of the sample are fastened and then pulled horizontally on the Instron 20 test machine. The wet tensile strength, N / m, is converted to the tension index Nm / g, dividing the tensile strength between the base weight g / m2. at ^ iata > - • - - * - * í- Í -j "- Typically, increasing the amount of Kymene® from 0.908 to 45.4 kg per ton of fiber can increase the tensile strength from 0.15 Nm / g to 0.66 Nm / g and the wet tension of about 1.5 Nm / ga approximately 2.4 Nm / g 5 EXAMPLE 8 Taber stiffness for representative mixed cross-linked absorbent materials The stiffness of representative cross-linked absorbent materials formed in accordance with the present invention was determined by the Taber stiffness method. Representative mixed materials were formed by wet laying and foam methods. These mixed materials included matrix fibers (48 percent by weight, southern pine) Commercially available from Weyerhaueser Co. under the designation NB416), elastic fibers (12 weight percent, interlaced polymaleic acid fibers) and absorbent material (40 weight percent, superabsorbent material commercially available from Stockhausen). One of the mixed materials formed by wet laying and one formed in foam also included 20 a moisture resistance agent (approximately 0.5 weight percent polyamide-epichlorohydrin resin commercially available from Hercules under the designation Kymene®.

The stiffness of the mixed materials formed in foam was significantly lower than the mixed wet laid materials constituted similarly. The results also indicate that, for mixed wet laid materials, the inclusion of a moisture resistance agent increases the stiffness of the mixed material.

EXAMPLE 9 Formation of crosslinked absorbent mixed material: representative wet laying method This example illustrates a representative wet laying method for forming a crosslinked mixed material using a Rotoformer papermaking machine. In short, the suspensions of absorbent material and fibers in water were introduced into the Rotoformer headbox. The fibrous suspension was introduced into the head box in the conventional manner. The absorbent suspension was introduced through the use of a dispersion unit consisting of a series of sprinklers. The sprinklers were fed from the head supplied by the absorbent suspension supply. The dispersion unit is mounted in the headbox of the Rotoformer with the sprinklers inserted into the fiber supply material of the head box such that the flow of the absorbent suspension is against the flow of the fiber supply material. Saying .t *. -i i? í -i.

Reverse flow for the absorbent suspension is believed to provide more effective mixing of absorbent material and fibers than would occur for the flow of absorbent material in the same direction as the fiber supply material. The absorbent material is introduced into the headbox of the Rotoformer as a suspension in water. Other methods that provide adequate results for introducing absorbent material into the head boxes is a mixing system that includes a funnel fixed directly to the inlet of a pump in which cooled water is fed at a controlled rate. The funnel receives water and dry absorbent material supplied from the supply of absorbent material by worm dosing and forms a reservoir containing absorbent material and water. The absorbent suspension is preferably pumped from the funnel to the headbox at approximately the same speed as the water is supplied to the funnel. This system minimizes the exposure of the absorbent material to water. In practice, the absorbent suspension is supplied from the mixing system to the headbox through a conduit of 3.05 to 15.25 m in less than about 10 seconds. In a typical formation operation, the flow of fiber supply material to the headbox of the Rotoformer was approximately 340 Ipm (liters / minute) and the flow of absorbent suspension (1- 2.6% solids) was approximately 37.8 Ipm . Before starting the flow of fiber supply material to the box head and the introduction of ÍA? : í. & * A.imá ~ -. -A ^. and -atJy.

Absorbent suspension to the dispersion unit, water was flowed to the dispersion unit to the head box to prevent the fibers from covering the sprinklers. Once the target fiber weight of the fiber was reached, the absorbent worm dosing system was initiated and the 5 absorbent suspension in the head box. For operations to be performed according to the method described above, the basis weight of the target fiber was about 370 gsm (g / m2) and the production rate was about 3.05 m per minute (m / min). The relatively slower production speed was a consequence of the capacity 10 of relatively flat drying of the flat bed dryer of the machine. The contents of the head box including fibers and absorbent material were deposited on a forming wire and dehydrated to provide a wet mixed material. The wet mixed material was then dried at a moisture content of from about 9 to about 15 by 15 weight percent based on the total weight of the mixed material to form a representative cross-linked absorbent mixed material. The mixed absorbent materials having a variety of base weights can be prepared from the mixed material formed as described above by the pre-drying or post-drying densification methods known to those skilled in the art. Example 10-15 illustrates the formation of representative cross-linked absorbent materials using the method described above.

EXAMPLE 10 A representative mixed material was formed as described in Example 9. The mixed material includes about 60% by weight of fibers and about 40% by weight of absorbent material based on the total weight of a mixed material. The fiber supply material was a mixture of 80% by weight of standard wood pulp fibers (Southern pine dried once available from Weyerhaeuser Company under the designation FR416) and 20% by weight of interlaced pulp fibers. The absorbent material was an interlaced polyacrylate commercially available from Stockhausen under the designation SXM 77, which was sieved using a 300-mesh mesh to remove fine powders before use. The mixed material also included approximately 11.35 kg of moisture resistance agent (a polyacrylamide-epichlorohydrin resin commercially available from Hercules under the designation Kymene® 557LX) per tonne of fibers. The target density of the mixed absorbed material was achieved by calendering using a single grip without applying load. The performance data for the representative mixed material formed as described above (mixed material B) is presented in Tables 5 and 6 in Example 16.

EXAMPLE 11 A representative mixed material was formed as described in Example 10 except that the mixed material was calendered at 7.6 m / min. The performance data for the representative mixed material formed as described above (mixed material C) is presented in Tables 5 and 6 in Example 16.

EXAMPLE 12 A representative mixed material was formed as described in Example 11 except that the amount of moisture resistance agent in the mixed material was reduced to 5.67 kg per tonne of fiber and the standard wood pulp fibers were FR416 fibers never dried . The performance data for the representative mixed material formed as described above (mixed material D) is presented in Tables 5 and 6 in Example 16.

EXAMPLE 13 A representative mixed material was formed as described in Example 12 except that the mixed material was not densified.

The performance data for the representative mixed material formed as described above (mixed material E) is presented in Tables 5 and 6 in Example 16.

EXAMPLE 14 A representative mixed material was formed as described in example 12 except that the wood fiber pulps were FR416 fibers dried once. The performance data for the representative mixed material formed as described above (mixed material F) is presented in Tables 5 and 6 in Example 16.

EXAMPLE 15 A representative mixed material was formed as described in example 12 except that the amount of fiber in the mixed material was increased to approximately 80% by weight and the amount of absorbent present in the mixed material was reduced to approximately 20% by weight of the Total mixed material. The performance data for the representative mixed material formed as described above (mixed material G) is presented in Tables 5 and 6 in Example 16. Í. *. * Í .¿ -t-J-gt-. . *? * Í.

EXAMPLE 16 The performance of representative mixed materials (BD mixed material) prepared as described in Examples 10-15 is summarized in Tables 5 and 6. Capillary liquid absorption, absorbent capacity, wet and dry tensile strength, and moisture resistance of the representative mixed materials are compared with a conventional hand sheet in Table 5. The conventional hand sheet had a weight of base and density comparable to the representative mixed materials and included 60% by weight of fibers (25%). of interlaced fibers and 75% of standard wood pulp fibers), 40% by weight of superabsorbent material and 5.67 kg of Kymene per tonne of fibers. The results presented in Table 5 are the average of three measurements except for the voltage values, which are averaged for the measurements. In the table, "DM" refers to the machine direction of the mixed materials and "DT" refers to the cross machine direction. The capillary absorption values were obtained by the methods described in example 5 and the wet and dry tension values were obtained by the method described in example 7. The moisture resistance value was calculated and defined as the ratio of wet tension values to dry tension. The value of the mass flow rate (g / min / g) was determined by measuring the gain in weight of a portion of a mixed material (22 cm x 5 cm) divided by the least of the time t. »? -F*. ***** A * t ~. ^ .hm required for the liquid to be absorbed 15 cm or 15 minutes, divided by the weight of the original sample.

TABLE 5 Performance characteristics Capillary Absorption Stress Tension in Wet Moisture Resistance Dry to Moisture TiemAbCapaVeloCapaDM DT DM DT DT DT -popocidad Cidad cidad (9 / 2.5 Mate (g / 2. ^ 25 (g254 (%) (%) para para in 5 of hin- 4 cm) 54 om) cm) -rial 10 15 cm final min chacm flow) cm (sec) (cm) (vert) of mien- (sec) (45 (g / g) mass to free min (g / min / in 15 max) g) minutes B 45 234 23 7.6 1.9 20 1585 1222 > 480 4385 < 32 28 0 C 47 221 24 8.3 2.3 19 1317 1241 > 480 4277 < 27 29 0 D 59 > 400 18 9.3 < 1.4 24 673 488 2940 2455 23 20 E 160 > 400 19 9.4 < 1.4 22 1091 764 > 480 3771 < 23 20 0 F 38 144 25 7.7 3.2 15 1654 1291 > 520 5100 < 31 < 25 0 G 52 245 22 8.4 2.1 20 1686 980 > 520 4800 < 32 < 21 0 sheet manu159 > 300 16 10.9 2.2 31 226 al The absorbent capacity of several of the representative mixed materials is summarized in Table 6. In this capacity test, portions of the representative mixed materials (ie, 10 cm squares) were immersed in a 1% saline solution. The samples were allowed to absorb liquid and swell for 10 minutes. The difference in the weight of the mixed material before and after the swelling of 10 minutes is the capacity reported as cm3 / g.

TABLE 6 Absorbent capacity 10 EXAMPLE 17 Method for determining capillary fluid absorption for representative mixed materials The absorbent properties of representative mixed materials 15 can be determined by measuring the height of unrestricted vertical capillary absorption, which is indicative of the ability of the mixed material to absorb and distribute fluid. The vertical capillary absorption height not restricted to 15 minutes was measured for representative mixed materials as described below.

Material: Synthetic urine for absorption - 0.9% saline solution "blood bank" Samples: Size 6.5 cm (DT) x 25 cm (DM), marked with permanent lines and permeable to water at 1, 11, 16 and 21 cm along DM.

Method: 1) Determine percent solids on the sample material and record. 2) Cut the sample and record (as such) the weight and caliber dry. 3) Hold the sample 1 cm from the top. 4) Immerse in liquid up to the line of 1 cm. 5) Start timing the time immediately. 6) At the end of 5, 10 and 15 minutes, record the capillary absorption height by measuring down from the next higher line. Report the capillary absorption height to the nearest 0.5 cm. 7) At 15 minutes, raise the sample of fluid and while it is fastened, cut the sample to 1 cm and in lines of 15 cm in height. Discard the 1 cm section. 8) Wet weigh 15 cm of sample length and record. 9) Release the remaining sample and add the rest in order to record all the wet weight of the pad. 10) Report the total capillary absorption height in 15 minutes. 11) Report entire pad capacity as such and based on D.O. (g / g) calculating: Total wet weight capacity (as such or weight of D.O.) * give the = pad as such or Deso de D.O.

* Weight of the pad (-1 cm section) = (total weight of the sample x 0.96) 15) Calculate the absorbed capacity of the pad if it is necessary: Capacity 24 capacity absorbed in the = total of the x almnhaHill? Pad, height Hfi ah? nrni? n pn 15 mini in? The unrestricted vertical absorption height for materials representative mixes is described in the following examples.

EXAMPLE 18 Performance characteristics of representative mixed materials having fibrous webs The performance characteristics of representative mixed materials prepared as described above are summarized in Table 7. The vertical unconstrained capillary absorption height and the total fluid absorbed in 30 minutes and the absorption and flow rate at 12 cm are compared for materials mixtures formed in accordance with the present invention and for commercially available air laid cores. In Table 7, the mixed material I is a cross-linked absorbent composite material formed in accordance with the present invention having a composition that includes about 58% by weight of absorbent material, 32% by weight of interlaced fibers and 8% by weight of matrix fibers based on the total weight of the composition. The mixed materials J and K are mixed materials that include two fibrous webs. For these mixed materials, the fibrous matrix included 69% by weight of absorbent material, 24% by weight of interlaced fibers and 6% by weight of matrix fibers based on the total weight of the matrix. The mixed material J had fibrous webs composed of interwoven and matrix fibers in which the ratio of the interlaced fibers to the matrix fibers was 1: 4. The mixed material K had a ratio of interwoven fibers to matrix fibers of 1: 1. feíí-i-i? i?, t -. *, ai'í¿ y. < »TABLE 7 Parameters of unrestricted vertical capillary absorption of representative mixed material 10 15 * Loss of integrity after 6 minutes. As shown in Table 7, the mixed materials formed in accordance with the present invention far exceeded the commercially available air laid core. The mixed materials J and K, which 20 included fibrous bands, had absorption and liquid distribution characteristics that were increased compared to mixed material I, a mixed material that lacked fibrous bands.

* ** EXAMPLE 19 Performance characteristics of a representative mixed material having two fibrous bands The performance characteristics for a representative mixed material having two fibrous webs (mixed material L) was compared to a mixed material similarly constituted that lacked fibrous webs (control). The mixed control material had a basis weight of 700 g / min and included 50% by weight of superabsorbent material; 25% by weight of interlaced cellulosic fibers; 25% by weight of fluffy pulp fibers (refined southern pine) based on the total weight of the mixed material. The mixed material having fibrous webs was constructed from the mixed control material and the fibrous strips. The components adhered together to provide the mixed material (see, for example, figure 31). The mixed material had a length of 25 cm, width of 5 cm, and included two fibrous strips having a width of 0.75 cm. The capillary absorption height in 15 minutes, capacity at 15 cm, and the capacity of the moistened area for the mixed materials was compared graphically in figure 32. As shown in figure 32, the absorption height and the absorption capacity in 15 minutes for the mixed material L was increased in relation to the mixed control material. The properties and characteristics of the mixed material L and the control are summarized in table 8.

TABLE 8 Unrestricted vertical capillary absorption performance EXAMPLE 20 Method for determining flexibility and softness for representative mixed materials The flexibility and softness of the mixed material are factors to determine the suitability of the mixed materials to be incorporated in absorbent products for personal care. The flexibility of the mixed material can be indicated by crushing the ring by the edges of the mixed material, which is a measure of the force required to compress the mixed material as described below. For a mixed material to be incorporated into an absorbent personal care product, the ring crushing values vary from about 400 to about 1600 grams / 2.54 cm. The smoothness of the mixed material can be indicated by a variety of parameters including edge compression of the mixed material. Edge compression (CB) is the force required to compress the mixed material corrected by the basis weight of mixed material as described below. For a mixed material to be suitably incorporated into an absorbent product for personal care, the mixed material has a ring crushing value in the range of 400-1600 g and a basis weight in the range of about 250 to about 650 g / min. The flexibility and softness of representative crosslinked absorbent composite materials formed by wet laying and foaming methods according to the present invention were determined by measuring edge crushing and edge compression of mixed material. The flexibility and smoothness of the representative mixed materials was determined by the ring-edge crushing method. In the method, a length of the mixed material (typically approximately 30.48 cm) is formed in a cylinder and its ends are brought together to provide a cylinder having a height equal to the width of the mixed material (typically about 6.35 cm). The crushing of ring by edges is measured by adding mass to the upper part of the ring of mixed material sufficient to reduce the height of the cylinder of the mixed material by half. The more flexible the mixed material, the lower the weight will be required to reduce the height in the measurement. Ring crushing by edges is measured and reported as a mass (g). Edge compression (CB) is the ring crushing reported in units of g / gm in the following tables. The following is a description of the ring crushing method.

Samples: 6.35 cm X 30.5 cm) Analysis in triplicate (A, B, C) Method: 1) Cut triplicate of sample size, lengthwise in the direction of the machine (DM) of the mixed material. 2) Condition the samples for 2 hours at a relative humidity of 50% or environmental conditions. 3) With the wire side on the outside, form the individual samples in loops so that two narrow ends meet without any overlap. Using four staples, attach the ends to each other at the top, bottom and two times in half. The upper and lower staples should be 0.3-0.5 cm from the edge and the middle staples should be less than 2 cm from each other and the respective upper or lower staple. Finally, make sure that each staple penetrates the fiber only in the areas. 4) Fix the lower platform on a level, smooth surface. . * ~? 5) Place the sample, by edges and in the center, between the upper and lower platforms. 6) Gently place a 100 g weight on the center of the upper platform (or weigh 500 g) and wait 3 seconds. 7) Next, gently stack 3 weights over 100 g at 3-second intervals. 8) If the ring collapses 50% or more of its original height within a 3-second interval, then record the total amount of weight needed to do so, that is, add the weight of the upper platform and the other combined weights. 9) If the combined weight does not crush the sample, then carefully remove the four 100 g weights. 10) Gently add one (another) 500g weight and weigh 3 seconds. 11) If the ring collapses 50% or more of its original height within a 3 second interval, then record the total amount of weight needed to do so, ie add the weight of the upper platform and the other weights. 12) Repeat step 6 to step 11, increasing the number of weights of 500 g by one for each cycle. 13) Repeat steps 5 to 11 for other replicas. 14) Record the average weight for replicates in g.f rounded to the nearest 10 g. », - y- i ...... ...." Calculations: Average ring crushing weight = (weight A + weight B + weight C) / 3 Ring crushing values determined as described above for representative mixed materials formed according to the present invention are summarized in Example 21. The softness of the representative crosslinked absorbent composite materials formed in accordance with the present invention can be indicated by edge compression. Edge compression is discussed in The Handbook of Phvsical and Mechanical Testing of Paper and Paperboard. Richard E. Mark, Dekker 1983 (Vol. 1). The compression by edges was determined by correcting the crushing of ring by edges, determined as described above, for a basis weight of the mixed body. The edge compression (CB) values for representative mixed materials formed in accordance with the present invention are summarized in Example 21.

EXAMPLE 21 Performance characteristics of representative foam-formed mixed materials having fibrous webs Performance characteristics of representative foam-formed mixed materials having fibrous webs (mixed materials M, N, O) were compared with similarly formed foam-formed composite materials lacking fibrous webs (control A and B). The mixed materials were prepared on a twin wire former as described above. The fluff pulp fibers for the mixed materials were unrefined softwood fibers (southern pine, 745 CSF), and the refined fibers were refined softwood (southern pine, 200 CSF). The superabsorbent polymer was a slightly interlaced polyacrylate (SR1001). All mixed materials included a moisture resistance agent (KYMENE), 0.45% by weight based on the total weight of the mixed material. Control A included 58% by weight of the superabsorbent material and 42% by weight of fibrous material based on the total weight of the mixed material. The fibrous material included 67% by weight of interlaced fibers and 33% by weight of fluff pulp fibers based on the total weight of the fibers. Control B included 50% by weight of the superabsorbent material and 50% by weight of fibrous material based on the total weight of the mixed material. The fibrous material included 67% by weight of interlaced fibers and 33% by weight of fluff pulp fibers based on the total weight of the fibers. Control B also included the fibrous material constituting the fibrous webs in the mixed materials M, N and O. The mixed materials M-O included two fibrous webs (50 gm) in a fibrous base. The fibrous base included 50% by weight of superabsorbent material and 50% by weight of fibrous material based on the total weight of the mixed material. The fibrous material included 67% by weight of fibers The interlaced jffl and 33% by weight of fluff pulp fibers are based on the total weight of the fibers. For the mixed material M, the fibrous webs included 50% by weight of interlaced fibers and 50% by weight of refined fibers based on the total weight of fibers in the webs. For the mixed material N, the fibrous webs included 80% by weight of interlaced fibers and 20% by weight of refined fibers based on the total weight of fibers in the webs. For the mixed material O, the fibrous webs included 50% by weight of interlaced fibers and 50% by weight of fluff pulp fibers based on the total weight of fibers in the webs. The saturation capacity (sat.cit.), Unrestricted vertical capillary absorption height (URVW), ring and tension crushing for controls A and B and the mixed materials M, N and O are summarized in table 9.

TABLE 9 Characteristics of representative mixed material 10 As shown in Table 9, capillary absorption for mixed materials having fibrous webs is increased as compared to mixed control materials. The fibrous bands also 15 increase the tension of the mixed material significantly. Ring crushing and tensile strength for mixed control and representative materials are correlated graphically in Figure 33. As shown in Figure 33, ring crushing increases drastically by increasing the tensile strength for the 20 mixed control material. On the other hand, the ring grinding remains substantially constant by increasing the tensile strength for the representative mixed material having fibrous webs. This correlation shows that greater tensile strengths can be achieved in these t? ti? . -mSI.-Jt Í ..? ... Í compositions without significantly increasing the ring crushing (ie, reducing the softness). The unrestricted vertical capillary absorption height and the saturation capacity for mixed control and representative materials are correlated graphically in Figure 34. As shown in the figure 34, capillary absorption decreases drastically by increasing the saturation capacity for the mixed control material. In contrast, the capillary absorption remains substantially constant by increasing the saturation capacity for the representative mixed material having fibrous webs. This correlation shows that greater capillary absorption and fluid distribution can be achieved for these mixed materials without reducing the saturation capacity. Ring trituration and tensile strength for mixed control and representative materials are compared graphically in Figure 35. The mixed materials M, N and O all show increased stress as compared to the controls. The unrestricted vertical capillary absorption height and the saturation capacity for mixed control and representative materials are compared graphically in Figure 36. The mixed materials M, N and O show all increased capillary absorption compared to the controls.

.Vt Ji Although the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes may be made therein without departing from the spirit and scope of the invention.

Claims

NOVELTY OF THE INVENTION CLAIMS 1. - A mixed absorbent material, comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material. 2. The mixed material according to claim 1, further characterized in that the webs are continuous along the length of the mixed material in the machine direction. 3. The mixed material according to claim 1, further characterized in that the bands are substantially parallel. 4. The mixed material according to claim 1, further characterized in that the bands are discontinuous along the length of the mixed material in the machine direction. 5. The mixed material according to claim 1, further characterized in that the fibrous matrix comprises fibers selected from elastic fibers, matrix fibers and mixtures thereof. 6. The mixed material according to claim 5, further characterized in that the elastic fibers are selected from the group consisting of chemically stiffened fibers, anfractuous fibers, chemithermomechanical pulp fibers, prehydrolyzed kraft pulp fibers, synthetic fibers and mixtures of the same. 7. The mixed material according to claim 6, further characterized in that the chemically stiffened fibers comprise interwoven cellulosic fibers. 8. The mixed material according to claim 7, further characterized in that the interlaced cellulosic fibers are interlaced with an interlacing agent selected from the group consisting of urea-based crosslinking agents and polycarboxylic acid. 9. The mixed material according to claim 6, further characterized in that the synthetic fibers are selected from the group consisting of polyolefin, polyester, polyamide, and thermobondable bicomponent fibers. 10. The mixed material according to claim 9, further characterized in that the polyester fibers are polyethylene terephthalate fibers. 11. The mixed material according to claim 5, further characterized in that the matrix fibers comprise cellulosic fibers. 12. The mixed material according to claim 11, further characterized in that the cellulosic fibers comprise fibers selected from fibers of wood pulp, cotton fluff, cotton fibers, hemp fibers and mixtures thereof. 13. - The mixed material according to claim 5, further characterized in that the elastic fibers are present in the base in an amount of about 10 to about 60 weight percent of the total mixed material. 14. The mixed material according to claim 5, further characterized in that the matrix fibers are present in the base in an amount of from about 10 to about 50 weight percent of the total mixed material. 15. The mixed material according to claim 1, further characterized in that the absorbent material is a superabsorbent material. 16. The mixed material according to claim 15, further characterized in that the superabsorbent material is selected from the group consisting of superabsorbent particles and superabsorbent fibers. 17. The mixed material according to claim 1, further characterized in that the absorbent material is present in an amount of from about 0.1 to about 80 weight percent of the total mixed material. 18. The mixed material according to claim 1, further characterized in that the absorbent material is present in about 40 percent by weight of the total mixed material. 19. - The mixed material according to claim 1, further characterized in that the absorbent material absorbs around 5 to approximately 100 times its weight in 0.9 percent saline. 20. The mixed material according to claim 1, further characterized in that it comprises a moisture resistance agent. 21. The mixed material according to claim 20, further characterized in that the moisture resistance agent is a resin selected from the group consisting of polyamide-epichlorohydrin and polyacrylamide resins. 22. The mixed material according to claim 20, further characterized in that the moisture resistance agent is present in the mixed material in an amount of from about 0.01 to about 2 weight percent of the total mixed material. 23. The mixed material according to claim 20, further characterized in that the moisture resistance agent is present in the mixed material at about 0.25 weight percent of the total mixed material. 24. The mixed material according to claim 1, further characterized in that it has a basis weight of about 50 to about 1000 g / m2. 25. - The mixed material according to claim 1, further characterized in that it has a density of about 0.02 to about 0.7 g / cm3. 26. The mixed material according to claim 1, further characterized in that the fibrous webs (one or more) comprise fibers selected from the group consisting of elastic fibers, matrix fibers and mixtures thereof. 27. The mixed material according to claim 26, further characterized in that the elastic fibers are selected from the group consisting of chemically stiffened fibers, anfractuous fibers, chemithermomechanical pulp fibers, prehydrolyzed kraft pulp fibers, synthetic fibers and mixtures thereof. same. 28.- The mixed material according to claim 27, further characterized in that the chemically stiffened fibers comprise interwoven cellulosic fibers. 29. The mixed material according to claim 28, further characterized in that the interwoven cellulosic fibers are interlaced with an interlacing agent selected from the group consisting of urea-based crosslinking agents and polycarboxylic acid. 30. The mixed material according to claim 26, further characterized in that the matrix fibers comprise cellulosic fibers. 31. - The mixed material according to claim 30, further characterized in that the cellulosic fibers comprise selected fibers of wood pulp fibers, cotton fluff, cotton fibers, hemp fibers and mixtures thereof. 32. The mixed material according to claim 30, further characterized in that the cellulosic fibers comprise spongy pulp fibers. 33. The mixed material according to claim 30, further characterized in that the cellulosic fibers comprise refined pulp fibers. 34.- The mixed material according to claim 26, further characterized in that the elastic fibers are present in the mixed material in an amount of about 15 to about 90 weight percent of the total mixed material. 35.- The mixed material according to claim 26, further characterized in that the matrix fibers are present in the mixed material in an amount of from about 10 to about 85 percent by weight of the total mixed material. 36.- A wet-laid mixed absorbent material comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material. iat * A.,? * < c * k * 'l ~. * ** .. t- 37.- An absorbent mixed material formed with foam comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of Absorbent material. 38.- An absorbent article containing a mixed absorbent material comprising one or more fibrous webs on a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material. 39. An absorbent article containing a wet-laid absorbent composite material comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material . 40.- An absorbent article containing a mixed absorbent material formed with foam comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material . 41.- An absorbent article that includes: a liquid-permeable front sheet; a storage layer containing a mixed absorbent material comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and a material The absorbent absorbent material and wherein the webs are substantially free of absorbent material; and a back sheet impervious to liquid. 42.- An absorbent article comprising: a front sheet permeable to liquid; an acquisition layer to acquire and distribute liquid; a storage layer containing a mixed absorbent material comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material; and a back sheet impervious to liquid. 43. An absorbent article comprising: a front sheet permeable to liquid; an acquisition layer to acquire and distribute liquid; a storage layer containing a mixed absorbent material comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material; an intermediate layer interposed between the acquisition layer and the storage layer; and a back sheet impervious to liquid. 44. The absorbent article according to claim 43, further characterized in that the intermediate layer is selected from the group consisting of a liquid-permeable fabric and a distribution layer. 45.- The absorbent article according to claim 41, further characterized in that the article is a product for female care. ~ ** 46. - The absorbent article according to claim 45, further characterized in that the upper sheet is joined to the backsheet. 47. The absorbent article according to claim 42, further characterized in that the article is a diaper. 48.- The absorbent article in accordance with the claim 47, further characterized in that it comprises harvesting in the region of the legs. 49. An absorbent article comprising: a front sheet permeable to liquid; an acquisition layer to acquire and distribute liquid; a storage layer; and a back sheet impervious to liquid; wherein the acquisition layer contains a mixed absorbent material comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material. 50.- The absorbent article in accordance with the claim 49, further characterized in that the acquisition layer has an upper surface area smaller than the upper surface area of the storage core. 51. The absorbent article according to claim 49, further characterized in that the acquisition layer has an upper surface area approximately equal to the upper surface area of the storage core. 52. - The absorbent article according to claim 49, further characterized in that the storage layer comprises absorbent material. 53. The absorbent article according to claim 49, further characterized in that the storage layer contains a mixed absorbent material comprising one or more fibrous webs in a fibrous base, wherein the base comprises a fibrous matrix and an absorbent material and wherein the webs are substantially free of absorbent material. 54.- The absorbent article in accordance with the claim 49, further characterized in that the article is a diaper. 55.- The absorbent article according to claim 49, further characterized in that it comprises harvesting in the region of the legs. 56.- A method for forming a fibrous web, comprising the steps of: (a) forming a first suspension comprising fibers in an aqueous dispersion medium; (b) forming a second suspension comprising fibers in an aqueous dispersion medium; (c) move a first foraminous element in a first trajectory; (d) moving a second foraminous element in a first path, a grip area provided at a location along the first and second trajectories; (e) passing the first suspension in contact with the first foraminous element moving in the first path; (f) passing the second suspension in contact with the first foraminous element moving in the second path; (g) passing a third material between the first and second suspensions, wherein the third material does not contact the foraminous elements, and wherein the third material is introduced at a plurality of points; and (h) extracting liquid from the first and second suspensions and the third material through the first and second foraminous elements, respectively, to provide a fibrous web. 57.- The method according to claim 56, further characterized in that the step of passing a third material between the first and second suspensions by introducing the material in a plurality of points provides bands of the third material in the formed fabric. 58.- The method according to claim 57, further characterized in that the step of passing a third material between the first and second suspensions introducing the material in a plurality of points consists in adjusting the positions of at least some of the plurality of points to adjust the introduction points in a first dimension towards and away from the grip area. 59. The method according to claim 57, further characterized in that the step of passing a third material between the first and second suspensions introducing the material in a plurality of points consists in adjusting the positions of at least some of the plurality of points to adjust the introduction points in a second &. ^ -. dimension substantially perpendicular to the first dimension, closer to one foraminous element or the other. 60. The method according to claim 57, further characterized in that the step of passing a third material between the first and second suspensions introducing the material in a plurality of points is carried out using a plurality of conduits. 61.- The method according to claim 60, further characterized in that the plurality of conduits comprises conduits having at least two different lengths. 62. The method according to claim 60, further characterized in that steps (e), (f) and (g) are carried out providing dividing walls that extend over a part of the length of the conduits to the area of grip. 63.- The method according to claim 56, further characterized in that the step of passing a third material between the first and second suspensions consists in passing the third material between the first and second suspensions after the first and second suspensions. they have made contact with the first and second foraminous elements, respectively and extracted the liquid thereof. 64.- The method according to claim 56, further characterized in that the fibers are selected from the group consisting of elastic fibers, matrix fibers, synthetic fibers and mixtures thereof. 65. - The method according to claim 56, further characterized in that the fibers comprise intertwined cellulosic fibers and wood pulp fibers. 66.- The method according to claim 56, further characterized in that the third material comprises a fibrous suspension. 67.- The method according to claim 56, further characterized in that the first suspension is different from the second suspension. 68.- The method according to claim 56, further characterized in that the first and second trajectories are substantially vertical. 69. The method according to claim 56, further characterized in that it is carried out with a twin wire former. 70. The method according to claim 69, further characterized in that the twin wire former is a vertical downflow former. 71. The method according to claim 56, further characterized in that it comprises the step of drying the wet mixed material to provide a mixed absorbent material. 72. The method according to claim 56, further characterized in that the method is a wet laying method. 73. - The method according to claim 56, further characterized in that the method is a method of foam formation. Ih- -JL-. ? .JU.tU * li.t + í * á £ iÍl.-m * m í. ~ L *, y¿.¿4 »^»