Patent Publication Number: US-2003236512-A1

Title: Absorbent core with folding zones for absorbency distribution

Description:
FIELD OF THE INVENTION  
       [0001] The present invention generally relates to absorbent garments and their manufacture. In particular, this invention relates to an absorbent core having folded high absorbency zones and a method for manufacturing such an absorbent core.  
       BACKGROUND OF THE INVENTION  
       [0002] Traditionally, disposable absorbent garments, such as infant diapers, training pants, adult incontinence briefs and other such products were constructed with a moisture-impervious outer or backing sheet (often referred to as a “backsheet”), a moisture-pervious body-contacting inner liner sheet (often referred to as a “topsheet”), and a moisture-absorbent core sandwiched and encased between the topsheet and backsheet.  
       [0003] The moisture-absorbent cores of absorbent garments typically use a fibrous matrix of material into which particles of superabsorbent material, in the form of granules, beads, fibers, flakes and so on, are dispersed. Such superabsorbent materials generally are polymeric gelling materials that are capable of absorbing large quantities of liquids such as water and body wastes relative to their weight, and can retain such absorbed materials even under moderate pressure. The use of such superabsorbents, however, has given rise to problems with the design of absorbent garments. One problem with superabsorbents it that they may impede the rapid absorption of fluids by a phenomenon known as “gel blocking.” Another problem with superabsorbents is that they are relatively expensive.  
       [0004] The ability of a superabsorbent material to absorb liquid depends, at least in part, upon the form, position, and/or manner in which the superabsorbent particles are incorporated into the absorbent core. Whenever a particle of superabsorbent material in an absorbent core is wetted, it swells and forms a gel. Gel formation can block liquid transmission into the interior of the absorbent core, a phenomenon called “gel blocking.” Gel blocking in portions of the absorbent core that typically receive the initial liquid contact (“insult points”) may prevent liquid from rapidly diffusing or wicking past the “blocking” superabsorbent particles and into the rest of the absorbent core; further imbibition of liquid by the absorbent core must then take place via a diffusion process that can be much slower than the rate at which liquid is applied to the core. Gel blocking thus can result in leakage from the absorbent article well before the absorbent core is fully saturated.  
       [0005] Due to the relative expense of superabsorbent materials, various attempts have been made to provide the absorbent garment with “zoned absorbency;” providing those portions of the garment that are most likely to require absorbent capacity with greater concentrations of superabsorbent material. U.S. Pat. No. 5,248,524 to Soderlund, which is incorporated herein by reference, discusses various attempts to provide zoned absorbency. Generally, prior attempts to provide zoned absorbency have concentrated on providing greater or lesser densities of superabsorbent in various parts of a fibrous matrix that has a generally uniform density. While many of the known zoning systems have provided acceptable products, they have been subject to undesirable product variability due to uncontrolled variations in the forming process. For example systems using pulsed (i.e., intermittently activated) superabsorbent particle depositing devices have complicated airflow, hysteresis, timing and momentum problems that may be difficult to predict or control, particularly when production rates increase.  
       [0006] In some cases, providing zoned absorbency may increase the likelihood that gel blocking will occur in an absorbent garment. This may be the case when greater concentrations of superabsorbent are desired to be positioned at the garment&#39;s insult point.  
       [0007] These are just a few of the disadvantages of the known absorbent articles and absorbent materials that the preferred embodiments seek to address. The foregoing description of certain materials, methods and systems with their attendant disadvantages in no way is meant to infer that the present invention excludes such materials, methods, and systems. Indeed, certain embodiments of the invention may solve some of the aforementioned disadvantages and other disadvantages, yet may utilize the same or similar materials, methods and/or systems.  
       SUMMARY OF THE INVENTION  
       [0008] There exists a need to provide an absorbent core structure and method of making such a structure that provides greater control over the location of high absorbency zones. There also exists a need to provide high absorbency zones having a reduced susceptibility to gel blocking.  
       [0009] The features of the invention generally may be achieved by an absorbent core having a longitudinal dimension, a lateral dimension, and a fibrous matrix with superabsorbent particles distributed within the fibrous matrix. The absorbent core has a folded zone that has at least one laterally-extending fold. The folded zone extends through at least a portion of the longitudinal dimension of the absorbent core.  
       [0010] In one embodiment, the folded zone extends through substantially the entire lateral dimension of the absorbent core.  
       [0011] In another embodiment, a first tissue layer is disposed on a first side of the fibrous matrix, and a second tissue layer is disposed on a second side of the fibrous matrix. The first tissue layer and the second tissue layer may be portions of a single tissue sheet.  
       [0012] In still another embodiment, the folded zone comprises two or more laterally-extending folds. A laterally-extending void may be located between each adjacent pair of laterally extending folds.  
       [0013] In various other embodiments, the fibrous matrix may include tow fibers, which may be cellulose acetate tow fibers, and the superabsorbent particles and fibrous matrix may be a uniform basis weight fibrous matrix/superabsorbent polymer mixture. In another embodiment, the folded zone has greater absorbent properties than other portions of the absorbent core.  
       [0014] In still other embodiments, the absorbent core may be disposed between the topsheet and backsheet of an absorbent garment, and the folded zone may be positioned proximal to an insult point on the topsheet, where exudates from an intended wearer initially strike the topsheet when the garment is worn by the intended wearer. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0015]FIG. 1 is an isometric view of an absorbent garment having an absorbent core according to a preferred embodiment of the present invention;  
     [0016]FIG. 2 is a sectional view of a portion of the folded zone of the garment of FIG. 1, as shown from reference line A-A;  
     [0017]FIG. 3 is a side view of an exemplary core forming apparatus; and  
     [0018]FIG. 4 is a side view of an embodiment of a preferred folded core forming apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0019] As understood herein, “manufacturing line,” “processing line” and “line” refer to any manufacturing or assembly line. Such a processing line may operate substantially non-stop or intermittently, and may move in substantially one direction or may operate in several directions. Manufacturing lines typically comprise a number of devices to process materials in various ways. The various devices may be operated substantially independently of one another, or they may be partially or entirely integrally controlled by a single driving system having a relatively small number of partially or wholly-independent controllers. Such a system may be based on a modular system such as those disclosed in U.S. Pat. Nos. 5,492,591 and 5,383,988, both to Herrmann et al., each of which is incorporated herein by reference in its entirety.  
     [0020] The “machine direction,” as used herein, is the primary direction in which material or parts are traveling through a processing line at any given point. The material moving through the processing line generally originates from the upstream direction and moves in the downstream direction as it is processed. The “cross-machine direction” or “cross direction” is perpendicular to the machine direction and generally parallel to the plane of the material being processed. The cross machine direction generally corresponds to the width of the material being conveyed. The “z-direction” is orthogonal to the plane defined by crossed vectors in the machine direction and cross machine direction, and generally corresponds to the thickness of the material being conveyed.  
     [0021] As used herein, the term “absorbent garment” or “garment” refers to garments that absorb and contain exudates, and more specifically, refers to garments that are placed against or in proximity to the body of a wearer to absorb and contain various exudates discharged from the body. A non-exhaustive list of examples of absorbent garments includes: diapers, diaper covers, disposable diapers, training pants, feminine hygiene products and adult incontinence products. The term garment includes all variations of absorbent garments, including disposable absorbent garments that are intended to be discarded or partially discarded after a single use (i.e., they are not intended to be laundered or otherwise restored or reused) and unitary disposable absorbent garments that have essentially a single structure (i.e., do not require separate manipulative parts such as a diaper cover and insert). Embodiments of the present invention may be used with all classes of absorbent garments, including those described above and others not described herein.  
     [0022] Absorbent garments and diapers may have a number of different constructions. In each of these constructions it is generally the case that an absorbent core is disposed between a liquid pervious, body-facing topsheet, and a liquid impervious, exterior facing backsheet. In some cases, one or both of the topsheet and backsheet may be shaped to form a pant-like garment. In other cases, the topsheet, backsheet and absorbent core may be formed as a discrete assembly that is placed on a main chassis layer and the chassis layer is shaped to form a pant-like garment. The garment may be provided to the consumer in the fully assembled pant-like shape, or may be partially pant-like and require the consumer to take the final steps necessary to form the final pant-like shape, such as by fastening one or more fastener tabs. In the case of training pant-type garments and most adult incontinent products, the garment often is provided fully formed with factory-made side seams and the garment is donned by pulling it up the wearer&#39;s legs. In the case of diapers, a caregiver usually wraps the diaper around the wearer&#39;s waist and joins the side seams manually by attaching one or more fastener tabs, thereby forming a pant-like structure. Other garments, such as many feminine care products, do not have a pant-like construction, and the present invention may be used with these garments as well. For clarity, the present invention is described herein only with reference to a diaper-type garment in which the topsheet, backsheet and absorbent core are assembled into a structure that forms a pant-like garment when secured on a wearer using fastening devices, although the invention also may be used with any other type of absorbent garment that may benefit from the use or addition of an absorbent core.  
     [0023] For clarity, features that appear in more than one Figure have the same reference number in each Figure.  
     [0024] A preferred embodiment of the present invention may be used with a disposable absorbent garment  100  of the diaper type, such as shown, for example, in FIG. 1. The garment  100  of FIG. 1 is shown with the contractile forces of its elastic members removed for clarity in the Figures and the description. The garment  100  chassis is shown having a hourglass shape, but the garment chassis also may have a rectangular shape, a trapezoidal shape, a “T” shape, or any other suitable shape that allows the garment to be affixed to or placed near a wearer. The garment  100  generally has a longitudinal direction 1 corresponding to the front-to-back axis of a wearer, and a lateral direction 2 corresponding to the side-to-side axis of a wearer. The garment generally is symmetrical about a longitudinal centerline 3, but also may have asymmetrical components or shapes.  
     [0025] The garment preferably comprises a topsheet  102 , a backsheet  104 , which may be either a different size than the topsheet  102  or may be substantially coterminous with the topsheet  102 , and an absorbent core  106  disposed between at least portions of the topsheet  102  and the backsheet  104 . It should be understood that additional layers may be present between the absorbent core  106  and the topsheet  102  and/or the backsheet  104 . Also, additional layers or sheets may be disposed on the topsheet  102  and/or backsheet  104  on the side opposite the absorbent core  106 . Such additional layers may be provided to enhance the performance of the garment  100 . The dimensions of the additional layers may be the same as or different from the dimensions of the absorbent core  106  and/or topsheet  102  and backsheet  104 . Examples of such layers include acquisition layers, transfer layers, wicking layers, storage layers, fluid handling layers, rewet barriers, and the like. These and other useful layers are generally known in the art, and their suitability for use with the present invention will be apparent to those skilled in the art based on the teachings herein, and the invention encompasses all types of additional layers.  
     [0026] A pair of leg cutouts  110  may extend along either side of the garment  100  to provide the garment  100  with a better fit on the wearer. In addition, one or more sets of leg elastics  112  may be disposed to extend along the leg cutouts  110  to contract the leg cutouts around the wearer&#39;s legs. The garment  100  further may include a waist elastic system  114 , for contracting the garment  100  around the wearer&#39;s waist, and a pair of fastener tabs  101  to hold the garment  100  on the wearer. Waste containment systems also may be incorporated into the garment  100 . Examples of waste containment systems include such devices as pockets and waste containment flaps  116  (also known as unitary leg gathers or standing leg gathers).  
     [0027] A variety of backsheet and topsheet constructions and materials are available and known in the art, and the invention is not intended to be limited to any specific materials or constructions of these components. The backsheet  104  may be made from any suitable pliable liquid-impervious material known in the art. Typical backsheet materials include films of polyethylene, polypropylene, polyester, nylon, and polyvinyl chloride and blends of these materials. For example, the backsheet may comprise a pigmented polyethylene film having a thickness in the range of 0.02-0.04 mm. In some cases, it may be desirable to provide a partially- or wholly-gas pervious backsheet  104  to encourage airflow in the garment  100  to reduce discomfort, skin rashes and bacterial infections. For example, all or part of the backsheet  104  (or other parts of the garment  100 ) may be fabricated from a porous film, such as that disclosed in U.S. Pat. No. 6,258,196 to Suzuki et al., which is incorporated herein by reference in its entirety. In addition, to improve the look and feel of the garment  100 , the backsheet  104  may be covered with a fibrous, nonwoven fabric layer (not shown) such as is disclosed, for example, in U.S. Pat. No. 4,646,362, which is incorporated herein by reference in its entirety.  
     [0028] The backsheet  104  may comprise a laminate and/or multiple panels of material, such as three panels wherein a central poly backsheet panel is positioned adjacent the absorbent core while outboard non-woven breathable side backsheet panels are attached to the side edges of the central poly backsheet panel. The backsheet also may be formed from microporous poly coverstock for added breathability. The backsheet may further be treated to render all or part of it hydrophilic or hydrophobic, as desired, and may have one or more visual indicators associated with it, such as labels indicating the front or back of the garment, wetness indicators or other characters or colorations. The present invention is not limited to any particular backsheet  104  material or construction.  
     [0029] The moisture-pervious topsheet  102  may comprise any suitable relatively liquid-pervious material known in the art that permits sufficient passage of liquid therethrough. Non-woven topsheet materials are exemplary because such materials readily allow the passage of liquids to the underlying absorbent core  106 . Examples of suitable topsheet materials include non-woven spunbond or carded webs of polypropylene, polyethylene, nylon, polyester and blends of these materials.  
     [0030] The topsheet  102  may be formed from one or more panels of material and may comprise a laminated sheet construction. For example, in an embodiment in which multi-panel construction is used, a three-panel topsheet may comprise a central topsheet panel extending along the length of the garment  100 , and outer topsheet panels positioned laterally outside of the central topsheet panel. The central topsheet panel preferably is formed from a liquid-pervious material that is either hydrophobic or hydrophilic. The central topsheet panel may be made from any number of materials, including synthetic fibers (e.g., polypropylene or polyester fibers), natural fibers (e.g., wood or cellulose), apertured plastic films, reticulated foams and porous foams to name a few. One preferred material for a central topsheet panel is a cover stock of single ply non-woven material which may be made of carded fibers, either adhesively or thermally bonded, perforated plastic film, spunbonded fibers, or water entangled fibers, which generally weigh from 0.3-0.7 oz./yd 2  and have appropriate and effective machine direction and cross-machine direction strength suitable for use as an absorbent garment cover stock material, as are known in the art. The outer topsheet panels of a multi-panel construction preferably are substantially liquid-impervious and hydrophobic, preferably at least in the crotch area. The outer edges of the outer topsheet panels may substantially follow the corresponding outer perimeter of the backsheet  104 . The outer topsheet panels preferably comprise polypropylene and may be woven, non-woven, spunbonded, carded or the like, depending on the application.  
     [0031] The backsheet  104  and the topsheet  102  preferably are “associated” with one another. The term “associated” encompasses configurations whereby the topsheet  102  is directly joined to the backsheet  104  by affixing the topsheet  102  directly to the backsheet  104 , and configurations whereby the topsheet  102  is indirectly joined to the backsheet  104  by affixing the topsheet  102  to intermediate members which in turn are affixed to the backsheet  104 . Various bonding methods or combinations of methods may be used to join the topsheet  102  backsheet  104 , and any of the other parts comprising the garment  100 . Exemplary bonding methods include: adhesive bonding, ultrasonic bonding, heat bonding, chemical bonding, autogenous bonding, and the like.  
     [0032] The garment  100  preferably is fastened onto a wearer by one or more, and preferably two, fastener tabs  101 . The fastener tabs  101  preferably are affixed to the chassis of the garment  100  to extend laterally outward (i.e., in the lateral direction 2) from a waist region of the garment, preferably the waist region corresponding to the rear of a wearer when the garment  100  is donned. The fastener tabs  101  may be attached to any part of the garment chassis, such as the topsheet  102 , backsheet  104 , outer covering, as specially adapted fastening patch or other layer or part of the garment  100 . The fastener tabs  101  also may be attached to either side of the garment&#39;s chassis, to multiple layers of the chassis, or may be sandwiched between the various sheets comprising the chassis of the garment  100 . Variations on the number, location, and attachment configuration of the fastener tabs  101  and other securement devices will be apparent to those skilled in the art based on the teachings herein, and all such variations are within the scope of the present invention. Exemplary fastener tabs include those described in U.S. Pat. Nos. 3,800,796 to Jacob, 4,552,560 to Tritsch, 5,545,159 to Lancaster et al. and 5,685,873 to Bruemmer, each of which is incorporated herein by reference in its entirety. The present invention is not intended to be limited to the use of any particular fastener tabs  101  or to the use of fastener tabs  101  at all.  
     [0033] A waste containment system, such as waste containment flaps  116 , may be integrated into the garment  100  to provide an additional physical barrier to the movement or leakage of exudates. Waste containment flaps  116  (also known as unitary leg gathers or standing leg gathers) preferably extend in the longitudinal direction 1 throughout all or part of the longitudinal extent of the garment  100  along opposite sides of the garment&#39;s longitudinal center line 3. Other flaps may be positioned in parallel to waste containment flaps  116 , or may be positioned to extend across the width of the garment  100  (i.e., in the lateral direction 2) at or near either end of the garment  100  to inhibit the longitudinal flow of exudates.  
     [0034] The waste containment flaps  116  preferably include an elastic material that contracts the flaps around the wearer&#39;s body during use. Suitable elastics include elastomeric films, scrims, ribbons, strands, and elastic laminates. The waste containment flaps  116  may be formed from portions of the topsheet  102  and/or backsheet  104 , or may be separate assemblies that are attached to the topsheet  102  and/or backsheet  104 . The waste containment flaps  116  may be treated with a suitable surfactant to modify their hydrophobicity/hydrophilicity or imbued with skin wellness products as desired. Various other configurations of topsheets  102 , backsheets  104  and waste containment systems, such as flaps  116 , are known in the art, and the present invention is not intended to be limited to any particular design for these components, or to the use of a waste containment system at all. Exemplary waste containment systems are disclosed in U.S. Pat. Nos. 5,246,431 to Minetola et al., 5,403,301 to Huffmann et al., and 6,123,694 to Pieniak et al. (flaps), U.S. Pat. No. 6,077,254 to Silwanowicz et al. (pockets), and U.S. Pat. No. 6,222,092 to Hansen et al. (flow impediment structures on the topsheet). Each of these disclosures is incorporated herein by reference in its entirety.  
     [0035] Waist elastics  114  may be provided at or near one or both longitudinal ends of the garment  100 . The waist elastics  114  may be the same or different at each end of the garment  100  to impart similar or different elastic characteristics to the front and back waist portions of the garment  100 . Preferably, the waist elastics  114  comprise elastically extensible foam strips. The foam strips preferably are about 0.50 inches to about 1.50 inches wide and about 3 inches to about 6 inches long. The foam strips preferably are secured between the topsheet  102  and the backsheet  104  by adhesives, heat bonding, ultrasonic bonding, or any other suitable bonding method. The foam strips preferably are polyurethane, but could be any other suitable material that preferably decreases waist band roll over, reduces leakage from the waist ends of the absorbent garment, and generally improves comfort and fit. The front and back waist elastics  114  preferably are stretched to about 150% to about 250% of their unstretched length (in the lateral direction 2), and most preferably to about 200% of their unstretched length, before being adhesively secured between the backsheet  104  and topsheet  102 . Alternatively, a plurality of elastic strands or a patch of elastomeric film or scrim material may be employed as waist elastics  114  rather than foam strips. Waist elastics are known in the art, and disclosed, for example, in U.S. Pat. No. 4,430,086 to Repke, which is incorporated herein by reference in its entirety. The present invention is not limited to the use of a particular waist elastic system, or to the inclusion of waist elastics  114  at all.  
     [0036] Leg elastics  112  may be provided along either side of the garment to contract the leg openings around the wearer&#39;s legs. In a preferred embodiment the leg elastics  112  comprise three elastic strands on each side of the garment  100 , the strands being positioned between the topsheet  102  and the backsheet  114  and extending adjacent each leg cutout  110 . Various commercially available materials may be used for the leg elastics  112  and other elastic members that may be incorporated into the garment  100 , such as natural rubber, butyl rubber or other synthetic rubber, urethane, elastomeric materials such as spandex, which is marketed under various names, including LYCRA (DuPont), GLOSPAN (Globe) and SYSTEM 7000 (FULFLEX), and so on. The leg elastics  112  may be ultrasonically bonded, heat/pressure sealed using a variety of bonding patterns, glued to the garment  100 , or affixed using any other known or later developed method or combination of methods. The present invention is not limited to any particular elastic material, shape, size or number of elastics, or elastic joining method. The selection of appropriate leg elastics  112  and the construction of leg elastic containment systems is known in the art, and disclosed, for example, in U.S. Pat. Nos. 4,573,991 to Pieniak et al., 4,626,305 to Suzuki et al. and 5,660,664 to Herrmann, each of which is incorporated herein by reference in its entirety.  
     [0037] An absorbent core  106  is provided beneath the topsheet  102  to absorb and contain body exudates. Although the absorbent core  106  depicted in FIG. 1 has a substantially rectangular shape, other shapes may be used, such as a “T” shape or an hourglass shape. The absorbent core  106  may extend into either or both of the garment&#39;s waist regions, or may be located primarily in the crotch. The absorbent core  106  also may comprise a number of layers of similar or different construction. The absorbent core  106  may be attached to or captured between the topsheet  102  and backsheet  104 , or maybe joined to the garment by any other suitable method, as will be appreciated by those skilled in the art.  
     [0038] The absorbent core  106  may be made from any absorbent material or materials, or combinations of such materials, known in the art or hereafter discovered. Absorbent core materials are known in the art and exemplary core materials are disclosed, for example, in U.S. Pat. Nos. 4,610,678 to Weisman et al., 5,246,429 to Poccia et al., 5,137,537 to Herron et al., 5,147,345 to Young et al., 5,281,207 to Chmielewski et al., 6,068,620 to Chmielewski, and U.S. Statutory Invention Registration No. H1,565 to Brodof et al., each of which is incorporated herein by reference in its entirety. Preferably the absorbent core  106  comprises a combination of a porous fibrous web and superabsorbent particles. The absorbent core  106  may be chosen to absorb particular fluids or to absorb fluids generally. The absorbent core  106  preferably is thin in order to improve the comfort and appearance of a garment  100  containing the absorbent core  106 .  
     [0039] Referring now to FIG. 2, a preferred absorbent core  106  comprises a fibrous matrix  202  into which superabsorbent particles (SAP)  204  have been dispersed. The fibrous matrix  202  and SAP  204  preferably are partially or wholly contained within tissue layers  206 ,  208 . In other embodiments, however the tissue layers  206 ,  208  may be omitted.  
     [0040] The fibrous matrix  202  may comprise any suitable absorbent core material. Exemplary materials for the fibrous matrix  202  include cellulosic fibers such as wood pulp fluff or fluffed bleached kraft softwood pulp, cotton, cotton linters, rayon, fibrous absorbent gelling materials, cellulose acetate, synthetic polymeric fibers, and the like. Such materials are known in the art and disclosed, for example, in U.S. Pat. No. 4,610,478 to Weisman et al., which is incorporated herein by reference in its entirety. The fibrous matrix  202  also may comprise foam material. Preferably, the fibers or other material comprising the fibrous matrix  202  are hydrophilic. Other suitable absorbent core materials, as are known in the art or later discovered, also may be used.  
     [0041] In a preferred embodiment, the fibrous matrix  202  comprises a relatively low density matrix of opened tow fibers. Tow fibers are relatively long fibers of material that are bundled together to form a continuous web of material, known as a tow web. The tow web may be stored in a compact form, then “opened” (i.e., fluffed or bloomed) into a cotton-like form before integration into the absorbent core  106 . Various devices may be used to open the tow web, such as mechanical agitators and high velocity air streams, such as those disclosed in U.S. Pat. Nos. 5,331,976 to St. Pierre, and 4,525,385 to Pryor, each of which is incorporated herein by reference in its entirety. The relatively long fibers of the tow impart additional tensile strength to the absorbent core  106 , allowing less tow material to be used to make a stable absorbent core  106  that will not disintegrate during manufacture or use. The resulting absorbent cores  106  typically have a lower overall density than other types of core that provide an equivalent amount of absorbent capacity, and are relatively thin and light. Absorbent cores  106  using such materials are referred to herein as “tow-based” cores. The construction and use of such tow-based cores are disclosed generally in U.S. Pat. No. 6,068,620 to Chmielewski, and U.S. Statutory Invention Registration No. H1,565 to Brodof et al., each of which is incorporated herein by reference in its entirety.  
     [0042] A preferred process for manufacturing a tow-based core is shown in FIG. 3. In the process of FIG. 3, a first tissue layer  206  is provided (as a continuous supply) to a rotating drum  302 , and a fibrous matrix  202  of opened tow material is applied on top of the first tissue layer  206 . Superabsorbent material  204  is then deposited onto the fibrous matrix  202  and first tissue layer  206 , and a second tissue layer (in the form of a continuous supply) is placed on top of the fibrous matrix  202  and SAP  204  by a press roll  308  to form a continuous core supply  310 . The first and second tissue layers  206 ,  208  may be adhesively-, ultrasonically-, heat-, or otherwise bonded to one another and to the fibrous matrix  202  and/or SAP  204 . Adhesive may be applied to the first and/or second tissue layer  206 ,  208  prior to forming the tow-based core. The fibrous matrix  202  preferably is provided from a forming chamber  304  that uses compressed air or a mechanical means to open a tow web into a fluffed form.  
     [0043] The SAP  204  preferably is provided by a depositing mechanism  306  that meters out SAP  204  at the desired rate, which may be controlled to vary appropriately, as the speed of the operation increases or decreases, to provide the desired SAP distribution in the fibrous matrix  202 . Any particulate matter feeding system may be used as the depositing mechanism  306  so long as it is capable of providing SAP  204  at the desired flow rate. Exemplary depositing mechanisms  306  include auger-type feeders, such as those available from SolidsFlow Corporation of Fort Mill, S.C. (which may use a loss-in-weight metering system or other types of metering systems), pneumatic feed systems that use a stream of SAP particles entrained in an air flow, and the like. Other processes also may be used for forming a tow-based core, such as the processes described in U.S. Pat. No. 6,068,620 and U.S. Statutory Invention Registration H1,565. The present invention is not intended to be limited to any particular process for forming a tow-based absorbent core  106 .  
     [0044] Regardless of whether a tow-based construction, a conventional fluff construction or other construction is used, the absorbent cores  106  preferably are provided with a substantially uniform amount of SAP  204  per unit length of the fibrous matrix  202 , as they are being produced, to create a uniform basis weight fibrous matrix/SAP mixture. In a uniform basis weight fibrous matrix/SAP mixture, the amount of SAP per unit length or per unit weight of the fibrous matrix does not vary by more than about 50% throughout the unfolded length of the absorbent core  106 , and more preferably does not vary by more than about 35% throughout the unfolded length of the absorbent core  106 , and most preferably does not vary by more than about 20% throughout the unfolded length of the absorbent core  106 . In other embodiments, however, the absorbent cores may be produced having a zoned SAP distribution, in which the amount of SAP  204  substantially varies along the length or width of the absorbent core  106 . It will be understood that, in some instances, during further processing and use the SAP may migrate through the fibrous matrix  202 . This SAP migration may ultimately lead to a relatively disordered SAP distribution or to local high or low concentrations of SAP  204 , even in absorbent cores  106  that were originally produced with a uniform basis weight fibrous matrix/SAP mixture.  
     [0045] In other preferred embodiments, the SAP  204  may be omitted from the absorbent core  106 . Such an embodiment may be desirable, for example, in products intended to be used in aqueous environments, such as while the wearer is swimming or otherwise submerged or exposed to substantial amounts of environmental moisture.  
     [0046] Certain fibrous materials preferably are used to form the fibrous matrix  202  of a tow-based absorbent core  106  of the present invention. Preferably, the tow materials maintain high SAP efficiencies, even when the SAP concentration is relatively high. Preferred tow materials include cellulose esters, such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose caproate, cellulose caprylate, cellulose stearate, highly acetylated derivatives thereof such as cellulose diacetate, cellulose triacetate and cellulose tricaproate, and mixtures thereof such as cellulose acetate butyrate. A suitable cellulose ester preferably has some ability to absorb moisture (but absorptive capability is not necessarily required), preferably is biodegradable, and is influenced not only by the substituent groups but also by the degree of substitution. The relationship between substituent groups, degree of substitution and biodegradability is discussed in W. G. Glasser et al., BIOTECHNOLOGY PROGRESS, vol. 10, pp. 214-219 (1994), the disclosure of which is incorporated herein by reference in its entirety. Other suitable fibrous materials include rayon fibers, Courtauld&#39;s LYOCELL fibers, polyacrylonitrile fibers, surface-modified (hydrophilic) polyester fibers, surface-modified polyolefin/polyester bicomponent fibers, surface-modified polyester/polyester bicomponent fibers, cotton fibers, blends of the foregoing materials, and the like.  
     [0047] Of the foregoing, cellulose acetate tow fibers are the most preferred materials for use as the fibrous matrix  202  of a tow-based absorbent core  106 . Cellulose acetate has been found to provide high SAP efficiencies, even when relatively high SAP concentrations are used, and is moisture-absorbent and biodegradable. Preferably, the denier per fiber (dpf) of each cellulose acetate fiber will be in the range of about 1 to 9, preferably about 3 to 6, and most preferably about 4. For the same weight product, filaments of lower dpf may provide increased surface area and increased moisture absorption. The total denier of the tow may vary within the range of about 20,000 to 60,000, depending upon the process used, and preferably is about 35,000. The fibers may have a circular, ovate, rectilinear, or any other cross section. In one preferred embodiment, the fibers have a tri-lobal cross section with an area of about 3.36×10 −6  cm 2 . Such a cross-sectional shape may provide improved bending stiffness, increased wicking, or other beneficial properties.  
     [0048] Also in a preferred embodiment, the tow has crimped filaments. Crimps aid with opening the tow, increase the available filament surface area for superabsorbent material immobilization and increase moisture absorption. It is anticipated that gel blocking also may be reduced by using crimped tow in the absorbent core  106 . As therefore may be understood, more crimp is typically better, with an excess of about 20 crimps per inch being preferred. Continuous filament cellulose acetate tow having crimped filaments with about 25 to 40 crimps per inch is commercially available from Hoechst Celanese Corporation of Charlotte, N.C.  
     [0049] If desired, an absorbent core  106  of multiple layer thickness may be provided. To this end, the tow may be, for example, lapped or crosslapped in accordance with conventional procedures. In this way, a superabsorbent, absorptive material of a desired weight and/or thickness may be provided. The specific weight or thickness will depend upon factors including the particular end use.  
     [0050] Any superabsorbent particles (SAP)  204  now known or later discovered may be used in the absorbent core  106  (whether of conventional construction, tow-based construction or other construction), so long as it is capable of absorbing liquids. Useful SAP materials are those that generally are water-insoluble but water-swellable polymeric substances capable of absorbing water in an amount that is at least ten times the weight of the substance in its dry form. In one type of SAP, the particles or fibers may be described chemically as having a backbone of natural or synthetic polymers with hydrophilic groups or polymers containing hydrophilic groups being chemically bonded to the backbone or in intimate admixture therewith. Included in this class of materials are such modified polymers as sodium neutralized cross-linked polyacrylates and polysaccharides including, for example, cellulose and starch and regenerated cellulose which are modified to be carboxylated, phosphonoalkylated, sulphoxylated or phosphorylated, causing the SAP to be highly hydrophilic. Also included are water swellable polymers of water soluble acrylic or vinyl monomers crosslinked with a polyfunctional reactant. Such modified polymers also may be cross-linked to reduce their water-solubility, and such cross-linked SAPs have been found to provide superior performance in some absorbent cores. A more detailed recitation of superabsorbent polymers is found in U.S. Pat. No. 4,990,541 to Nielsen, which is incorporated herein by reference in its entirety.  
     [0051] The SAP preferably is selected to provide high absorbency performance for the particular application. The measure of the SAP&#39;s absorbency performance may be evaluated in a number of ways, as will be understood by those skilled in the art, and preferred SAPs  204  may be selected based on one or more of these evaluation criteria. For example, it may be desirable to provide a SAP having a high measure of saline flow conductivity (SFC), as is described in U.S. Pat. No. 5,562,646 to Goldman et. al, which is incorporated herein by reference in its entirety. In all cases, it is preferred that the SAP be fully, rapidly and efficiently utilized while in the absorbent core; that is, the SAP  204  should be provided in sufficient quantity and have sufficient properties to absorb all of the fluid exudates introduced to the garment  100  without having leakage caused by gel blocking or other inhibitions to the imbibition of fluid, but should not be present in great excess of the required amount.  
     [0052] Commercially available SAPs include a starch modified superabsorbent polymer available under the trade name SANWET® from Hoechst Celanese Corporation, Portsmouth, Va. SANWET® is a starch grafted polyacrylate sodium salt. Other commercially available SAPs include a superabsorbent derived from polypropenoic acid, available under the trade name DRYTECH® 520 SUPERABSORBENT POLYMER from The Dow Chemical Company, Midland Mich.; AQUA KEEP manufactured by Seitetsu Kagaku Co., Ltd.; ARASORB manufactured by Arakawa Chemical (U.S.A.) Inc.; ARIDALL 1125 manufactured by Chemdall Corporation; and FAVOR manufactured by Stockhausen Inc. Still other commercially available SAPs include SA55SX, available from Sumitomo Chemical Co. Ltd. of Osaka, Japan, and T7700 and T7200 and other SAP provided by BASF of Mount Olive, N.J.  
     [0053] The SAP may be provided in any particle size, and suitable particle sizes vary greatly depending on the ultimate properties desired. Preferably, a fine particulate rather than a coarse particulate, is used in the invention, and preferably a fine particulate that passes through an about 200 mesh screen is used.  
     [0054] It has been known to prepare absorbent cores comprising cellulose acetate tow or other polymeric fibers and SAP, as described in U.S. Statutory Invention Registration H1565, and U.S. Pat. Nos. 5,436,066 to Chen, and 5,350,370 to Jackson et al., each of which is incorporated by reference herein in its entirety. It was conventional to add tackifying agents, specific size fibers, or specific fibers in combination with fluff, in order to prepare the absorbent core and immobilize the SAP particles. These additional materials may add to the density of the core, or otherwise adversely affect the overall performance of the absorbent garment made therefrom. Thus, it is preferred not to use ethylene glycol, tackifying agents, and very small particulate fibers in the invention, although they may be used to the extent they do not unduly reduce the overall performance of the absorbent core  106  of the present invention.  
     [0055] The amount of SAP  204  provided to the absorbent core  106  may vary depending on the absorbent properties of the SAP  204  and the particular application for which the absorbent core  106  is being prepared. In various embodiments, the SAP concentration may be as high as 95% or more (by weight) of the combined weight of the fibrous matrix  202  and the SAP  204 . In those embodiments having a tow-based construction, the SAP  204  concentration generally may be higher than those using conventional constructions because the relatively strong tow material allows the construction of a lighter fibrous matrix  202  for a desired weight of SAP  204  than is possible or practical using other types of fibrous matrix  202 .  
     [0056] Additional particles or fibrous additives may be added to the fibrous matrix  202  of regular absorbent cores or tow-based absorbent cores to help maintain high SAP efficiency, to reduce the cost of the garment, or to provide other benefits. In one embodiment, for example, about 1-10%, and preferably about 5%, by weight of thermally bondable synthetic fibers may be added to the fibrous matrix  202  to impart additional wet strength to the laminate. These additive fibers may improve the stability of the absorbent core  106  during use of the diaper. The preferred synthetic fibers for such an embodiment are polyolefin/polyester fibers and polyester/polyester bicomponent fibers.  
     [0057] In a tow-based core, the fibrous matrix  202  may comprise a combination of preferred tow materials, such as a blend of cellulose ester and conventional soft or hard wood fibers. Such combinations may be useful to maintain the improved SAP efficiency available from a crimped filament tow-based absorbent core  106  while providing additional benefits. For example, it has been discovered that an absorbent core  106  having a 150 g/m 2  composite comprised of 80% SAP, 10% cellulose acetate, and 10% conventional fluff pulp has a SAP efficiency of about 85%, whereas an absorbent core  106  comprised of 80% SAP and 20% fluff pulp SAP has a SAP efficiency of about 70%.  
     [0058] Preferred particulate additives that may be added to the absorbent core  106  (whether conventional or tow-based) may comprise insoluble, hydrophilic polymers with particle diameters of 100 μm or less. These particulate additives may be chosen to impart optimal separation of the SAP particles  204 . Examples of preferred particulate additive materials include, but are not limited to, potato, corn, wheat, and rice starches. Partially cooked or chemically modified (i.e., modifying hydrophobicity, hydrophilicity, softness, hardness, etc.) starches also may be effective. Most preferably, the particulate additives comprise partially cooked corn or wheat starch because in this state, the corn or wheat are rendered larger than uncooked starch and in the cooked state remain harder than even swollen SAP. In any event, regardless of the particulate additive chosen, one of the many important criteria is to use particulate additives that are hard hydrophilic materials relative to swollen SAP or which are organic or inorganic polymeric materials about 100 microns in diameter. Fibrous and particulate additives can be used together in these absorbent laminates. Examples of SAP/particulate and SAP/fiber/particulate additives include those described in, for example, U.S. Pat. No. 6,068,620.  
     [0059] Other particulate or powdered additives also may be deposited within the absorbent core  106  to provide odor control, skin wellness, and improved appearance. For example, zeolites, sodium bicarbonate and perfumes may be added to the fibrous matrix  202  or the tissue layers  206 ,  208  to reduce or mask odors, and titanium dioxide or other color-imbuing compounds may be added to provide the absorbent core  106  with a more pleasant color.  
     [0060] The fibrous matrix  202  and SAP  204  preferably are partially or wholly contained within tissue layers  206 ,  208 . The tissue layers  206 ,  208  preferably comprise a low basis weight fibrous material having sufficient wet and dry strengths to contain the fibrous matrix  202  and SAP  204  during manufacture and use of the garment  100 , sufficient permeability to allow relatively unimpeded passage of fluids and other exudates therethrough, and sufficient pore size to prevent substantial migration of SAP therethrough. The tissue layers  206 ,  208  may comprise any material, such as a crepe-wadding, forming tissue or barrier tissue manufactured from a batt of wood pulp fluff fibers, or synthetic materials, and may be treated with a surfactant to render them hydrophilic. The use and selection of tissue layers  206 ,  208  are generally known in the art, and a skilled artisan will be able to employ suitable tissue layers  206 ,  208  without undue experimentation based on the teachings herein.  
     [0061] In a preferred embodiment, the tissue layers  206 ,  208  comprise two separate layers that encase the absorbent core  106 . The tissue layers  206 ,  208  optionally also may encase one or more additional layers, as noted elsewhere herein. Preferably, a first tissue layer  206  is located generally between the topsheet  102  and the absorbent core  106 . A second tissue layer  208  preferably is located between the backsheet  104  and the absorbent core  106 . Also in a preferred embodiment, the first tissue layer  206  is hydrophilic and fluid pervious, and the second tissue layer  208  is hydrophobic and fluid impervious, although both tissue layers  206 ,  208  may have similar properties. The tissue layers  206 ,  208  also may comprise separate portions of a single tissue sheet that has been folded to encase the absorbent core  106 . In such a case, the portion of the tissue sheet that forms the second tissue layer  208  may be zone treated to render it hydrophobic and fluid impervious. The perimeter of the tissue layers  206 ,  208  may be crimped, folded, sealed or bonded to further help contain the fibrous matrix  202  and SAP  204 .  
     [0062] In one embodiment, portions of the fibrous matrix  202  and SAP  204  of the absorbent core  106  may be adhesively or thermally bonded to improve the absorbent core&#39;s wet strength and core stability. Such bonding, however, may result in reduced absorption rates and SAP efficiency. In another embodiment the SAP  204  and fibrous matrix  202  may be hydrogen bonded to one or both of the tissue layers  206 ,  208 . It has been found that when a tow-based fibrous matrix  202  having a high concentration of SAP  204  is hydrogen bonded to first and second tissue layers  206 ,  208  to form an absorbent core  106 , the SAP efficiency is not impaired, wet strength increases, and the first and second tissue layers  206 ,  208  add stability to the core  106  during manufacture. This performance improvement is believed to be the result of beneficial liquid distribution provided by the intimate bond between the fibers of the fibrous matrix  202  and the tissue layers  206 ,  208 .  
     [0063] In another preferred embodiment, the first and second tissue layers  206 ,  208  may be coated with adhesive prior to being placed on either side of the absorbent core  106 , thereby providing strength to the absorbent core  106  and adhesively holding a portion of the SAP  204  in place during use. The tissue layers  206 ,  208  may be provided having a width greater than the fibrous matrix  202 , and the portions of the tissue layers  206 ,  208  extending past either side of the fibrous matrix  202  may be bonded to one another to provide further SAP and fiber retention capability. In still another embodiment, the fibrous matrix  202  may be provided having about 1-5% by weight of thermally bondable synthetic fibers, which may be heated to thermally bond the fibrous matrix  202  to the tissue layers  206 ,  208 .  
     [0064] The absorbent core  106  preferably is formed using a dry process, however wet processes or other processes also may be used to form the absorbent core  106 . Dry processes are believed to have numerous benefits over wet processes (which sometimes are called “wet-laid” processes). In wet processes, the material that eventually forms the fibrous matrix  202  typically is immersed in a fluid having superabsorbent particles  204  mixed or suspended therein, and may require additional drying steps and other steps that add to the complexity and cost of the core forming process. In addition, wet processes often require the absorbent core to be manufactured off of the main assembly line. An exemplary wet-forming processes is disclosed in U.S. Pat. No. 5,997,690 to Woodrum, which is incorporated herein by reference in its entirety. Dry processes typically have lower operating costs than wet processes because the equipment used in dry processes typically is less complex and can run at higher line speeds. Other advantages also may be realized by the use of a dry process, as will be understood by those skilled in the art. Furthermore, dry forming processes may often be adapted for use directly on the line of conventional diaper machines. As such, the absorbent cores  106  of a preferred embodiment of the present are manufactured by a dry forming process.  
     [0065] In an embodiment of the invention in which the absorbent core  106  is a dry formed tow-based core, the total basis weight of the absorbent core  106 , including the fibrous matrix  202 , SAP  204 , tissue  206 ,  208 , and any additional layers and/or additives, preferably may be from about 100 grams per square meter (gsm) to about 1,000 gsm. Most preferably, the total basis weight of such an absorbent core  106  is about 500 gsm to about 700 gsm.  
     [0066] The absorbent core  106  of the invention preferably is provided with zones having relatively high absorbent capacity by folding portions of the absorbent core  106  over on itself to increase the amount of fibrous matrix  202  and SAP  204  present in those zones. These high-capacity folded zones  118  preferably are positioned adjacent insult points where body fluids are most likely to strike the garment  100 , but also may be located in other regions of the absorbent core  106 , such as in regions where fluids are likely to settle during use. Exemplary insult points are located in the front half of the garment&#39;s crotch (for male wearers) and in the longitudinal center of the crotch (for female wearers). The folded zone or zones  118  also may be positioned to impede the migration of bowel movement within the garment  100 . An unfolded zone or zones  120 , where the garment is not folded onto itself, preferably is positioned where less absorbent capacity is likely to be required. The present invention may be adapted to have a single folded zone  118  or a number of separate folded zones  118 . An absorbent core  106  of the present invention also may have a single folded zone  118  and no unfolded zones  120 . In addition, absorbent garments  100  incorporating a folded absorbent core of the present invention may be produced for gender-specific applications to accommodate the specific absorbency zoning requirements of male and female wearers. For example, folded zones  118  may be positioned in or towards the front half of a garment  100  intended for male wearers. Other considerations regarding the desirable location of locations for the zoned absorbency provided by the present invention are disclosed, for example, in U.S. Pat. Nos. 4,333,463 to Holtman, 4,685,915 to Hasse et al., and 5,009,650 to Bernardin, each of which is incorporated herein by reference in its entirety. The present invention is not intended to be limited to any particular location for the folded zone or zones  118  that provide such zoned absorbency.  
     [0067] Each folded zone  118  preferably comprises one or more laterally extending “z” or “s” shaped folds  210  (FIG. 2). Each fold  210  comprises folded portions of the fibrous matrix  202 , and preferably also includes the adjacent portions of the tissue layers  206 ,  208 . Each fold  210  has approximately three times the amount of SAP  204  per unit area than the unfolded portion of the absorbent core  106 . If greater SAP concentration is desired, the folds may themselves be doubled over, however care must be taken not to make the folded zone  118  excessively bulky, which may impair the garment&#39;s comfort or appearance. Laterally extending voids  212  may be provided between each fold  210 , as shown in FIG. 2. Alternatively, the folds  210  may be compressed together in the longitudinal direction 1 so that the voids  212  are substantially eliminated. The folds  210  may be held in the folded position by any suitable mechanism. For example the folds  210  may be held in position by being contained between the topsheet  102  and the backsheet  104 , by being adhesively or otherwise secured to the topsheet  102  and/or backsheet  104  or by being adhesively or otherwise secured in the folds themselves. If adhesive is used to hold the folds  210 , the adhesive preferably is applied at discrete locations to minimize any impediment to fluid flow that the adhesive may cause.  
     [0068] A single, relatively long fold  210  may be used to provide zoned absorbency to the absorbent core  106 , but more preferably, a number of shorter folds  210  are provided. The number and length of the folds  210  may be a function of the foldability of the absorbent core  106 , the desired size of the folded zone  118 , and the desire to obtain improved SAP utilization. It is anticipated that the use of folds  210  will provide greater SAP utilization, because the folds  210  provide passages to the lower portions of the absorbent core  106  (i.e., the portions of the absorbent core  106  that are closer to the backsheet  104 , and relatively far, in the z-direction, from the topsheet  102  and the insult point or points). Furthermore, the folds  210  may impede the migration of SAP  204  through the fibrous matrix  202 , thereby reducing the incidence of localized zones of relatively high and low SAP concentration when such concentrations are not desired.  
     [0069] The expected improved access to the SAP  204  provided by the present invention is demonstrated by the arrows F 1  and F 2  of FIG. 2, which represent fluid flows into the absorbent core  106 . Arrow F 1  designates an anticipated primary flow of fluid directly into the absorbent core  106  as it is expelled from the wearer. The primary flow of fluid into the garment  100  may be facilitated by using a relatively low-density fibrous matrix  202 , such as a tow-based fibrous matrix  202 . It has been found that tow-based fibrous matrices  202  may allow a faster initial influx of fluid, and greater overall core permeability than conventional fibrous matrices  202  comprised of fluff pulp or similar materials.  
     [0070] Arrow F 2  designates an anticipated secondary flow of fluid into the voids  212 , which then moves, by mass flow, diffusion, capillary action or the like, into the lower portion of the absorbent core  106 . It is believed that the secondary flow into the voids  212  and the lower portions of the absorbent core  106  will provide improved core permeability, thereby allowing improved core utilization and reduced gel blocking (or a reduction in the negative consequences of any gel blocking that does occur) by providing an additional flow path to supplement the primary flow. The voids  212  also may act as temporary storage reservoirs for fluid that is not immediately absorbed.  
     [0071] It is also anticipated that the folds  210  may act as physical barriers to impede the displacement or relocation of bowel movement contained within the garment  100 . In one embodiment, the folds may be sized and positioned to act as “pockets” to help contain bowel movement in a longitudinal direction. Such pocket-like folds may be sealed at their ends (i.e. along the lateral edges of the absorbent core  106 ) or at other locations to help prevent the lateral displacement of bowel movement.  
     [0072] The secondary flow&#39;s penetration into the core&#39;s lower portion may be facilitated or improved by using a first tissue layer  206  that has high wicking properties or other beneficial fluid transfer properties that convey the fluid in the longitudinal direction 1. An additional layer of material (not shown), preferably having high longitudinal wicking properties, also may be provided on the first tissue layer  206 , either before or after the absorbent core  106  is folded, to provide improved secondary flow penetration. Also, the fold  210  may be constructed to leave gaps between the portions of the first tissue layer  206  that face one another. Other methods of improving the secondary flow penetration into the lower portion of the core will become apparent to those skilled in the art based on the teachings herein and practice of the invention.  
     [0073] The secondary flow penetration also may be adjusted by varying the number, spacing and length of the folds  210 . All of the folds  210  of an absorbent core  106  of the present invention may have substantially the same length L F  (i.e., the length of the fold in the longitudinal direction 1) and/or spacing (i.e., the distance from the base of one fold  210  to the next). Alternatively, an absorbent core  106  of the present invention may be provided with numerous folds  210  that have various different spacings and lengths L F . It is anticipated that shorter fold lengths L F  may allow greater SAP utilization, but may be more difficult to keep in their desired folded-over position during manufacture and use of the garment  100 . The minimum fold length L F  also may be constrained by the physical properties of the absorbent core  106 , the stiffness of which may resist the formation of shorter folds. For this reason, in a particularly preferred embodiment, the absorbent core  106  is a tow-based core. Tow-based cores generally are thinner, less bulky and less dense than cores having conventional fluff pulp or other conventional materials as the fibrous matrix  202 . As such, tow-based cores may be produced to be less rigid, and thus better suited to being folded, than other types of absorbent core  106 . In addition, the thinness of tow-based cores may allow the folds  210  to have tighter bends without tearing the tissue layers  206 ,  208  or substantially damaging the fibrous matrix  202 . In some cases, however, it may be desirable to permanently compress, break or sever the fibrous matrix  202  at the point at which it is folded to reduce the bulk of the absorbent core  106 . In a preferred embodiment, in which the absorbent core  106  is a tow-based core, the folds have a length of about 10 millimeters (mm) to about 300 mm. In another preferred embodiment, the absorbent core  106  is a tow-based core having about 5 to about 15 folds  210 , each having a length L F  of about 20 mm to about 50 mm.  
     [0074] The secondary flow shown by arrow F 2  also may have a lateral component that assists with redistributing the fluid along the width of the absorbent core  106  to help fully utilize the SAP  204  in the absorbent core&#39;s lateral reaches. This lateral component may be adjusted by changing the size of the voids  212 , modifying the lateral wicking properties of the topsheet  102  and first tissue layer  206 , adding physical flow barriers or by any other methods, as will be apparent to those skilled in the art based on the teachings herein and practice of the invention.  
     [0075] It is preferred that fold  210  extend through substantially the entire lateral dimension of the core, and most preferably fold  210  extends through the entire lateral dimension. Various embodiments of the invention include those in which fold  210  does not extend across the entire lateral dimension, but only 75% or so of the lateral dimension, thereby extending through the entire lateral dimension.  
     [0076] It is anticipated that the additional improved fluid flow characteristics of a tow-based absorbent core of an embodiment of the present invention will allow the use of a variety of different superabsorbent polymer materials. The various different superabsorbent polymers have different properties with respect to their capacity (i.e., the total amount of fluid that can be retained per unit weight of the SAP), permeability (i.e., the degree to which a fluid-swollen SAP particle allows additional fluid to pass or diffuse through it) and absorbency under load (i.e., the SAP&#39;s ability to retain fluids under pressure). In some cases, these properties may balance off of one another, for example, a SAP having relatively high absorbency under load and/or total capacity may have relatively low permeability, making such a SAP likely to suffer from gel blocking. The improved fluid permeability of an embodiment of the present invention, particularly an embodiment using a tow-based construction, allows the use of SAP  204  that has relatively high absorbency under load and/or total capacity and relatively low permeability, without suffering from reduced core utilization caused by gel blocking. Other beneficial uses of different SAP  204  materials also may be provided using embodiments of the present invention.  
     [0077] Referring now to FIG. 4, a preferred apparatus and process for manufacturing an absorbent core having folded zones is described. A folded core manufacturing device preferably comprises a pair of counter-rotating folding rolls  402  that provide multiple creases in portions of a continuous core supply  310 . The continuous core supply  310  may be fabricated as described with reference to FIG. 3, or may be fabricated by any other suitable methods or means. The present invention is not intended to be limited to any particular method or device for forming the absorbent core supply  310 .  
     [0078] In a preferred embodiment, the folding rolls  402  each have sets of teeth  404  between which the continuous core supply  310  passes as the folding rolls  402  rotate. The teeth  404  of each folding roll  402  are shaped and positioned to mesh with the corresponding teeth  404  of the other folding roll  402 , and are spaced apart from one another enough to prevent damage to the continuous core supply  310 , but are close enough to one another to deform the continuous core supply  310  to have a number of creases or folds. Smooth surfaces  406  are disposed between each set of teeth  404  on the folding rolls  402 . The continuous core supply  310  is not folded as it passes between the smooth surfaces  406 , which preferably are spaced from the corresponding smooth surface  406  of the opposite folding roll at a distance suitable to grasp and convey the continuous core supply  310  without damaging or over-compressing it.  
     [0079] Other folding devices may be used to provide folds  210  in the continuous absorbent core supply  310 . For example, the folds  210  may be formed by ribbed belts, feeding the continuous core supply  310  into a chamber that moves slower than the absorbent core supply  310  (preferably by momentarily accelerating the absorbent core supply  310 ) to cause the formation of folds, applying alternating jets of compressed air to the absorbent core supply  310 , stamping the absorbent core supply  310  between interlocking crossbars, and so on. It also will be understood that the absorbent cores  106  may be folded after being severed from a continuous core supply  310 , or may be processed as individual cores from the outset, or may be processed without ever being part of a continuous core supply  310 . These and other steps of the core forming process may be manipulated, reordered, omitted, or supplemented without departing from the scope of the present invention, as will be understood by those skilled in the art.  
     [0080] The creased continuous core supply  310  then is conveyed to a pair of press rolls  408  that flatten the creases into folds. The press rolls  408  are spaced from one another to provide the desired amount of compression to the creases, and may be adjustable. Alternatively, press belts, reciprocating presses, or other devices may be used in place of the press rolls, as will be understood by those skilled in the art. Air jets or mechanical guides (not shown) also may be provided to operate in conjunction with the press rolls  408  to initiate the formation of the folds  210  in the desired direction.  
     [0081] An adhesive applicator  410 , such as a commercially available CF- 200  series CONTROLLED FIBERIZATION™ hot melt adhesive applicator available from Nordson Corporation of Norcross, Georgia, or other applicators  410 , may be used to apply an adhesive to one or both sides of the continuous core supply  310 . The adhesive may be useful for bonding the folds  210  in place, however it should not be applied such that it will contact the press rolls  408  or other parts of the machinery. Preferably, the adhesive is discretely applied only within the creases so that it is only present between the folds  210 .  
     [0082] The folding rolls  402  and press rolls  408  form a continuous supply of core material that has spaced apart folding zones  118 . The continuous core supply  310  then is severed into individual absorbent cores  106 . In order to manufacture a series of absorbent cores  106  having folding zones  118  in the desired location, a proper selection of the diameter of the folding rolls  402  and positions of the sets of teeth  404  should be made. Generally, the absorbent core length L C  may be modified by providing larger or smaller diameter folding rolls  402 . The size of the folding zones  118 , the number of folds  210 , the length of the folds L F , and, to some degree, the spacing between the folded zones  118  may be modified by changing the sets of teeth  404  and smooth surfaces  406  on the folding roll, which may be replaceable as interchangeable modules. The proper selection of these dimensions and locations will depend on the desired shape and size of the absorbent cores being manufactured, and those skilled in the art will be able to properly size and set up the folding rolls  402 , teeth  404  and smooth surfaces  406  without undue experimentation.  
     [0083] The individual absorbent cores  106  may be severed from the continuous core supply  310  using any suitable device. In a preferred embodiment, a rotating cut roll  412  having one or more knife edges may be provided to separate individual absorbent cores  106  by pressing the continuous core supply  310  against an anvil roll  414 . The speed of the cut roll  412  and/or the diameter of the cut roll  412  may be adjusted or changed to produce absorbent cores  106  having different lengths L C . These and other well known or later developed cutting devices, such as laser cutters, water cutters, and the like, also may be used, as will be understood by those skilled in the art. The present invention is nit intended to be limited to the use of any particular cutting device or to the use of a cutting device at all.  
     [0084] The details of the design of the folding rolls  402 , press rolls  408  and cutting roll  412  will depend on the type and dimensions of the particular continuous core supply  310  being processed. Those skilled in the art will be able to provide these and other devices to fold the continuous core supply  310  without undue experimentation based on the teachings herein.  
     [0085] A tension arm  416  or other tensioning device preferably is provided upstream of the folding rolls  402 . Assuming that the folding rolls  402  rotate at a substantially constant angular velocity, the teeth  404  will pull the continuous core supply  310  faster than the smooth surfaces  406  do. So as the folding rolls  402  rotate, the continuous core supply  310  will periodically accelerate and decelerate. To accommodate for this change in speed, the tension arm  416 , which may have a tensioning spring  418 , pivots back and forth to take up slack in the continuous core supply during the slower pull speed periods and to let out slack during the faster pull speed periods. The tensioning spring  418  may comprise any suitable spring or retracting device, such as coil springs, leaf springs, hydraulic and pneumatic rams and the like, and the present invention is not limited to the use of any particular device for the tensioning spring  418 . The design and use of tension arms  416  and other tensioning devices, such as moving bars or rollers, festoons and the like, is known in the art, and a skilled artisan will be able to employ such devices with the present invention without undue experimentation based on the teachings herein.  
     [0086] It is anticipated that using folded zones  118  to create zoned absorbency absorbent cores, as provided by the present invention, will provide several benefits over known SAP targeting devices and zoned absorbent cores. For example, the absorbent core  106  may be constructed having a uniform distribution of SAP  204  within the fibrous matrix  202 , yet still provide zoned absorbency. As such, the device that provides the SAP  204  to the fibrous matrix  202  may be a operated at a relatively continuous, stable rate to provide consistency even at relatively high line speeds, and does not require the use of relatively imprecise or difficult to control devices that attempt to modulate the flow rate or positioning of the SAP  204  in the fibrous matrix  202 . In addition, the use of folds  210  provides greater access to the SAP  204  and may reduce gel blocking, as described elsewhere herein. The present invention also may provide numerous other benefits with respect to manufacturing and garment performance and in other regards.  
     [0087] Other embodiments, uses and advantages of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification should be considered exemplary only, and the scope of the invention is accordingly intended to be limited only by the following claims.