Patent Description:
Disposable absorbent articles such as feminine hygiene products, taped diapers, pant-type diapers and incontinence products are designed to absorb fluids from the wearer's body. Users of such disposable absorbent articles have several concerns. Leakage from products like catamenial pads, diapers, sanitary napkins, and incontinence pads is a significant concern. Comfort and the feel of the product against the wearer's body is also a concern. To provide better comfort, current disposable absorbent articles are typically provided with a topsheet that is flexible, soft feeling, and non-irritating to the wearer's skin. The topsheet does not itself hold the discharged fluid. Instead, the topsheet is fluid-permeable to allow the fluids to flow into an absorbent core.

Additionally, in regards to comfort, consumers desire a pad that is thin and flexible enough to not impair their movements while being thick and stiff enough to provide the desirable amount of protection. This objective becomes even more challenging when considering the dynamic nature of the absorbent article. As fluid enters the article, the weight, thickness, and flexibility of the absorbent article may all change. Hence, an article that may meet the desirable criteria before use may no longer be comfortable to the user after a given amount of fluid has been absorbed by the absorbent article. In addition, dependent upon the materials chosen, a thin and flexible article may be created that is not consumer suitable due to issues such as rewet. For example, one could create a flexible article using solely fluff cellulose. However, the product would likely have issues with rewet, disintegration, and possibly leakage.

<CIT> relates to a method for producing materials for application in hygiene products, which have a rough or abrasive surface on one side and a soft surface on the other side. The materials comprise three nonwoven webs with different fiber compositions, which are hydroentangled to form a homogeneous structure. <CIT> is concerned with a nonwoven manufacturing process, in which a combination of mechanical and thermal bonding of a fibrous composition consisting of at least three layers is applied. The two outer layers have a different fiber composition than the middle layer.

<CIT> discloses non-woven fabrics composed of at least four layers, which may be used as acquisition and distribution layers in absorbent articles. The fineness of fibers in the layer in contact with the flow to be treated is different than the that of the other layers. <CIT> relates to composite nonwoven materials permeable to body fluids and suitable for applications as topsheet in diapers or the like. The material comprises at least two layers of carded fibers joined together by needling. The layers may be additionally heat bonded employing bicomponent or other melting fibers. A third non-woven layer may also be bonded by melting to one of the carded layers. <CIT> discloses multi-component nonwoven fabrics for disposable absorbent articles. The fabrics are formed with integrated liquid-acceptance and liquid-distribution layers by hydroentanglement on a three-dimensional image transfer device. Further a liquid-retention layer may be present.

As such there is a need to create an absorbent article that accounts for all the possible tradeoffs such that it is both comfortable while maintaining performance. In particular, there exists a need to create an absorbent article that balances performance and comfort.

Accordingly, the development of new and improved absorbent article and absorbent article core is of continued interest.

A carded staple fiber nonwoven as defined in the claims is provided.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter that is regarded as the present invention, it is believed that the invention will be more fully understood from the following description taken in conjunction with the accompanying drawings. Some of the figures may have been simplified by the omission of selected elements for the purpose of more clearly showing other elements. Such omissions of elements in some figures are not necessarily indicative of the presence or absence of particular elements in any of the exemplary embodiments, except as may be explicitly delineated in the corresponding written description. None of the drawings are necessarily to scale.

As used herein, the following terms shall have the meaning specified thereafter:
"Absorbent article" refers to wearable devices, which absorb and/or contain liquid, and more specifically, refers to devices, which are placed against or in proximity to the body of the wearer to absorb and contain the various exudates discharged from the body. Absorbent articles can include diapers, training pants, adult incontinence undergarments (e.g., liners, pads and briefs) and/or feminine hygiene products.

The "longitudinal" direction is a direction running parallel to the maximum linear dimension, typically the longitudinal axis, of the article and includes directions within <NUM>° of the longitudinal direction. "Length" of the article or component thereof, when used herein, generally refers to the size/distance of the maximum linear dimension, or typically to the size/distance of the longitudinal axis, of an article or part thereof.

The "lateral" or "transverse" direction is orthogonal to the longitudinal direction, i.e. in the same plane of the majority of the article and the longitudinal axis, and the transverse direction is parallel to the transverse axis. "Width" of the article or of a component thereof, when used herein, refers to the size/distance of the dimension orthogonal to the longitudinal direction of the article or component thereof, i.e. orthogonal to the length of the article or component thereof, and typically it refers to the distance/size of the dimension parallel of the transverse axis of the article or component.

The "Z-direction" is orthogonal to both the longitudinal and transverse directions.

"Machine Direction" or "MD" as used herein means the direction parallel to the flow of the carded staple fiber nonwoven through the nonwoven making machine and/or absorbent article product manufacturing equipment.

"Cross Machine Direction" or "CD" as used herein means the direction parallel to the width of the carded staple fiber nonwoven making machine and/or absorbent article product manufacturing equipment and perpendicular to the machine direction.

"Absorbent core" refers to a structure typically disposed between a topsheet and backsheet of an absorbent article for absorbing and containing liquid received by the absorbent article. The absorbent core may comprise one or more substrate layer(s), absorbent material disposed on the one or more substrate layer(s), and a thermoplastic adhesive composition on the absorbent material. The thermoplastic adhesive composition may be on the absorbent material and at least a portion of the one or more substrate layer. In a certain embodiment, the absorbent core would consist essentially of the one or more substrate layers, the absorbent material, the thermoplastic adhesive composition, and optionally a cover layer.

"Nonwoven material" refers to a manufactured web of directionally or randomly orientated fibers, excluding paper and products which are woven, knitted, tufted, stitch-bonded incorporating binding yarns or filaments, or felted by wet-milling, whether or not additionally needled. Nonwoven materials and processes for making them are known in the art. Generally, processes for making nonwoven materials comprise laying fibers onto a forming surface, which can comprise spunlaying, meltblowing, carding, airlaying, wetlaying, coform and combinations thereof. The fibers can be of natural or man-made origin and may be staple fibers or continuous filaments or be formed in situ.

The term "hydrophilic" describes fibers or surfaces of fibers, which are wettable by aqueous fluids (e.g., aqueous body fluids) deposited on these fibers. Hydrophilicity and wettability are typically defined in terms of contact angle and the strike-through time of the fluids, for example through a nonwoven fabric. This is discussed in detail in the <NPL>). A fiber or surface of a fiber is said to be wetted by a fluid (i.e., hydrophilic) when either the contact angle between the fluid and the fiber, or its surface, is less than <NUM>°, or when the fluid tends to spread spontaneously across the surface of the fiber, both conditions are normally co-existing. Conversely, a fiber or surface of the fiber is considered to be "hydrophobic" if the contact angle is greater than <NUM>° and the fluid does not spread spontaneously across the surface of the fiber.

The term "Pore Volume Ratio" means the ratio of the peak of the pore volume versus the pore radii curve divided by the width of the same pore radii curve at half the peak of the pore volume.

The term "Pore Volume Radius Mode" means the radius at which the peak of the pore volume versus pore radii curve occurs.

The term "Pore Volume Factor" is the product of the Pore Volume Ratio and the Pore Volume Radius Mode.

A carded staple fiber nonwoven as disclosed herein can be used in a variety of disposable absorbent articles, but is particularly useful in diapers, feminine hygiene products and incontinence products such as sanitary napkins and incontinence pads. One non-limiting embodiment of a disposable absorbent article that incorporates a carded staple fiber nonwoven as detailed herein is shown as a sanitary napkin in <FIG> and <FIG>. In another embodiment, an incontinence pad incorporates a carded staple fiber nonwoven as detailed herein. Although a sanitary napkin will be specifically illustrated and described within this application, any of the features or elements of the sanitary napkin that are disclosed are also contemplated for any other embodiment of absorbent article, including incontinence pads.

A sanitary napkin <NUM> can have any shape known in the art for feminine hygiene articles, including the generally symmetric "hourglass" shape as shown in <FIG>, as well as pear shapes, ovals, oblong ovals, pill shapes, bicycle-seat shapes, trapezoidal shapes, or wedge shapes. Sanitary napkins and pantiliners can also be provided with lateral extensions known in the art as "flaps" or "wings" (not shown in <FIG>). Such extensions can serve a number of purposes, including, but not limited to, protecting the wearer's panties from soiling and keeping the sanitary napkin secured in place. The illustrated absorbent article has a body-facing upper side that contacts the user's body during use. The opposite, garment-facing lower side contacts the user's clothing during use.

The upper side of the sanitary napkin <NUM> generally has a topsheet <NUM> that can be liquid pervious. The lower side (seen in <FIG>) has a backsheet <NUM> that can generally be liquid impervious and is joined with the topsheet <NUM> at the edges <NUM> of the sanitary napkin <NUM>. In some embodiments of adult incontinence products not pictured herein, the topsheet and the backsheet are not joined at the edges. An absorbent core <NUM> is positioned between the topsheet <NUM> and the backsheet <NUM>. The illustrated sanitary napkin <NUM> has a body-facing upper side <NUM> that contacts the user's body during use. The opposite, garment-facing lower side <NUM> contacts the user's clothing during use. As shown in <FIG>, the absorbent core <NUM> may include a fluid acquisition/distribution layer <NUM> and a fluid storage layer <NUM>. The fluid acquisition/distribution layer <NUM> may include three or more stratums (<NUM>, <NUM>, <NUM>) wherein the stratums each have unique properties while being integrated to form a single layer. Two or more stratums may have the same properties within the acquisition layer. For example, an acquisition layer may have four stratums wherein the first and third stratum have the same composition and properties. Alternatively, an acquisition layer may have four stratums wherein two adjacent stratums have the same composition and properties. As shown in <FIG>, the fluid storage layer <NUM> may have a smaller width than the fluid acquisition/distribution layer <NUM>.

As shown in <FIG>, the absorbent core <NUM> may include a fluid acquisition/distribution layer <NUM> and a storage layer <NUM>. The fluid acquisition/distribution layer <NUM> may include three or more stratums (<NUM>, <NUM>, <NUM>) wherein the stratums each have unique properties while being integrated to form a single layer. The fluid distribution layer having a first surface or a body facing surface <NUM> and a second surface or a garment facing surface <NUM>. As shown in <FIG>, the fluid storage layer <NUM> may have an equal width than the fluid acquisition/distribution layer <NUM>.

As shown in <FIG>, the absorbent core <NUM> may include a fluid acquisition/distribution layer <NUM> and a storage layer <NUM>. The fluid acquisition/distribution layer <NUM> may include three or more stratums (<NUM>, <NUM>, <NUM>, <NUM>) wherein the stratums each have unique properties while being integrated to form a single layer. As shown in <FIG>, the acquisition/distribution layer <NUM> may include the topsheet <NUM> as its outermost stratum <NUM>. In this manner, the upper stratum <NUM> may be joined with the backsheet <NUM> by an additional strip of material <NUM> thereby allowing the acquisition layer <NUM> to serve as the topsheet <NUM> of the absorbent article <NUM>.

The backsheet <NUM> and the topsheet <NUM>, as shown in <FIG> and <FIG>, can be secured together in a variety of ways. Adhesives manufactured by H. Fuller Company of St. Paul, Minn. under the designation HL-<NUM> or H-<NUM> have been found to be satisfactory. Alternatively, the topsheet <NUM> and the backsheet <NUM> can be joined to each other by heat bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, a crimp seal, or by any other suitable securing method. As shown in <FIG>, a fluid impermeable crimp seal <NUM> can resist lateral migration ("wicking") of fluid through the edges of the product, inhibiting side soiling of the wearer's undergarments.

The fluid acquisition/distribution layer is shown in the scanning electron microscope images of <FIG> are SEMs of two different examples of embodiment <NUM> of Table <NUM>. <FIG> shows the body facing side <NUM> of a fluid acquisition/distribution layer <NUM>. <FIG> shows the garment facing side <NUM> of a fluid acquisition/distribution layer <NUM>. <FIG> shows a fluid acquisition/distribution layer <NUM> which is a cross section of <FIG>. The fluid acquisition/distribution layer <NUM> may include three or more stratums (<NUM>, <NUM>, <NUM>) wherein the stratums each have unique properties while being integrated to form a single layer. The fluid distribution layer having a first surface or a body facing surface <NUM> and a second surface or a garment facing surface <NUM>. <FIG> shows a magnified version of a portion of <FIG>. As shown in <FIG>, the fluid acquisition/distribution layer <NUM> has a garment facing surface <NUM> and a plurality of stratums (<NUM>, <NUM>).

<FIG> shows the body facing side <NUM> of a fluid acquisition/distribution layer <NUM>. <FIG> shows the garment facing side <NUM> of a fluid acquisition/distribution layer <NUM>. <FIG> shows a fluid acquisition/distribution layer <NUM> which is a cross section of <FIG>. The fluid acquisition/distribution layer <NUM> may include three or more stratums (<NUM>, <NUM>, <NUM>) wherein the stratums each have unique properties while being integrated to form a single layer. The fluid distribution layer having a first surface or a body facing surface <NUM> and a second surface or a garment facing surface <NUM>. <FIG> shows a magnified version of a portion of <FIG>. As shown in <FIG>, the fluid acquisition/distribution layer <NUM> has a garment facing surface <NUM> and a plurality of stratums (<NUM>, <NUM>).

As is typical for sanitary napkins and the like, the sanitary napkin <NUM> of the present disclosure can have panty-fastening adhesive disposed on the garment-facing side of backsheet <NUM>. The panty-fastening adhesive can be any of known adhesives used in the art for this purpose, and can be covered prior to use by a release paper, as is well known in the art. If flaps or wings are present, a panty fastening adhesive can be applied to the garment facing side so as to contact and adhere to the underside of the wearer's panties.

The primary topsheet (also referred to herein "topsheet") of the sanitary napkin <NUM> may be joined to the backsheet <NUM> by attachment methods (not shown) such as those well known in the art. Suitable attachment methods are described with respect to joining the backsheet <NUM> to the absorbent core <NUM>. The topsheet <NUM> and the backsheet <NUM> may be joined directly to each other in the incontinence pad periphery and may be indirectly joined together by directly joining them to the absorbent core <NUM> or additional optional layers within the chassis like a secondary topsheet which spans the entire or partial area of the article. This indirect or direct joining may be accomplished by attachment methods which are well known in the art.

The absorbent article may comprise any known or otherwise effective primary topsheet, such as one which is compliant, soft feeling, and non-irritating to the wearer's skin. Suitable primary topsheet materials include a liquid pervious material that is oriented towards and contacts the body of the wearer permitting bodily discharges to rapidly penetrate through it without allowing fluid to flow back through the topsheet to the skin of the wearer. The primary topsheet, while being capable of allowing rapid transfer of fluid through it, also provides for the transfer or migration of the lotion composition onto an external or internal portion of a wearer's skin. A suitable topsheet can be made of various materials such as woven and nonwoven materials; apertured film materials including apertured formed thermoplastic films, apertured plastic films, and fiber-entangled apertured films; hydro-formed thermoplastic films; porous foams; reticulated foams; reticulated thermoplastic films; thermoplastic scrims; or combinations thereof.

Apertured film materials suitable for use as the topsheet include those apertured plastic films that are non-absorbent and pervious to body exudates and provide for minimal or no flow back of fluids through the topsheet. Nonlimiting examples of other suitable formed films, including apertured and non-apertured formed films, are more fully described in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>. Commercially available formed filmed topsheets include those topsheet materials marketed by the Procter & Gamble Company (Cincinnati, Ohio) under the DRI-WEAVE® tradename.

Nonlimiting examples of woven and nonwoven materials suitable for use as the topsheet include fibrous materials made from natural fibers, modified natural fibers, synthetic fibers, or combinations thereof. These fibrous materials can be either hydrophilic or hydrophobic, but it is preferable that the topsheet be hydrophobic or rendered hydrophobic. As an option, portions of the topsheet can be rendered hydrophilic, by the use of any known method for making topsheets containing hydrophilic components. One such method include treating an apertured film component of a nonwoven/apertured thermoplastic formed film topsheet with a surfactant as described in <CIT>. Other suitable methods describing a process for treating the topsheet with a surfactant are disclosed in <CIT> and <CIT>. The topsheet may have hydrophilic fibers, hydrophobic fibers, or combinations thereof.

A particularly suitable topsheet comprises staple length polypropylene fibers having a denier of about <NUM>, such as Hercules type <NUM> polypropylene marketed by Hercules, Inc. of Wilmington, Del. As used herein, the term "staple length fibers" refers to those fibers having a length of at least about <NUM> (<NUM> inches).

When the primary topsheet comprises a nonwoven fibrous material in the form of a nonwoven web, the nonwoven web may be produced by any known procedure for making nonwoven webs, nonlimiting examples of which include spunbonding, carding, wet-laid, air-laid, meltblown, needle-punching, mechanical entangling, thermo-mechanical entangling, and hydroentangling. A specific example of a suitable meltblown process is disclosed in <CIT>. The nonwoven may be compression resistant as described in <CIT>. The nonwoven web may have loops as described in <CIT>.

Other suitable nonwoven materials include low basis weight nonwovens, that is, nonwovens having a basis weight of from about <NUM>/m<NUM> to about <NUM>/m<NUM>. An example of such a nonwoven material is commercially available under the tradename P-<NUM> from Veratec, Incorporation, a division of the International Paper Company located in Walpole, Massachusetts. Other nonwovens are described in <CIT> and <CIT>.

The topsheet may comprise tufts as described in <CIT>, <CIT>, <CIT>, or <CIT>. The primary topsheet may have an inverse textured web as described in <CIT>. Tufts are also described in <CIT>.

The primary topsheet may have a pattern of discrete hair-like fibrils as described in <CIT> or <CIT>.

The primary topsheet may comprise one or more structurally modified zones as described in <CIT>. The primary topsheet may have one or more out of plane deformations as described in <CIT>. The primary topsheet may have a masking composition as described in <CIT>.

Another suitable primary topsheet or a primary topsheet combined with a secondary topsheet may be formed from a three-dimensional substrate as detailed in a <CIT> and entitled "A Three-Dimensional Substrate Comprising a Tissue Layer". This three-dimensional substrate has a first surface, a second surface, land areas and also comprises three-dimensional protrusions extending outward from the second surface of the three-dimensional substrate, wherein the three-dimensional protrusions are surrounded by the land areas. The substrate is a laminate comprising at least two layers in a face to face relationship, the second layer is a tissue layer facing outward from the second surface of the three-dimensional substrate, and the tissue layer comprises at least <NUM>% pulp fibers by weight of the tissue layer.

The primary topsheet may have comprises one or more layers, for example a spunbond-meltblown-spunbond material. The primary topsheet may be apertured, may have any suitable three-dimensional features, and/or may have a plurality of embossments (e.g., a bond pattern). The topsheet may be apertured by overbonding a material and then rupturing the overbonds through ring rolling, such as disclosed in <CIT>. Additional lateral extensibility in the chassis <NUM> (i.e., in the primary topsheet and/or the backsheet) may be provided in a variety of ways. For example, either the primary topsheet or backsheet may be pleated by any of many known methods. Alternatively, all or a portion of the chassis (i.e., also the primary topsheet and/or backsheet) may be made of a formed web material or a formed laminate of web materials like those described in <CIT> Such a formed web material includes distinct laterally extending regions in which the original material has been altered by embossing or another method of deformation to create a pattern of generally longitudinally oriented alternating ridges and valleys. The formed web material also includes laterally extending unaltered regions located between the laterally extending altered regions.

The backsheet may be positioned adjacent a garment-facing surface of the absorbent core and may be joined thereto by attachment methods (not shown) such as those well known in the art. For example, the backsheet may be secured to the absorbent core by a uniform continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines, spirals, or spots of adhesive. Alternatively, the attachment methods may comprise using heat bonds, pressure bonds, ultrasonic bonds, dynamic mechanical bonds, or any other suitable attachment methods or combinations of these attachment methods as are known in the art. Forms of the present disclosure are also contemplated wherein the absorbent core is not joined to the backsheet, the topsheet, or both.

The backsheet may be impervious, or substantially impervious, to liquids (e.g., urine) and may be manufactured from a thin plastic film, although other flexible liquid impervious materials may also be used. As used herein, the term "flexible" refers to materials which are compliant and will readily conform to the general shape and contours of the human body. The backsheet may prevent, or at least inhibit, the exudates absorbed and contained in the absorbent core from wetting articles of clothing which contact the absorbent article such as undergarments. However, in some instances, the backsheet may permit vapors to escape from the absorbent core <NUM> (i.e., is breathable) while in other instances the backsheet may not permit vapors to escape (i.e., non-breathable). Thus, the backsheet may comprise a polymeric film such as thermoplastic films of polyethylene or polypropylene. A suitable material for the backsheet is a thermoplastic film having a thickness of from about <NUM> (<NUM> mil) to about <NUM> (<NUM> mils), for example. Any suitable backsheet known in the art may be utilized with the present invention.

The backsheet acts as a barrier to any absorbed bodily fluids that may pass through the absorbent core to the garment surface thereof with a resulting reduction in risk of staining undergarments or other clothing. Further, the barrier properties of the backsheet permit manual removal, if a wearer so desires, of the interlabial absorbent article with reduced risk of hand soiling. A preferred material is a soft, smooth, compliant, liquid and vapor pervious material that provides for softness and conformability for comfort, and is low noise producing so that movement does not cause unwanted sound.

The backsheet may comprise a wet laid fibrous assembly having a temporary wet strength resin incorporated therein as described in <CIT>. The backsheet may further be coated with a water resistant resinous material that causes the backsheet to become impervious to bodily fluids without impairing the spreading of adhesive materials thereon.

Another suitable backsheet material is a polyethylene film having a thickness of from about <NUM> (<NUM> mil) to about <NUM> (<NUM> mils). The backsheet may be embossed and/or matte finished to provide a more clothlike appearance. Further, the backsheet may permit vapors to escape from the absorbent core <NUM> (i.e., the backsheet is breathable) while still preventing body fluids from passing through the backsheet. A preferred microporous polyethylene film which is available from Tredegar Corporation, Virginia, USA, under Code No. XBF-<NUM>12W.

For a stretchable but non-elastic backsheet, one material can be used is a hydrophobic, stretchable, spun laced, non-woven material having a basis weight of from about <NUM> to <NUM>/m2 , formed of polyethylene terephthalate or polypropylene fibers. This material is breathable, i.e. permeable to water vapour and other gases.

For an elastic backsheet, one material which can be used is an elastic film sold under the trade mark EXX500 by Exxon Corporation. The material of this film is formed from an elastomeric base composition consisting of a styrene block copolymer. However, this material is not breathable. Another material which can be used for an elastic backsheet is a plastic film that has been subjected to a process that provides it with elastic-like properties without attaching elastic strands to the film, and may for example comprise a formed film made in accordance with <CIT>) and <CIT>).

Suitable breathable backsheets for use herein include all breathable backsheets known in the art. In principle, there are two types of breathable backsheets, single layer breathable backsheets which are breathable and impervious to liquids and backsheets having at least two layers, which in combination provide both breathability and liquid imperviousness. Suitable single layer breathable backsheets for use herein include those described for example in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

The backsheet may have two layers: a first layer comprising a gas permeable aperture formed film layer and a second layer comprising a breathable microporous film layer as described in <CIT>. Suitable dual or multi-layer breathable backsheets for use herein include those exemplified in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>.

The backsheet may be a relatively hydrophobic <NUM> grams per square meter (gsm) spunbonded nonwoven web of <NUM> denier polypropylene fibers. The backsheet may also be a laminate as is known in the art.

The backsheet may be vapor permeable as described in <CIT> or <CIT>. The backsheet can be formed from any vapor permeable material known in the art. Backsheet can be a microporous film, an apertured formed film, or other polymer film that is vapor permeable, or rendered to be vapor permeable, as is known in the art.

The backsheet may be a nonwoven web having a basis weight between about <NUM> gsm and about <NUM> gsm. In one embodiment, the backsheet is a relatively hydrophobic <NUM> gsm spunbonded nonwoven web of <NUM> denier polypropylene fibers available from Fiberweb Neuberger, under the designation F102301001. The backsheet may be coated with a non-soluble, liquid swellable material as described in <CIT>. The backsheet has a garment-facing side and an opposite body-facing side. The garment-facing side of the backsheet comprises a non-adhesive area and an adhesive area. The adhesive area may be provided by any conventional means. Pressure sensitive adhesives have been commonly found to work well for this purpose.

Still referring to <FIG>, the absorbent core <NUM> of a sanitary napkin serves to store bodily fluids discharged during use. The absorbent core <NUM> can be manufactured in a wide variety of sizes and shapes, and may be profiled to have different thickness, hydrophilic gradients, superabsorbent gradients, densities, or average basis weights at different positions across the face of the sanitary napkin <NUM>.

As shown in <FIG>, the absorbent core <NUM> can have a fluid distribution layer <NUM> as well as a secondary storage layer <NUM>. The fluid distribution layer may transfer the received fluid both downwardly and laterally, and generally has more permeability than the secondary storage layer. The carded staple fiber nonwovens detailed herein may also assist in transferring the received fluid both downwardly and laterally to the core.

The secondary storage layer can contain conventional absorbent materials. In addition to conventional absorbent materials such as creped cellulose wadding, fluffed cellulose fibers, Rayon fibers, wood pulp fibers also known as airfelt, and textile fibers, the secondary storage layer often includes superabsorbent material that imbibes fluids and form hydrogels. Such materials are also known as absorbent gelling materials (AGM), and may be included in particle form. AGM is typically capable of absorbing large quantities of body fluids and retaining them under moderate pressures. Synthetic fibers including cellulose acetate, polyvinyl fluoride, polyvinylidene chloride, acrylics (such as ORLON), polyvinyl acetate, non-soluble polyvinyl alcohol, polyethylene, polypropylene, polyamides (such as nylon), polyesters, bicomponent fibers, tricomponent fibers, mixtures thereof and the like can also be used in the secondary storage layer. The secondary storage layer can also include filler materials, such as PERLITE, diatomaceous earth, VERMICULITE, or other suitable materials, that lower rewet problems.

The secondary storage layer or fluid storage layer may have absorbent gelling material (agm) in an uniform distribution or may have agm in a non-uniform distribution. The agm may be in the in the form of channels, pockets, stripes, criss-cross patterns, swirls, dots, or any other pattern, either two or three dimensional, that can be imagined by man.

In some embodiments, portions of the secondary storage layer <NUM> of the absorbent core <NUM> can be formed only of superabsorbent material, or can be formed of superabsorbent materials dispersed in a suitable carrier such as cellulose fibers in the form of fluff or stiffened fibers. One example of a non-limiting absorbent core <NUM> is a first layer formed only of superabsorbent material that is disposed on a second layer that is formed from a dispersion of superabsorbent material within cellulose fibers.

Detailed examples of absorbent cores formed of layers of superabsorbent material and/or layers of superabsorbent material dispersed within cellulose fibers that may be utilized in the absorbent articles (e.g., sanitary napkins, incontinence products) detailed herein are disclosed in <CIT>. Absorbent cores comprising relatively high amounts of SAP with various core designs are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>. These may be used to configure the secondary storage layer.

As shown for example in the embodiments of <FIG>, the absorbent core storage layer <NUM> can comprise a first layer, or substrate layer, <NUM>, a layer of absorbent polymer material <NUM>, a layer of adhesive <NUM>, and a second layer, or cover layer, <NUM>. In the following description the terms "first layer" and "second layer" can be used interchangeably with "substrate layer" and "cover layer" respectively when describing a possible storage layer, and are meant to respectively refer to layers <NUM> and <NUM> in <FIG>. As shown in <FIG>, the storage layer may be used as shown in <FIG> or upside down as shown in <FIG>. The terms "substrate" and "cover", referred to the first layer <NUM> and to the second layer <NUM>, reflect one possible orientation of the absorbent core structure <NUM> when for example incorporated into an absorbent article, such as for example the sanitary napkin <NUM> shown in <FIG>, wherein the first layer <NUM> can actually constitute a substrate layer in that it is a bottom layer, i.e. for example closer to the backsheet <NUM>, and the second layer <NUM> can actually constitute a cover layer in that it is a top layer, i.e. closer to the topsheet <NUM>. Typically the adhesive can be a hot melt adhesive. According to the present invention, the layer of adhesive <NUM> can be typically for example a layer of fiberized hot melt adhesive <NUM>. The substrate layer <NUM> can for example comprise a fibrous material. Suitable materials for the cover layer can be for example nonwoven materials.

The substrate layer <NUM>, the layer of absorbent polymer material <NUM>, the layer of adhesive <NUM>, and the cover layer <NUM> each comprise a first surface and a second surface. Conventionally, in all the sectional views illustrated in the attached drawings the first surface of each layer is meant to correspond to the top surface, in turn, unless stated otherwise, corresponding to the wearer facing surface of the article incorporating the absorbent storage layer, while the second surface corresponds to the bottom surface, hence in turn the garment facing surface.

In general, in the storage layer of the present invention the arrangement of the various layers is such that the second surface of the layer of absorbent polymer material <NUM> is facing the first surface of the first or substrate layer <NUM>, the first surface of the layer of absorbent polymer material <NUM> is facing the second surface of the layer of adhesive <NUM>, and the second surface of the second or cover layer <NUM> is facing the first surface of the layer of adhesive <NUM>.

As shown in <FIG>, portions of the first surface of the substrate layer <NUM> can be in contact with the layer of absorbent polymer material <NUM>. This layer of absorbent polymer material <NUM> comprises a first surface and a second surface, and can be typically a uniform or non-uniform layer, wherein by "uniform" or "non-uniform" it is meant that the absorbent polymer material <NUM> can be distributed over the substrate layer <NUM> respectively with uniform or non-uniform basis weight over the area interested by the distribution. Conversely, the second surface of the layer of absorbent polymer material <NUM> can be in at least partial contact with the first surface of the substrate layer <NUM>. According to the present invention, the layer of absorbent polymer material <NUM> can also be a discontinuous layer that is a layer typically comprising openings, i.e. areas substantially free of absorbent polymer material, which in certain embodiments can be typically completely surrounded by areas comprising absorbent polymer material. Typically these openings have a diameter or largest span of less than <NUM>, or less than <NUM>, or <NUM>, or <NUM>, or <NUM> and of more than <NUM>, or <NUM>. At least portions of the second surface of the absorbent polymer material layer <NUM> can be in contact with at least portions of the first surface of the substrate layer material <NUM>. The first surface of the layer of absorbent polymer material <NUM> defines a certain height of the layer of absorbent polymer material above the first surface of the layer of substrate material <NUM>. When the absorbent polymer material layer <NUM> is provided as a non-uniform layer, typically for example as a discontinuous layer, at least some portions of the first surface of the substrate layer <NUM> can be not covered by absorbent polymer material <NUM>. The absorbent core <NUM> further comprises a layer of adhesive <NUM>, for example typically a hot melt adhesive. This typically hot melt adhesive <NUM> serves to at least partially immobilize the absorbent polymer material <NUM>. According to the present invention, the adhesive <NUM> can be typically a fiberized hot melt adhesive, i.e., being provided in fibres as a fibrous layer.

The storage layer comprises a cover layer <NUM> having respective first and second surface, positioned such that the second surface of the cover layer <NUM> can be in contact with the first surface of the layer of typically hot melt adhesive <NUM>.

According to the present invention comprising e.g. a non-uniform layer of absorbent polymer material <NUM> the typically hot melt adhesive <NUM>, for example typically provided as a fibrous layer, can be partially in contact with the absorbent polymer material <NUM> and partially in contact with the substrate layer <NUM>. <FIG> and <FIG> show such a structure in an exemplary embodiment of the present invention. In this structure the absorbent polymer material layer <NUM> is provided as a discontinuous layer, a layer of adhesive <NUM> is laid down onto the layer of absorbent polymer material <NUM>, typically, for example, a layer of hot melt adhesive in fiberized form, such that the second surface of the adhesive layer <NUM> can be in direct contact with the first surface of the layer of absorbent polymer material <NUM>, but also in direct contact with the first surface of the substrate layer <NUM>, where the substrate layer is not covered by the absorbent polymer material <NUM>, i.e. typically in correspondence of the openings of the discontinuous layer of the absorbent polymer material <NUM>. By saying "in direct contact", as well as more generally "in contact", as used herein, in contrast to more generally saying "facing", it is meant that there is no further intermediate component layer between e.g. the layer of adhesive <NUM> and the other respective layer in direct contact thereto, such as for example a further fibrous layer. It is however not excluded that a further adhesive material can be comprised between the layer of adhesive <NUM> and the cover layer <NUM>, or the layer of absorbent polymer material <NUM> or, more typically, the substrate layer <NUM>, such as for example a supplementary adhesive material provided onto the first surface of the substrate layer <NUM> to further stabilize the overlying absorbent polymer material <NUM>. "In direct contact" and "in contact" can hence be considered to comprise in this context a direct adhesive contact between the layer of hot melt adhesive <NUM> and another respective layer as explained above, or more in general direct and, typically, adhesive contact between two layers, e.g. the layer of absorbent polymer material and the substrate layer. This imparts an essentially three-dimensional structure to the fibrous layer of hot melt adhesive <NUM> which in itself is essentially a two-dimensional structure of relatively small thickness (in z-direction), as compared to the extension in x- and y-direction. In other words, the layer of adhesive <NUM> undulates between the first surface of the absorbent polymer material <NUM> and the first surface of the substrate layer <NUM>. The areas where the layer of adhesive <NUM> is in direct contact with the substrate layer <NUM>, when present according to an embodiment of the present invention, are the areas of junction <NUM>.

Thereby, in such an embodiment the adhesive <NUM> can provide spaces to hold the absorbent polymer material <NUM> typically towards the substrate layer <NUM>, and can thereby immobilize this material. In a further aspect, the adhesive <NUM> can bond to the substrate <NUM> thus affixing the absorbent polymer material <NUM> to the substrate <NUM>. Typical hot melt adhesive materials can also penetrate into both the absorbent polymer material <NUM> and the substrate layer <NUM>, thus providing for further immobilization and affixation.

In the embodiment of <FIG> portions of the cover layer <NUM> bond to portions of the substrate layer <NUM> via the adhesive <NUM>. Thereby, the substrate layer <NUM> together with the cover layer <NUM> can provide spaces to immobilize the absorbent polymer material <NUM>.

Of course, while the typically hot melt adhesive materials disclosed herein can provide a much improved wet immobilization, i.e. immobilization of absorbent polymer material when the article is wet or at least partially loaded, these hot melt adhesive materials can also provide a very good immobilization of absorbent polymer material when the article is dry.

In accordance with the present invention, the absorbent polymer material <NUM> may also be optionally mixed with fibrous material, which can provide a matrix for further immobilization of the absorbent polymer material. However, typically a relatively low amount of fibrous material can be used, for example less than about <NUM> weight %, less than about <NUM> weight %, or less than about <NUM> weight % of the total weight of the absorbent polymer material <NUM>, positioned within the areas of absorbent polymer material.

According to the present invention, in a typically discontinuous layer of absorbent polymer material <NUM> the areas of absorbent polymer material can be connected to one another, while the areas of junction <NUM> can be areas, which in an embodiment may correspond to the openings in the discontinuous layer of absorbent polymer material, as shown for example in <FIG>. The areas of absorbent polymer material are then referred to as connected areas. In an alternative embodiment, the areas of junction <NUM> can be connected to one another. Then, the absorbent polymer material can be deposited in a discrete pattern, or in other words the absorbent polymer material represents islands in a sea of adhesive <NUM>. Hence, in summary, a discontinuous layer of absorbent polymer material <NUM> may comprise connected areas of absorbent polymer material <NUM>, as e.g. illustrated in <FIG>, or may alternatively comprise discrete areas of absorbent polymer material <NUM>.

The present invention, and for example the embodiments described with reference to <FIG> can be typically used to provide the absorbent core of an absorbent article, as illustrated in <FIG>. In that case, no further materials wrapping the core, such as for example a top layer and a bottom layer are being used. With reference to the embodiment of <FIG> the optional cover layer <NUM> may provide the function of a top layer and the substrate layer <NUM> may provide the function of a bottom layer of an absorbent core, wherein top and bottom layers respectively correspond to the body facing and garment facing surfaces of the core <NUM> in an absorbent article.

With reference to <FIG>_B, according to exemplary embodiments of the present invention, the areas of direct contact between the adhesive <NUM> and the substrate material <NUM> are referred to as areas of junction <NUM>. The shape, number and disposition of the areas of junction <NUM> will influence the immobilization of the absorbent polymer material <NUM>. The areas of junction can be for example of squared, rectangular or circular shape. Areas of junction of circular shape can have a diameter of more than <NUM>, or more than <NUM>, and of less than <NUM>, or less than <NUM>, or less than <NUM>, or less than <NUM>, or less than <NUM>. If the areas of junction <NUM> are not of circular shape, they can be of a size as to fit inside a circle of any of the diameters given above.

The areas of junction <NUM>, when present, can be disposed in a regular or irregular pattern. For example, the areas of junction <NUM> may be disposed along lines as shown in <FIG>. These lines may be aligned with the longitudinal axis of the absorbent core, or alternatively they may have a certain angle in respect to the longitudinal edges of the core. A disposition along lines parallel with the longitudinal edges of the absorbent core <NUM> might create channels in the longitudinal direction which can lead to a lesser wet immobilization, hence for example the areas of junction <NUM> can be arranged along lines which form an angle of about <NUM> degrees, or about <NUM> degrees, or about <NUM> degrees, or about <NUM> degrees with the longitudinal edges of the absorbent core <NUM>. Another pattern for the areas of junction <NUM> can be a pattern comprising polygons, for example pentagons and hexagons or a combination of pentagons and hexagons. Also typical can be irregular patterns of areas of junction <NUM>, which also can give a good wet immobilization. Irregular patterns of areas of junction <NUM> can also give a better fluid handling behaviour in case of absorption of menses or blood or vaginal discharges, since fluid can start diffusing in whichever direction from any initial acquisition point with substantially the same probability of contacting the absorbent polymer material in the e.g. discontinuous layer. Conversely, regular patterns might create preferential paths the fluid could follow with lesser probability of actually contacting the absorbent polymer material.

According to the present invention the layer of adhesive <NUM> can comprise any suitable adhesive material. Typically, the layer of adhesive <NUM> can comprise any suitable hot melt adhesive material.

The absorbent articles detailed herein may also have integrated or attached cuffs (e.g., incontinence articles with barrier leg cuffs attached to the longitudinal edges of the article). The leg cuffs may take the form of absorbent article leg cuffs known in the art. In one non-limiting example, the article can have leg cuffs as described in <CIT>.

The absorbent article <NUM> can have a secondary topsheet <NUM> that can be interposed between the absorbent core <NUM> and the topsheet <NUM>, and serves to rapidly draw discharged body fluids, in particular menstrual fluids and/or urine, through the adjacent permeable (primary) topsheet <NUM>. This allows the surface of the primary topsheet <NUM> adjacent the wearer of the article to remain relatively clean and dry (it also provides acquisition/distribution functions).

The fluid distribution layer, as described below, comprises of three or more stratums integrated together so that they cannot be manually separated. The fluid distribution layer is substantially free of airlaid materials. Each stratum maintains its unique properties for at least a portion of the stratum along the z-direction, even when integrated into a larger fluid distribution layer. Unlike prior core systems that rely on layering materials, Applicants have found that by integrating a plurality of stratums, one can create fluid distribution layer that acts differently upon the fluid as it travels in the Z direction while improving the manner in which the fluid transitions between stratums due to the integration of fibers. The fluid distribution layer provides capillary suction to "pull" fluid through the topsheet <NUM>, which is competing for trickle/low flow conditions. The fluid distribution layer <NUM> also can contain a gush by providing distribution functions to efficiently utilize the absorbent core <NUM>, as well as provide intermediate storage until the absorbent core <NUM> can accept fluid.

Each stratum of the fluid distribution layer exhibits a pore size distribution that contributes to the overall pore size distribution of the fluid distribution layer. Pore size distribution can be expressed in a pore volume ratio parameter and/or the pore volume factor, which is measured as detailed below in the methods section. In some embodiments of the articles detailed herein, the pore volume ratio can be greater than about <NUM>, or greater than about <NUM>, or greater than about <NUM>. The pore volume factor can be greater than about <NUM><NUM>/ µm·g. In some forms, the pore volume factor may be greater than about <NUM><NUM>/ µm·g or greater than about <NUM><NUM>/ µm·g or greater than about <NUM><NUM>/ µm·g or about <NUM><NUM>/ µm·g. In some forms, the pore volume factor may be between about <NUM><NUM>/ µm·g to about <NUM><NUM>/ µm·g or from about <NUM><NUM>/ µm·g to about <NUM><NUM>/ µm·g specifically including all values within these ranges and any ranges created thereby. Pore size distribution can also be expressed in a pore volume radius mode, which is measured as detailed in the methods herein. In some embodiments of the articles detailed herein, the pore volume radius mode can be between about <NUM> and about <NUM>, or between about <NUM> and about <NUM>, or between about <NUM> and about <NUM>.

The fluid distribution layer has a first surface and a second surface. Between the first surface and the second surface, the fluid distribution layer comprises of three or more stratums along the Z-direction. The fluid distribution layer does not contain adhesives, latex, and pulp. The fluid distribution layer can have a basis weight of up to <NUM> grams per square meter (gsm); or a basis weight of up to <NUM> gsm; or a basis weight in the range of about <NUM> gsm to about <NUM> gsm; or in the range of about <NUM> gsm to about <NUM> gsm; or in the range of about <NUM> gsm to about 135gsm; or in the range of about <NUM> gsm to about <NUM> gsm, or in a range of about <NUM> gsm to about <NUM> gsm including any values within these ranges and any ranges created thereby.

The fluid distribution layer has a caliper of between <NUM> millimeters (mm) and <NUM>; between <NUM> and <NUM>; between <NUM> and <NUM>; or between <NUM> and <NUM> including any values within these ranges and any ranges created thereby.

The fluid distribution layer can also have a cross machine direction (CD) flexural rigidity of about <NUM> mN·cm to about <NUM> mN·cm. In some embodiments, the fluid distribution layer has a CD flexural rigidity of about <NUM> mN cm to about <NUM> mN cm or from about <NUM> mN cm to about <NUM> mN·cm or from about <NUM> mN·cm to about <NUM> mN·cm including any values within these ranges and any ranges created thereby. In some embodiments, the fluid distribution layer has a MD flexural rigidity of less than about <NUM> mN cm. In some embodiments, the MD flexural rigidity can be greater than about <NUM> mN·cm. The MD flexural rigidity can be from about <NUM> mN·cm to about <NUM> mN·cm specifically including all values within this range and all ranges created thereby.

As noted previously, it may be desirable to have stiffness and flexural rigidity in the CD to reduce bunching while maintaining comfort and body fit. For this reason, in some forms, it may be beneficial for the flexural rigidity in the CD to be close to the flexural rigidity of the MD. In some embodiments, the CD flexural rigidity / MD flexural rigidity can be between about <NUM>% to about <NUM>% or from about <NUM>% to about <NUM>%, specifically including all values within these ranges and all ranges created thereby.

The carded staple fiber nonwoven of the fluid distribution layer <NUM> can be manufactured from an assortment of suitable fiber types that produce the desired mechanical performance and fluid handling performance. The carded staple fiber nonwoven is formed from a combination of stiffening fibers, absorbing fibers and filler fibers. The stiffening fibers, for example, can form about <NUM>% to about <NUM>%, by weight, of the carded staple fiber nonwoven. For some example fluid distribution layers, the stiffening fibers can form about <NUM>% to <NUM>%, by weight, of the carded staple fiber nonwoven. In other embodiments, the stiffening fibers can form about <NUM>%, by weight, of the carded staple fiber nonwoven.

As a total, stiffening fibers can be up to <NUM>% of the fluid distribution layer. Stiffening fibers can be between <NUM>% and <NUM>% of a stratum within the fluid distribution layer, such as, for example, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, or <NUM>% of a stratum within the fluid distribution layer.

Absorbent fibers can be up to <NUM>% of the fluid distribution layer. Absorbent fibers can be between <NUM>% and <NUM>% of a stratum within the fluid distribution layer, such as, for example, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, <NUM>% of a stratum within the fluid distribution layer, or <NUM>% of a stratum within the fluid distribution layer.

The stiffening fibers comprise polyethylene terephthalate (PET) fibers. The PET fibers have a dtex in the range of about <NUM> to about <NUM>, or in the range of about <NUM> to about <NUM>. The staple length of the stiffening fibers can be in the range of about <NUM> to about <NUM>, or in the range of about <NUM> to about <NUM>. Some carded staple fiber nonwovens include stiffening fibers with a staple length of about <NUM> to <NUM>. The stiffening fibers comprise fibers made of hollow/spiral PET. Optionally, the stiffening fibers may be spiral-crimped or flat-crimped. The stiffening fibers may have a crimp value of between about <NUM> and about <NUM> crimps per inch (cpi), or between about <NUM> and about <NUM> cpi, or between about <NUM> and about <NUM> cpi, or between about <NUM> and about <NUM> cpi. Particular non-limiting examples of stiffening fibers can be obtained from Wellman, Inc. Ireland under the trade names H1311 and T5974. Other examples of suitable stiffening fibers for utilization in the carded staple fiber nonwovens detailed herein are disclosed in <CIT>.

As described above, the fluid distribution layer comprises of three or more stratums. The ratio of fibers described above may be different for each stratum. Once integrated, the stratums form one heterogeneous structure that cannot be separated.

Other suitable examples of stiffening fibers include polyester/co-extruded polyester fibers. The stiffening fibers may be so-called bi-component fibers, where individual fibers are provided from different materials, usually a first and a second polymeric material. The two materials may be chemically different (hence the fibers are chemically heterogeneous) or they may differ only in their physical properties while being chemically identical (hence the fibers are chemically homogeneous). For example, may the intrinsic viscosity of the two materials be different, which has been found to influence the crimping behavior of the bi-component fibers. Bi-component fibers that are suitable as stiffening fibers are side-by-side bi-component fibers as disclosed for example in <CIT>. The stiffening fibers may also be a blend of bi-component fibers with polyester fibers. With specific reference to bicomponent fibers comprised of a polypropylene/polyethylene fiber composition, in a cross-sectional view of a fiber, the material with a higher softening temperature can provide the central part (i. e, the core) of the fiber. The core typically is responsible for the bicomponent fiber's ability to transmit forces and have a certain rigidity or otherwise provide structures with resiliency. The outer coating on the core (i.e., the sheath) of the fiber can have a lower melting point and is used to facilitate thermally bonding of substrates comprising such fibers. In one embodiment, a polypropylene core is provided with a polyethylene coating on the outside, such that about <NUM>%, by weight, of the fiber material is polypropylene and <NUM>%, by weight, of the fiber material is polyethylene. Other quantitative amounts can of course be selected. For example, bicomponent fibers can have a composition from about <NUM>% to about <NUM>%, by weight, polyethylene, while others have about <NUM>% to about <NUM>%, by weigh polyethylene. In some embodiments, bicomponent fibers can have a composition from about <NUM>% to about <NUM>% or about <NUM>% to about <NUM>%, by weight, polyethylene.

Another suitable bi-component stiffening fiber is a fiber of circular cross section with a hollow space in the centre that is spiral crimped. It is preferred that <NUM>-<NUM>% of the cross sectional area are hollow, more preferably <NUM>-<NUM>% of the cross sectional area are hollow. Without wishing to be bound by theory, it is believed that the spiral crimping of fibers is beneficial for their liquid acquisition and distribution behaviour. It is assumed that the spiral crimp increases the void space in an acquisition member formed by such fibers. Often, an absorbent article, when being worn, is exposed to a certain pressure exerted by the wearer, which potentially decreases the void space in the acquisition member. Having good permeability and sufficient void space available are important for good liquid distribution and transport. Also, spiral-crimped fibers believed to provide for good permeability as for a given fiber dtex value, the hollow fiber cross-section allows for a larger outer diameter of the fiber as compared to a compact cross-section. The outer diameter of a fiber appears to determine the permeability behavior of an acquisition member formed by such fibers.

The absorbing fibers, for example, can form about <NUM>% to about <NUM>%, by weight, of the carded staple fiber nonwoven. For some example fluid distribution layers, the absorbing fibers can form about <NUM>% to about <NUM>%, by weight, of the carded staple fiber nonwoven. In other embodiments, the absorbing fibers can form about <NUM>%, by weight, of the carded staple fiber nonwoven. Within a stratum, they may be up to <NUM>% of the individual stratum.

The absorbing fibers comprise rayon, such as viscose rayon. For carded staple fiber nonwovens including rayon, the rayon has a dtex in the range of about <NUM> to about <NUM>. The staple length of the absorbing fibers can be in the range of about <NUM> to about <NUM>, or about <NUM> to about <NUM> or about <NUM> to about <NUM>. The rayon fibers can have any suitable structure or shape. The rayon fibers may be a blend of any suitable structures and shapes. For example, the rayon fibers can be round or have other shapes, such as spiral, scalloped oval, trilobal, other multi-lobal shapes, scalloped ribbon, and so forth. Further, the rayon fibers can be solid, hollow or multi-hollow. In some embodiments of the carded staple fiber nonwoven, the absorbing fibers may be trilobal in shape, or another shape with a multiple lobes in cross section. Other examples of suitable multi-lobed absorbing fibers for utilization in the carded staple fiber nonwovens detailed herein are disclosed in <CIT>, <CIT>, and <CIT>.

One advantage of multiple lobed absorbing fibers is their greater bulk over single-limbed fibers, because the circumferential area of the multiple lobed fibers is larger than their actual cross-sectional area. For example, <CIT> describes a filament yarn consisting of X- or Y-shaped continuous viscose filaments that is used in textile applications where bulk is important, for example in pile weaves. Another advantage of multi-limbed absorbing fibers is their increased absorbency over single-limbed fibers.

The filler fibers, for example, can form about <NUM>% to about <NUM>%, by weight, of the carded staple fiber nonwoven. For some example fluid distribution layers, the filler fibers can form about less than about <NUM>%, by weight, of the carded staple fiber nonwoven. In other embodiments, the filler fibers can form about <NUM>%, by weight, of the carded staple fiber nonwoven. Filler fibers may be placed in any stratum of the fluid distribution layer. For example, filler fibers may be located in the topmost layer to help with capillary suction of fluid from the topsheet into the absorbent structure.

The filler fibers comprise thermoplastic fiber, such as polypropylene (PP), or other suitable thermoplastic fibers known in the art. The carded staple fiber nonwovens including thermoplastic fibers have a dtex of greater than about <NUM>. Some carded staple fiber nonwovens can include PP having a dtex in the range of about <NUM> to about <NUM>. The staple length of the filler fibers can be in the range of about <NUM> to about <NUM>, or about <NUM> to about <NUM> or about <NUM> to about <NUM>. The thermoplastic fibers can have any suitable structure or shape. For example, the thermoplastic fibers can be round or have other shapes, such as spiral, scalloped oval, trilobal, scalloped ribbon, and so forth. Further, the PP fibers can be solid, hollow or multi-hollow. In some embodiments of the carded staple fiber nonwoven, the third filler fibers may be solid and round in shape. Other suitable examples of filler fibers include polyester/co-extruded polyester fibers. Additionally, other suitable examples of filler fibers include bi-component fibers such as polyethylene / polypropylene, polyethylene / polyethylene terephthalate, polypropylene / polyethylene terephthalate. These bi-component fibers may be configured as a sheath and a core. The bi-component fibers may provide a cost effective way to increase basis weight of the material while additionally enabling optimization of the pore size distribution.

The carded staple fiber nonwoven of the fluid distribution layer <NUM> formed in accordance with the present disclosure imparts a number of desirable physical properties, including its narrow pore size distribution, wicking/capillarity, permeability, wet Z-direction crush resistance and flexural rigidity. Generally, the absorbing fibers of the carded staple fiber nonwoven, such as rayon, provide capillarity, which serves to transport fluid from the topsheet <NUM> to the absorbent core <NUM>. The stiffening fibers of the carded staple fiber nonwoven, such as PET, provide Z-direction strength to prevent, or at least limit, collapse of the fluid distribution layer <NUM> when wetted while also providing desirable permeability. The filler fibers of the carded staple fiber nonwoven, such as polypropylene fibers, serve to provide a cost effective way to increase basis weight of the material while having minimal effect on pore size distribution.

The secondary storage layer can have a smaller cross direction width than the fluid distribution layer. The secondary storage layer can have a smaller cross direction length than the fluid distribution layer. The secondary storage layer can have a cross direction width that is a percent of the fluid distribution layer cross direction width, such as, for example, <NUM>% of the fluid distribution layer cross direction width, <NUM>% of the fluid distribution layer cross direction width, <NUM>% of the fluid distribution layer cross direction width, <NUM>% of the fluid distribution layer cross direction width, <NUM>% of the fluid distribution layer cross direction width, <NUM>% of the fluid distribution layer cross direction width, <NUM>% of the fluid distribution layer cross direction width, <NUM>% of the fluid distribution layer cross direction width, or <NUM>% of the fluid distribution layer cross direction width. The secondary storage layer can have a cross direction length that is a percent of the fluid distribution layer cross direction length, such as, for example, <NUM>% of the fluid distribution layer cross direction length, <NUM>% of the fluid distribution layer cross direction length, <NUM>% of the fluid distribution layer cross direction length, <NUM>% of the fluid distribution layer cross direction length, <NUM>% of the fluid distribution layer cross direction length, <NUM>% of the fluid distribution layer cross direction length, <NUM>% of the fluid distribution layer cross direction length, <NUM>% of the fluid distribution layer cross direction length, or <NUM>% of the fluid distribution layer cross direction length. If the fluid distribution layer is any shape other than a rectangle, the width and length used to calculate the percent is the longest width and length of the distribution layer.

The fluid acquisition/distribution layer can exhibit desirable parameters in terms of Mean pore value, capillary work potential, wicking ratios, and plane permeability ratios. Because one can integrate different stratums with tailored properties each having unique parameters, the fluid acquisition/distribution layer can exhibit different parameters within a layer having each stratum tailored to a desired parametric range so that the overall layer functions in a tailored manner.

As shown in Table <NUM>, the upper layer of each embodiment (stratum <NUM>) includes viscose in combination with tri-lobal fibers. Applicants have found that by including viscose fibers (tri-lobal, round, or combinations of tri-lobal and round) one can create a distribution layer that has an absorbent outer layer which can quickly wick fluid. The subsequent layers including Polyethylene/Coextruded polyethylene, Polyethylene/terathalate allow for fluid to pass through the structure to the wicking layer thus allowing the fluid to be wicked by the lower layer(s) in the product. This is enabled by placing a higher level of viscose in the stratum that serves as the lower stratum of the acquisition layer in the absorbent article. Additionally, the acquisition layer may have a gradient level of viscose in each stratum thereby allowing wicking to increase per stratum.

Further, the fluid continuity and integration of the layers such that they are integrated is enabled by the fiber lengths. Unlike other traditional air-laid layers, the embodiments above utilize the fiber length(s) to integrate the different stratums thereby creating the fluid distribution layer with the desirable properties.

As shown in Table <NUM> and Table <NUM>, a fluid acquisition/ distribution layer may include three or more stratum. Each stratum may have a different composition, gsm, or other properties. The stratums are integrated to create a single fluid acquisition/ distribution layer. Applicants have found that by integrating three or more stratum without the use of adhesives, one can create a layer that has higher basis weight allowing for improved comfort in the form of improved flexibility and loftness while not hindering fluid acquisition and absorption. Additionally, without being held by theory, it is believed that the higher basis weight without the use of adhesives in the integrated layer has improved rewet in comparison to non integrated materials that have similar basis weight. As such, without being bound by theory, the acquisition/distribution layer allows for better leakage protection, flexibility, and rewet protection while delivering parallel absorbency and acquisition by delivering a new structure that lies in a new area of performance.

Additionally, without being bound by theory, it is believed that by placing higher permeability in the top layers and high wicking in the lower layers, one can create an acquisition /distribution layer that will take in the fluid while reducing the stain size caused by the menses passing through the acquisition layer. This is unlike a homogenous construction, wherein the stain would be consistent and larger. Instead, by allowing the fluid to be pulled vertically instead of laterally, the stain size can be reduced.

As shown in Table <NUM>, one can include cellulose in the body facing stratum (stratum <NUM>) by adding viscose. Without being bound by theory, the additional cellulose improves the connectivity between the upper stratum or body facing stratum and the lower stratums and may additionally improve the capillary suction of the upper stratum which first contacts the fluid.

Additionally, it has been surprisingly found that while a small amount of cellulose leads to benefits in capillary suction and fluid connectivity, having a higher percentage of cellulose in the body facing stratum may lead to a collapse in caliper of the acquisition/distribution layer. This is exemplified by Embodiment <NUM> which contains <NUM>% in the body facing stratum in the form of Viscose <NUM> and showed a collapse in caliper versus samples with little or no cellulose as shown in Table <NUM>. All the embodiments of Tables <NUM>, <NUM>, and <NUM> listed in Table <NUM> where made using the same process parameters and have the same overall basis weight. As shown in Table <NUM>, a small increase of <NUM>% cellulose (from <NUM>% to <NUM>%) in the body facing stratum may lead to an overall caliper drop of <NUM> millimeters versus Embodiment <NUM> which contains no viscose or cellulose or a drop in caliper of <NUM>% while <NUM>% viscose may lead to a drop in caliper of about <NUM>% as shown by Embodiment <NUM>. Unlike Embodiment <NUM>, Embodiment <NUM> includes an increasing amount of cellulose from top to bottom unlike embodiments <NUM> and <NUM> which have a consistent percentage amount in the three stratums beginning with the body facing stratum.

<FIG> depicts a simplified, schematic view of one example of a continuous carded staple fiber nonwoven manufacturing process. As is to be appreciated, the carded staple fiber nonwoven produced by the process of <FIG> can be used in the manufacturing of a variety of absorbent articles, such as the sanitary napkin <NUM> of <FIG>, as well as a variety of other absorbent articles, including diapers, training pants, adult incontinence undergarments, and the like.

As is generally known in the art, hydroentanglement (sometimes referred to as spunlacing, jet entanglement, water entanglement, hydroentanglement or hydraulic needling), is a mechanical bonding process whereby fibers of a nonwoven web are entangled by means of high pressure water jets. Patterning can be achieved by use of patterned drums or belts which cause the fibers to form a negative image of the drum design in the fabric. The formed web of various fibrous components (usually airlaid, wetlaid, or carded, but sometimes spunbond or melt-blown, etc.) can first be compacted and prewetted to eliminate air pockets and then water-needled. With reference to <FIG>, a fibrous structure <NUM> is formed from cellulosic fibers, non-cellulosic fibers and bicomponent fibers, e.g. filler fibers, absorbing fibers, and stiffening fibers. The fibrous structure <NUM> has an unbonded portion 30A upstream of a jet head <NUM> and a bonded (i.e., hydroentangled) portion 30B downstream of the jet head <NUM>. During the entanglement process, the fibrous structure <NUM> is passed by the jet head <NUM> that comprises a plurality of injectors that are positioned to generally form a water curtain (for simplicity of illustration, only one injector <NUM> is illustrated in <FIG>). A water jet <NUM> is directed through the fibrous structure <NUM> at high pressures, such as <NUM> or <NUM> bar. As is to be appreciated, while not illustrated, multiple rows of injectors <NUM> are typically used, which can be positioned on one or both sides of the fibrous structure <NUM>.

The fibrous structure <NUM> can be supported by any suitable support system <NUM>, such as a moving wire screen (as illustrated) or on a rotating porous drum, for example. While not illustrated, it is to be appreciated that hydroentanglement systems can expose the fibrous structure <NUM> to a series of jet heads <NUM> along the machine direction, with each delivering water jets at different pressures. The particular number of jet heads <NUM> utilized can be based on, for example, desired basis weight, degree of bonding required, characteristics of the web, and so forth. As the water jet <NUM> penetrates the web, a suction slot <NUM> positioned proximate beneath the fibrous structure <NUM> collects the water so that it can be filtered and returned to the jet head <NUM> for subsequent injection. The water jet <NUM> delivered by the jet head <NUM> exhausts most of its kinetic energy primarily in rearranging fibers within the fibrous structure <NUM> to turn and twist the fibers to form a series of interlocking knots.

Once the fibrous structure <NUM> has been hydroentangled (shown as bonded portion 30B), the fibrous structure <NUM> is then passed through a dewatering device where excess water is removed. In the process illustrated in <FIG>, the dewatering device is a drying unit <NUM>. The drying unit <NUM> can be any suitable drying system, such as a multi-segment multi-level bed dryer, a vacuum system, and/or an air drum dryer, for example. The drying unit <NUM>, or other dewatering device, serves to substantially dry the fibrous structure <NUM>. The term "substantially dry" is used herein to mean that the fibrous structure <NUM> has a liquid content, typically water or other solution content, less than about <NUM>%, less than about <NUM>%, or less than about <NUM>%, by weight.

The fibrous structure can be heat stiffened. The fibrous structure can be heat stiffened at temperatures between <NUM> degrees Celsius and <NUM> degrees Celsius; between <NUM> degrees Celsius and <NUM> degrees Celsius; between <NUM> degrees Celsius and <NUM> degrees Celsius; or between <NUM> degrees Celsius and <NUM> degrees Celsius specifically including all values within these ranges and any ranges created thereby.

Once the hydroentangled fibrous structure <NUM> is substantially dry, the hydroentangled fibrous structure <NUM> can be heated to an elevated temperature. By heating the hydroentangled fibrous structure <NUM> to a particular temperature, or temperature range, the flexural rigidity of the fibrous structure can be increased (i.e., stiffened). Stiffening the fibrous structure results in a number of desired results. For example, the increase of stiffness of the hydroentangled fibrous structure <NUM> allows the structure to tolerate the subsequent manufacturing processes. Additionally, when the hydroentangled fibrous structure <NUM> is subsequently incorporated into an absorbent article, such as sanitary napkin <NUM>, for example, cross machine direction (CD) bunching is reduced, leading to less leakage and more comfort for a wearer.

By introducing additional heat to the hydroentangled fibrous structure <NUM> to raise its temperature during the thermal bonding process, the sheath of the bicomponent fibers will first begin to soften. As these softened bicomponent fibers touch each other, bonds will form between the sheaths, thereby increasing the overall flexural rigidity of the structure due to the formation of these bond sites. The elevated temperature of the hydroentangled fibrous structure <NUM> is not high enough, however, to cause other types of fibers within the hydroentangled fibrous structure to flow or otherwise soften, bond, or collapse. The formation of the bond sites within the hydroentangled fibrous structure <NUM> adds to the stiffness of the web, yet the fluid handling performance of the hydroentangled fibrous structure <NUM> remains as desired. It will be recognized that raising the final drying stage temperature (or otherwise introducing heat to the hydroentangled fibrous structure) to just above a softening temperature of a portion of the bicomponent fiber provides an increase in mechanical performance while also maintaining liquid handling performance. If, however, the hydroentangled fibrous structure is heated to too high of temperature, the rigidity of the structure increases and the liquid handling performance of the structure can suffer.

Once the fibrous structure <NUM> is manufactured in accordance with the present disclosure it can be incorporated into, for example, an absorbent material. With regard to the sanitary napkin <NUM> of <FIG>, the fluid distribution layer <NUM> incorporating the fibrous structure <NUM> can be bonded to, or otherwise attached to the topsheet <NUM>. In some embodiments, thermal point calendaring or other suitable bonding is utilized. In other embodiments, the fibrous structure <NUM> can serve as an absorbent core of an absorbent article. For example, pantiliners and incontinence pads can be formed with the fibrous structure <NUM> positioned between a topsheet and a bottom sheet to function as at least part of an absorbent core, as described above with respect to <FIG>. Furthermore, in some embodiments, the fibrous structure <NUM> does not include a binder component.

The fibrous structure described above may be utilized to have multiple stratums available to one manufacturing system. Dependent upon the desired properties of the fluid distribution layer, the system can selectively choose which stratums to utilize in the manufacturing of the fluid distribution layer. In this manner, the system can create an array of fluid distribution layers that vary in composition, thickness, and dependent upon the selection of stratums and manufacturing parameters, different fluid handling properties and different physical parameters such as, for example, pore size volume. For example, a fluid distribution layer to be used with a film topsheet can have different properties from a fluid distribution layer to be used with a nonwoven topsheet. This can be achieved while still maintaining the desirable targeted z-direction compressibility.

Pore volume distribution measurements are made on a TRI/Autoporosimeter (TRI/Princeton Inc. of Princeton, N. ) The TRI/Autoporosimeter is an automated computer-controlled instrument for measuring pore volume uptake and pore-size distribution in porous materials. Here, measurements are performed on an initially dry specimen using a <NUM> psi confining pressure during an absorption, desorption and second absorption cycle. Pores between <NUM> micron (µm) and <NUM> are measured. Information on the TRI/Autoporosimeter, its operation and data treatments can be found in<NPL>, incorporated here by reference.

A representation of the TRI equipment is shown in <FIG> and consists of a balance <NUM> with fluid reservoir <NUM> which is in direct fluid communication with the sample <NUM> which resides in a sealed, air-pressurized sample chamber <NUM>. An example experiment cycle is shown in <FIG>.

Determining the Pore Volume Uptake or Pore-Size Distribution involves recording the increment of liquid that enters or leaves a porous material as the surrounding air pressure is altered. A sample in the test chamber is exposed to precisely controlled changes in air pressure. As the air pressure increases or decreases, the void spaces or pores of the porous media de-water or uptake fluid, respectively. Total fluid uptake is determined as the total volume of fluid absorbed by the porous media.

Pore-Size Distribution can further be determined as the distribution of the volume of uptake of each pore-size group, as measured by the instrument at the corresponding pressure. The pore size is taken as the effective radius of a pore and is related to the pressure differential by the following relationship. <MAT> where γ = liquid surface tension, and Θ = contact angle.

For this experiment: γ = <NUM> dyne/cm<NUM> divided by the acceleration of gravity; cos Θ = <NUM>°.

The automated equipment operates by precisely changing the test chamber air pressure in user-specified increments, either by decreasing pressure (increasing pore size) to cause fluid uptake by the porous media, or by increasing pressure (decreasing pore size) to de-water the porous media. The liquid volume absorbed (drained) at each pressure increment yields the pore size distribution. The fluid uptake is the cumulative volume for all pores taken up by the porous media, as it progresses to saturation (e.g. all pores filled).

Take a <NUM> diameter, <NUM> membrane filter (mixed cellulose esters, Millipore GSWP, EMD Millipore Corp. , Billerica MA) by adhering the filter to a <NUM> centimeter diameter by <NUM> thick Monel porous frit <NUM> using KRYLON® spray paint (FilmTools Gloss White Spray Paint #<NUM>). Allow the frit/membrane to dry before use.

Fill the inner base <NUM> of the sample chamber with hexadecane (available from Sigma-Aldrich <NPL>). Place the frit <NUM> membrane side up onto the base of the sample chamber <NUM>, and secure it into place with a locking collar <NUM>. Fill the connecting tube <NUM>, reservoir <NUM>, and the frit <NUM> with hexadecane assuring that no bubbles are trapped within the connecting tube or the pores within the frit and membrane. Using the legs of the base <NUM>, level the sample camber and align the membrane with the top surface of the fluid within the reservoir.

Dye cut a specimen <NUM> square. Measure the mass of the specimen to the nearest <NUM>. A <NUM> square, Plexiglas cover plate <NUM> and confining weight <NUM> are selected to provide a confining pressure of <NUM> psi.

Place the top of the sample chamber <NUM> in place and seal the chamber. Apply the appropriate air pressure to the cell (connection <NUM>) to achieve a <NUM> effective pore radius. Close the liquid valve <NUM>. Open the sample chamber, place the specimen <NUM>, cover plate <NUM> and confining weight <NUM> into the chamber onto the membrane <NUM> and seal the camber. Open the liquid valve <NUM> to allow free movement of liquid to the balance.

Progress the system through a sequence of pore sizes (pressures) as follows (effective pore radius in µm): <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>,<NUM>, <NUM>,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>,<NUM>, <NUM>,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The sequence is progressed to the next radius when an equilibrium rate of less than <NUM>/min is measured at the balance.

In like fashion, measure the acquisition/drainage/acquisition cycle blank without a sample.

Based on the incremental volume values, calculate the blank-corrected values for cumulative volume versus equivalent pore radius. <MAT> <MAT>.

Plot Pore Volume (mm<NUM>/µm·g) vs. Effective Radius (µm). Referring to <FIG>, determine from the drainage curve, the Pore Volume value (H) at the mode of the Effective Radius. Where a vertical line parallel to the Y-axis extending from the value (H) to the X-axis defines Pore Volume Radius Mode. From the peak calculate the width (W) at half height ( ½ H) by connecting the data points with straight lines and calculate the Pore Volume Ratio as H/W and report to the nearest <NUM><NUM>/µm·g/µm.

Claim 1:
A carded staple fiber nonwoven comprising three or more stratums, the carded staple fiber nonwoven having a basis weight of up to <NUM> grams per square meter (gsm), the carded staple fiber nonwoven comprising a blend of absorbing fibers, stiffening fibers and filler fibers, wherein the stiffening fibers comprise hollow, spiral fibers formed from polyethylene terephthalate (PET), wherein the stiffening fibers have a linear density between <NUM> dtex and <NUM> dtex , and wherein the carded staple fiber nonwoven is heat stiffened and wherein the three or more stratums are integrated without adhesives;
wherein the carded staple fiber nonwoven has a caliper between <NUM> and <NUM>;
wherein the absorbing fibers comprise fibers formed from rayon, wherein the absorbing fibers have a linear density of between <NUM> dtex and <NUM> dtex; and
wherein the filler fibers are carded staple thermoplastic fiber and have a dtex of greater than <NUM>.