CA1301440C

CA1301440C - High density absorbent members having lower density and lower basis weight acquisition zones

Info

Publication number: CA1301440C
Application number: CA000542042A
Authority: CA
Inventors: Miguel Alemany; Charles John Berg
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1986-07-18
Filing date: 1987-07-14
Publication date: 1992-05-26
Anticipated expiration: 2009-05-26
Also published as: PT85340A; AU7575687A; EP0254476A2; FI88253C; FI88253B; PT8851U; HK134497A; IE871941L; JP2635599B2; DK175648B1; IE65287B1; DE3751044D1; ES2067446T3; NZ221113A; AU614932B2; DK375587A; US4834735A; EP0254476A3; FI873172A; EP0254476B1

Abstract

HIGH DENSITY ABSORBENT MEMBERS
HAVING LOWER DENSITY AND
LOWER BASIS WEIGHT
ACQUISITION ZONES

ABSTRACT

An absorbent article wherein the deposition region of its absorbent member comprises a storage zone and an acquisition zone having a lower average density and a lower average basis weight per unit area than the storage zone. The acquisition zone is positioned toward the front of either the absorbent member or the absorbent article so that the acquisition zone may most effectively and efficiently rapidly acquire discharged liquids.
The absorbent member also comprises a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material to enhance the absorbent capacity of the absorbent member.

Description

iilGH DENSITY ABSORBENT MEMBERS
HAVING LOWER DENSITY AND
LOWER BASIS WEIGHT ACOUISITION ZONES

FIELD OF THE INVENTION

This invention relates to absorbent members having a mixture of hydrophilic fibrous material and discrete particles of an absorbent gelling material. More particularly, the invention relates to a relatively high density absorbent member having a relatively lower average density and lower average basis weight acquisition zone positioned in the area of typical liquid deposit~on to more quickly acquire and distribute liquids within the absorbent member.
i3ACKGROUND OF THE INVENTION
_ Absorbent articles such as disposable diapers, adult incontlnent pads, sanitary napkins and the like are generally provided with absorbent members to receive and retain body liquids. In order for such absorbent artlcles to function efficiently, the absorbent members must quickly acquire body 2!~ liquids into the structure from the point of application and subsequently distribute the body liquids within and throughout the absorbent member to provide maxlmum leakage containment.
In addition, the absorbent members should be capable of retaining 13(1~4~`~

liquids when placed under loads. Prlor art attempts to improve the effectiveness of such absorbent members have included ~istributing particles of absorbent gelllng material throughout or in portions of the absorbent member. For example Procter Gamble; United States Patent 4,610,Ç78 issued Septem-ber 9, 1986 discloses absorbent members wherein particles of absorbent gelling material (hydrogel) are dispersed in an air-laid web of hydrophilic fibrous material and compressed to a particular density. In addition, U.S. Patent 4,673,402 issued on June 16, 1987 to The Procter & Gamble Company discloses a dual-layer absorbent core wherein an absorbent acquisition layer overlays a lower fluid storage layer that consists essentially of a uniform combination of hydrophllic fihrous material and discrete partlcles of absorbent L5 gelling material.

Absorbent gelling materials are polymeric materials which are capable of absorbing large quantities of liquids relative to their weight such as water and body wastes and which are further capable of retaining such absorbed liquids under moderate pressures. These absorption characteristics of absorbent gelling materials make them especially useful for incorporation into absorbent artlcles such as disposable dlapers adult incontinent pads sanitary napkins and the like. However in spite of the extremely hlgh absorptlon capacltles of such absorbent gelling materials their performance when used In disposable absorbent artlcles has stlll not been optlmlzed.

The effectlveness of absorbent gelling materlals in disposable absorbent articles Is qulte dependent upon the form posttion and/or manner In whlch the particles of absorbent gelllng material are incorporated Into the absorbent member. In some cases for example the effectiveness of absorbent members containing partlcles of absorbent gelllng material can be adversely affected by a phenomenon called gel blocklng. The term gel blocklng describes a sltuatlon that occurs when a partlcle of absorbent gelling material Is wetted the surface of the particles swelllng so . ,~

~3V1~40 as to inhibit liquk1 transmission into the interior of the absorbent member. Wetting of the interior of the absorbent member, therefore, takes place via a very slow diffusion process. In practical terms, this means that acquisition of liquids by the absorbent member is much slower than the discharge of the liquid to be absorbed, and leakage from the absorbent article may take place well before the particles of absorbent gelling material in the absorbent member are fully saturated or before the liquid can diffuse or wick past the blocking particles into the rest of the absorbent member. The slow acquisition rate also fails to take advantage of the rapid wicking of liquids to other parts of the absorbent member provided by a densified absorbent member containing particles of absorbent gelllng material.

Thus, it would be advantageous to provide an absorbent member that more quickly acquires and distributes liquids within itself while minimizing gel blocking during the liquid acquisition phase. It is therefore a primary objective of the present invention to provide absorbent members which are especially effective and efficient in their use of absorbent gelling materials.

SUMMARY OF THE INVENTION

The present inventlon provides an absorbent article such as disposable diapers, incontinent pads, sanitary napkins or the like that have an absorbent member that is suitable for acquiring and containing liquids in an especially effective and efficient manner.
Such an absorbent article comprises a liquid pervious topsheet, a liquid impervious backsheet, and an absorbent member positioned between the topsheet and the backsheet.

The absorbent member has a deposition region which comprises a storage zone of a relatively high density and high basis weight to absorb and retain liquids acquired by the absorbent member and an acquisition zone of a relatively lower average density and lower average basis weight than the storage ~3t~440 zone to quickly acquire and temporarily hold discharged liquids.
The absorbent member also comprises a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material .

In accordance with one aspect of the present invention, the acquisition zone is positioned toward the front of the absorbent member so that the acquisition zone may be positloned in the area of typical llquid deposition. The acquisition zone is also sized so that the top surface area of the acquisition zone comprises less than about 50% of the top surface area of the front section of the absorbent member.

I n accordance with another aspect of the present invention, the ratio of the average density of the storage zone to the average density of the acquisitlon zone is preferably about equal to or greater than 1 . 25: l, and most preferably about equal to or greater than 2 :1 . The acquisition zone preferably has a density of from about 0.07 to about 0.15 g/cm; the acquisitlon zone also preferably having a uniform density and uniform basis weight throughout .

I n a preferred embodiment of the present invention, a relatively high gel strength absorbent gelling material is mixed with hydrophilic fibrous material to not only minimize gel blocking but also to help maintaln an open capillary structure within the absorbent member to enhance planar transport of liquids away from the area of typical liquid deposition to the rest of the absorbent member. The mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material preferably have a fiber-to-particulate weight ratio of from about 40:60 to about 98:2, more preferably about 50:50 to about 91:9.
.

The present invention also relates to dual-layer absorbent cores of the type having an absorbent acquisition core which consists essentially of hydrophilic fibrous material and an absorbent member which consists of a mixture of hydrophilic ~3~144() fibrous material and discrete particles of absorbent gelling material. The absorbent member has a top surface area which is from about 0 . 25 to about 1 . 0 times the top surface area of the absorbent acquisition core. The absorhent member is further positioned relative to the backsheet of the absorbent article in which its positloned such that at least about 75~ of the absorbent gelling material is found within the front two-thirds portion of the absorbent article. The acquisition zone of the absorbent member is also positioned relative to the backsheet such that it is completely positloned within the front two-thirds portion of the absorbent article.

DETAILED DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims which particularly point out and distinctly claim the subject matter regarded as forming the present invention, it is believed the invention will be better understood from the following descriptlon taken in conjunctlon with the accompanying drawings in which:

Figure 1 is a plan view of a disposable diaper embodiment of the present invention wherein most of the topsheet has been cut-away to more clearly show the underlying absorbent member of the diaper;

Figure 2 is a longitudinal sectional view of only the absorbent member of the disposable diaper taken along sectional line 2-2 of Figure 1;

Figure 3 is a transverse sectlonal view of only the absorbent member of the disposable diaper taken along sectlonal line 3-3 of Figure 1;

Figure 4 is a perspective view of the absorbent member of the disposable diaper shown in Figure 1;

13(;~40 Figure 5 is a perspective view of an alternative embodiment of the absorbent member of the present invention;

Figure 6 is a perspective view of a dual-layer absorbent core having a further alternative embodiment of the absorbent member of the present invention:

Figure 7 is a sectional view of the dual-layer absorbent core of Figure 6 taken along sectional line 7-7 of Figure 6; and Figure 8 is a plan view of a still further alternative embodiment of the absorbent member of the present invention.

DETAILED DESCRIPTION OF THE IN`~ENTION

The absorbent members of the present invention will be described herein in relationship to their use in disposable absorbent articles; however, it should be understood that the potential application of the absorbent members of the present inventlon should not be limited to disposable absorbent articles.
As used herein, the term "disposable absorbent article" refers to articles which absorb and contain body exudates and more specifically refers to articles which are placed against or in proxlmity to the body of the wearer to absorb and contain the varlous exudates discharged from the body, and which are intended to be discarded after a single use (i.e., they are not intended to be laundered or otherwise restored or reused). A
preferred embodiment of a disposable absorbent article, diaper 20, is shown in Figure 1. As used herein, the term "diaper" refers to a garment generally worn by infants and incontinent persons that is worn about the lower torso of the wearer. It should be understood, however, that the present invention is also applicable to other disposable absorbent articles such as incontlnent briefs, sanitary napkins, and the like.

~3(~44D
~ 7 i-igure 1 is a plan view of the diaper 20 of the present invention in its flat-out uncontracted state (i.e. with all elastic ,~duced contractlon removed) with portions of the structure being cut-away to more clearly show the construction of the diaper 20 and with the portion of the diaper 20 which contacts the wearer facing the viewer. The diaper 20 is shown in i Igure 1 to have a front waistband region 22 a back waistband region 24 a crotch region 26 and a periphery 28 which is deflned by the outer edges of the diaper in which the longitudinal edges are designated 30 and the end edges are designated 32. The diaper additionally has a transverse centerline which is designated 34 and a Iongitudinal centerline which is designated 36.

The diaper 20 comprises a liquid pervious topsheet 38: a liquid impervious backsheet 40; an absorbent member 42; and elastic members 44. While the topsheet 38 the backsheet 40 the absorbent member 42 and the elastic members 44 may be assembled in a variety of well known configurations a preferred diaper configuration is described generally in U . S. Patent 3 8~0 003 entitled Contractable Side Portions for Disposable Diaper which issued to K. B. Buell on January 14 1975.

Figure 1 shows a preferred embodiment of the diaper 20 in which the topsheet 38 and the backsheet 40 are co-extensive and have length and wldth dlmenslons generally larger than those of the absorbent member 42. The topsheet 38 is associated with and superlmposed on the backsheet 40 thereby formlng the periphery 28 of the dlaper 20. The periphery ~8 defines the outer perlmeter or the edges of the diaper 20. The perlphery 28 comprises the end edges 32 and longltudlnal edges 30.

The diaper 20 has front and back waistband regions 22 and 24 respectlvely extending from the end edges 32 of the dlaper periphery 28 toward the transverse centerline 34 of the dlaper a distance from about 2~ t~ about 10~ preferably about 5~ of the length of the diaper 20. The waistband regions comprise those ' , ~`'' : , 13(~4~) upper portions of the diaper 20, which when worn, encircle the waist of the wearer. The crotch region 26 is that portlon of the diaper 20 between the waistband regions 22 and 24, and comprises that portion of the diaper 20 which, when worn, is positioned between the legs of the wearer and covers the lower torso of the wearer. Thus, the crotch region 26 defines the area of typical liquid deposition for a diaper 20 or other disposable absorbent article .

The topsheet 38 is compliant, soft feeling, and non-lrritating to the wearer s skin. Further, the topsheet 38 is liquld perv7Ous permitting liquids to readily penetrate through its thickness. A
suitable topsheet 38 may be manufactured from a wide range of materials, such as porous foams, reticulated foams, apertured plastic films, natural fibers (e.g., wood or cotton fibersi, synthetic fibers (e.g., polyester or polypropylene fibers) or from a combinatlon of natural and synthetic fibers. Preferably, the topsheet 38 is made of a hydrophobic material to isolate the wearer s skin from liquids in the absorbent member 42.

A particularly preferred topsheet 38 comprises staple length polypropylene fibers having a denier of about 1. 5 . such as Hercules* type 151 polypropylene marketed by Hercules, Inc. of Wilmington, Delaware. As used herein, the term staple length flbers refers to those flbers havlng a length of at least about 15.9 mm (0.62 Inches).

There are a number of manufacturing techniques which may ~;e used to manufacture the topsheet 38. For example, the topsheet 38 may be woven, non-woven, spunbonded, carded, or the llke. A preferred topsheet Is carded, and thermally bonded by means well known to those skilled In the fabrics art.
Preferably, the topsheet 38 has a welght from about 18 to about 25 grams per square meter, a minimum dry tensile strength of at least about 400 grams per centimeter In the machine direction and a wet tenslle strength of at least about 55 grams per centimeter in the cross machine dlrection.

*Trade mark " ~ ~ . .

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~3~14~0 The backsheet 40 is impervious to liquids and is preferably manufactured from a thin plastic film although other flexible liquid impervious materials may also be used. The backsheet 40 prevents the exudates absorbed and contained in the absorbent member 42 from wetting articles which contact the diaper 20 such as bed sheets and undergarments. Preferably the backsheet 40 is polyethylene film having a thickness of from about 0.012 mm (0.5 mil) to about 0.051 centimeters (2.0 mils) although other flexible liquid impervious materials may be used. As used herein the term flexible refers to materials which are compliant and which will readily conform to the general shape and contours of the wearer s body.

A suitable polyethylene film is manufactured by Monsanto Chemical Corporation and marketed in the trade as Film No. 8020.
The backsheet 40 is preferably embossed and/or matte finished to provide a more clothlike appearance. Further the backsheet 40 may permit vapors to escape from the absorbent member 42 while still preventing exudates from passing through the backsheet 40.

The size of the backsheet 40 is dictated by the size of the absorbent member 42 and the exact diaper design selected . I n a preferred embodiment the backsheet 40 has a modified hourglass-shape extending beyond the absorbent member 42 a minimum distance of at least about 1.3 centimeters to about 2.5 centimeters (about 0.5 to about 1.0 inch) around the entire diaper periphery 28.
The topsheet 38 and the backsheet 40 are associated together in any suitable manner. As used herein the term associated encompasses configurations whereby the topsheet 38 is directly joined to the backsheet 40 by affixing the topsheet 38 directly to 3!~ the backsheet 40 and configurations whereby the topsheet 38 is indirectly joined to the backsheet 40 by affixing the topsheet 38 to intermediate members which in turn are affixed to the backsheet 40. In a preferred embodiment the topsheet 38 and the backsheet 40 are affi>ced directly to each other in the diaper ~3~ 0 periphery 28 by attachment means (not shown) such as an adhesive or any other attachment means as known in the art.
For - example, a unitorm continuous layer of adhesive, a patterned layer of adhesive, or an array of separate lines or spots of adhesive may be used to affix the topsheet 38 to the backsheet 40.

Tape tab fasteners 46 are typically applied to the back waistband region 24 of the diaper 20 to provide a fastening means for holding the diaper on the wearer. Only one of the tape tab fasteners is shown in Figure 1. The tape tab fasteners 46 can be any of those well known in the art, such as the fastening tape disclosed in U.S. Patent 3,848,594 issued to K. B. Buell on November 19, 1974. These tape tab fasteners 46 or other diaper fastening means, such as pins, are typically applied near the corners of the diaper 20.

The elastic members 44 are disposed adjacent the periphery 28 of the diaper 20, preferably along each longitudinal edge 30 so that the elastic members 44 tend to draw and hold the diaper 20 against the legs of the wearer. Alternatively, the elastic members 44 may be disposed adjacent either or both of the end edges 32 of the diaper 20 to provide a waistband as well as or rather than leg cuffs. For example, a suitable waistband is disclosed in U.S. Patent 4,515,595 issued to David J.
Kievit and Thomas F. Osterhage on May 7, 1985. In addition, a method and apparatus suitable for manufacturing a disposable diaper having elastically contractlble elastic members is described in U.S. Patent 4,081,~01 entitled "Method and Apparatus for Continuously Attaching I)lscrete, Stretched Elastic Strands to Predeterm~ned Isolated Portions of D7sposable Absorbent Products" which issued to K. B.
Buell on March 28, 1978.

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13~14~) l1 The elastic members 44 are secured to the diaper 20 in an elastically contractible conditlon so that in a normally unrestrained configurat~on, the elastic members 44 effectively contract or gather the diaper 20. The elastic members 44 can be secured in an elastically contractible condition in at least two ways. For example, the elastic members 44 may be stretched and secured while the diaper 20 is in an uncontracted conditlon.
Alternatively, the diaper 20 may be contracted, for example, by pleating, and the elastlc members 44 secured and connected to the diaper 20 while the elastic members 44 are in their unrelaxed or unstretched condition.

In the embodiment illustrated in Figure 1, the elastic members 44 extend essentially the entire length of the diaper 20 in the crotch region 26. Alternatively the elastic members 44 may extend the entire length of the diaper 20, or any other length suitable to provide elastically contractable line. The length of the elastic members 44 is dictated by the diapers' design.

The elastic members 44 may take a multitude of configurations. For example, the width of the elastic members 44 may be varied from about .25 millimeters (0.01 inches~ to about 25 millimeters (1.0 inch) or more; the elastic members 44 may comprise a single strand of elastic material or may comprise several parallel or non-parallel strands of elastic material; or the elastic members 44 may be rectangular or curvilinear. Still further, the elastic members 44 may be affixed to the diaper in any of several ways which are known in the art. For example, the elastic members 44 may be ultrasonically bonded, heat and pressure sealed into the diaper 20 using a variety of bonding patterns or the elastic members 44 may simply be glued to the diaper 20.

The absorbent member 42 is positioned between the topsheet 38 and the backsheet 40 to form the diaper 20. The absorbent member 42 is generally compressible, conformable, non-irritating to the wearer's skin, and capable of absorbing and retaining 13~40 l2 liquids and certain body exudates. It should be understood that for purposes of this invention that an absorbent member is not necessarily llmited to a single layer or sheet of material. Thus, the absorbent member 42 may actually comprise laminates or combinations of several sheets or webs of the requisite types of materials as hereinafter described. Thus as used herein, the term "member" includes the term "members" or "layers" or " layered . "

Figure 4 is a perspective view of a preferred embodiment of the absorbent member 42 of the present invention. The absorbent member 42 is shown in Figure 4 to comprise a back section 48 and a front section 50. The front section 50 is shown to have an end region 52 and a deposition region 54. The deposition region 54 comprises an acquisitlon zone 56 (shown by the dotted lines~ and a storage zone 58. Further, the front section 50 is transversely divided into three regions comprising two transversely spaced ear regions 60 and 62 respectively, and a central region 64. The absorbent member 42 additionally has a transverse centerline which is designated 66 and a longitudinal centerline which~,~is designated 68.

The absorbent member 42 has a back section 48 and a front section 50 that is cont7guous with the back section 48. The back sectlon 48 and the front sectlon 50 of the absorbent member 42 extend respectlvely from the end edges 70 of the absorbent member 42 toward the transverse centerline 66, the front portion 50 extending a dlstance from about one half to about three-fourths, preferably about two-thirds, of the length of the absorbent member 42. The front section 50 is preferably greater than one half of the total length of the absorbent member 42 so that it will encompass all of the area of typical liquid deposition of an absorbent member 42 when it is placed in a diaper or other absorbent article.

The tront portion 50 has an end region 52 and a depositlon region 54. The end reglon 52 comprises that portion of the front 13(~440 section 50 extending from the respective end edge 70 of the absorbent member 42 toward the transverse centerline 66 a distance from about 2% to about 10~, preferably about 5~, of the length of the absorbent member 42. I he deposition region 54 comprises that portion of the front portion 50 that is contiguous with and positioned between the end region 52 and the back section 48 and encompasses the area of typical liquid deposition of the absorbent member 42.

The front portion 50 further has two transversely spaced ear regions 60 and 62 respectively, and a central region 64 disposed intermediate said ear regions 60 and 62. The ear regions 60 and 62 comprise those portions which generally extend from the longitudinal edges 30 of the periphery 28 toward the longitudinal centerline a distance from about one-tenth to about one-third of the width of the absorbent member 42. Thus, the ear regions 60 and 62 are those portions that engage the side marginal portions of the wearer s waist and torso, whereas the central region 64 engages the medial portion of the wearer s waist and torso. The central region thus defines the transverse area of typical liquid deposition.

The absorbent member 42 may be manufactured in a wide variety of sizes and shapes (e.g., rectangular, hourglass, asymmetrical, etc. ~ and from a wide variety of materials. The total absorbent capacity of the absorbent member 42 should, however, be compatible with the design liquid loading for the intended use of the absorbent article or diaper. Further, the size and absorbent capacity of the absorbent member 42 may be varied to accommodate wearers ranging from infants through adults. The absorbent member 42 preferably comprises a mixture of hydrophilic fibrous material and particular amounts of discrete particles of absorbent gelling material.

Various types of hydrophilic fibrous material can be used in the absorbent member 42. Any type of hydrophilic fibrous material which is suitable for use in conventional absorbent 1301~40 products are suitable for use in the absorbent member 42 of the present invention. Specif7c examples of such hydrophilic fibrous material include cellulose fibers, rayon, and polyester fibers.
Other examples of suitable hydrophilic fibrous materials include hydrophilized hydrophobic fibers, such as surfactant-treated or silica-treated thermoplastic fibers. For reasons of availability and cost, cellulose fibers, in particular wood pulp fibers which are also referred to as airfelt, are preferred.

As used herein, the term hydrophilic describes fibers or the surfaces of fibers which are wetted by the liquids deposited onto the fibers. The state of the art respecting wetting of materials allows definition of hydrophilTcity (and wetting) in terms of contact angles and the surface tension of the liquids and solids invovled. This is dlscussed 7n detail in The American Chemical Society publication entitled Contact Angle, Wetability, and Adhesion edited by Robert F. Gould and copyrighted in 1964. A
fiber or surface of a fiber is said to be wetted by a liquid either when the contact angle between the liquid and the f7ber or surface is less than 90 or when the fluid will tend to spread spontaneously across the surface; both conditions normally coexist.

In additlon to hydrophilic fibrous material, the absorbent member 42 also contains particular amounts of discrete particles of absorbent gelling material. Such absorbent gelling material may be inorganic or organic compounds capable of absorbing liquids and retaining them under moderate pressures.

Suitable absorbent gelling materials can be inorganic materials such as silica gels or organic compounds such as cross-linked polymers. Cross-linking may be by covalent, ionic, van der Waals, or hydrogen bonding. Examples of absorbent gelling material polymers include polyacrylamldes, polyvinyl alcohol, ethylene maleic anhydride copolymers, polyvinyl ethers, hydroxypropyl cellulose, carboxymethyl cellulose, polyvinylmorpholinone, polymers and copolymers of vinyl sulfonic :~ :

i 3~1440 acid, polyacrylates, polyacrylamides, polyvinyl pyridine and the like. Other suitable hydrogels are disclosed in Assarson et al., U.S. Patent 3,901,236 issued August 26, 1975.
Particularly preferred polymers for use in the absorbent member are hydrolized, acrylonitrile grafted starch, acrylic acid grafted starch, polyacrylates and isobutylene maleic anhydride copolymers, or mixtures thereof.

Processes for preparing hydrogels are disclosed in Alasuda et al., U.S. Patent 4,076,663, issued February 28, 1978;
Tsubakimoto et al. U.5. Patent 4,286,082, issued August 25, 1981 and further In U.S. Patents 3,734,876, 3,661,815, 3,670,731, 3,664,343, 3,783,871 and Belgium Patent 785,850.

Absorbent gelling material used in the absorbent member 42 is in the form of discrete particles . Particles of absorbent gelling material can be of any desired shape, e.g., spiral or semi-spiral, cubic, rod-like, polyhedral, etc. Shapes having a large greatest dimension/smallest dimension ratio, like needles, flakes, and fibers, are also contemplated for use herein.
Conglomerates of partTcles of absorbent gelling material may also be used In the absorbent member 42.

Although the absorbent gelling material-containing absorbent member ,s expected to perform well with particles having a size varying over a wide range, other considerations may preclude the u~e of very small or very large partlcles, For reasons of industrial hyglene, average parttcle slzes smaller than about 30 microns are less desirable, Particles having a smallest dimension larger than about 2 millimeters may also cause a feellng of grittiness in the absorbent member, which Is undesirable from a consumer aesthetlcs standpoint. Furthermore, the rate of fluid absorption is affected by particle size. Larger particles have very much reduced rates of absorption. Preferred for use herein are particles having an average size of from about 50 microns to ~, .4. ~

13(~

about 1 millimeter. "Particle size" as used herein means the weighted average of the smallest dimension of the individuat particles .

Although most absorbent gelling materials will perform well in the absorbent member 42 of the present invention, absorbent gelling materials having high gel strength are particularly useful.
Gel strength must be such that the particles of absorbent gelling material do not deform and fill to an unacceptable degree the capillary void space in the absorbent member 42, thereby inhibitlng both absorbent capacity of the structure and fluid distribution throughout the structure.

Gel strength refers to the tendency of the particles of absorbent gelling material to deform or spread under stress once the particles absorb liquids. For a given type of absorbent gelling material, gel strength will generally decrease as the gel volume increases. It has been found that it is desirable to utilize an absorbent member 42 whose polymer materials have as high a gel strength as possible consistent with the realization of absorbent gelling materials of acceptably high gel volume.

It has been found that gel strength, i.e. gel deformation tendency, (in the context of absorbent gelling materials incorporated into absorbent members and absorbent articles) correlates directly with the shear modulus of the absorbent gelling material. Accordingly, polymer materials of absorbent gelling material having sufficient gel strength can be appropriately characterized by specifying gel strength in terms of the shear modulus of the particles of absorbent gelling material.

Shear modulus can be conventlonally measured, for example, by a procedure which involves the use of a stress rheometer to determine the ratio of (a) stress applied to a given sample versus (b) the resulting strain exhibited by the sample. The absorbent gelling material sample tested in this manner is swollen to its gel volume with synthetic urine. Using a procedure described in greater detail hereinafter, the stress/strain ratio is determined.
The shear modulus of the resulting sample in dynes/cm2 is then subsequently calculated from this ratlo. Absorbent gelling materials which have been found to be particularly useful in the present invention exhibit a shear modulus of at least about 2,000 dynes/cm2. More preferably, the absorbent gelling materials have a shear modulus within the range of about 2500 to about 92000 dynes/cm2 and most preferably of from about 5,000 to about 35, 000 dy nes I cm2 .

Without wishing to be bound by any particular theory, it is believed that absorbent gelling materials having high gel strength as reflected in their shear modulus values will resist deformation upon fluid absorption and will have a reduced tendency to flow into the void spaces between fibers. Thus, high gel strength absorbent gelling materials may actually serve to maintain separation of the individual fibers of the hydrophilic fibrous material. Such fiber separation improves both the wicking and the absorbent capacity of such absorbent members. Low gel strength materials, on the other hand, merely flow into the void spaces between the fibers upon fluid absorption and can thereby actually reduce the acquisition rate and the absorbent capacity of the absorbent members and absorbent articles 7nto which they are incorporated .

Gel strength of absorbent gelling materials is quantified by ;~5 means of determining the shear modulus of a sample of the swollen particles. Shear modulus is determined using a stress rheometer which comprises a circular lower plate onto which the swollen particle sample is placed. A truncated conical upper element havlng the same projected surface area as the area of the lower circular plate is positioned above the circular lower plate. This upper element is lowered into the mass of swollen particle material on the circular lower plate and is positioned at the proper gap relative to the circular lower plate. This gap corresponds to the point at which an untruncated cone would contact the lower plate.

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~3~4~) An oscillating torque (stress) is applied torsionally to the conical eiement, and the resulting angular displacement of the cone is determined as a function of the applied torque.

The sample being tested is swollen to its gel volume in synthetic urine. Synthetlc Urine is typically 15.0 parts of 1%
Triton X-100, 60.0 parts of NaCI, 1.8 parts of CaC12 2H2O, and 3 . 6 parts of MgCL2 6H2O, diluted to 6000 parts with distilled H2O. The resulting solution has an absorbence of about 0.25 at its absorbence maximum of 617 mm.

Excess free synthetic urine is removed from the sample by blotting, and approximately 1.5 cc of the swollen material is placed in the gap between the lower circular plate and the upper conical element of the rheometer. This mass is usually formed from an agglomeration of swollen particles which have unswollen particle dtmensions less than 710 microns. Spherical particles should be ground to form irregular shaped particles before testing .

Stress and strain measurements are taken under the fol lowîng condîtions:

Parameter Value Type of Rheometer Sangamo Vlsco-elastic Analyzer Configuration Oscillating Cone and Plate Plate Radius 2 . 5 cm Cone Radius (Edge to vertex) 2.5 cm Cone Angle * 43.6 milliradians Oscillation Frequency 1 . 0 Hertz Strain Amplitude 2 . 5%
~ample Temperature 21 . 4C

* Angle between surface of the lower plate and the surface of the cone i.e. (Pi/2 - semi-vertical angle).

~3~144~) Under these conditions, an oscillatory torque (stress) is applied via the upper conical element to the swollen particles.
This results in an oscillatory response (strain) of the sample which is reflected by the magnitude of the angle through which the conical element rotates in response to the applied torque.
The shear modulus of the particles is calculated from the ratio of (i) the applied stress to (ii) the amplitude of the in-phase component of the resultant strain.

For the particular cone/plate geometry employed in this testing, the ratio of stress (g-cm) to strain (milliradians) is converted to shear modulus (dynes/cm2) using the following tormu la:

Shear Modulus =
3 x 981 x Cone Angle x CoslPhase Angle) x Torque 2 x Pi x Plate Radius3 x Strain wherein the cone angle and strain are expressed in units of milliradians, the plate radius in units of cm and torque in units of g-cm. For absorbent gelling materials, the phase angle is close to zero and so the cosine of the phase angle is taken as :~o unity. The factor 981 is that which converts g-cm to dyne-cm.
Thus Shear Modulus (dynes/cm2 ) =
1308 x Torque (gm-cm) Strain (milliradians) for the partlcular equipment used in this test method.

The relative amount of hydrophilic fibrous material and particles of absorbent gelling material used in the absorbent member 42 of the present invention can be most conveniently expressed in terms of a weight percentage of the absorbent member 42. The absorbent member 42 preferably contains from about 29~ to about 60%, more preferably from about 10~ to about 25% by welght, of the absorbent member 42 of absorbent gelling material. This concentration of absorbent gelling material can also be expressed in terms of a weight ratio of fiber to ~3al~0 particulate. These ratios may range from about 40:60 to about 98:2. For most commercially available absorbent gelling materials, the optimum fiber-to-particulate weight ratio is in the range of from about 50:50 to about 91 :9. Based on a cost/performance analysis, ratlos of from about 75: 25 to about 90: 10 are most preferred for use in the absorbent member 42.

In addition, the particles of absorbent gelling material may be dispersed in various weight ratios throughout different regions and thicknesses of the absorbent member 42.

For example, the mixture of hydrophilic fibrous material and particles of absorbent gelling material may be disposed only in the deposition region 54 of the absorbent member 42 and not in the back section 48 or the end region 52. In addition, the acquisition zone 56 need not comprise the fiber/particulate mixture. While an acquisition zone 56 containing only hydrophilic fibrous material may work satisfactorily in rapidly acquiring liquids, such an embodiment is not preferred. When particles of an absorbent gelling material are maintained in the acquisition zone 56, especially high gel strength absorbent gelling materials, the partlcles help maintain an open capillary structure when the acquisition zone 56 is wetted so as to enhance planar transport of liquids away from the acquisition zone 56 to the rest of the absorbent member 42. Thus, the acquisition zone 56 preferably contains a uniformlly distributed mixture of hydrophilic fibrous materlal and discrete particles of absorbent gelling material. It is most preferred that the particles are substantlally uniformly dispersed throughout the entire absorbent member 42.

The deposition region 54 comprises an acquisitlon zone 56 and a storage zone 58 In fluid communication with at least a portion of the acquisitlon zone 56. The acquisitlon zone 56 comprises portions of the deposition region 54 designated by the dotted lines in Figure 4. The storage zone 58 generally comprises the remainder of the deposition region 54 and more preferably the remainder of the absorbent member 42.

~30:14~0 It has been found that a relative capillarity difference between the acquisition zone 56 and the storage zone 58 T5 of ~portance Tn the overal I efficiency and effectTveness of the absorbent member 42. While liciuid capillarTty can be defTned Tn several ways (e.g ., pore size, density, basis weight, etc. ), the density and basTs weight of the structure are the preferred parameters to defTne ITquid capillarity in the absorbent member 42 of the present TnventTon. Thus, the acquisition zone 56 must have both a relatlvely lower average density and lower average basis weight per unit area than the storage zone 58 to establish the preferred capillary force gradient between them. Thus, the ratio of the average density of the storage zone 58 to the average density of the acquisitlon zone 56 should preferably be about equal to or greater than about 1.25:1, more preferably about L~ 1 . 5 :1 and most preferably about 2 ~

Without wishing to be bound by theory, it is believed that the dlfferentTal lower capillarity, the lower average density and lower average basis weight, of the acquisition zone 56 in comparison to the storage zone 58 7s slgnificant in achieving both a more optimized ITquld acquTsltTon rate Tnto the absorbent member 42 and a relatively hlgh ITquid planar wTckTng rate throughout the absorbent member 42. When an absorbent member 42 having a mixture of hydrophTlTc fTbrous material and particles of absorbent gelllng materTal is denslfied to the densitles approximating those ;~5 of the storage zone 58, the ITquTd planar wTckTng rate becomes much faster. It T5 belTeved that densTfying the absorbent member 4~ results Tn better planar wTckTng of ITquTd throughout the ~bsorbent member 42 (the x-y direction) because of the higher capillary force due to the smaller pore size of the densifTed fTbers. DensifyTng the absorbent member 42 further results in a reductlon Tn the bulk of the structure (which is desTrable from a consumer standpoint for aesthetic reasons).

However, the densTfTcation of the absorbent member 42 also results in a reduction in the rate ot ITquid acquisTtTon Tnto the absorbent member 42 In the dlrection normal to planar wTckTng ~:' :;
: :' . ~., ~3~ 40 (i.e. the z-direction). It is believed that as higher concentratlons of absorbent gelling material are located in the area of typical liquid deposition, a maximum gel blocking effect is achieved, thereby reducing the liquid acquisition rate. Thus, it is important to provide a means for dellvering the liquid into the absorbent member 42 at a high rate. The acquisition zone 56 of lower average density and lower average basis weight per unit area than the densified absorbent member 42 or storage zone 58 provides such a means. The acquisition zone 56 has a smaller concentration of particles of absorbent gelling material in the area of typical liquid deposition, thereby reducing the incidence of gel blocking in this area during the liquid acquisition phase and thus improving the liquid acquisition rate.

The capillary force gradient created at the interface between the acquisitlon zone 56 and the storage area 58 also improves the containment characteristics of the absorbent member 42. Liquids deposited on the acquisition zone 56 tend to be acquired quickly into structure by the action of the acquisitlon zone 56. Because the storage zone 58 has a higher capillarity than the acquisition zone 56, the acquired liquids tend to be drawn into the storage zone 58 and are then del ivered to the other portions of the storage zone 58 by the enhanced planar wicking rate achieved in the storage zone 58; the liquids being retained even under moderate pressure by the particles of absorbent gelling material in the storage zone 58. Thus, it has been found that an absorbent member 42 having an acquisition zone 56 having a lower average density and lower average basis weight per unit area than the storage zone 58 improves leakage containment by more quickly acquiring and distributing liquids into and throughout the absorbent member 42.

In addition, it is believed that the acquisition zone 56 provides an additional mechanism whereby an absorbent member 4~
that has already been wetted may contain and more readily acquire further discharged liquids. A property of the particles of absorbent gelling material is that they expand when wetted.

~30~440 Thus when the absorbent member 42 is wetted the particles of absorbent gelllng material in both the acqulsitlon zone 56 and the S~orage zone 58 expand. However because there is a greater concentration of particles of absorbent gelling material in the higher average density and higher average basis weight storage zone 58 the storage zone 58 tends to expand to a greater thickness than the acquisition zone 56. Thus If the acquisitlon zone 56 is surrounded by the storage zone 58 a well or hole effect is created . Th is wel l is advantageous for second depositions of liquids because the liquids will tend to be drawn into the well because it is In effect a zero density acquisition area. This is especially helpful in the case of diapers for overnight use wherein the wearer sleeps on the stomach because gravity additionally tends to pull the later discharged liqulds into the well whereupon they distribute Into the acquisition zone 56 and are wicked into the storage zone 58. Thus the acquisit~on zone 56 provides an additional advantage for wetted absorbent members .

The storage zone 58 is thus the relatively high capillarity high density and high basis weight) portion of at least the deposition region 54. The primary functions of the storage zone 58 are to absorb discharged liquids that are either deposited dlrectly onto the storage zone 58 or transferred to the storage zone 58 via the caplllary force gradients established between the acqulsit~on zone 56 anci the storage zone 58 and to reta~n such iiqulds under the pressures encountered as a result of the w~arer s movements. Preferably the storage zone 58 consists essentially of the structure disclosed in U.S. Patent 4,610,678 and the lower fluid storage layer disclosed in U.S. Patent 4,673,402, although other high capillarity structures may also be used.

The storage zone 58 preferably has a relatively high density and a high basis weight in relation to the acquisition zone 56.
The density and basis weight values of the storage zone 58 :'' ~,:
,~
; , 4~

include the weight of the particles of absorbent gelling material, such that the density and basis weight values will vary depending upon the amount of particles dispersed throughout the absorbent member 42. Thus, the storage zone 58 will generally have a density of from about 0.06 to about 0.4 g/cm3, and more preferably within the range of from about 0.09 to about 0.20 g/cm3 for an absorbent member 42 containing about 15% by weight of particles of absorbent gelling material. The basis weight of such a storage zone 58 can range from about 0.02 to about 0.186 g/cm preferably from about 0.038 to about 0.12 g/cm2. For an absorbent member 42 containing about 50% by weight of particles of absorbent gelling material, the density will typically range from about 0.1 to about 0.68 g/cm3 with a basis weight from about 0.034 to about 0.31 g/cm2. The density of the storage zone 58 is calculated from its basis weight and caliper measured on newly unpacked, unfolded and dissected diapers. The caliper is measured using a standard guage with the sample under a "aentle" load of 10 g/cm2. The basis weight is measured by die-cutting a certain size sample and weighing the sample on a standard scale, the weight and area of the sample determining the basis weight. ( It should be noted that the density and basis weight values include the weight of the particles of absorbent gelling material. ) While the storage zone 58 may take on a number of sizes and shapes, it is preferred that the storage zone 58 comprises the portion of at least the deposition region 54 wherein there is no acquisition zone 56. (i.e. The entire deposttion region 54 comprises a storage zone 58 except for the acquisition zone 56. ) While the back section 48 and the end region 52 need not comprise storage zones, in the partlcularly preferred embodiments of the absorbent member 42 as shown in Figures 2, 3 and 4, the entire absorbent member 42 except for the acquisitlon zone 56 consists of one or more storage zones 58. In addition, while the storage zone 58 need not completely surround the acquisition zone 56 (i.e. it is in liquid communication with at least a portion of the acquisitlon zone 56), in preferred embodiments of the present 13(:)'14~0 invention, the storage zone 58 surrounds the acquisition zone 56 so as to take full advantage of the capillarity difference between them .

The acquisition zone 56 has a relatively lower capillarity and thus preferably a lower average density and a lower average basis weight per unit area than the storage zone 58. The acquisitlon zone 56 serves to quickly collect and temporarlly hold discharged liquids. Since such liquids are generally discharged In gushes, the acquisition zone 56 must be able to quickly acquire and transport liquid by wicking from the point of liquid contact to other parts of the absorbent member 42. The acquisitlon zone 56 preferably has a density of from about 0 . 03 to 0. 24 g/cm3, more preferably from about 0.05 to about 0.15 g/cm3 for an absorbent member 42 containing about 15~ by weight of particles of absorbent gelling material. The basis weight of such an acquisition zone 56 will preferably range from about 0. 015 to about 0.1 g/cm2 and more preferably from about .018 to about .06 g/cm2. For an absorbent member 42 containing about 5096 by weight of particles of absorbent gelling material, the density will typically range from about .05 to about .41 g/cm3 with a basis weight of from about 0.025 to about 0.17 g/cm2. The density of the acquisition zone 56 is calculated from its basis weight and caliper measured on newly unpacked, unfolded and dissected diapers. The caliper is measured using a standard guage with the sample under a "gentle" load of 10 g/cm2. The basis weight is measured by die-cutting a certain size sample and weighing the sample on a standard scale, the weight and area of the sample determining the basis weight. (The density and basis weight values include the weight of the particles of absorbent gelling 3(~ material. ~

While the acquisition zone 56 may conceivably have density and basis weight values equal to zero, i.e. a hole or void space, such an embodiment is not as preferred as an acquisitlon zone 56 having some minlmal value of density and basis weight. The transfer of liquids through the topsheet 38 has been found to be 13~1~40 diminished in an absorbent member 42 having an acquisition zone 56 of zero density and basis weight due to the lack of intimate contact between any fibers of the acquisition zone 56 and the topsheet 38. Thus, liquid may tend to pool or collect on the topsheet 38 thereby creating a wet feeling for the wearer. Thus, it is preferred that the acquisition zone 56 have some minimum density and basis weight.

While the density and basis weight of the acquisition zone 56 may vary throughout its area and thickness, such an embodiment is also not preferred. The acquisition zone 56 preferably has a substantially unlform density and uniform basis weight throughout its area and thickness. This uniform density and basis weight provides a uniform capillary force gradient across the interface between the acquisitlon zone 56 and the storage zone 58 that provides even liquid transfer.

The shape, size and positioning of the acquisitlon zone 56 is of importance in determining the effectiveness of the resulting absorbent member 42 in rapidly acquiring discharged liquids. In accordance with the present invention, the acquisition zone 56 should be placed in a specific positional relationship with respect to the area of typical liquid deposition of the absorbent member 42. While portlons of the acquisition zone 56 may be positioned in the back section 48 of the absorbent member 42, the acquisition zone 56 is preferably positloned generally in the front section 50 of the absorbent member 42 so that the acquisition zone 56 is positioned in the area of typical liquid deposition, i.e. the depositlon region 54. Thus, the acquisition zone 56 is placed in the vicinity of the point of discharge of liquids so as to be capable of quickly acquiring such llquids at their contact zone.

The generally forward positioning of the acquisition zone 56 can be defined by specifying the percentage of the top surface area of the acquisition zone 56 which is found forward of particular points along the length of the absorbent member 42.
While the positioning of the acquisition zone 56 can alternatively ~3C~1440 be defined with respect to the volume of the acquisition zone positioned forward of particular points it has been found that the top surface area of the acquisition zone 56 is a more desirable definition because the top surface area actually defines the initial area avallable for liquid acquisition. In addition slnce the thickness of the absorbent member 42 is preferably uniform in the deposition region 54 and the acquisition zone 56 has a generally rectangular cross-sectional area the top surface area definition is equal to a volumetric definitlon in a preferred embodiment.
Thus the posit~oning of the acquisitlon zone 56 will be referenced throughout the specltication as related to its top surface area.
~ i . e . The percentage of the top surface area of the acquisition zone positioned in a given area. ) Thus in accordance with the present invention at least a portlon of the acquisition zone 56 must be placed in the deposition region 54 even though the remaining portlon may be positioned anywhere in the absorbent member 42 including the back section 48 and the end regions 52. ~ It being understood that if plural acquisition zones are utilized at least a portion of one of the acquisition zones must be positloned in the depositlon region 54. ) However the acquisition zone 56 is preferably positioned relat7ve to the absorbent member 42 such that the top surface area of the acqulsltion zone 56 is completely positioned within the front sectlon S0 of the absorbent member 42. More preferably the acquisition zone 56 Is positioned relative to the absorbent member 42 such that the top surface area of the acquisition zone 56 is completely positioned within the deposition region 54 of the absorbent member 42. Even more preferably at least 30% of the top surface area of the acquisition zone 56 is positioned in the front half of the front section (approximately the front 1 /3 of the overall absorbent member 42) of the absorbent member 42.

The forward positioning of the acquisition zone 56 may alternatively be defined by speclfying the percentage of the top sur-ace area of the acquisitlon zone 56 that is found forward of , ~;
. .
:

~3~ L44~

particular points along the length of the diaper 20 or other absorbent article. Thus, the acquisition zone 56 is preferably positioned on the absorbent member 42 relative to the backsheet 40 such that at least a portion of the top surface area of the acquisition zone 56 is in the crotch region 26 of the diaper 20.
More preferably, the acquisition zone 56 is positioned such that its top surface area is completely positioned in the front two-thirds portion of the diaper 20, most preferably in the front half portion of the diaper 20; the top surface area also most preferably being completely positioned in the crotch region 26 of the diaper 20. ~As noted herein, portions of the diaper 20 or other absorbent article can be defined by reference to the top surface area of the unfolded diaper 20 or absorbent article found in front of a given point on the line which defines the length of the diaper 20).

For purposes of determining the positioning of such acquisition zone 56, the length of the absorbent member 42 or diaper 20 will be taken as the normal longest longitudinal dimension of the elongated structure. This normal longest dimension can be defined with respect to the structure as it is applied to the wearer. When worn, the opposing ends of the backsheet are fastened together so that the ends form a circle around the wearer s waist. The normal length of the absorbent member 42 or diaper 20 will thus be the length of the line running through the absorbent member 42 or diaper 20 from the point on the edge of it at the middle of the wearer s back waist, through the crotch, to the point on the opposite edge of the absorbent member 42 or diaper 20 at the middle of the wearer s front waist.

3~ The top surface area of the acquisition zone 56 may be found - - using either of two techniques. The primary and simplest way is to place the absorbent member 42 on a standard light box, such as the transluminator model manufactured by Aristo grid Lamp Products, Inc. The acquisition zone 56, because it has a lower average density and lower average basis weight than the ~3~1~40 surrounding storage zone 58, will appear lighter or brighter due to the fact that more light will be transmitted through the acquisition zone 56. The acquisition zone 56 can then be mapped onto paper having grids to measure the top surface area of the acquisition zone 56.

The alternatlve method comprises mapping the density profile of the absorbent member 42 to determine the top surface area of the acquisition zone 56. The absorbent member 42 is cut into samples having small areas. The density and basis weight of each of the samples are then calculated using the techniques discussed above. Thus, the relatively lower density and lower basis weight samples are charted against the relatlvely higher density and higher basis weight samples to measure the top surface area of the acquisition zone 56.

The acquisition zone 56 can be of any desired shape consistent with the absorbency requirements of the absorbent member 42 or diaper 20 including, for example, circular, rectangular, triangular, trapezoidal, oblong, hourglass-shaped, funnel-shaped, dog-bone-shaped or oval. Preferred shapes of the acquisitlon zone 56 are those that increase the perimeter of the interface between the acquisition zone 56 and the storage zone 58 so that the relative capillarity difference between the zones is fully util1zed. In a preferred embodiment, the acquisition zone will be oval shaped having a top surface area of about 450m2 (7in2) .
In order to maintain a certain minimal absorbency level in the front section 50 of the absorbent member 42, the top surface area or volume of the storage zone 58 must comprise some minimal amount of the top surface area or volume of the front section 50.
- 30 Thus, it has been found that the acquisition zone 56 should preferably comprise less than the entire top surface area and/or volume of the front section 50 of the absorbent member 42.
(Since in a preferred embodiment the acquisition zone 56 is of generally uniform thickness and cross-sectional area, volume can ~3~:;14~

be interchanged with top surface area as a definltlonal point. ) The top surface area of the portion of the acquisition zone 56 positioned in the front section 50 of the absorbent member 42 preferably comprises less than about 50~ of the top surface area of the front section 50. More preferably, the top surface area of the acquisition zone 56 comprises less than about 35% of the top surface area of the front sectlon 50 of the absorbent member 42, with less than about 20~6 being especially preferred. In additlon, the top surface area of the acquisition zone 56 preferably comprises less than about 5096 of the top surface area of the deposition region 54, more preferably less than about 35%, and most preferably less than about 20%.

The acquisition zone 56 may also have a number of different cross-sectional areas and configurations including those wherein the area of portions of the acquisition zone 56 is less or greater than its top surface area (i.e., The acquisition zone 56 is smaller or wider below the top surface of the absorbent member 42.) For example, the acquisition zone 56 may have conical, trapezoidal, T-shaped or rectangular cross-sectlonal areas. As shown in Figures 2 and 3, the acquisition zone 56 preferably has a rectangular cross-sectional area so as to provide a uniform acquisition zone 56.

In addition, the acqulsitlon zone 56 need not comprise the entire thickness of the absorbent member 42, but may extend through only a fraction of its total thickness. The acquisition zone 56 may also have a different thickness than the surrounding storage zone 58. However, in a preferred embodiment as shown in Figures 2 and 3, the acquisition zone 56 preferably extends through the entlre thickness of the absorbent member 42 and has a thickness equal to the thickness of the surroudning storage zone 58 in the deposition region 54.

While the acquisitlon zone 56 may be transversely positioned anywhere along the absorbent member 42, it has been found that the acquisitlon zone 56 functlons the most efficiently when it is ~: ' .

13014~) transversely centered within the front section 50 or the deposition region 54 of the absorbent member 42. Thus, the acquisition zone 56 is preferably centered about the longitudinal centerline 68 of the absorbent member 42. More preferably, the acquisitlon zone 56 is transversely positioned only in the central region 64 of the front section 50 or deposition region 54 of the absorbent member 42 such that none of the acquisition zone 56 is located in the ear regions 60 and 62.

Such an absorbent member 42 is preferably made by airlaying a thickness profiled absorbent member-preform and then calendering the absorbent member 42 in a fixed-gap calender roll to effect densifying the absorbent member 42. The thickness profiled absorbent member 42 initially has areas of higher basis weight which deflne the storage zone 58 and of lower basis weight which define the acquisition zone 56. The absorbent member 42 is then calendered preferably to at least a uniform thickness in the deposition region. Thus, a lower average density and a lower average basis weight per unit area acquisition zone 56 is created relative to the higher average density and higher average basis weight storage zone 58. Additionally, discrete particles of absorbent gelling material are added to an air-entrained stream of fibers prior to their deposition onto the preform to affect uniform distribution of absorbent gelling material throughout the preformed absorbent member 42. Thus, the resultant absorbent member 42 contains a uniform mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material.

In use, the diaper 20 is applied to a wearer, by positioning the back waistband region 24 under the wearer's back, and drawing the remainder of the diaper 20 between the wearer's legs so that the front waistband region 22 is positioned across the front of the wearer. The ends of the tape-tab fasteners 46 are then secured preferably to outwardly facing areas of the diaper 20. I n use, disposable diapers or other absorbent articles having such absorbent members 42 having a relatively lower average density and lower average basis weight acquisition zone 56, tends 13~1440 to more quickly acquire liquids Into the acquisition zone 56 and to distribute these liquids to the remalning portlons of the absorbent member 42 and to remain drv or dryer due to the preferential capillarity between the storage zone and the acquisitlon zone 56 of 5 the absorbent member 42. Thus, such an absorbent member 42 helps to alleviate leakage around the edges of such absorbent articles .

Figure 5 shows an alternative embodiment of an absorbent member 542 of the present invention. As shown in Flgure 5, the front section 550 of the absorbent member 542 has a thickness, T1, greater than the thickness, T2, of the back section 548.
The acquisition zone 56 Ts preferably of the same thickness, T1, as the storage zone 58 positioned in the front section 550 of the absorbent member 542; the front section 550 having a terraced character by virtue of the thickness difference between the front section 550 and the back section 548 and by virtue of the relatively steep slope formed by a density/basis weight transition zone which is designated 572. Preferably, T1 is at least about 1.5 times as great as T2 and preferably about 2.0 times as great as T2. In this preferred embodiment, about three-fourths of the absorbent material is disposed in the front section 550 of the absorbent member 542 thereby providing an absorbent member 542 whereln the front section 552 has high absorbent capacity as well as rapld acquisitlon characteristlcs.

Figures 6 and 7 show a further alternatlve embodiment of an absorbent member 642 the present invention. An absorbent 7cquisition core 674 is positioned over the absorbent member 642 of the present invention to form a dual-layer absorbent core. An example of a simllar dual-layer absorbent core Is discussed in more detail in U.S. Patent 4,673,402, issued to The Procter and Gamble Company, June 16, 1987.

The absorbent acquisition core 674 preferably consists essentlally of hydrophilic fibrous material. This absorbent ,,~.~;

13~ 40 acquisition core 674 thus serves to quickly collect and temporarily hold discharged liquids and to transport such liquids by wicklng from the point of initial contact to other parts of the absorbent acquisition core 674. Since the primary function of the absorbent acquisition core 674 is to receive liquids passing through the topsheet 38 and to transport such I iquids to other areas of the absorbent acquisition core 674 and eventually onto the absorbent member 642, the absorbent acquisition core 674 can be substantially free of absorbent gelling material. Alternatively, the absorbent acquisition core 674 can contain particular amounts of absorbent gelling material. Thus, the absorbent acquisition core 674, for example, can contain up to about 50%, or preferably up to between about 25g6 and 40%, by its weight of particles of absorbent gelling material. In the most preferred embodiments, the absorbent acquisition core contains up to about 8% by its weight of particles of absorbent gelling material. In some instances, the presence of particles of absorbent gelling material in the absorbent acquisition core 674 can actually serve to maintain its density within the optimum range to promote fluid distribution. The specific type of absorbent gelling material optionally used in the absorbent acquisition core 674 does not have to be the same as the type essential Iy employed in the absorbent member 642.

The shape, size and character, including capillarity of the absorbent acquisition core 674, is of some importance in determining the effectiveness of the resulttng diaper 20 or other absorbent article. The absorbent acquisition core 674 in the unfolded configuration can be of any desired shape, for example, rectangular, oval, oblong, assymmetric or hourglass-shaped.
T he shape of the absorbent acquisition core 674 will frequently define the general shape of the resulting diaper 20. In preferred - embodiments of the present invention as shown in Figure 6, the absorbent acquisition core 674 will be hourglass-shaped and will be of a substantially uniform density within the range of from about 0.07 to about 0.20 g/cm3. Preferably, the core will have a basis weight ranging from about 0.007 to about 0.075 g/cm2.

~3U14~0 The absorbent acquisition core 674 may alternatively comprise core acquisition zone tnot shown) having a lower average density and a lower average basis weight than the remainder of the absorbent acquisition core 674. This core acquisition zone may have the same shape, positioning and characteristics as the acquisitlon zone 656 of the absorbent member 642, or it may have different shapes, positioning and/or characteristics. Preferably, the core acquisition zone of the absorbent acquisition core 674 overlays at least a portion of the acquisitlon zone 656 of the absorbent member 642, and more preferably the entire acquisition zone 656 of the absorbent member 642, so as to provide an overall acquisition zone extending throughout the entire thickness of the dual-layer absorbent core system.

The absorbent member 642 of the present invention need not be as large as the absorbent acquisition core 674 and can, in fact, have a top surface area which is substantially smaller than the top surface area of the absorbent acquisition core 674.
Generally, the absorbent member 674 will have a top surface area from about 0.25 to about 1.0 times that of the absorbent acquisitlon core 674. Most preferably, the top surface area of the absorbent member 642 will be only from about 0.25 to about 0.75, and most preferably from about 0.3 to about 0.5, times that of the absorbent acquisition core 674.

The absorbent member 642 is preferably placed in a specific positional relationsh7p with respect to the backsheet 40 and/or the absorbent acquisition core 674 in the diaper or other absorbent article. More particularly, the absorbent member 642 is positloned generally toward the front of the diaper so that absorbent gelling material is most effectively located to acquire and hold discharged liquids from the absorbent acquisition core 674.

The forward postioning of the absorbent member 642 can be defined by specifying the percent of total absorbent gelling material which is found forward of particular points along the ~3~4~0 length of the diaper or other absorbent article. Thus, in accordance with the present invention, the absorbent member 642 is positioned relative to the backsheet and/or the absorbent acquisitlon core such that t 1) at least about 75% of the total absorbent gelling material in the absorbent member 642 is found within the front two-thirds portion of the diaper or other absorbent article, and (2) at least about 55% of the total absorbent gelling material in the absorbent member 642 is found within the front half portion of the diaper or other absorbent article. More preferably, the absorbent member 642 is positioned relative to the backsheet 38 and/or the absorbent acquisition core 674 such that at least about 90% of the total absorbent gelling material in the absorbent member 642 is found in the front two-thirds portion and at least about 60% of the total absorbent gelling material is found in the front half portion of the diaper or other absorbent artlcle. ~As noted, for purposes of the present invention, "portions" of the diaper or other absorbent article can be defined by reference to the top surface area of the unfolded diaper 20 or absorbent article found in front of a given point on the line which defines the length of the diaper 20 or absorbent article, ) In the usual instance when the absorbent acquisitlon core 674 generally defines the shape of the diaper or other absorbent article, the normal length of the backsheet 38 will be approached by the longest longitudinal dimension of the absorbent acquisition core 674. In such instances, the positioning of the absorbent member 642 can also be def7ned with respect to its location toward the front portion of the absorbent acquisitlon core 674. However, in some applications (e.g. adult incontinence articles) wherein bulk reduction or minimum cost are important, the absorbent acquisition core would not take on the general shape of the diaper or incontinence structure. Rather it would be generally located to cover only the gential region of the wearer and could in this case have approximately the same top surface area as the absorbent member 642. In this instance, both the absorbent acquisition core 674 and the co-extensive absorbent member 642 ~U~4~0 would be located toward the front of the article as defined by only the backsheet 38 such that the requisite percentages of a~sorbent gelling material would be found in the front two-thirds and front half sections respectively of the diaper or other absorbent article.

The absorbent member 642 of the dual-layer absorbent core can be of any desired shape consistent with comfortable fit including, for example, circular, rectangular, trapezoidal, oblong, hourglass-shaped, dog-bone-shaped or oval. If desired, the absorbent member 642 can be wrapped in a high wet strength envelope web such as tissue paper or a synthetic fine pore, e . g ., nonwoven material, to minimize the potential for particles of absorbent gelling material to migrate out of the absorbent member 642. Another objective of such overwrapping is to desira~y increase the in-use integrity of the dual layer absorbent corç.
Such a web can, in fact, be glued to the absorbent member 642.
Suitable means for carrying out this gluing operation include the glue spraying procedure described in U.S. Patent 4,573,986 issued to Minetola and Tucker, on March 4, 1986.

I n preferred embodiments, the absorbent member 642 of the dual layer absorbent core will be oblong. In especially preferred embodtments, an oblong absorbent member 642 overwrapped with spray-glued tissue will be employed.

8ecause the absorbent member 642 of the dual-layer absorbent core is generally smaller than the absorbent acquisition core 674 such that the absorbent member 642 may entirely be placed in the area of typical liquid deposition, and because the absorbent member 642 is preferably positloned in a specific positional relationship with respect to the backsheet 38 and/or the absorbent acquisition core 674, the acquisition zone 656 may be positioned anywhere in the absorbent member 642. The acquisition zone 656 is not necessarily limited to a portion of the depositlon region, since in effect the entire absorbent member 642 130~44~) of the dual-layer absorbent core is in the deposition region .
The acquisition zone 656 is however preferably positioned in a specific positional relationship with respect to the backsheet 38 and/or the absorbent acquisitlon core 674 of the diaper or other absorbent article. More particularly the acquisition zone 656 should be positioned generally toward the front of the diaper at least partially in the crotch region 26 so that the acqulsition zone 656 is most effectively located to quickly acquire and distribute liquids within the absorbent member 642. Thus the positioning of the acquisitlon zone 656 in the diaper or other absorbent article can be defined by specifying the percentage of the top surface area (and/or volume) which is found forward of a particular point along the length of the diaper or other absorbent article . I n accordance with the present invention the acquisition zone 656 is preferably positioned relative to the backsheet 39 and/or the absorbent acquisition core 674 such that the top surface area of the acquistion zone 656 is completely positioned within the front two-thirds portion of the diaper or absorbent article. More preferably the acquisitlon zone 656 is positioned relatlve to the backsheet 38 and/or the absorbent acquisition core 674 such that the top surface area of the acquisition zone 656 is completely positloned within the front half portion of the diaper or absorbent artlcle and most preferably such that at least about 30% of the top surface area is located in the front one-third section of the diaper or absorbent article. The acquisition zone 656 is aiso most preferably completely positioned within the crotch region 26 of the diaper or absorbent article.

In order to maintain a certain minimal absorbency level in the front portions of the diaper or other absorbent article it has been found that the top surface area of the acquisition zone 656 should comprise less than the ent7re top surface area of the absorbent member 642 of the dual-layer absorbent core. The top surface area (and/or volume) of the acquisit7On zone 656 preferably comprises less than about 50% of the top surface area (and/or volume) of the absorbent member ~42. More preferably the top surface area of the acquisition zone 656 comprises less , ~ ~

13()~440 than about 35% of the top surface area of the absorbent member 642 and most preferably less than about 20% of the top surface area of the absorbent member 642. Al l other aspects of the acquisition zone 656 may be similar to the acquisition zone 56 discussed with respect to the absorbent member 42.

Figure 8 shows a still further alternative embodiment of an absorbent member 842 of the present invention. The absorbent member 842 has an asymmetric shape ( i . e., the absorbent member 842 is not symmetrical about its transverse centerline). In addition, the ear regions 860 and 862 and the ear regions of the back section 848 preferably have a different thickness than the central region 864. Further, the density and basis weight values of the ear regions 860 and 862 and the back section 848 are different from the storage zone 858 positioned in the central region 864 by virtue of the method by which the absorbent member 842 is formed.

The ear regions 860 and 862 and the back section 848 are preferably formed with a lesser basis weight than the storage zone 858 of the central region 864 so as to hold down the cost of such absorbent members 842 because less materials are being used. The absorbent member 842 is calendered to a uniform thickness in the central region 864 and the back section 848 except for its ear regions: the storage zone 858 of the central region 864, therefore, having a greater average density than the back sectlon 848 except for its ear regions. ( It should be understood that all or portions of the back section 848 may alternatively be calendered to a lesser thickness than the central region 864 such that the back section 848 has about an equal or a greater average density than the storage zone 858. ) The ear regions 860 and 862 and the ear regions of the back section 848 - are preferably calendered such that they have substantially less thickness than the central region 864 and a greater average density than the storage zone 858 of the central region 864. The thickness difference between the ear regions and the central region 864 is such that the absorbent member 842 may be easily 13U1~40 ~9 folded to a thin configuration during packaging with the ear regions overlaying the respectlve central region 864 and the back section 848. The ear regions are also preferably more dense than the storage zone 858 to provide an additional capillarity difference so that liquids will tend to be pulled toward the ear regions so that the total absorbent capacity of the absorbent member 842 will be utilized .

The acquisition zone 856 of the absorbent member 842 has a funnel shape. The funnel shape is defined by a generally triangular portion 884 in combination with a stem or rectangular portion 886. The triangular portion 884 is especially effective in absorbing liquids discharged by a male wearer, while the stem portion 886 is effective for a female wearer. While it is possible that the shape of the acquisitlon zone 856 may vary according to the type of wearer contemplated, such as only a triangular portlon 884 for a male wearer and only a stem portion 886 for a female wearer, it is preferred that the acquisition zone 856 comprise both elements.

Yet another alternative to each of the embodiments of the above absorbent members of the present invention comprises varying the pore size of the fibers without necessarily varying the density of the fibers to form an acquisition zone and a storage zone. For example, fine fiber dimensions of hardwood fluff can be utilized to advantage by substituting at least about 50%, and preferably about 80% to 100%, hardwood fluff fibers of approximately the same density as lower density softwood fluff fibers for the softwood fibers in the storage zone. This can be done because the hardwood fluff has a smaller pore size than the softwood fluff material. As result, a capillarity difference will still be obtained within the scope of the invention, even if the density of each zone is the same. Thus, for example, an :1 3~ 0 absorbent member can be obtained from using a predominately softwood pulp with a fine pore structure to define the acquisitlon zone and a predominately hardwood flutf pulp to define the storage zone.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

Claims

1. An absorbent member having a back section and a front section contiguous with said back section, said front section having an end region and a deposition region contiguous with said end region and said back section so that said deposition region is positioned between said end region and said back section, the absorbent member comprising:
a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material;
a storage zone positioned in at least said deposition region of the absorbent member; and an acquisition zone positioned in at least said deposition region of the absorbent member, said acquisition zone having a density and basis weight per unit area greater than zero, said acquisition zone having a lower average density and a lower average basis weight per unit area than said storage zone, said storage zone at least partially laterally surrounding the perimeter of said acquisition zone so as to be in liquid communication with at least a portion of the lateral area of said acquisition zone.

2. The absorbent member of claim 1 wherein said acquisition zone extends from the top surface of the absorbent member through at least a fraction of the total thickness of the absorbent member, the top surface area of said acquisition zone being completely positioned within said front section.

3. The absorbent member of claim 2 wherein the top surface area of said acquisition zone comprises less than about 50% of the top surface area of said front section.

4. The absorbent member of claim 1 wherein said acquisition zone extends from the top surface of the absorbent member through at least a fraction of the total thickness of the absorbent member, the top surface area of said acquisition zone being completely positioned within said deposition region.

5. The absorbent member of claim 4 wherein the top surface area of said acquisition zone comprises less than about 50% of the top surface area of said front section.

6. The absorbent member of claim 4 wherein the top surface area of said acquisition zone comprises less than about 35% of the top surface area of said front section.

7. The absorbent member of claim 4 wherein the top surface area of said acquisition zone comprises less than about 20% of the top surface area of said front section.

8. The absorbent member of claim 7 wherein said acquisition zone is positioned so that at least 30% of the top surface area of said acquisition zone is positioned in the front half of said front portion.

9. The absorbent member of claim 5 wherein said acquisition zone has a thickness approximately equal to the thickness of said storage zone.

10. The absorbent member of claim 9 wherein said back section has a thickness approximately equal to the thickness of said deposition region.

11. The absorbent member of claim 10 wherein said end region has a thickness approximately equal to the thickness of said deposition region.

12. The absorbent member of claim 11 wherein said acquisition zone extends through the entire thickness of the absorbent member.

13. The absorbent member of claim 12 wherein the top surface area of said acquisition zone is transversely centered within said deposition region.

14. The absorbent member of claim 13 wherein the top surface area of said acquisition zone has a generally triangular shape.

15. The absorbent member of claim 9 wherein said deposition region has a thickness greater than an about 1.5 times the thickness of said back section.

16. The absorbent member of claim 9 wherein said deposition region has a thickness greater than about 2.0 times the thickness of said back section.

17. The absorbent member of claim 16 wherein the top surface area of said acquisition zone is transversely centered within said deposition region.

18. The absorbent member of claim 17 wherein the top surface area of said acquisition zone has an oval shape.

19. The absorbent member of claim 9 wherein said front section further has two transversely spaced ear regions and a central region disposed intermediate said ear regions, said acquisition zone being positioned within said central region.

20. The absorbent member of claim 19 wherein said ear regions have a thickness substantially less than the thickness of said central region of said front portion.

21. The absorbent member of claim 20 wherein said ear regions and said central regions are demarked from each other by sufficiently abrupt thickness differences that said front section has a terraced character.

22. The absorbent member of claim 20 wherein said ear regions have a greater average density than said storage zone positioned within said central region.

23. The absorbent member of claim 13 wherein the top surface area of said acquisition zone has a funnel shape.

24. The absorbent member of claim 13 wherein the absorbent member has an asymmetrical shape.

25. The absorbent member of claim 24 wherein the average density of said back section is less than the average density of said storage zone of said deposition region.

26. The absorbent member of claim 25 wherein the top surface area of said acquisition zone has a generally triangular shape.

27. The absorbent member of claim 1 wherein the ratio of the average density of said storage zone to the average density of said acquisition zone is about equal to or greater than 1.25:1.

28. The absorbent member of claim 1 wherein the ratio of the average density of said storage zone to the average density of said acquisition zone is about equal to or greater than 2:1.

29. The absorbent member of claim 28 wherein the density of said acquisition zone is from about 0.05 to about 0.15 grams/cm3.

30. The absorbent member of claim 29 wherein said acquisition zone has a substantially uniform density and uniform basis weight throughout.

31. The absorbent member of claim 1 wherein only said deposition region has discrete particles of absorbent gelling material dispersed therein.

32. The absorbent member of claim 1 wherein said mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material has a fiber-to-particulate weight ratio of from about 40:60 to about 98:2.

33. The absorbent member of claim 1 wherein said mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material has a fiber-to-particulate weight ratio of from about 50:50 to about 91:9.

34. The absorbent member of claim 33 wherein said particles of absorbent gelling material have a gel strength such that said particles have a shear modulus of at least about 2000 dynes/cm2.

35. The absorbent member of claim 33 wherein said hydrophilic fibrous material and said discrete particles of absorbent gelling material are uniformally dispersed with respect to each other throughout the absorbent member.

36. An absorbent article comprising:
a liquid pervious topsheet;
a liquid impervious backsheet associated with said topsheet; and an absorbent member according to any one of claims 1, 2, 4, 9, 12, 16, 18, or 24 positioned between said topsheet and said backsheet.

37. An absorbent member having a back section and a front section contiguous with said back section, said front section having an end region and a deposition region contiguous with said end region and said back section so that said deposition region is positioned between said end region and said back section, the absorbent member comprising:
a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material;
a storage zone positioned in at least said deposition region of the absorbent member; and an acquisition zone positioned in at least said deposi-tion region of the absorbent member, said acquisition zone having a larger average pore size of the fibers than said storage zone, said storage zone at least partially laterally surrounding the perimeter of said acquisition zone so as to be in liquid communication with at least a portion of the lateral area of said acquisition zone.

38. An absorbent article having a front waistband region, a back waistband region, and a crotch region disposed between said front waistband region and said back waistband region, said absorbent article comprising:
a liquid pervious topsheet;
a liquid impervious backsheet associated with said topsheet; and an absorbent member positioned between said topsheet and said backsheet, said absorbent member comprising a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material; a storage zone positioned in at least said crotch region of said absorbent article; and an acquisition zone positioned in at least said crotch region of said absorbent article, said acquisition zone having a density of from about 0.05 g/cm3 to about 0.41 g/cm3, said acquisition zone having a lower average density and a lower average basis weight per unit area than said storage zone, said acquisition zone extending from the top surface of the absorbent member through at least a fraction of the total thickness of the absorbent member, the top surface area of said acquisition zone comprising less than about 35% of the top surface area of said absorbent member, said storage zone laterally surrounding the perimeter of said acquisition zone so as to be in liquid communication with the lateral area of said acquisition zone.

39. The absorbent article of claim 38 wherein said absorbent member has a uniform thickness and said acquisition zone extends through the entire thickness of said absorbent member.

40. The absorbent article of claim 39 additionally comprising an absorbent acquisition core positioned between said topsheet and said absorbent member.

41. The absorbent article of claim 40 wherein said absorbent member is generally oblong and has a top surface area that is from about 0.25 to about 1.0 times that of said absor-bent acquisition core, said absorbent member being positioned relative to said backsheet and said absorbent acquisition core in a manner such that at least 75% of the absorbent gelling material in said absorbent member is found within the front two-thirds portion of the absorbent article.

42. The absorbent article of any one of claims 38, 40, or 41 wherein said acquisition zone is positioned relative to said backsheet such that the top surface area of said acquisition zone is completely positioned within the front two-third sections of the absorbent article.

43. The absorbent article of claim 41 wherein said acquisition zone is positioned relative to said backsheet such that the top surface area of said acquisition zone is completely positioned within the front one-half section of the absorbent article.

44. The absorbent article of claim 43 wherein the top surface area of said acquisition zone is completely positioned within said crotch region.

45. The absorbent article of claim 41 wherein said absorbent acquisition core has a core acquisition zone having a lower average density and a lower average basis weight than the remainder of said absorbent acquisition core.

46 46. The absorbent article of claim 45 wherein said core acquisition zone of said absorbent acquisition core overlays at least a portion of said acquisition zone of said absorbent member.

47. The absorbent article of claim 46 wherein said absorbent acquisition core contains particles of absorbent gelling material in an amount up to about 50% by weight of said absorbent acquisition core.

48. An absorbent core comprising:
an absorbent member comprising a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material, a storage zone, and an acquisition zone having a lower average density and a lower average basis weight per unit area than said storage zone, said acquisition zone having a density of from about 0.05 to about 0.41 g/cm3, said storage zone at least partially laterally surrounding the perimeter of said acquisition zone so as to be in liquid communication with at least a portion of the lateral area of said acquisition zone;
and an absorbent acquisition core positioned adjacent said absorbent member, said absorbent acquisition core comprising hydrophilic fibers that are substantially free of absorbent gelling material, said absorbent acquisition core having a core acquisition zone having a lower average density and a lower average basis weight per unit area than the remainder of said absorbent acquisition core, said core acquisition zone being positioned with respect to said acquisition zone of said absorbent member so as to provide an overall acquisition zone throughout the entire thickness of the absorbent core.

49. The absorbent core of claim 48 wherein said core acquisition zone has the same shape as said acquisition zone of said absorbent member.

50. The absorbent core of claim 48 or 49 wherein said absorbent member and said absorbent acquisition core are a continuous web of fibrous material.

51. The absorbent core of claim 50 wherein said overall acquisition zone is funnel-shaped.

52. The absorbent core of claim 50 wherein said overall acquisition zone has a generally triangular shape.

53. An absorbent member having a back section and a front section contiguous with said back section, said front section having an end region and deposition region contiguous with said end region and said back section so that said deposi-tion region is positioned between said end region and said back section, the absorbent member comprising:
a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material;
a storage zone positioned in at least said deposition region of the absorbent member; and an acquisition zone positioned in said deposition region of the absorbent member, said acquisition zone having a density of from about 0.03 to about 0.15 g/cm3; said acquisition zone having a lower average density and a lower average basis weight per unit area than said storage zone, said acquisition zone extending from the top surface of the absorbent member through the entire thickness of the absorbent member, the top surface area of said acquisition zone being completely posi-tioned within said deposition region and comprising less than about 35% of the top surface area of said deposition region, said storage zone laterally surrounding the perimeter of said acquisition zone so as to be in liquid communication with the lateral area of said acquisition zone.

54. The absorbent member of claim 53 wherein the absorbent member has a uniform thickness.

55. The absorbent member of claim 54 wherein the absorbent member comprises a substantially uniform mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material distributed throughout the absorbent member.

56. The absorbent member of claim 55 wherein said acquisition zone has a rectangular cross-sectional area.

57. The absorbent member of claim 56 wherein the ratio of the average density of said storage zone to the average density of said acquisition zone is about equal to or greater than 1.25:1.

58. The absorbent member of claim 57 wherein said mixture of hydrophilic fibrous material and said particles of absorbent gelling material are disposed in the absorbent member in a fiber-to-particulate weight ratio of from about 40:60 to about 98:2.

59. The absorbent member of claim 58 wherein said back section has less average basis weight per unit area than said storage zone positioned in said deposition region.

60. The absorbent member of claim 59 wherein the top surface area of said acquisition zone has a generally triangular shape.

61. The absorbent member of claim 60 wherein the absorbent member has an asymmetric shape.

62. The absorbent member of claim 61 wherein the top surface area of said acquisition zone comprises less than about 20% of the top surface area of said deposition region.

63. The absorbent member of claim 62 wherein the ratio of the average density of said storage zone to the average density of said acquisition zone is about equal to or greater than 1.5:1.

64. The absorbent member of claim 58 wherein the top surface area of said acquisition zone has an hour-glass shape.

65. The absorbent member of claim 58 wherein said acquisition zone comprises plural acquisition zones.

66. An absorbent article comprising:
a liquid pervious topsheet;
a liquid impervious backsheet associated with said topsheet; and an absorbent member according to any one of claims 53, 54, 55, 57, 58, 60, 61, 63, 64 or 65 positioned between said topsheet and said backsheet.

67. An absorbent member having a back section and a front section contiguous with said back section, said front section having an end region and a deposition region contiguous with said end region and said back section so that said deposi-tion region is positioned between said end region and said back section, the absorbent member comprising:
a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material;
a storage zone positioned in at least said deposition region of the absorbent member; and an acquisition zone positioned in said deposition region of the absorbent member, said acquisition zone having a density of from about 0.05 to about 0.41 g/cm3, said acquisition zone having a lower average density and a lower average basis weight per unit area than said storage zone, said acquisition zone extending from the top surface of the absorbent member through a fraction of the total thickness of the absorbent member, the top surface area of said acquisition zone being completely positioned within said deposition region and compris-ing less than about 35% of the top surface area of said deposi-tion region, said storage zone laterally surrounding the perimeter of said acquisition zone so as to be in liquid communication with the lateral area of said acquisition zone.

68. The absorbent member of claim 67 wherein said storage zone and said acquisition zone have the same thickness.

69. The absorbent member of claim 68 wherein the absorbent member has a uniform thickness.

70. The absorbent member of claim 69 wherein said back section does not comprise said storage zone.

71. The absorbent member of claim 70 wherein only said storage zone comprises said mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material.

72. The absorbent member of claim 70 wherein only said storage zone and said acquisition zone comprise said mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material.

73. The absorbent member of claim 72 wherein the top surface area of said acquisition zone has a generally triangular shape.

74. The absorbent member of claim 73 wherein the absorbent member has an asymmetric shape.

75. An absorbent article comprising:
a liquid pervious topsheet;
a liquid impervious backsheet associated with said topsheet; and an absorbent member according to any one of claims 67, 69, 72, 73 or 74 positioned between said topsheet and said backsheet.

76. A disposable diaper comprising:
a liquid pervious topsheet a liquid impervious backsheet associated with said topsheet;
an absorbent member according to any one of claims 1, 48, 53 or 67 positioned between said topsheet and said back-sheet; and an elastic member disposed along each longitudinal edge of said disposable diaper.

77. An absorbent core comprising:
an absorbent member comprising a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material; and an absorbent acquisition core positioned adjacent said absorbent member, said absorbent acquisition core comprising a mixture of hydrophilic fibrous material and up to about 8% by weight of said absorbent acquisition core of discrete particles of absorbent gelling material; a storage zone positioned in at least a portion of said absorbent acquisition core; and a core acquisition zone positioned in said absorbent acquisition core, said acquisition zone having a density and basis weight per unit area greater than zero, said core acquisition zone having a lower average density and a lower average basis weight per unit area than said storage zone, said core acquisition zone extend-ing from the top surface of the absorbent member through the entire thickness of the absorbent acquisition core, the top surface area of said core acquisition zone comprising less than about 35% of the top surface area of said absorbent acquisition core, said storage zone laterally surrounding the perimeter of said core acquisition zone so as to be in liquid communication with the lateral area of said core acquisition zone.

78. An absorbent article having a front region, a back region, and a crotch region disposed between said front region and said back region, said absorbent article comprising:
a liquid pervious topsheet;
a liquid impervious backsheet associated with said topsheet;
an absorbent member comprising a mixture of hydrophilic fibrous material and discrete particles of absorbent gelling material; and an absorbent acquisition core positioned between said topsheet and said absorbent member, said absorbent acquisition core comprising a mixture of hydrophilic fibrous material and up to about 8% by weight of said absorbent acquisition core of discrete particles of absorbent gelling material; a storage zone positioned in at least said crotch region of said absorbent article; and a core acquisition zone positioned in said crotch region of said absorbent article, said core acquisition zone having a density and basis weight per unit area greater than zero, said core acquisition zone having a lower average density and a lower average basis weight per unit area than said storage zone, said core acquisition zone extending from the top surface of the absorbent member through the entire thickness of the absorbent member, the top surface area of said core acquisition zone comprising less than about 35% of the top surface area of said absorbent member, said storage zone laterally surrounding the perimeter of said core acquisition zone so as to be in liquid communication with the lateral area of said core acquisition zone.