CA2249214C - Absorbent cores having improved acquisition capability, and absorbent articles containing them - Google Patents

Abstract

The invention relates to an absorbent core capable of absorbing discharged aqueous body fluids, said absorbent core comprising: (1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the fluid acquisitlon/distribution components being positioned in the fluid discharge region of the absorbent core; (2) at least one upper fluid storage component positioned at least partially underneath and in fluid communication with the upper fluid acquisition/distribution component(s), the upper fluid storage component being capable of expanding in the z-direction when contacted with aqueous body fluids to form a fluid acquisition zone; (3) a fluid acquisition zone capable of receiving aqueous body fluids, the fluid acquisition zone being at least partially surrounded by said at least one upper fluid storage component(s); (4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids being positioned at least partially underneath and in fluid communication with the upper fluid storage component(s); and (5) preferably, at least one lower fluid storage component positioned underneath the lower fluid acquisition/distribution component and in fluid communication therewith. The invention further relates to an absorbent article useful for absorbing discharged aqueous body fluids that comprises: A) a fluid pervious topsheet; B) a backsheet; and C) an absorbent core of the present invention.

Description

-I-ABSORBENT CORES HAVING IMPROVED ACQUISITTON CAPABILTTY, AND ABSORBENT ARTICLES CONTAINING THEM
TECHNICAL FIELD
This application relates to absorbent articles such as diapers, adult incontinence pads, sanitary napkins, and the like capable of handling multiple discharges of aqueous body fluids. The application particularly relates to articles comprising an absorbent core having a fluid acquistion zone, formed by the swelling of a fluid storage material, positioned beneath a fluid acquisition/distribuiion material.
BACKGROUND OF THE l2dVENT'ION
The development of highly absorbent members for use as disposable diapers, adult incontinence pads and briefs, and catamenial products such as sanitary napkins, are the subject of substantial commercial interest. A highly desired characteristic for such products is thinness. For example, thinner diapers are less bulky to wear, fit better under clothing, and are less noticeable. They are also more compact in the package, making the diapers easier for the consumer to carry and store. Compachzess in packaging also results in reduced distribution costs for the manufacturer and distributor, including less shelf space required in the store per diaper unit.
The ability to provide thinner absorbent articles such as diapers has been contingent on the ability to develop relatively thin absorbent cores or structures that can acquire and store large quantities of discharged body fluids, in particular urine. In this regard, the use of certain absorbent polymers often referred to as "hydrogels," "superabsorbents"
or "hydrocolloid" material has been particularly important. See, for example, U.S. Patent 3,669,103 (Harper et al), issued June 13, 1972, and U.S. Patent 3,670,731 (Harmony, issued June 20, 1972, that disclose the use of such absorbent polymers (hereafter "hydrogel-forming absorbent polymers") in absorbent articles. Indeed, the development of thinner diapers has been the direct consequence of thinner absorbent cores that take advantage of the ability of these hydrogel-forming absorbent polymers to absorb large quantities of discharged aqueous body fluids, typically when used in combination with a fibrous matrix. See, for example, U.S. Patent 4,673,402 (Weisman et al), issued June 16, 1987 and U.S. Patent 4,935,022 (Lash et al), issued June 19, 1990, that disclose dual-layer core structures comprising a fibrous matrix and hydrogel-forming absorbent polymers useful in fashioning thin, compact, nonbulky diapers.
Prior to the use of these hydrogel-forming absorbent polymers, it was general practice to form absorbent structures, such as those suitable for use in infant diapers, entirely from wood pulp fluff. Given the relatively low amount of fluid absorbed by wood pulp fluff WO 97/34557 PCT/~JS97/04341 on a gram of fluid absorbed per gram of wood pulp fluff, it was necessary to employ relatively large quantities of wood pulp fluff, thus necessitating the use of relatively bulky, thick absorbent structures. The introduction of these hydrogel-forming absorbent polymers into such structures has allowed the use of less wood pulp fluff;: These hydrogel-forming absorbent polymers are superior to fluff in their ability to absorb large volumes of aqueous body fluids, such as urine (i.e., at least about 15 g/g), thus making smaller, thinner absorbent structures feasible.
Prior absorbent structures have generally comprised relatively low amounts (e.g., less than about 50 % by weight) of these hydrogel-forming absorbent polymers.
See, for example, U.S. Patent 4,834,735 (Alemany et al), issued May 30, 1989 (preferably from about 9 to about 50% hydrogel-forming absorbent polymer in the fibrous matrix). There are several reasons for this. The hydrogel-forming absorbent polymers employed in prior absorbent structures have generally not had an absorption rate that would allow them to quickly absorb body fluids, especially in "gush" situations. This has necessitated the inclusion of fibers, typically wood pulp fibers, to serve as temporary reservoirs to hold the discharged fluids until absorbed by the hydrogel-forming absorbent polymer.
More importantly, many of the known hydrogel-forming absorbent polymers exhibited gel blocking. "Gel blocking" occurs when particles of the hydrogel-forming absorbent polymer are wetted and the particles swell so as to inhibit fluid transmission to other regions of the absorbent structure. Wetting of these other regions of the absorbent member therefore takes place via a very slow diffusion process. In practical terns, this means acquisition of fluids by the absorbent structure is much slower than the rate at which fluids are discharged, especially in gush situations. Leakage from the absorbent article can take place well before the particles of hydrogel-forming absorbent polymer in the absorbent member are fully saturated or before the fluid can diffuse or wick past the "blocking"
particles into the rest of the absorbent member. Gel blocki~:ø can be a particularly acute problem if the particles of hydrogel-forming absorbent polymer do not have adequate gel strength and deform or spread under stress once the particles swell with absorbed fluid. See U.S. Patent 4,834,735 (Alemany et al), issued May 30, 1989.
This gel blocking phenomena has typically necessitated the use of a fibrous matrix in which are dispersed the particles of hydrogel-forming absorbent polymer. This fibrous matrix keeps the particles of hydrogel-forming absorbent polymer separated from one another. This fibrous matrix also provides a capillary structure that allows fluid to reach the hydrogel-forming absorbent polymer located in regions remote from the initial fluid discharge point. See U.S. Patent 4,834,735 (Alemany et al), issued May 30, 1989.
However, dispersing the hydrogel-forming absorbent polymer in a fibrous matrix at relatively low concentrations in order to minunize or avoid gel blocking can lower the overall fluid storage capacity of thinner absorbent structures. Also, absorbent cores comprising hydrogel-forming absorbent polymers dispersed uniformly throughout the fibrous matrix will typically not have the ability to rapidly acquire and distribute fluids during "gush" situations or when the core has become saturated from prior discharges of body fluids.
The need for rapidly acquiring and distributing discharge body fluids has led to the development of dual-layer core structures noted above. These dual-layer core structures basically comprise: (1) an upper fibrous layer adjacent to the fluid pervious topsheet that is substantially free of hydrogel-forming absorbent polymers that acquires the discharged fluid;
and (2) a tower layer that stores this acquired fluid and is typically either:
(a) a fibrous matrix having hydrogel-forming absorbent polymers uniformly dispersed therein;
or (b) a laminate structure where hydrogel-forming absorbent polymer is between.two tissue layers.
See, for example, U.S. Patent 4,673,402 (Weisman et al), issued June 16, 1987.
See also U.S. Patent 4,935,022 (Lash et al), issued June 19, 1990 and U.S. Patent 5,217,445 (Young et al), issued June 8, 1993, where certain chemically stiffened curly, twisted celluiosic fibers are used in this upper layer to provide improved acquisition and distribution performance.
Another variation is to "profile" the absorbent core such that there is an acquisition zone substantially free of hydrogel-forming absorbent polymers in the fluid discharge area and a storage area having dispersed therein hydrogel-forming absorbent polymers that is in fluid communication with the acquisition zone. See U.S. Patent 4,834,735 (Alemany et al), issued May 30, 1989 and U.S. Patent 5,047,023 (Berg), issued September 10, 1991.
Even with the fluid handling improvements provided by these prior absorbent designs, it has been found that the ability to readily acquire fluid diminishes rapidly as the absorbent core becomes saturated with aqueous body fluids. This occurs because the void spaces between fibers and the hydrogel-forming absorbent polymers in the absorbent core become partially filled with fluid during the first "gush" and therefore can not rapidly accept the necessary volume of fluid during subsequent "gushes". Furthermore, the risk of leakage increases as the number of loads increases.
Another problem that can occur with some prior absorbent core designs is a phenomenon referred to as~ "rewet." Rewet occurs when there is acquired fluid that is freely mobile and available in that portion of the absorbent core adjacent the topsheet. This is typically experienced as the absorbent core becomes saturated with acquired fluid. Under mechanical pressure from the wearer of the article, this mobile fluid is pumped out of the absorbent core and upwards through the topsheet. As a result, the topsheet becomes "rewetted" with this pumped fluid such that there is not adequate topsheet dryness.
Accordingly, it would also be desirable to provide an absorbent core that: ( 1 ) has an absorbent material, capable of swelling upon absorbing discharged body fluid to form a fluid acquisition zone, in the absorbent core for desired total fluid capacity and thinness; (2) is able .,4_ to acquire discharged fluid rapidly during "gush" situations, even when the core has become saturated in the loading area from prior discharges of fluids; and (3) when incorporated into an absorbent article, preferably miriicruzes rewetting of the topsheet.
SUMMARY OF THE INVENTION
The present invention relates to an absorbent core capable of absorbing discharged aqueous body fluids, the absorbent core comprising:
(1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the fluid acquisition/distribution components being positioned in the fluid discharge region of the absorbent core;
(2) at least one upper fluid storage component positioned at least partially underneath and in fluid communication with the upper fluid acquisition/distribution component, said at least one fluid storage component being capable of expanding in the z~lirection when contacted with aqueous body fluids to form a fluid acquisition zone;
(3) a fluid acquisition zone capable of receiving aqueous body fluids, the fluid acquistion zone being at least partially surrounded by said at least one upper fluid storage component and positioned at least partially beneath the fluid discharge region of the absorbent core;

(4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids, the lower fluid acquisition/distribution component being positioned at least partially underneath and in fluid communication with said at least one upper fluid storage component; and (5) preferably, at ~east one lower fluid storage component positioned underneath the lower fluid acquisition/distribution component and in fluid communication therewith, at least a portion of this lower storage component being positioned underneath the fluid acquisition zone.
The present invention further relates to an absorbent article useful for absorbing discharged aqueous body fluids that comprises: A) a fluid pervious topsheet;
B) a backsheet; , and C) an absorbent core of the present invention.
The absorbent articles of the present invention have an improved ability to rapidly acquire, distribute and store discharged body fluids due to the presence of (I) the fluid acquisition zone that is formed by the swellable fluid storage component(s);
and (2) the upper fluid acquisition/distribution component that is capable of receiving gushes of body fluids and rapidly desorbing these gushes to other components of the core. The positioning of the fluid storage component(s), which is essential in forming the fluid acquisitions zone, beneath the upper fluid acquistion/distribution component offers the benefit of providing a large area for - S -acquiring fluid - i.e. fluid can be initially acquired even if it enters the diaper outside the fluid acquisition zone; and the acquisition/distribution material provides an aesthetically soft feel next to the wearer's skin, compared with certain of the material used as the upper fluid storage component (e.g., hydrogel-forming polymer).
This is important during "gush" situations or when portions of the absorbent core become saturated from prior multiple discharges of such fluids. The absorbent articles of the present invention also minimize rewetting of the topsheet, in-part due to the locating of the fluid acquisition zone remote from the wearer's skin. This provides good skin dryness for the wearer of an article containing the cores of the present invention.
According to one embodiment of the present invention, there is provided an absorbent core capable of absorbing discharged aqueous body fluids, the absorbent core comprising:
(1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the upper fluid acquisition/distribution component being positioned in the fluid discharge region of the absorbent core;
(2) at least one upper fluid storage component positioned at least partially underneath and in fluid communication with the upper fluid acquisition/distribution component, said at least one fluid storage component being capable of expanding in the z-direction by at least 100% when fully saturated with aqueous body fluids to form a fluid acquisition zone and being restrained from substantial swelling toward the interior of said fluid acquisition zone formed from said expansion of said at least one fluid storage component;
(3) a fluid acquisition zone capable of receiving aqueous body fluids, the fluid acquistion zone being at least partially surrounded by said at least one upper fluid storage component and positioned at least partially beneath the fluid discharge region of the absorbent core; and (4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids, the lower fluid acquisition/distribution component being positioned at least partially underneath and in fluid communication with said at least one upper fluid storage component.
According to a further embodiment of the present invention, there is provided an absorbent core capable of absorbing discharged aqueous body fluids, said -Sa-absorbent core comprising:
(1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the upper fluid acquisition/distribution component being positioned in the fluid discharge region of the absorbent core and comprising chemically stiffened cellulosic fibers that are thermally bonded with a thermoplastic material;
(2) two upper fluid storage components capable of expanding in the z-direction by at least 100% when fully saturated with aqueous body fluids, the two upper fluid storage components being in the form of strips that run longitudinally in the absorbent core and are spaced apart so as to form a fluid acquisition zone upon contact with aqueous body fluids, and wherein both fluid storage components comprise a fluid stable macrostructure of interconnected, hydrogel-forming absorbent polymer particles;
(3) a fluid acquisition zone capable of receiving aqueous body fluids, said fluid acquisition zone being at least partially surrounded by the two upper fluid storage components and positioned at least partially beneath the fluid discharge region of the absorbent core;
(4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids, the lower fluid acquisition/distribution component being positioned at least partially underneath and in fluid communication with said upper fluid storage components, wherein the lower fluid acquisitionldistribution component comprises from 10 to about 30%, by weight, of a hydrogel-forming polymer; and (5) a lower fluid storage component positioned underneath the lower fluid acquisition/distribution component and in fluid communication therewith, the lower fluid storage component being wider than the fluid acquisition zone, wherein the lower fluid storage component comprises a fluid stable macrostructure of interconnected, hydrogel-forming absorbent polymer particles.
According to a further embodiment of the present invention, there is provided an absorbent article for absorbing discharged aqueous body fluids, the absorbent article comprising:
(A) a topsheet;
(B) a backsheet; and -Sb-(C) the absorbent core of any one of claims 1 to 10 located between the topsheet and backsheet.
According to a further embodiment of the present invention, there is provided a diaper comprising:
(A) a topsheet;
(B) a backsheet; and (C) an absorbent core located between the topsheet and backsheet, the absorbent core comprising:
(1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the upper fluid acquisition/distribution component being positioned in the fluid discharge region of the absorbent core;
(2) at least one upper fluid storage component positioned at least partially underneath and in fluid communication with the upper fluid acquisition/distribution component, said at least one upper fluid storage component being capable of expanding in the z-direction by at least 100% when fully saturated with aqueous body fluids to form a fluid acquisition zone and being restrained from substantial swelling toward the interior of said fluid acquisition zone formed from said expansion of said at least one upper fluid storage component;
(3) a fluid acquisition zone capable of receiving aqueous body fluids, said fluid acquisition zone being at least partially surrounded by said at least one upper fluid storage component and positioned at least partially beneath the fluid discharge region of the absorbent core; and (4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids, the lower fluid acquisition/distribution component being positioned at least partially underneath and in fluid communication with said upper fluid storage component.
Figure 1 is a top plan view of an absorbent article according to the present invention where the topsheet is transparent so as to more clearly show the absorbent core.
Figure 2 is a cross-sectional view taken along line 2-2 of Figure 1.

- ~rr -Figure 3 is a cross-sectional view of an absorbent article showing an alternative absorbent core according to the present invention.
Figure 4 is a cross-sectional view of an absorbent article showing another alternative absorbent core according to the present invention.
Figure 5 is a cross-sectional view of an absorbent article showing another alternative absorbent core according to the present invention.
Figure 6 is a cross-sectional view of an absorbent article showing yet another alternative absorbent core according to the present invention.
A. R~fipf~
As used herein, the term "aqueous body fluids" includes urine, menses and vagina discharges.
As used herein, "direct communication" means that fluid can transfer readily between two absorbent article components (e.g., the upper storage components) and the lower fluid acquisition/distribution component) without substantial accumulation, transport, or restriction by an interposed layer. For example, tissues, nonwoven webs, construction adhesives, and the like may be present between the upper acquisition/distribution layer and upper storage layer while maintaining "direct communication" as long as they do not substantially accumulate (store), transport (wick), or restrict the fluid as it passes from the storage layer to the acquisition/distribution layer.

PCTNS97~04341 w0 97r3a557 .6_ As used herein the term "Z-dhrvenaion" refers to the dimarsion or~Oga~at w the length and width of the manber, core or article. The Z-dima~sion usually con~espa~nds to the thiclrness of the member, core or article.
As used herein, the term "X-Y dimension" refers to the place orthogonal to the thickness of the merraber, core or article. The X and Y dimensions correspond to the length and width, respxavely, of the rruxnber, core or article.
As usod herein, the term "absorbent core" refers to the component of the absorbent article that is primarily responsible for fluid >n~ling prnpcctles of the article, including acquiring, transporting, distributing and storing aquooua body fluids. As such the absorbent core typically does not include the topshea or backsbeet of the abaorbeat article.
As used herein, the term "Ioad~ or "gush" generally refers to an insult or deposition of urine or other bodily fluid that would typically result during use. The term load may also refer to the total amount of liquid contained in an absorbent article, but typically refers to one fluid insult.
As use herein, the term "layer" reFen to as ab:arbau manta whose primary dirrrension is X-Y, i.a., alarg its length cad width. It abould be uaderuoad that the tens layer is not neoes:ari>y limited to single hyena or sboas of matuial. llws the layer can camprix laminate or cambinatio~ of se~eml chests a wpbs of the requisite type of niataiata.
~lc~D$ly, the term "layer" tncluda the tams "Isya:" arid "
Fa purposes of this iavaotioo, it should also ba understood that the term "upper"
refers to absorbent cae eornpoo~a, sorb as layers, that are nearrst to the w~er of the absorbent article, and are typically rarer the top:beet of as absorbaot amide;
y, the term "lower' re5ecs ~ sbsorbeat corn oompooass that are furtbamost awsy from the wearer of tide sbsorbert amide and are ty~oliyr nearer tlu3 back~oet.
As med herein, fbC term "ooea~pru~" mains various aomponena, sips and the !lice can be coq jom<fy amploy~ed aooosdi~ Lo tLe ~vmtion. Aooordlegly, tba tenrr "aamp~io~" aoooaApatses the more r~~idive ~ "aaa~ially oP' and "a~oamti~ off" these ~, more r~ie~ve terms ha'viog than ansdard mpg as nadastood is the art.
All paaarta~e~s, ratios and proportions usod basis are by vrei~t unless a~ecvvise B. ,S~m.~~lml F,~omnplary core oompoaaet useful is schieviag i~ov~ed acquistion performance are dessribod beio~w.
1.

_7_ The cores of the present invention comprise an upper and a lower fluid acquisition/distribution component. The respective fluid acquisition/distribution components can provide a variety fimctions in the absorbent cores of the present invention. One fiuiction, particularly for the upper acquisition/distribution component, is to initially acquire the discharged body fluids. Another key fiu~ction is to transport and distribute these acquired fluids to other absorbent core components, and in particular the fluid storage components of the absorbent core. In some instances, the fluid acquisition/distribution components according to the present invention can include at least some hydrogel-forming absorbent polymer and thus provide some fluid storage capacity for the absorbent core.
The detailed description that follows refers generally to the materials useful as eithedboth of the acquistion/distribution components. Though referred to in the singular, the description applies to both of these core components. As incorporated into the cores, the upper and lower components may be substantially the same, or they may be different, as discussed below.
The fluid acquisition/distribution component of the present invention can comprise a variety of fibrous materials that form fibrous webs or fibrous matrices.
Fibers useful in the fluid acquisition/distribution component include those that are naturally occurring fibers (modified or unmodified), as well as synthetically made fibers. Examples of suitable unmodified/modified naturally occurring fibers include cotton, Esparto grass, bagasse, kemp, flax, silk, wool, wood pulp, chemically modified wood pulp, jute, rayon, ethyl cellulose, and cellulose acetate. Suitable synthetic fibers can be made from polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene chloride, polyacrylics such as ORLON~, polyvinyl acetate, polyethylvinyl acetate, non-soluble or soluble polyvinyl alcohol, polyolefins such as polyethylene (e.g., PULPEX~ and polypropylene, polyamides such as nylon, polyesters such as DACRON~ or KODEL~, polyurethanes, polystyrenes, and the like. The fibers used can comprise solely naturally occurring fibers, solely synthetic fibers, or any compatible combination of naturally occurring and synthetic fibers.
The fibers useful in fluid acquisition/distribution components of the present invention can be hydrophilic, hydrophobic fibers that are made hydrophilic, or can be a combination of both hydrophilic and hydrophilized hydrophobic fibers. As used herein, the term "hydrophilic" describes fibers, or surfaces of fibers, that are wettable by aqueous fluids (e.g., aqueous body fluids) deposited on these fibers. Hydrophilicity and wettability are typically defined in terms of contact angle and the surface tension of the fluids and solids involved.
This is discussed in detail in the American Chemical Society publication entitled Contact Angle. Wettabilitv and Adhesion, edited by Robert F. Gould (Copyright 1964). A
fiber, or surface of a fiber, is said to be wetted by a fluid (i.e., hydrophilic) when either the contact angle between the fluid and the fiber, or its surface, is less than 90°, or when the fluid tends PCT/US97r0434 l wo 9~rr3.~s3~
to spread spontaneously across the surface of the fiber, both conditions aorraally coexisting.
Conversely, a fiber or surface is considered to be hydrophobic if the contact angle is greattr than 90° and the fluid does not spread spoatarroously across the surface of the fiber.
Other fibers useful as the fluid aquistitiooldistributioo component are hydrophobic fibers that are vrettable due to their geometry. Such fibers include "capillary channel fibers"
such as those described in U.S. Patent No. 5,200,248, to 'Zhornpson a al. and U.S. Patatt No. 5,268,229.
Suitable hydrophilic fibers for ux lo the Ardent intreMion include cellufosic 5bers, madifiad cellulosic fibers, rayon, polyester fibers such as polyeshykne terephthalata (e.g., DACRON~, hydrophilic nylar (HYDROFIL.~, and the like. Suitable hydrophilic fibers can also be abtaioed by hydropluli~og 6ydrap6obie 6bara, suds as surfiu~t-seated or silica-treated thannoplaatic fibers derivrod from, for a~pk, polyokftas such as pdyothYkac ~ PdYProPY~. PdY~fi'~ PdY~~. PdY~Y~. P~and the tike. For reasons of availability sad cost, exltukisic fibers, in particular wood pulp fibers, are prekcred f~ use in the present iav~ioa.
Suitable wood pulp fiber: can be obtioed Eras wdl-imown 1 pmoessa such a: dse KraB and sulfite prx~a. It is espocially pte~rred to derive these wocxi pulp fibers from southern sob wood: due to their pranium abso<barcy charactaistica. 7be:~
wood pulp fibers can a!~ be abed from mechanical proxase:, such as ground v~aod, refines mechanical, tbermoatechaaieal, drasrimechanical, and dtmai-t6ann~aneda~~iraf pule processes. Recycled a secondary wood purr fibers, ss wet! as bred and toblnched wood pulp fiber:, can be usod.
A desirabb sauroe of hydrophilic fibees fx use in the premnt mvearxoa are chms~lly s~ased ael4rlovic 5bars. A: usod herdo, , tha tetra "c6anically stiffared allubaic fibem" mew edluloefc fiber: that have bemWmod by dtmtin! mnoa to iacraue me of the ~s trader both dry and aqueous eonditiaoa. suds rams can mdrds tha addhioo of s dterswnl agent dnt, 5or mnr~l0. corns aodla imps tire . Sw~ ntms can also ioddde the of the sba3 by wring the char~a!
sDr>~n0. eg.. 6Y PdY~ c~i~.
Pdymaia sgmts that can coat a impoegtsate the oellukisic fibers indudc:
cationic modified snrdra hsviog >~m~~g (e.s-. ~ ) ~ of those available 5nm N~iooal Stardr and C~ai Carp., Bridgewater, NJ, USA;
latexes;
wet rain: arch a: polyamiderepichlordrydriri resin (e.g., lCyenene~ SfIII, ~iarules, lnc. w-O. , ~1~ PdY~Yres~r a~ibea, for ex~r~k, in u.s.
Patent 3,556,932 (Coacia et. al), iswed Ianuary 19, 1971; oomarercially available PdY~ bY ° CC°~ S~mford, CT, USA, ands the tiadmame Parea~ 631 NC; ores formaldehyde std mdamma focnatiddiyde resira, sad WO 97/3457 PC'f/US97/04341 _g.
polyethylenunick resins. A general dissertation ~ wet strength rcsu~ utilized in the paper art. and generally applicable herein, can be found in T.~PPI monograph seder No. 29. "VIlet Strength in Paper and Paperboard", Technical Association of the Putp and Paper Industry (New York, 1965).
These fibers can also be sti$enod by chemical reaction. For example, crosslinking agents can be applied to the fibers that, subsequent to application, are caused to chemically form intrafiber crosslink bonds. These croaatirdc bonds can increase the s<i~uas of the fibers. While the utilimtimr of iatrafiber crosslink bonds to chanicaliy stiffest the fiber is preferred., it is trot meant to exclude other types of rta~ctiona for chemical stiffening of the fibers. Fibers stiffened by crosslink bonds in iadividualimd form (i.e., the individualized stiffed fibers, as weU as processes f~ their preparation) are discb:ed, for example, is U.S.
Patent 3,224,926 (Hernardin), issued December 21, 1965; U.S. Patent 3,440,135 (C6ung), issued April 22, 1969; U.S. Patetu 3,932,209 (Clntterjee), ias~red laauary 13, 1976; sad U.S. Patent 4,035,147 (Sangeais et al), issued July 12, !9i''I. More preferred stiffened 5bers are disclosed in U.S. Patent 4,822,453 (Dean a a1), issued April 18, 1989;
U.S. Patent 4,888,093 (Dean a al), issued Dearrrber 19, 1989; U.S. Patent 4,898,642 (Moors a al), issued February 6, 1990; and U.S. Patent 5,137,537 (Flaroo a al), issued August 11, 1992.
In the more preferred stiffened fibers, chemical processing includes intraflber crosslinking with cxosslinking, agents while such fibers are in a relatively dehydrated, defibrated (i.e., individualized), twisted, curled condition. See, for example, U.S.
Patent 4,898,642.
These chilly atiffmed alluloac fibers have certain propexda that ca~o u~iOe them particartarly usefitl in 9uid aequisitioddi:tributioo caenponaots acoordiog to the pteaeat mv~ioo, r~iv~e to m~tiffeaed ceUuloaic fibers. 1n addition to beia fi 6ydnophilic, these sriffeoed fibers have uoiqae canb~ona ~ and resiliency. 'Ibis a1>aws ti~enetaliy banded Said ao~ioddistriMttion oompoomts made with tiuaie fibers to rnaiutsia 6ig6 l~eb of >~oc~ivay, and to exhibit high kvds of reai>ieacy and an expao:ionaiy ~ive~ m wetting. I:t psrtiathV, the resiliency of these tamed fiber arsbies the fluid soqu»tioddi~stribtttian oorrtpooent to better aaaicita~ its capillary stntcdrr~e m the prn~oe of both fluid and oornpreaaive forces ooemaUy aroountered during use and are thus more resist»t to oo>ypse.
to the a~ of tbamally bonded 9uid soQv~tiodd~trib~ioo oompooa~ useful is the prat inva~o~, a tbamophmtic material is inchrded wah the fibers. Upon mdtiog, at least s portion of this tha~mopta~ic mateci~al megtatm to the iatecsoctiooa of the fibers, typically due to iattr5ber apillary gradients. 'Ibex iatersecx>oos become hood sites for the tbamopfasde material. When ooolod, the tbennopiaatic mataisls sit these iaooetsectioos solidify to form the bond sites that hold the matrix or web of fibers together in each of the respective layers.
Amongst its various effects, bonding at these fiber intersections increases the overall compressive modulus and strength of the resulting thermally bonded fluid acquisition/distribution component. In the case of the chemically stiffened cellulosic fibers, the melting and migration of the thermoplastic material also has the effect of increasing the average pore size of the resultant web, while maintaining the density and basis weight of the web as originally formed. This can improve the fluid acquisition properties of the thermally bonded fluid distribution component upon initial discharges, due to improved fluid permeability, and upon subsequent discharges, due to the combined ability of the stiffened fibers to retain their stiffness upon wetting and the ability of the thermoplastic material to remain bonded at the fiber intersections upon wetting and upon wet compression. In net, thermally bonded webs of stiffened fibers retain their original overall volume, but with the volumetric regions previously occupied by the thermoplastic material becoming open to thus increase the average interfiber capillary pore size.
Thermoplastic materials useful in fluid distribution components of the present invention can be in any of a variety of forms including particulates, fibers, or combinations of particulates and fibers. Thermoplastic fibers are a particularly preferred form because of their ability to form numerous interfiber bond sites. Suitable thermoplastic materials can be made from any thermoplastic polymer that can be melted at temperatures that will not extensively damage the fibers that comprise the primary web or matrix of each layer.
Preferably, the melting point of this thermoplastic material will be less than about 190°C, and preferably between about 75°C and about 175°C. In any event, the melting point of this thermoplastic material should be no lower than the temperature at which the thermally bonded absorbent structures, when used in absorbent articles, are likely to be stored. The melting point of the thermoplastic material is typically no lower than about 50°C.
The thermoplastic materials, and in particular the thermoplastic fibers, can be made from a variety of thermoplastic polymers, including polyolefins such as polyethylene (e.g., P(JLPEX~ and polypropylene, polyesters, copolyesters, polyvinyl acetate, polyethylvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polyacrylics, polyamides, copoiyamides, polystyrenes, polyurethanes and copolymers of any of the foregoing such as vinyl chloride/vinyl acetate, and the like. One preferred thermoplastic binder fiber is PLEXAFIL~
polyethylene microfibers (made by DuPont) that are also available as an about 20% blend with 80% cellulosic fibers sold under the tradename KI1TYHAWK~ (made by Weyerhaeuser Co.). Depending upon the desired characteristics for the resulting thermally bonded absorbent member, suitable thermoplastic materials include hydrophobic fibers that have been made hydrophilic, such as surfactant-treated or silica-treated thermoplastic fibers derived from, for example, polyolefins such as polyethylene or polypropylene, polyacrylics, polyamides, polystyrenes, polyurethanes and the Like. The surface of the hydrophobic thermoplastic fiber can be rendered hydrophilic by treatment with a surfactant, such as a nonionic or anionic surfactant, e.g., by spraying the fiber with a surfactant, by dipping the fiber into a surfactant or by including the surfactant as part of the polymer melt in producing the thermoplastic fiber. Upon melting and. resolidification, the surfactant will tend to remain at the surfaces of the thermoplastic fiber. Suitable surfactants include nonionic surfactants such as Brij~ 76 manufactured by ICI Americas, Inc. of Wilmington, Delaware, and various surfactants sold under the Pegosperse~ trademark by Glyco Chemical, lnc. of Greenwich, Connecticut. Besides nonionic surfactants, anionic surfactants can also be used. These surfactants can be applied to the thermoplastic fibers at levels of, for example, from about 0.2 to about 1 g. per sq. of centimeter of thermoplastic fiber.
Suitable then~noplastic fibers can be made from a single polymer (monocomponent fibers), or can be made from more than one polymer (e.g., bicomponent fibers).
As used herein, "bicomponent fibers" refers to thermoplastic fibers that comprise a core fiber made from one polymer that is encased within a thermoplastic sheath made from a different polymer. The polymer comprising the sheath often melts at a different, typically lower, temperature than the polymer comprising the core. As a result, these bicomponent fibers provide thermal bonding due to melting of the sheath polymer, while retaining the desirable strength characteristics of the core polymer.
Suitable bicomponent fibers can include sheath/core fibers having the following polymer combinations: polyethylenelpolypropylene, polyethylvinyl acetatelpoly-propylene, polyethylene/polyester, polypropylene/polyester, copolyester/polyester, and the like.
Particularly suitable bicomponent thermoplastic fibers for use herein are those having a polypropylene or polyester core, and a lower melting copolyester, polyethylvinyl acetate or polyethylene sheath (e.g., DANAKLON~, CELBOND~ or CHISSO~ bicomponent fibers).
These bicomponent fibers can be concentric or eccentric. As used herein, the terms "concentric" and "eccentric" refer to whether the sheath has a thickness that is even, or uneven, through the cross-sectional area of the bicomponent fiber. Eccentric bicomponent fibers can be desirable in providing more compressive strength at lower fiber thicknesses.
Suitable bicomponent fibers for use herein can be either uncrimped (i.e.
unbent) or crimped (i.e. bent). Bicomponent fibers can be crimped by typical textile means such as, for example, a stuffer box method or the gear crimp method to achieve a predominantly two-dimensional or "flat" crimp.
In the case of thermoplastic fibers, their length can vary depending upon the particular melt point and other properties desired for these fibers.
Typically, these thermoplastic fibers have a length from about 0.3 to about 7.5 cm long, preferably from about 0.4 to about 3.0 cm long, and most preferably from about 0.6 to about 1.2 cm long.
The properties, including melt point, of these thermoplastic fibers can also be adjusted by varying the diameter (caliper) of the fibers. The diameter of these thermoplastic fibers is typically defined in terms of either denier (grams per 9000 meters) or decitex (grams per 10,000 meters). Suitable bicomponent thermoplastic fibers can have a decitex in the range from about 1.0 to about 20, preferably from about 1.4 to about 10, and most preferably from about 1.7 to about 3.3.
The compressive modulus of these thermoplastic materials, and especially that of the thermoplastic fibers, can also be important. The compressive modulus of thermoplastic fibers is affected not only by their length and diameter, but also by the composition and properties of the polymer or polymers from which they are made, the shape and configuration of the fibers (e.g., concentric or eccentric, crimped or uncrimped), and like factors.
Differences in the compressive modulus of these thermoplastic fibers can be used to alter the properties, and especially the density characteristics, of the respective absorbent members during preparation of the absorbent core.
As noted previously, in some absorbent cores according to the present invention, the fluid acquisition/distribution component can include hydrogel-forming absorbent to provide some fluid storage capacity for the core. In those instances, the fluid acquisition/distribution component can comprise up to about 50% hydrogel-forming absorbent polymer.
Preferably, the fluid distribution component comprises up to about 30% hydrogel-forming absorbent polymer. Most preferably, the fluid distribution component comprises up to about 15%
hydrogel-foaming absorbent polymer. For the upper fluid/acquisition/distribution component, it is generally preferred that there be essentially no hydrogel-forming polymer.
The fluid acquisition/distribution component can also or altennatively comprise a polymeric foam material. Particularly suitable absorbent foams have been made from HIPEs. Though they differ with respect to certain properties from those foams discussed as being useful as the fluid storage component, the foams are open-celled, polymeric materials.
See, for example, U.S. Patent 5,260,345 (DesMarais et al), issued November 9, 1993 and U.S. Patent 5,268,224 (DesMarais et al), issued December 7, 1993. These absorbent RIPE
foams provide desirable fluid handling properties, including: (a) relatively good wicking and fluid distribution characteristics to transport the imbibed urine or other body fluid into the unused portion of the absorbent article to allow for subsequent gushes of fluid to be accommodated; and (b) a relatively high storage capacity with a relatively high fluid capacity under load, i.e. under compressive forces. These HIDE absorbent foams are also sufficiently flexible and soft so as to provide a high degree of comfort to the wearer of the absorbent article. See also U.S. Patent 5,147,345 (Young et al), issued September 15, 1992 and U.S.
Patent 5,318,554 (Young et al), issued June 7, 1994, which discloses absorbent cores having wo 9~r~ass~ pCTms9mo~ ~

a fluid acquisition/distribution component that can be a hydrophilic, flexible, open-cellod foam such as a melamine~focmaldehyde foam (e.g., BASOTECT made by BASF), and a fluid storagdredistribution component that is a HIPfi-based absorbent foam.
Then foam-basod acquisitioa/disuibution components should allow rapid fluid acquisition, as well as efficient partitioning or distribution of fluid to other componarts of the absorbent core having higtarr absorption pressures than the desorps~n pressure of the acquisition/distribution foam. 'ibis properly of fluid deaotption Lo otter core components is important in en6mcing the ability to accept tepatad d<schacgca or badings of fluid and to maintain <be akin dryness of the wearer. It alw allows the a~uisitioddistributioo foam to serve as a void volume reservoir, or buf5er aone~, to sar~CSriiy hold Said that can be acprased imm the storage comporxats of the core when extrac~rdinatily high pn~ura are mcouatered ~uiog ux of the abaabem srticle.
Lr giving this fluid to other core oompor~, these foam-based aaquisitioddistributioa compoomts should do :o vvi~out defying or collsp:acrg.
Form-based aoquia~tiaa/ disonibutioa oompoomxs s6arld ado radily accept $uid, with a without the aid of gravity. Foam-bred soqu>aidoo/distn'bution oompomrta ahouki fuether provide good aa, be sots and railinot in :au~re, sad have good pl~al qty in bode wet and dry sees.
Other foams useful as such acquisition/distribution components are described and claimed in U.S. Patent No. 5,563,179, issued October 8, 1996, by Stone et al.
These foams offer improved fluid retention and desorption (i.e., ability to relinquish fluid to other absorption components) properties, resulting from the processing conditions descried therein. Briefly, the ability to provide these improved foams lies with the use of low shear conditions and a robust emulsifier system during HIPE processing.
Still other foams useful as the acquisition/distribution components are described and claimed in U.S. Patent No. 5,550,167, issued August 27, 1996 by DesMarais.
These foams offer still better acquisition and desoprtion , properties, again because of advancements made in the processing (e.g., low shear) and the emulsifier employed.
2. ~id.~~o 'the nnseflst as e6o fluid atorsge ooaapoomt tl~t are apsbk of a~rb~ lad ~ ~Y ~. ~ a wilt other optiaost oompooea~ such as 8ben, tbetaAOpIssac material, etc. In addmaa to die propatiea, .
mated as dre upper fluid storage component must be aipable of swdtiag ira the z-d~ctian t>pc~ 9Wd, so as ~o form the 9uid a~ui:aioo aoaa Mama capable of pa: the upper fluid ~on~e ooarpoomt(s) ioW de subirsuatiaUy water-imolnbk, water swellable absorbent polymer materials commonly referred to as "hydrogels", "hydrocolloids", or "superabsorbent" materials (for the purposes of the present invention, these materials are collectively referred to as "hydrogel-forming absorbent polymers"); and open-celled foam materials that remain in a collapsed (i.e., unexpanded) state until contacted with aqueous body fluids.
A principle function of these fluid storage components is to absorb the discharged body fluids either directly or from other absorbent core components (e.g., the fluid acquisition/distribution component), and then retain such fluids, even when subjected to pressures normally encountered as a result of the wearer's movements. Another important funtion of the upper storage components) is their ability to swell to form the fluid acquisition zone. (It should be understood that the fluid storage components) can serve functions other than fluid storage and formation of a fluid acquisition zone, such as improving body $t.) Regardless of the material used, it is preferred that the upper storage component be capable of expanding in the z-direction from the dry, compressed state by at least 100% when fully saturated. Such z-directional expansion will effectively increase the volume of the fluid acquisition zone. However, those skilled in the art will recognize that the width and length of the fluid acquisition zone is also important to overall volume, and materials that do not swell in the z-direction by 100% may still be useful herein.
a. Hvdrogel-forming Absorbent Polymers When hydrogel polymers are used, an important aspect of these fluid storage components according to the present invention is that they contain a relatively high concentration of the absorbent polymers. In order to provide relatively thin absorbent articles capable of absorbing and retaining large quantities of body fluids, it is desirable to increase the level of these hydrogel-forming absorbent polymers and to reduce the level of other components, in particular fibrous components. In measuring the concentration of hydrogel-forming absorbent polymer, the percent by weight of the hydrogel-forming polymer relative to the combined weight of hydrogel-forming polymer and any other components (e.g., fibers, thermoplastic material, etc.) that are present in the fluid storage component is used. With this in mind, the concentration of the hydrogel-forming absorbent polymers in a given fluid storage component according to the present invention can be in the range of from about 50 to 100°/g preferably from about 60 to 100%, more preferably from about ?0 to 100%, and most preferably from about 80 to 100°/., by weight of the storage component(s).
A wide variety of hydrogel-forming absorbent polymers can be used in the fluid storage components of the present invention. These hydrogel-forming absorbent polymers have a multiplicity of anionic, functional groups, such as sulfonic acid, and more typically carboxy, groups. Examples of absorbent polymers suitable for use herein include those which are prepared from polymerizable, unsaturated, acid-containing monomers, including WO 97i3.t557 PCflUS97/Od3d1 -IS-the olesnically unsaturated acids and anhydride that contain at least one carbon to carbon olcfinic double bond. Morc specifically, these monomers can be selected from olefuoically unsaturated carboxylic acids and acid anhydride. ote5nically unsaturatod sulfonic acids. aad mixtures thereof. See U.S. Patent 5,324,561 (Rezai et al), issued June 23, 1994, which describes suitable absorbent polymers and their preparation.
Preferred by~oSel-fo~ a~orb~ Po~ use in the pta~ invedtiaa chin carboxy groups. ~ include hydroiymd staerh.atxyfonitrife ~R oopolyrr~, P~t~lly oattcaliaed cryboitrik ~ aoPdYmas. s~tc6-acrYlic acid daft copolymers, partistty nmtraliaed starch-acrylic scud BzaR copolymers.
sapaoi5ed vinyl a~oaatcacryiic ewer oopolyttras, hydsoiymd aay>~i~ie of a~a~dc ~PdY~~
ndwatit crossiiniaed polymers a~' any of tlse ~ote~ oopofyrners. partiaDY
aatttalised polyaay4c acrd, asyd :Li~dy oe~odc csossliokad polymers of part>slty a~attralimd polyactylic acid. ?Itase polymers caa be seed either solely or ~ t6e Form of s ntu~ue ef two a mere di~amt pdymas. Fxampln of tbme potymar maps are disclosed in v.S.
Pateat 3,661,$75, U.S. Patmt 4,076,663, U.S. Pa~at 4,093,776, U.S. Pa~teoit 4,666,983, and ~US. Patent 4,734,<?a.
M~ort probated lsydea8d-P~ we in the ptaao~t ioveatioo are sli~dy ae~otiC crotslinlaed Polymer: ~'°~°d polyay fK aads aad std derivatives <baeo~ Most p~raWY. the absaeb~ P°°0~°'m abo~
i0 to abort 73X, netttnliaed, shy ~dmd, poryaayl~ aad about 95'X., p~SaaMy (i.e. poly (sodwbuen aay~d~Yl~ ~). l~ooaea for m~oeic eroaliddoS the Pdym~
and typr~t ~k ai ~ '° ~ m ~ 6aeiobeEoro-ee6aaooed U.S. Paoeot 4,076,663. -.~ ~y~..~ebmt pdywa~ as be Fonaed in aey oosW nd . ~,' 1~ absotboot polysiees a~ those tlhisct i~oive s~.o~ ,~rt~ ~ a~ eon pd. s.e. ~ Vie. v.s. »e Pare 32,6~9 (Bmndt et al). ~ 19~ 1963. W6ik it is pfd dart dse abeor~c potymeea be o~a~u~d ~i ~ s°~°°
p°~~~'°° ~'°°~' ~ is oleo poke m wry not die ~ P~ ~ PdY~~°° ~°°~
~ as ia» pdYa i~se sat~i~os pofYua~°
pcooedutes. Sae U.S. Pst~t 4.310.'106 tObay~ a an. ~d ~Y ~~ 1982, v.S. Patrac 4,506,052 ~(Fletwbar d alj, iswved 19, 1981, and U.S. Pamoe 4,733,917 (Maoris et al).
issued AprB ~5, 1988. ~r P~ invoMng inverse suspension polyme~~n.
These absorbent polymer - ~ synthesized ~ or made in . a variety of shapes' and sizes. including fibers, granules, flakes a~ puMen~nts. However, these absorbent poi are most commonly supplied as absorbent particles or particulates.

PCT~tlS9~~os3a a WO 9 ~!3455~
-16~
One preferred class of hvdrogel~fonrtung absorbent polymers useful w the present invention are those which exhibit a high absorptive capacity. Absorptive capaary reins to the capacity of a given polymer matrrial to absorb liquids with which it comes into contact.
Absocptivc capacity can vary signifiantly with the nature of the liquid being absorbed and with the manner in winch the liquid coarsen the polymer material. For purposes of this invention, Absorptive Capacity is deftoed in terms of the amount of Synthetic Urux absorbed by any gives poiyma raataial in tai of grams of Sy~tic Urine per gram of polymer nsaterial is a procedure dtbnod is the Test Metlfods satiuo of L?.S. Pate::t 5,324,56: fRraa et al), issued June 23, 19)4. Preferred absorbent polymers having a high absorptive arc those which nave an Absorptive Capacity of a_t least about 20 gams, more preferably at Icsst about 25 grams, of Synthetic Urine per gram of polymer material. Typically, there highly absorptive polymers Crave an Absorptive Cap:city of from about 20 grams to about 70 gr» of Synthetic Urine per gram of potyma e:saterial. Absocbeat potyntecs having ties relatively high absorpaive capacity charuserisac are spatially uxful in fluid storage oompoo~s of the peusmt iaveation slate they hold desirably hig>tz amarn<s of discharged body aaadatex such as urine.
Another preferred class of hydrogel-forming absorbent polymers useful in the present invention are those having relatively high Saline Flow Conductivity (SFC) values and relatively high Performance Under Pressure (PUP) capacity. See U.S.
Patent No. 5,599,335 (Goldman et al), issued February 4, 1997, where SFC
values and PUP capacity are defined and methods for measuring these parameters are provided. Absorbent polymers useful in the present invention can have SFC
vrslues of at lest about 30 x 10'y cm3aec/g, Pr~sabiy at leant about 50 x 10'~
au3seclg.
and most prefrxably at (east about 100 x 10'~ aa3sedg. Typically, these SFC
values are is the raa~e of from shoot 30 to abaft 1000 x 10'~ car3xc~g, aaee typically fran about 50 to about SOO x lord ~aeclg, sad most typically »an about 100 to about 350 x 10-~
~r~d~. Ab:ocbeot potymes3 uadut in the prat invention ~Saliy have s PUP
capacity at isnt abaft Z3 g/g: p~lY rt least about 25 g/g, and moat p:~aably at least about 29 glg, Typiolly, tie PUp~ opacity value arc in the range of ifrarr about 23 to about 35 glg, .
raoee typically from about 25 to about 33 gag, sad most typically from about 29 to about 33 Surface crossliohg ~' the initially formed polyaras is s preferred process for obmioia~g hydrogd-forming absorhcot PdY~ ~~ 5' ~ SFC and PUP capacity A ~ pfx ;ntra~ciog surface crosslioio arc disclosed in the art.
These ioaude those where: (i) a di- or poly~fiurcdoeial reagrat(s) (e.g., glyaxal, 1.3-dioxolaa-2~ate, polyvalent instil ioos~ P~Yqu~'~'S' ~) ~k of ratting with g ~ ~ ~ _polyena a applied to tire WO 9713t55~ PC'T/L~S9"043x1 -1?-surface of the hvdrogel-forming absorbent poiyaner; (ii) a 4i- or poly-functional reagent that is capable of rcactmg with other added reagents and possibly existing funcuonal groups within the hydrogel-fonnu~g absorbent polymer such as to increase the level of crossliaking at the surface is app4ed to the surface (e.g., the addition of monomer plus crosstis>fcer sad the initiation of a second polymerization ncaction); (iii) no additional poiyfunctional rcagcnts arz addod, but additional reactions) is induced amongst existing eornponents within the hydrogel-forming absorbent polymer either during or aficr the primary poiymeri~tion process such as to generate a higher level of crosslinking at or near the surface (e.g., heating to induce the formation of anhydride and or esters c~slinks bamem existing polymer carboxylic acid and/or hydroxyl groups sad :uspeasion poiymerimtion procaaes wherein the crossIinker is iahereatly present at higher levels near the surface); and ('rv) other materials are added to the surf$ee such as to induce a highs level of crosslinldng or otherwise raduce the surfyx deformabiliey of the resultant hydrvgel. Cornbinaiiona of these s~ufsx crosslinidag prooesse:
either concurrently or in can ah3o be anployed. In addition to crosstiolaag rags.
other coenponans can be add6d to the surface to aidloontrol the distribution of crocsliaidag (e.g., the spreading and penetration of the surface crosslinking reagents.) See U.S. Patent No. 5,599,335, issued February 4, 1997 (Goldman et al).
Suitable general methods for wryin8 out surface c~ssliaidng of hydrogel-fotmia8 ~p~y~ ~~g to the Pcrsmt invention see discloaod is U.S. Patent 4,541,871 (Obayashi), issued S~b~ 17, 1985; published PCT' appiacaoion W092J16565 (Stsoky), published October 1, 1992, published PCT application W090/08789 (Tai), publishod Augur; 9, 1980; publis6~ed PGT appli~iod WO93/05080 (Stanley), published March 18, 1993; U.S. Parrot 4,824,901 (Almandet), is:wed April 23, 1989; U.S. Pam~t 4,789,861 (J~n), i:suod January 17, 1989; U.S. Pateert 4,387,308 (Maidsa), issued Msy 6.
1986;
U.S. Paseo~ 4,734,478 (Tsubakirooto), issued Match 29, 1988; U.S. Patent 5,164,459 (>IGeoes at al.~ issa>ed Nwemba 17, 1992; published Gan~aa past applieabon 4,020,780 (~, pub~a6ed August 29. 1991: and pubtis6ad European Part application 509,708 (Gariner), published October 21, 1992. See also U.S. Patent No. 5,599,335, issued February 4, 1997, (Goldman et al) and especially Examples 1 to 4 While t6ae hydt~l-foc~g abs~ P~ fly øan the same moo~omecs sad have the same propatia. ~s need Wbe the sure. For txampk, some sbsocbamt polya~s can oomptix a arch-a~hc acid graR oopoiyma while other alssarbait p~ can oonrpCi:c a slightly network croasiiniood polymer of partially neutnlired polyscryfic acid. Further, the absorbent polymers can vary is size, shape, absorptive ~p~,~ ~ ~,y ~. property a characxaiscic. la preferred embodiaamts of the present we 9u~a~sz invention, tlu absorbent polymers consist essentially of slightly c~etworlc crossliokod polymers of partially neutralized polyacrylic xid, each absorbent particle having simile properties.
Une prefierrod fluid storage carnponent xcarding to the presatt invention having a relatively high concauration of these hydtogd-fonnir~g absorbent polymers is in the fornn of porous, absorbent microstructures. nasccrostructuea sre forrrred from a multiplicity of intercmnectod hydrogd~foetning sbsarbart polyaAa psrticles. 'lose macrastructures are capable of absorbing large quantities of aqueous body fluids (e.g., urine or mean) and rhea rdainia~g such liquids under anod~a~e pressures. Becsuse they are fo~rred from particles, these macrostrtestura have pores between sdjaca~ particle:. 'Ibex pores are interconnected by intercornmunicatiog charmels such that the macrostrucNre is 8nid penr~abie (i.e., has ap~Y ).
Dire m the bonds formed betw~ear the articles, the resuhant ale macr~ostruc~res lave dnpro~red st~tat pity, wed fluid acquisition and distribvtiaa rates, noel mioirnal ~ charaarristics. W6aa wemod with aqneo~us fluids, the mac~cArre swells g~erally isodo~sllY eves ur>da abderate eoa5aio~
pressers, abate such into ttfe pores bdween the particles, and thm imbibes wch fluids into tb~s p~rticks. 'ILa isotropic sw~d~og of the ma~a~enrctdre slto~ws the psrdcla and the pores to rnaintaio their relative geea°atiy and apatW relamooships avm whm svsol~a.
'Ilws, the mact~o~ctura arc relatively "fluid stable" is that the pactida~ da not dissoa~e i~om eadi otba, tbaeby miaimiaog the mcideaoc of gel arrd allowing the ~arusds to be mend et~ed v~r6~ sw~otlm :o fast the a~rostructure can aocpeire sad tra~port mbsoof fiqnid, evm hq~. See U.S. Ps~t 5,102,597 (Roe a se, iswed ApN ?, 1992, and U.S. Pata~t 3,324,561 (Real a al), rued lu~ne 23, 1994. As referred to herein, these macrostru~tures of interconnected particles are referred to as "fluid stable microstructures" or "fluid stable aggregates".
W6~ these macnrtnretures can hsve a ameba of shapes and sins, they are typio~r is the feral of ~eetr, fibns, cYliodas. bioc~. apha'es. .. . a other ~S, 'Ibeae mace~oana~res will ReOerslllr hsve a or diam~a between abouE 0.2 maA and shoat l0.0 Win. Prey ehex tmcroatxu~ras are in the form of sheets or stt~. 'lba tams "s6ee~' of "stop:" as used harem ~er~ mec ooatnldttre's lrivtng s tbid~ of rt last about Q.2 mm. 'The sheets a drips wiU !y hstve a tbiiclas~a betw~em about, 0.5 mm and about 10-men, typically from about 1 nun to about 3 mm.
'I~e ructures :m Fonoed; by tba ,jog ac ad6aiug S of s particles- 'The sgaat is ~ PdY~ tit is prat is the of than psrtides. W6m these p~artida are framed with s, cras:iinloog agent and Phi , t~ P°lymer a~a~al presort in tire sarfaoe of these particle is 1~V0 97/34557 sufficiently plastic and cohesive (e.g., sticky) such that adjacent particles are adhered together, typically as discrete linking portions between the particles. The crosslinking reaction betvveea the particles then sets this adhered structure.
In preparing these microstructures, a crassliaking agent is used to provide crosslinking at the surface of the absorbent precursor particles. 'this typically occurs as a result of the crosslinking agent by rating with the pofyrnet ma:acrial in these particles.
Typically, the polymer material of the absorbent precursor particles has anionic, aid preferably carboxy, fiu~ctional groups that form a covalent, ester type bond with the crosslinking agent. These poi of the at~otbeat particle that have been effoctivdy crosslinked will swell lass in tht pt~ae~x of aqueous (body) fluids relative to the other uncrasstioked portions of the particle.
Suitable crosslinking agents for this purpose can be nonionic and possess at least two functional groups per molecule capable of reacting with the carboxy group.
See, for example, U.S. Patent 5,102,597 (Roe et al), issued April 7, 1992, which discloses a variety of nonionic crosslinking agents. The particularly preferred nonionic crosslinking agent is glycerol. A preferred crosslinking agent for use in these microstructures is adduct of epichlorohydrin with certain types of monomeric or polymeric amines. See U.S. Patent 5,324,561 (Rezai et al), issued June 23, 1994, and which discloses suitable cationic amino-epichlorohydrin adduct crosslinking agents. These amino-epichlorohydrin adducts, and especially the polymeric resin versions of these adducts, are preferred aosslinking agents because they react only with the polymer material at the surtace precursor particles.
In addition, the cationic functional groups (e.g.. azetedinium groups) of these adducts, particularly polymeric resin versions, are believed to react very rapidly with the anionic, typically carboxy, functional groups of the polymer material of the absorbent particles, even at room temperature (e.g., at from about 18° to about 25°C). Most preferred are certain polyamide-polyamine-epichlorohydrin resins particularly commeroially marketed by Hercules Inc. under the trade name Kymene~.
FapeaaUy ~ are Kymm~ SS'hI, Kynimem s57LX and Kymme~ 557 Phu, wbieb are the apiddatoby~drin adduct ~ Pdy~nido-pdyami~ that a~ the racsaon of diethyla~triamioe and adipic aid. 'Ihty are typnJly anrlaeted in the 6oem of aqueous sotudoos of the cationic resin maoeria! ~iutin,~ from about 10'Y. to about 33x. by weight of the lain aeriv~e.
in pre~aciog tbne porno:, absor6eat meec~trtafitra, the a6aorbart pawclea are traced with the agent, shag with auy otba ooatpooeata or agasts. For example, wata< is typically used with the ~osagent to ferns no aqueova orea~neot soitttion d~er~f Water promotd the uai~tm di:pessioN of the ao::Lolaog agent an the :,rr6oe of the absorbent ps~lee and auu~a pamation of the sgeat ion tba surface PCT~'L'S97i0d341 w~ 9~r3ass~
_20_ regiocLS of these particles. Water also promotes a stronger physical associauon becwecn the treattd precursor pacucla, providing greater integrity of the resultant inttrparuclc bonded crosslialced aggregates. See U.S. Patent 5,102,597 (Roe et al), issued April 7, 1992 (nonionic crotsliaking ageutt suci~ as glycerol), afld U.S. Patent 5,324,561 (Rcz3i et al), issued June 23, 1994 (cationic amiao~epichlorohydrin adduct etnsslinidng agents).
It is particularly peeferred that the treatment solution include a plasticiacr, especially wlua cationic amioo~picbtorohydria adducts are used as the uossiioking agent.
he preferred plasticiTrr is a etixurre of glycerol and water, partiNluly w~ included as part of as aqueous treatment soltation of tire otiose aetrioo-epic>dacohydrin adduct, lies a weigl't ratio of glycerol to water of front about 0.5:1 to about 2:1, p:eferably Sons about 0.8:1 to about 1.7:1. See U.S. Patent 5,324,561 (Rezai et al), issued June 23, 1994. Before, during, or after treatment with crossiinking agent, and optical plasticizer, the particles are physically assoaated together to fomn the aggregate macrostructures. A
preferred method and apparatus for continuously forming these aggregate macrostructures into sheets is described in U.S. Patent 5.324,561 (Rezai et al), issued June 23, 1994 (cationic amino-epichlorohydrin adduct crosslinking agents).
See especially Figure 9 from this patent and its associated description.
Once the particles have bees physically associated togema to form an aggregate ma~erorG tba crvatiokiog sge~ is rnctod with the poly~r nustaiat ~' t6c precursor p~cla, while ataintainiag the physial association of the particles, to provide effective surface crossiioioog iin the p~srtida is the ale macrostrucdue. See U.S.
Patent 5,102,397 (Roe a aI~ isnted April 7, 1992 (moiooic e:rusliolang agea~ such as glycerol), snd U.S. Pa~eat 5,324,361 (Real a a>), issued June 23, 1994 (caniooic arnino-epichlorohydrin adduct crosslinking agents). When a~o.epie6lorohydriu add~ts are need as the aoas>ioloog amt, tfous aaaslidaog rescaon ci aawu at rdstivdy bw naeq~azntres, aacludaag aaabimd rooar tempaat<ua. Such ambient tcmpa~amte aa~ is partiattarly dai::bk w6ea tibe absorbent particles are treated a per, such as a m>xture of wares and giycaoL Curing at sigoy above a:ttbient temperatuas can Ouse the ph:ti~x to be driven off due to its volatility, t~
n~sitatiag as additional seep to pl~ticiae the resulting aggreg>st atacr~o~orte.
If' de~td, these rnxmsttucdca can include various types of 5bas to act as rdoforrang nrrmbQS. 'these include cellulose Sbers, modised cellulose 5bers, rayon, poiypropyleoe, and pdyester Sbea such a: poiyetiryiaoe te~thalatt (DACROI~, hydro~ilic sryioo (HYDROFR.~ and the lilac. F.xampks of other sber aerials err bydroplsiIimd hydmp>sobic fiber, such a surfxtaot-treated a silio-t:eatod lasflic WO 97I3d557 PCT/US97lOd3d1 -2l-5bers derived, for example, from poivokfuu such as polyethylene or polypropylene, potvacrylics, polyamides. polystyrrtn;s. polyurethanes and the ~ike. In fact, hydrop6ili~ed hydrophobic fibers that arc in and of thentselvcs not very absorbent and which, therefore, do got provide webs of suf5cient absorbent capacity to be useful in conventional absorbent structures, are suitable for use in these microstructures by virtue of their good wicking properties. Synthetic fibers sre generally preferred for use lu;rein as the fiber compooeat of the maoroswcture. Most preferred arc potyok5n fibers, preferably polyethylene f hers.
Oth~a suitable Huid storage aompo~ scc~dirtg to ~e present iaventioa can be is the form of a layer of Isydrogd-fa<mi~ absorbent polymer particles cootaiaed bawoen two other fibrous layers, e.g., a laminated fluid storage ooanponent. Suitable iamiraated 9uid storage components auxrding to the prams invaaioa can be prepared using prooodura similar to those described in U.S. Patent 4,260,443 (Lindsay et al); U.S.
Patent 4,467,012 (Pedas~ et an, issued August 21, 1984; U.S. 4,715,918 ~ (Laog~, issued December 29, 1987; U.S_ Patae 4,851,069 (Padcar~d a al), iaued July 25, 1989; U.S.
Patent 4,950,264 (Osbocn), issued August 2l, 1990; U.S. Paoatt 4,994,037 (Hauardin), issued February 19, 1991; U.S. Patatt 6,009,650 (8aoardin), issued Aluil 23, 1991; U.S. PaD~tt 5,009,653 (Osban~ issued April 23, 1991; U.S. Pstent 5,128,082 (Mak~asti), July 7, 1992;
U.S. Patent 3,149,335 (Kellmberga d alb issued Sept~tba 22, 1992; and U.S. Patent 5,176,668 (Bemardin), issued January 5, 1993. These laminated fluid storage components can be in the form of thermally bonded fibrous layers, adhesively bonded fibrous layers (e.g., glue bonding between the fibrous layers or between the fibrous layers and the hydrogel-forming absorbent polymer particles), or fibrous layers that are held together by hydrogen bonding (e.g., by spraying the fibrous layers with water followed by compaction).
If desbed. t~ ~ maerostrucmra or absorbent particle can be a~chod to a ~,bstrate to ilxm the fluid storage compoocats. The substraoc can provide a variety of (1) i~owtng the distribution of fluids to be ab:abed by the ~~y~,~; and (2) s~,pp~og the macrostrudurdpartida by prod ad~iaa~al i~tY Y m the si~aeion w6ae the t particle b~ ~ svmll air ~,;d, 'fie attbsuate can be trade from various materials io~owa in the alt such as odhtlose filxm, mwebs, tissue webs, 5oams, po>yacr9>a~ fibers, apaaued ~, syot~C fibers, m~allic foils, d~omers, and the like. Most suds avbatritte materi~s can distribute l3uida to, as yell as support, tibe macroswctuce/parikks.
ph,, the subsor:te is comprised of cellubsic ntatecial or a ntsterid having cellulosic tY, p~,for ~~tiqg fluids art cellulosic materials. fibrous mss, tissues, solid foart~t, cellulasiG Foams, and polY~Yl alcohol 5oams. Pce6aied ~' ~8 the mscrostrucarcelparticks are tissues, ceuubaic PCT/US99l04341 -22~
materials, fibrous webs, nonwoven webs, fabrics, cellulosic fibrous webs, solid foams, cellulosic foams, and polyvinyl alcohol foams. .
The substrate is preferably flexible and pliable to a~courage such properties in tlx resulting absorbrnt composite with the macrostnicwreJparticks. The substrate can be substantially resilient and ran-stretchable, or it can be srretdtabk or deformable to a varying extent in response to fotri exerted normal to and in die plane of the surface of the .
The tbidmess and basis weight (weight pa unit area of substrate) of tire substrate m~rial can vary depending on tire type of substrate and propatia desired. The substrate can comprise a plurality of individual shoats, a plies, of a particular substrane material, or a cosnbinat;oa of one or more substrate layers in a laminate. One such suitable substrate is a Hounty~ shoat having a thicla~ss of from about 0.02 nuu to about 1.2 mni, nmne preferably frwn about 0.3 mm to about 0.8 nun; std a basis weigiu of fray about 5 g/m2 to about 100 g/m2, more preferably from about 10 g/m2 to about 60 g!m2, and most prefaab~r from about 13 g/m2 to about 40 ght~. Anotba suitable substrate is a cellulose foam having s dry ooa~r~ased of 5~oni about 0.5 aarn to about 3.0 mm, more pt#ersbly from about 0.8 mm no abo~ 2.0 turn; a wet expandod of frarr about 0.8 mm to about 6.0 aan>, more prtkrably from about 1.0 mm to about 5:0 mm; and a basis weight of from about SO
glm2 to about 2,000 glm2, more from about l00 g/enZ to about 1,000 g/mZ.
Sub:tratta snide for ~ppocdng the macma~trocwrdp~arh'P~Y eve a dry taaik aof from abo~ 500 gfm to about 8,000 g/'m, tna~e preferably from about 1,000 gfta to about 3,000 gtm; s wet tea:0e of San about 200 g~'w w about 5,000 g/in, though more p~5aably fraa about 400 g~l'm to about 1,000 g/'us; and a wet bunt of 5orn about 100 g to abort 2,000 g, t6ynore ably from about 200 g to about 1,000 g. Pr~rred of this type ioelode cxlhtlode 5~ous webs such as paper toads and tissues such those disdasod ~ U.S- Pata~t 3,953,638, isstrod April 27, 19T6, U.S. Past 4,469,'f35, issued Sept 4, 1984, U.S. Patent 4,468,428, issued Aog. 28, 1984, and U.S.
Pslsot 4,986,E8Z, issuod Jan. 22, 1991.
Tire porous sb:abent aaacrostrueturaolparos;ia e~ be a~cdaed to the by s variahr of ~nl. . ~d . ~ ~ the ascroatroctnrelpmtieks to sVbs~a ibclude glues and Got mdt ads. Pce&tably, the boodia~ betwoea tba spa and u~acurelpardcla is acbiavod by depositi~ the precuiaor abmorbeac party at dre , the d~oated p~trti~ wbh the s~o~ oo~risiag a ag~t and tttm suing the treated p~actictafas previously. In a pne6ared anbodiment of this >ne~od, a cellulosic (e.g., purer towel) is used. T6a prowrsor absorbent particles are rhea deposited on this edlulosic substrate. A tres~t tahrtion coanprisiqg as amioo-epichlanAydein addtxt, pc~aablY a wet rain such Kyeoase~, is then WO 97(34557 PCT/US97lOd341 appliod (e.g., sprayed) oa the cellulosic substrate and the absorbent particles. The treated substrate/particles are thrn cured at ambient temperatures such that the particles are bonded to the cellulosic substrate.
To enhance the overall flexibility of the cores of the present invention, the fluid stable microstructures may be slitter so as to be discontinuous. That is, the macrostructure strips may each be cut at various locations to form slits through the entire thickness (i.e., z-direction) of the structure. Such microstructures are described in U.S. Patent No.
5,536,264,, issued July 16, 1996 (filed October 22, 1993 by Hsueh et al.), U.S. Patent No.
5,713,881, issued Febntary 3, 1998 (filed October 30, 1995 by Rezai et al.), and U.S.
Patent No. 5,868,724, issued February 9, 1999 (filed October 30, 1995 by Dierckes et al.). Upon stretching the slitted macarostructures in the y-direction, a "netted" material results. The open spaces between the hydrogel-containing continuous portion permits freer swelling of the hydrogel structure, and also increases permeability through this component.
The porous, sbsorba~ macroa~ructur~a useful as 9uid storage compaomts axordiog to the preaas< iaveerdon can also be mdored or eavdaped within s tissue. Such tissue eavdopa can keep loose absabeM pattickx from mid vrfthia the abs~beut core aid can provide additia~l :ttuaurat icy to the enacrosttu~cdrre.
Regardlaa of the oaaue of t6a absorbent r~aial utilimd. ~ is i~por~t thst the aeorage matcrisl be retrained f:am to a :xa~t degee into the Said inquisition zone (i.e., in the x- and/or yparticularly toward the intuior ~ the abeorboo~t sore), while being free to swell ~ the z-direction. This will (dolt in s larger inquisition zone to aaxpt fluid . As is disar:sed wide hard to Fi~urx 3 and 4, sw~eging into the fluid saquistios :one an ba prated by, for a~pie, use of sdheave spot hood:. 'Ibis msy be paraculsrly baoe6cial wh~ dire particles ~ absarbmt polYnaer arse used as the upper fluid soorage arsoaial. In soave i~tanoes, the srraoof die various cone maoa~inla will pnovida the desired t~aioed b. p~pi~
As iedia~eed abaci, foeru m~iab ase6rl ~ the absabart :taage rna~o~t of the pcawat iovmtian should, in addirior< to o~erias adequste fluid stocsge avp~~ioty. be of exis:i~ is a oolla~aed, a drip, stsee until ooanc~ed with a body 8nid. 'T6e sbility to remain is sudr a: state a in providing ~ that sPP~ to tlra consumer. The use of these tons n~~iab provides the added advs~a of awelli~ almaet eadreiy is the z direc~ou. 'that is, upon imbr'b,~ fluid, the foerru swill :ipi5c~dy m the z~dir~ectioo, while e~Uy mairraimag that Imgth apd wilds dimensioae. This is in~or~t in that it alkyws for ~oenation of the fluid aoqui:itiaa mAe.
Re~ae~tiv~e foera, nthat are useful in the pram~t iavaxioo are those dasctbed in U.S. Plat No. 5,3E7,20'I ('"207 pateat'~, issued Februtry 7, 1993 to Dyer et al. Briefly, that patent describes polymeric foams derived from emulsions that have a relatively small amount of an oil phase (including the polymerizable monomers) and a relatively large amount of an aqueous phase. (Such emulsions are commonly referred to as high internal phase emulsions, or HIPEs.) These RIPE-derived foams are rendered hydrophilic by agents remaining after polymerization, or by post-polymerization treatment with a surfactant. The foams described in the '207 patent are open-celled.
That is, the individual cells (also referred to as pores) that represent the space occupied by individual water droplets in the emulsion are interconnected by numerous small holes.
These small holes in the walls of the cells allow fluid to transfer from one cell to another, throughout the entire foam structure.
T>m ability of the foams to rro~ain in the "t6io-ut~1-caret" state is believed to be arc to the caqllary foroGS wimin the fosrn, partialsrly the Ea'rn's capillary pleasure. To remain is the co>tlapsed stilt uatil w~eaed, the capillary pct within the 5o~an, must be e~uivalear or gte~a than ~e Iforoa exerted by the elastic reoova~y or modules of the fosra polymer, which work m ">p~" the 6osm back to ~ uoooropressad . Parametees that affect npitVry P~n~e ~du~ caPilluY ~~on :peci6c sur~oa area. foam d~tY. fluid auf~Oe teasioo aad av~a~a~e cell :ise. Parameoas that affect the enodutus of the iadudc avoaomes ooooat oaee~risio~ tha polymer, as well a: r~idu:i oil-solubk emulsi6ns which tmd m placate tba po~lyma, ther~y r~edu~ pol~mstr mo~lns. ~1 oon~k~Oe list of pce5amed rats fa there parameeas, as wed as a di:a~iop of other in~port~
pmpatra of the lassos, is set 5ortb ~ the past.
U.S. Patent No. 5,650,222, was filed November 29, 1995 by DesMarais et al., and also describes expandable foams that are useful in the present invention.
Though these collapsable foams are also prepared from HIPEs, the preparation of emulsions with higher water-oil ratios provides even higher porosity, lower density structures. The foams are prepared from emulsions having a water phase to oil phase ratio of from about 55:1 to about 100:1. These foams have a specii~ic surface area per foam volume of at least about 0.025 m2/cc, preferably at least about 0.05 m2/cc, more preferably at least about 0.07 mZ/cc (the density being measured in the expanded state). The foams have a capillary suction specific surface area of at ksst about 3 m~, pr~e~abiy 5'oas about 3 to about is n2/~ more priaably >Gom abort 4 to about 13. m2/, and moat pre~aably lfrant abort s 1o about 11 arZ~~. "Ibc 50~ have a ~ ~y, :s nerved in the ooltapsed ~ of 5roaa about 0.1 ~/oc to :bout 0.2 Bloc, pre6naWy from about o. l t ~/cc oa shout o. is sloe, more pxefaabiy from about o. t2 g/cc to sbvuE o.14 ~lcc. 'I"he 5osms further exhibit a 9uid surEaoe t~ioa of Sorer about 1 s w shout 6s dyoea/am, pco6a'abiy from about 20 to shout 65 dysas<cm, mora prefmsbiy San abort 20 to about 65 dyoes/an. Tba averaged all sire of these fEosms is pc~rabiy less than about s0lr m, more preferably from about Spm to about 35 Eun. These foams are particularly preferred as the fluid storage material when use of foams are desired. The foams will preferably exhibit a ratio of expanded (wet) to collapsed (dry) thickness of at least about 6:1, more preferably from about 6:1 to about 10:1; and a free absorbent capacity of from about 55 to about 100m1 of synthetic urine per gram of dry foam, more preferably from about 55 to 75 ml per gram.
3. Optional Lower Fluid Storage Component Preferred absorbent core designs according to the present invention further comprise a lower fluid storage component. This lower fluid storage component is positioned underneath the lower fluid acquisition/distribution component. A portion of this lower storage component is also positioned underneath the fluid acquisition zone.
This lower fluid storage component is in fluid communication, with the lower fluid acquisition/distribution component so as to be able to receive the acquired body fluids. Materials useful as the upper fluid storage component will also be useful as the optional lower fluid storage component.
However, it is not necessary that this component be capable of swelling in the z-direction upon imbibing fluid. Thus, the skilled artisan will recognize that any material capable of absorbing a significant amount of fluid can be utilized as this component.
The lower fluid storage component may comprise a fiber/hydrogel composite, or only a hydrogel material. In this case, the lower storage component will preferably have a concentration of hydrogel of from about 30% to 100%, more preferably from about 70% to 100%, by total weight of the lower storage component. The lower storage component may also comprise a hydrophilic polymeric foam, including those discussed above.
Foams that remain thin until wetted are preferred, again because they allow the manufacture, transport and store display of very thin absorbent articles.
D. Fluid Acouisition Zone The fluid acquisition zone, formed in-part by the swollen upper storage component(s), creates a void space beneath the upper and lower acquisition/distribution layers. Because of the void space created by the acquisition zone, the absorbent cores according to the present invention can more easily handle "gushes" of discharged body fluids.
This is especially important as portions of the absorbent core become saturated from prior multiple dischargeg of such fluids.
As can be seen by refering to the drawings, the fluid acquisition zone has three dimensions. The width (y-direction) and length (x-direction) of the acquisition zone is generally defined as the void area created by the fluid storage component(s), with the "top" of the zone being the lower surface of the upper acquisition/distribution component, and the "bottom" of the zone being the upper surface of the lower acquisition/distribution material.

(The skilled artisan will realize that while core components are described as being "beneath", "above", etc., such terms do not exclude embodiments where relatively thin materials (e.g., tissue paper) are located between such components.) Where two lateral storage components are spaced apart, the width of the acquisition zone is the gap between these components. The length in this case will be determined by the length of the storage components. The depth of the zone will be the height (z-direction) of the swollen storage components.
The fluid acquisition zone may be of irregular shape in the x-y directions, though generally rectangular is preferred. Further, while the volume of the acquisition zone required will vary according to various factors (e.g., the rate of absorbency of the storage material; the absorbency rate and capacity of the acquistion material; the size of the wearer; etc.), it is preferred that the acquisition zone have a volume, when the storage material is wetted, of at least about 30 cc, preferrably at least about 50 cc, and more preferably at least about 75 cc.
Of course, when in the dry state, the acquisition zone volume will be significantly smaller.
Those skilled in the art will recognize that measuring acquisition zone volumes will be imprecise, given the nature of the materials employed as the storage and acquisition/distribution components. As such, the preferred volume ranges listed are illustrative only, and are not intended to limit the scope of the invention.
E. Topsheets Topsheets useful in absorbent articles of the present invention are compliant, soft feeling, and non-irritating to the wearer's skin. These topsheets are fluid pervious to permit body fluids to readily penetrate through its thicla~ess. A suitable topsheet can be manufactured fiom a wide range of materials such as woven and nonwoven materials;
polymeric materials such as apertured formed thenmoplastic films, apertured plastic films, and hydroformed thermoplastic films; porous foams; reticulated foams;
reticulated thermoplastic films; and thermoplastic scrims. Suitable woven and nonwoven materials can be comprised of natural fibers (e.g., wood or cotton fibers), synthetic fibers {e.g., polymeric fibers such as polyester, polypropylene, or polyethylene fibers) or from a combination of natural and synthetic fibers.
Preferred topsheeTs for, use in the present invention are selected from high loft nonwoven topsheets and aperture formed film topsheets. Apertured formed films are especially preferred for the topsheet because they are pervious to body fluids and yet non-absorbent and have a reduced tendency to allow fluids to pass back through and rewet the wearer's skin. Thus, the surface of the formed film that is in contact with the body remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer.
Suitable formed films are described in U.S. Patent 3,929,135 (Thompson), issued December 30, 1975; U.S. Patent 4,324,246 (Mullane, et a(), issued April 13, 1982; U.S.
Patent 4,342,314 (Radei. et al), issued August 3, 1982; U.S. Patent 4,463,045 (Ahr et al), issued July 31, 1994; and U.S. 5,006,394 (Baird), issued April 9, 1991. Particularly preferred microapertured formed film topsheets are disclosed in U.S. Patent 4,609,518 (Curro et al), issued September 2, 1986 and U.S. Patent 4,629,643 (Curro et al), issued December 16, 1996. The preferred topsheet for use in catamenial products of the present invention is the formed film described in one or more of the above patents and marketed on sanitary napkins by The Procter & Gamble Company of Cincinnati, Ohio as "DRI-WEAVE~".
The body surface of the formed film topsheet can be hydrophilic so as to help body fluids to transfer through the topsheet faster than if the body surface was not hydrophilic so as to diminish the likelihood that fluid will flow off the topsheet rather than flowing into and being absorbed by the absorbent structure. In a preferred embodiment, surfactant is incorporated into the polymeric materials of the formed film topsheet such as is described in U.S. Statutory Invention Registration HI670, "Absorbent Article Having a Nonwoven and Apertured Film Coversheet" filed on November 19, 1991, by Aziz, et al. Alternatively, the body surface of the topsheet can be made hydrophilic by treating it with a surfactant such as is described in the above referenced U.S. 4,950,254.
F.
Backshe~s useful in ab:abent articta of the pre:art iaventiao :re typically i~ervious to body fluids and are preferably mamrfacturod from a thin plastic 51m, although other flexibk fluid impervious metecials msy also be usod. As usod herein, the term "flexible" refers to ~ta~iala that are coa~pliaot and will rradily ooofam to the ~aa~al shape and contour: of the human body. The bst~6eet prevents body fluids absorbod and ~aed in the ab~orbeat core from we~n~g .artidas that ooemd the such as pants.
pajamas, uodagarrmeats, and tire ir7ce. The can comprise a worm or nonwovm material, po~ymaic 81t~ wch :: tba~aropla:tic Elms c~ polyet6ykna a< polypropylaoe, or oon~site mrlerdb snob as a filmed ooawvweo material. PneSaably, the badaheet is a poiyef6ykx shn hsviog a ~' »om about 0.012 mm (0.5 rr~ to about o.os 1 mm (2.0 rte). Ex~ary polydhyleoa slurs are mamrsmtnred by Clopay Coeporatioa of Cioaomti, Ohi0. under the de:i8,nation P 18-0401 sad by Ethyl Caporatioo, Viaquan Division, of Terra I~te, Indiana, under the da~ation XP-3938s. The lracksbea is preferably anboased and/or matte snished to peovide s more cbthliloe appearance. Further, the baebbea can permit vapors to escape from the. absocbeot core (i.e., b~bk) while still pr~w~tins body fines ps,uing through the ba~a6ea:
Parti~larly dairsbk backsheas caa be made from a :trucarral daatic-liloe slur (SELF) web. A swcdrr>f elastic-liloe Elm web is as exteasibk ma~ial that exhibits as elastic-like behavior m the direction of elaogation without the use of added dastic materials.

PC-1','L'So_ ,~~ z~ 1 WO 9 % X34557 The SELF web Includes a strattsabie network havtag at icast two contiguous, drstu~a, and dissimilar regtoas. One of the regiotu ~s coctftgurod so that n will eachibn resistrvc forces ~n response to an applied axial elongation in a direet~on parallel to the predetcrmusod axis before a substantial portion of the other region develops significant resistive forces to the applied elongation. At leant one of the regioa5 has a surface-pain length that ~s greater than that of the other region as measured subsnaaally parallel to the prerdeceesrunod axis ~fiilc the material is is as unttasioned condition. The region exhibiting the bnger sur6ce-path length includes one or more deformations that extend beyond the plant of the other region. The SELF web exhibits at least two significaady different stags of controlled resistive force to elongation along at lean one predetermined axis wlxa subjected to sn applied e~ongation to a direction paralkl to the predetermined axis. The SELF web exhibits first resistive forces to the applied elo~tioo utail the dougstion of the web is suffsciau to cause a substantial portion of the region having the longer surf>vx-path length to enter the plane of applied eloag:tioo, whaeupoa the SELF web exhibits second resistive forces to further elongation.
'Ihe total resistive forea to elongation are higher than the 5rst rtaistive forces to elongation provided by the first rein. SELF webs suinbk for the present m.Kation arse mote completely described in commonly assigned U.S. Patent No. x.554.145 entitled "Absorbent Article with Multiple Zone Structural Elastic-Like Film Web Ext;;n;;iblc V~aast feature" filed by Donald C. Roe, et al. on February 24, 1994 and issued September 10, 1996.
G. ~,.
The absotbwt articles of the ptt~at invention gareraily oar>p:ise. ( 1 ) a topshat;
(2) a bac~eefi and (3) as absorbent core of the present invention positio~d baweea the sad tie bael~her.~t As used hewn, t>!re tam "absorbent atricle" refers to articles tfaat absorb and ooat~a boely $uids, sad cone spoetlxnliy re6ars to aroicla t#tat a~
placed against oc is pr~oodmay to the body of the wear m absorb sad ooataia the various $uids discharged Sts the body. Addi~tioaally, "diaponbfe" absocbeeat articles are those which are an~oded to be d'darded a8c ,l sr~k use (i.e., the o<igsoal absorbent artick in its wbok is not i>meoded m be brmdaod or atbawise srs~oeed a ratted as an absorbe:it attick, ahho~n cabin or aU of the absosbeat a:ticle may be recycled, rwxd, or campost~ed). A
prefer:ed etnbodin>mt of a disposabk absorbent article according to the present ir<v~tioea is a diaper.
As rated halo, the tam "dad' r>~ to a garrrrmt generally wore by ion and ioomtineat persons drat is wan about the lower torso of the wears. a should be understood.
>roweva, that the pram iova~on is also appli~cabk to outer sbso<beac articles such as incontinent briefs, inooerti«at pads, training Pane. ~. catameaial pads.
sanitary mpld:is, fseial tisssra, papa towels. and the like.

The absorbent core used in the absorbent articles of the present invention comprises at least one fluid storage component, as previously described, that is located relatively remote from the wearer. This is so the fluid that is temporarily located in the fluid acquistion zone is remote from the wearer, so as to avoid rewet and to enhance acquistions rates.
In a preferred embodiment, the absorbent core comprises at least and preferably two fluid storage components (in the form of strips) that are laterally spaced apart. By "laterally spaced apart" is meant that there is a gap between the fluid storage components. When these laterally spaced storage components swell in the z-direction upon absorbing body fluid, this gap between the fluid storage components, together with the acquisition/distribution layers positioned above and below, defines the fluid acquisition zone for receiving discharged body fluids. At least a portion of this fluid acquisition zone comprises a void space underneath the overlying upper acquisition/distribution component. Because of the void space in this acquisition zone, the absorbent core according to the present invention can more easily handle "gushes" of discharged body fluids. This is especially important as portions of the absorbent core become saturated from prior multiple discharges of such fluids.
Absorbent cores according to the present invention also comprise an upper fluid acquisition/distribution component that is capable of transporting the discharged body fluids to other components in the absorbent core. Given its location in the cores of the present invention, it is apparent that the primary function of this component is to rapidly acquire fluid gushes, and give those fluids up to other components so as to be free to accept the next fluid insult. As such, it is preferred that the upper acquisition/distribution component be constructed accordingly. To this end, it is preferred that this component contain little or no hydrogel-forming polymer. This upper fluid acquisition/distribution component is at least partially positioned underneath and typically proximate to the fluid discharge region of the core so as to be able to receive these discharged body fluids.
Preferred is where the upper acquisition/distribution material comprises chemically stiffened fibers, particularly where the fibers are thermally bonded. It is further preferred that the basis weight be in the range of from about 0.08 g/sq.in. to about 0.30 g/sq.in., more preferably from about 0.08 g/sq.in to about 0.15 g/sq.in.; and that the density be in the range of from about 0.05 g/cc to about 0.30 g/cc; more preferably from about 0.05 g/cc to about 0.15 g/cc.
The absorbent cores of the present invention further comprise a lower fluid acquisition/distribution component that is capable of transporting the discharged body fluids to other components in the absorbent core. This lower fluid acquisition/distribution component is at least partially positioned underneath the fluid discharge region of the core, and is positioned below the fluid storage component(s). This component can be either chemically stiffened fibers, cellulose fibers (also referred to as airfelt), or a fiberlabsorbent hydrogel-forming composite. Preferred is where the lower acquisition/distribution material comprises chemically stiffened fibers or cellulose fibers, particularly where the fibers are thermally bonded. It is further preferred that the basis weight be in the range of from about 0.08 g/sq.in. to about 0.30 g/sq.in., more preferably from about 0.08 g/sq.in to about 0.15 g/sq.in.; and that the density be in the range of from about 0.05 g/cc to about 0.30 g/cc; more preferably from about 0.05 g/cc to about 0.15 g/cc.
Where the lower acquisition/distribution component comprises a fiber/absorbent hydrogel composite, the component will preferably have a concentration of hydrogel of from about 10% to 65%, more preferably from about 15% to 30%, by total weight of the lower acquisition/distribution component.
In an alternative embodiment, absorbent cores according to the present invention comprise more than two (2) strips of storage material as the upper fluid storage component, positioned between the upper and lower fluid acquisition/distribution components. Where more than two strips are used, each should be laterally spaced from the others to provide channels between each strip. In reference to the figures, use of more than two spaced-apart fluid storage components would result in more than one fluid acquisition zone.
In one embodiment, four (4) strips of storage material are used, and form three channels, or three distinct fluid acquisition zones.
1n another embodiment, the absorbent core comprises a lower fluid storage component. Materials useful for the upper fluid storage component may also be useful in the lower fluid storage component. However, it is not necessary that this component be capable of swelling in the z~ir~ection upon imbibing fluid. Thus, the skilled artisan will recognize that any material capable of absorbing a significant amount of fluid can be utilized as this lower component.
An embodiment of an absorbent article in the fonm of a diaper 10 having one such absorbent core according to the present invention is shown in Figure 1. Figure 1 is a top plan view of diaper 10 in a flat-out, uncontracted state (i.e., with any elastic-induced contraction removed) having a topsheet 12, a backsheet 14, and an absorbent core indicated generally as 18 that is positioned between topsheet 12 and backsheet 14. Topsheet 12 is shown as being transparent so as to better illustrate the various components of absorbent core 18. Also, the upper fluid acquisition/distribution layer 41 (which is depicted in Figure 2) is not shown, to enable depiction of the other core components. However, in a preferred embodiment, this upper component is of approximately the same dimension as lower fluid acquisition/distribution layer 42, and is positioned between the topsheet 12 and two upper fluid storage components 34 and 36.
As also shown in Figure I, diaper 10 has a front waistband region ?2, a back waistband region 24, a crotch region 26 and a periphery 28 that is defined by the outer edge Wt? 97134557 1'CT~LIS97I043d1 of backshoet 14 and which has iongitudiaal edges designated 30 and cad odges designatod as 32. The longitudinal axis of diaper 10 essentially nuns parallel to longitudinal edges 30, while the transverse axis essentially runs parallel to end edges 32. The waistband regions 22 and 24 comprise those upper portions of the diaper 10, which when worst, encircle the waist of the wearer. The crotch region 26 is that portion of the diaper 10 between waistband regions 22 and 24, aad comprises that portion of the diaper 10 which when worn, is positiottod betvNeen the legs of the wearer and covers the lower torso of the wearer. Thus, the croup region 26 defines the sra of typical liquid deposition for a diaper 10 of other disposable absorbent article.
Topsheet 12 arrd bacicshoa 14 can be associated in any suitable. manner. As used herein, the tam "associated" eacompsasea eor~igucatio~ where topsheet i2 is directly joined to bacJCSheet 14 by effacing the topshect directly to the backsheet, and coa5guta#iods where the topaheet is indirectly joined to the backshoet by ai~Cirtg the tapsbea to intermediate mambas which is turn are off xod to the backslreet. Pcefecably, the tolrsh~oa 12 and backshea 14 are af~xod dic~tly to each other by sttachmaat titans (rat shown) such as an adhesive or any other attaci~t mn~ as lmon~ in the art. For example, a uaifam oorrtimaus bye of adhesive, s pa>xetned byer of aa~reaivr;, or as array of separate lines or spots of adhesive may be used to affnc tops6ea 12 to bicxs6ed 14. As shown is Figure 1, tapsheet 12 has a smaller size ooa5gueatian than badahaa 14. i~reva, topshea 12 and baclcshea 14 can both have the saaae, or a similar, size coofiguratioo (i.e., are coerae~ive) stub they are joiraod tog~her at periphery 28 of diaper 10. T6e sate of the bs~sbea 14 k dictated by ~e size of the absocbmt core 18 and the exact diaper design xlected. In t'be anboduamt s6o~wn io Figure 1, the btsd~hea 14 has as bourg~-:>saped configuration.
However, other ooo~gurstioa such as rec~agubr, I-sbapod and the lliloe arse also suitable.
Although oat :6awn, diaper 10 can have ebstic maabers that exert a contracting for~x an the diaper no that it ooo5gtua more ciasdy and more comfortably to the .
Titsre elsutic aaa~ers coo be assanbled an a variety of wdl imown ooafigura>iaoa, such as those described generally in U.S. Patent 3,860,003 (Buell), issued January 14, 1975.
The elastic members can be disposed adjacent the periphery 28 of the diaper 10, along each longitudinal edge 30, so that the elastic members tend to draw and hold the diaper 10 against the legs of the wearer. Alternatively, the elastic members can be disposed adjacent either or both the end edges 32 of diaper 10 to provide a waistband as well as or rather than leg cuffs. See, for example, U.S. Patent 4,515,595 (Kievit et al), issued May 7, 1985. The elastic members are secured to the diaper 10 in an elastically contractible condition so that in a normally unrestrained configuration, these elastic members effectively contract or gather the diaper 10.
The elastic members can be secured in an elastically contractible condition in at WO 97!34557 _ PCT/US97/04341 least two ways. For example, the elastic members can be stretched and secured while the diaper 10 is in an uncontricted condition. Alternatively, the diaper 10 can be contracted, for example, by pleating, and the elastic members secured and connected to the diaper 10 while they are in their unrelaxed or unstretched condition. The elastic members can extend essentially the entire length of the diaper 10 in the crotch region 26, or alternatively can extend the entire length of the diaper 10, or any other length suitable to provide an elastically contractible line. The length of these elastic members is typically dictated by the diaper's design.
Referring to Figure 1 and especially Figure 2, absorbent core 18 has an upper acquisition/distribution layer 41 located adjacent topsheet 12. The core 18 further comprises two upper fluid storage components 34 and 36 in the fonm of rectangular strips that comprise hydrogel-forming absorbent polymer (or a collapsible, hydrophilic polymeric foam) that are positioned between upper continuous acquisition/distributian layer 41 and lower continuous fluid acquisition/distribution component 42. The fluid storage components 34 and 36 are each respectively wrapped in a fluid pervious paper tissue 35 and 37, as shown specifically in Figure 2. These wrapped fluid storage components 34 and 36 are laterally spaced apart and define the fluid acquisition zone identified generally as 38. This fluid acquisition zone 38 is generally in the fluid discharge region of diaper 10.
The upper continuous fluid acquisition/distribution component 41 is in the form of chemically stiffened fibers, and is optionally wrapped in tissue 49. Though acquistion/distribution component 41 is shown in Figure 2 as being wrapped by tissue 49, preferred is where this component is not tissue-wrapped. (Where this component contains absorbent hydrogel-fonmin~ .=olymer, it may be preferred to wrap the component with tissue.) This upper fluid acquisition ~stribution component 41 has lateral portion 45 and 47. Lateral portion 45 is positioned above and in fluid communication with fluid storage component 36, while lateral portion 47 is positioned above and in fluid communication with fluid storage component 34.
The lower continuous fluid acquisition/distribution component 42 is in the form a fibrous web that is also wrapped in a paper tissue 43. The middle portion 44 of this fluid acquisition/distribution component 42 is positioned underneath the fluid acquisition zone 38.
This fluid acquisition/distribution component 42 also has lateral portion 46 and 48. Lateral portion 46 is positioned underneath and in fluid communication with fluid storage component 36, while lateral portion 48 is positioned underneath and in fluid communication with fluid storage component 34. As shown in Figure l, fluid distribution component 42 has arcuate concave edges 52 and 53 in the crotch section 26 of diaper 10 and thus assumes a somewhat hourglass shape.

As shown particularly in Figure 2, absorbent core 18 further includes a lower fluid storage component 60 in the form of a rectangular strip that comprises hydrogel-forming absorbent polymer or an absorbent foam material, and is wrapped in a paper tissue 61. This lower fluid storage component 60 has approximately the same length as fluid storage components 34 and 36, and is positioned underneath and in fluid communication with middle portion 44 of fluid distribution component 42. Lower storage component 60 is wider (in the y-direction) than the fluid acquisition zone 38 that is fonmed, in part, by the storage components 34 and 36. This lower fluid storage component 60 is positioned underneath the fluid acquisition zone 38.
As shown in Figure 1, lower fluid distribution component 42 is somewhat longer in length than upper fluid storage components 34 and 36, as well as lower fluid storage component 60, which is positioned beneath lower acquisition/distribution component 42.
(Lower storage component 60 is depicted as a broken line in Figure 1.) Upon first exposure to aqueous body fluids, upper storage components 34 and 36 begin to swell, increasing in caliper by at least 2 mm when fully saturated.
This increase in caliper increases the void volume of the acquisition zone 38. Consequently, the absorbent article is better able to handle subsequent "gushes" of aqueous body fluids.
Preferably, the upper storage components will expand by at least 100% in the z-direction. Of course, because the length and width of the fluid acquisition zone will also affect the core's void volume, 100% z~irection expansion may not be required in such cores.
Figure 3 shows a cross section of an absorbent article 110 having a topsheet 112, a backsheet 114 and an alternative absorbent core 118 positioned between the topsheet and the backsheet. Absorbent core 118 has an upper acquisition/distribution layer 141 located adjacent topsheet 112. The core I 18 further comprises two upper fluid storage components 134 and 136 in the form of rectangular strips that comprise hydrogel-fornting absorbent polymer (or a collapsable, hydrophilic polymeric foam) that are positioned between upper continuous acquisition/distribution layer 141 and lower continuous fluid acquisition/distribution component 142. These fluid storage components 134 and 136 are laterally spaced apart and define the fluid acquisition zone identified generally as 138. This fluid acquisition zone 138 is generally in the fluid discharge region of diaper 110. A paper tissue layer 143 is positioned between these upper fluid storage components 134 and 136 and the lower fluid acquisition/distribution component 142.
The upper continuous fluid acquisition/distribution component 141 is in the foam of a a web of chemically stiffened fibers, and is optionally wrapped in tissue 149.
This upper fluid acquisition/distribution component 141 has lateral portion 145 and 147.
Lateral portion 145 is positioned above and in fluid communication with fluid storage component 136, while lateral portion 147 is positioned above and in fluid communication with fluid storage component 134.
The lower continuous fluid acquisition/distributaon component 142 is in the form a fibrous web. The middle portion 144 of this fluid acquisition/distribution component 142 is positioned underneath the fluid acquisition zone 138. This fluid acquisition/distribution component 142 also has lateral portion 146 and 148. Lateral portion 146 is positioned underneath and in fluid communication with fluid storage component 136, while lateral portion 148 is positioned underneath and in fluid communication with fluid storage component 134.
Absorbent care 118 further includes a lower fluid storage component 160 that comprises hydrogel-forming absorbent polymer or an absorbent polymeric foam.
This lower fluid storage component 160 is positioned underneath and in fluid communication with middle portion 144 of fluid distribution component 142. This lower fluid storage component 160 is also positioned underneath the fluid acquisition zone 138, and is wider than the fluid acquistion zone 138. That is, the storage component 160 is wider than the gap between fluid storage components 134 and 136.
As shown in Figure 3, the components of absorbent core I 18, with the exception of the upper fluid acquisition/distributioa layer 141, are wrapped within a paper tissue 164.
Tissue 164 is adhesively bonded to tissue 143 at the points indicated by 166 and 168.
Upon first exposure to aqueous body fluids, upper storage components 134 and begin to swell, increasing in caliper by at least 2 mm when fully saturated.
Adhesive bonds 166 and 168 prevent lateral expansion of storage components 134 and 136 into acquisition zone 138. The increase in caliper increases the void volume of the acquisition zone 138.
Consequently, the absorbent article is better able to handle subsequent "gushes" of aqueous body fluids.
Figure 4 shows a cross section of an absorbent article 210 having a topsheet 212, a backsheet 214 and another altennative absorbent core 218 positioned between the topsheet and the hickshset. This alternate absorbent core 218 has an upper acquisition/distribution layer 241 located adjacent topsheet 212. The core 218 further comprises two upper fluid storage components 234 and 236 in the form of rectangular strips that comprise hydrogel-forming absorbent polymer (or a collapsible, hydrophilic polymeric foam) that are positioned between upper continuous acquisition/distribution layer 241 and lower continuous fluid acquisition/distribution component 242. These fluid storage components 234 and 236 are laterally spaced apart and define the fluid acquisition zone identified generally as 238. This fluid acquisition zone 238 is generally in the fluid discharge region of diaper 210. A paper tissue layer 243 is positioned between these upper fluid storage components 234 and 236 and the lower fluid acquisition/distribution component 242.

The upper continuous fluid acquisition/distribution component 241 is in the form of a web of chemically stiffened cellulosic fibers. This upper fluid acquisition/distribution component 241 has lateral portion 245 and 247. Lateral portion 245 is positioned above and in fluid communication with fluid storage component 236, while lateral portion 247 is positioned above and in fluid communication with fluid storage component 234.
The lower continuous fluid acquisition/distribution component 242 is in the form a fibrous web. The middle portion 244 of this fluid acquisition/distribution component 242 is positioned underneath the fluid acquisition zone 238. This fluid acquisitioddistribution component 242 also has lateral portion 246 and 248. Lateral portion 246 is positioned underneath and in fluid communication with fluid storage component 236, while lateral portion 248 is positioned underneath and in fluid communication with fluid storage component 234.
As shown in Figure 4, the components of absorbent core 218, with the exception of upper fluid acquisition/distribution layer 241, are wrapped within a paper tissue 264. Tissue 264 is adhesively bonded to tissue 243 at the points indicated by 266 and 268.
Upon first exposure to aqueous body fluids, upper storage components 234 and begin to swell, increasing in caliper by at least 2 mm when fully saturated.
Adhesive bonds 266 and 268 prevent lateral expansion of storage components 234 and 236 into acquisition zone 238. The increase in caliper increases the void volume of the acquisition zone 238.
Consequently, the absorbent article is better able to handle subsequent "gushes" of aqueous body fluids.
Figure 5 shows a cross section of an absorbent article 310 having a topsheet 312, a backsheet 314 and yet. another alternative absorbent core 318 positioned between the topsheet and the backsheet. This alternative absorbent has an upper fluid acquisition/
distribution layer 341 located adjacent topsheet 312. The core 318 further comprises a continuous component 320 comprising hydrogel-forming absorbent polymer or an absorbent polymeric foam that is partially wrapped around lower fluid distribution component 342, this continuous component 320 having the ability to expand in the z-direction upon absrobing body fluids. Continuous component 320 includes upper fluid storage components or sections 334 and 336 that are positioned between upper fluid acquistion/distribution layer 341 and lower fluid distribution component 342; and a lower fluid storage component or section 360 that is underneath lower fluid distribution component 342. The gap between fluid storage components/sections 334 and 336 define the fluid acquisition zone identified generally as 338. Middle portion 344 of fluid lower distribution component 342 is underneath fluid acquisition zone 338. Lateral portion 346 of lower fluid distribution component 342 is positioned underneath and in fluid communication with fluid storage component 336, while lateral portion 348 is positioned underneath and in fluid communication with fluid storage component 334. Lower fluid storage component or section 360 is underneath and in fluid communication with fluid distribution component 342.
Upon first exposure to aqueous body fluids, upper storage components or sections 334 and 336 begin to swell, increasing in caliper by at least 2 mm when fully saturated. The increase in caliper increases the void volume of the acquisition zone 338.
Consequently, the absorbent article is better able to handle subsequent "gushes" of aqueous body fluids.
Figure 6 shows a cross section of an absorbent article 410 having a topsheet 4I2, a backsheet 414 and an alternative absorbent core 418 positioned between the topsheet and the backsheet. This alternative absorbent core 418 also has to two upper fluid storage components 434 and 436 that comprise hydrogel-forming absorbent polymer or a polymeric absorbent foam, positioned between upper fluid acquisition/distribution layer 441 and lower fluid acquisition/distribution layer 442. These fluid storage components 434 and 436 are laterally spaced apart and define the fluid acquisition zone identified generally as 438. These fluid storage components 434 and 436 are further bonded to substrates 435 and 437 (when they comprise hydrogel-forming absorbent polymer) and are folded in a c-shape as shown in Figure 6.
A paper tissue layer 443 is positioned under the upper fluid storage components 434 and 436 and over lower fluid distribution component 442. This lower fluid distribution component 442 is positioned underneath and in fluid communication with fluid storage components 434 and 436 and under fluid acquisition zone 438.
Absorbent core , 418 further includes a lower fluid storage component 460 that comprises hydrogel-forming absorbent polymer. This lower fluid storage component 460 is positioned underneath and in fluid communication with lower fluid distribution component 442. This lower fluid storage component 460 is also positioned underneath the fluid acquisition zone 438.
Upon first exposure to aqueous body fluids, upper storage components 434 and begin to swell, increasing in caliper by at least 2 mm when fully saturated.
Substrate layers 435 and 437 prevent lateral expansion of storage components 434 and 436 into acquisition zone 438. The increase in caliper increases the void volume of the acquisition zone 438.
Consequently, the absorbent article is better able to handle subsequent "gushes" of aqueous body fluids.

Claims (13)

1. An absorbent core capable of absorbing discharged aqueous body fluids, the absorbent core comprising:
(1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the upper fluid acquisition/distribution component being positioned in the fluid discharge region of the absorbent core;
(2) at least one upper fluid storage component positioned at least partially underneath and in fluid communication with the upper fluid acquisition/distribution component, said at least one fluid storage component being capable of expanding in the z-direction by at least 100% when fully saturated with aqueous body fluids to form a fluid acquisition zone and being restrained from substantial swelling toward the interior of said fluid acquisition zone formed from said expansion of said at least one fluid storage component;
(3) a fluid acquisition zone capable of receiving aqueous body fluids, the fluid acquistion zone being at least partially surrounded by said at least one upper fluid storage component and positioned at least partially beneath the fluid discharge region of the absorbent core; and (4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids, the lower fluid acquisition/distribution component being positioned at least partially underneath and in fluid communication with said at least one upper fluid storage component.

2. The absorbent core of claim 1 further comprising at least one lower fluid storage component positioned underneath the lower fluid acquisition/distribution component and being wider than the fluid acquisition zone formed by the laterally spaced apart upper fluid storage components.

3. The absorbent core of any one of claims 1 and 2 wherein the core comprises two upper fluid storage components in the form of strips that run longitudinally in the absorbent core and the components are laterally spaced apart wo as to form the fluid acquisition zon upon contact with aqueous body fluids.

4. The absorbent core of claim 3 wherein a) a first tissue paper is positioned below the two upper fluid storage components and above the lower fluid acquisition/distribution; b) the two upper fluid storage components and the lower acquisition/distribution component are wrapped by a second tissue paper; and c) the first and second tissue papers are bonded at a location between the upper storage components so as to prevent swelling of the storage components into the fluid acquisition zone.

5. The absorbent core of any one of claims 1, 2, 3 and 4 wherein the upper fluid storage component(s) comprises from 50 to 100%, by weight of the respective storage component, of hydrogel-forming absorbent polymer.

6. The absorbent core of claim 5 wherein the upper fluid storage component(s) comprises from 70 to 100%, by weight of the respective storage component, of hydrogel-forming absorbent polymer.

7. The absorbent core of any one of claims 1 to 6 wherein the upper fluid storage component(s) comprises a collapsible polymeric foam material derived from a high internal phase water in oil emulsion.

8. The absorbent core of any one of claims 1 to 7 wherein the upper fluid acquisition/distribution layer comprises chemically stiffened cellulosic fibers.

9. The absorbent core of claim 7 wherein said chemically stiffened cellulosic fibers are thermally bonded with a thermoplastic material.

10. The absorbent core of any one of claims 1 to 9 wherein the upper fluid acquisition/distribution layer is free of hydrogel-forming absorbent polymer.

11. An absorbent core capable of absorbing discharged aqueous body fluids, said absorbent core comprising:

(1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the upper fluid acquisition/distribution component being positioned in the fluid discharge region of the absorbent core and comprising chemically stiffened cellulosic fibers that are thermally bonded with a thermoplastic material;

(2) two upper fluid storage components capable of expanding in the z-direction by at least 100% when fully saturated with aqueous body fluids, the two upper fluid storage components being in the form of strips that run longitudinally in the absorbent core and are spaced apart so as to form a fluid acquisition zone upon contact with aqueous body fluids, and wherein both fluid storage components comprise a fluid stable macrostructure of interconnected, hydrogel-forming absorbent polymer particles;

(3) a fluid acquisition zone capable of receiving aqueous body fluids, said fluid acquisition zone being at least partially surrounded by the two upper fluid storage components and positioned at least partially beneath the fluid discharge region of the absorbent core;

(4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids, the lower fluid acquisition/distribution component being positioned at least partially underneath and in fluid communication with said upper fluid storage components, wherein the lower fluid acquisition/distribution component comprises from 10 to about 30%, by weight, of a hydrogel-forming polymer; and (5) a lower fluid storage component positioned underneath the lower fluid acquisition/distribution component and in fluid communication therewith, the lower fluid storage component being wider than the fluid acquisition zone, wherein the lower fluid storage component comprises a fluid stable macrostructure of interconnected, hydrogel-forming absorbent polymer particles.

12. An absorbent article for absorbing discharged aqueous body fluids, the absorbent article comprising:
(A) a topsheet;
(B) a backsheet; and (C) the absorbent core of any one of claims 1 to 10 located between the topsheet and backsheet.

13. A diaper comprising:
(A) a topsheet;
(B) a backsheet; and (C) an absorbent core located between the topsheet and backsheet, the absorbent core comprising:
(1) an upper fluid acquisition/distribution component capable of receiving aqueous fluids, the upper fluid acquisition/distribution component being positioned in the fluid discharge region of the absorbent core;
(2) at least one upper fluid storage component positioned at least partially underneath and in fluid communication with the upper fluid acquisition/distribution component, said at least one upper fluid storage component being capable of expanding in the z-direction by at least 100% when fully saturated with aqueous body fluids to form a fluid acquisition zone and being restrained from substantial swelling toward the interior of said fluid acquisition zone formed from said expansion of said at least one upper fluid storage component;
(3) a fluid acquisition zone capable of receiving aqueous body fluids, said fluid acquisition zone being at least partially surrounded by said at least one upper fluid storage component and positioned at least partially beneath the fluid discharge region of the absorbent core; and (4) a lower fluid acquisition/distribution component capable of acquiring and transporting aqueous body fluids, the lower fluid acquisition/distribution component being positioned at least partially underneath and in fluid communication with said upper fluid storage component.