CA2144958C

CA2144958C - Sanitary napkin having shaping means

Info

Publication number: CA2144958C
Application number: CA002144958A
Authority: CA
Inventors: Peter Coles
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1992-09-21
Filing date: 1993-09-20
Publication date: 1998-08-04
Anticipated expiration: 2013-09-20
Also published as: DK0589102T4; EP0589102B1; DE69217364D1; FI951304A0; ES2097287T5; EG20190A; MX9305775A; NO951032L; AU5131593A; EP0589102B2; TR27983A; DK0589102T3; CN1089129A; SG52307A1; US5722967A; HK1006534A1; DE69217364T2; JPH08501473A; ATE148624T1; EP0589102A1

Abstract

In a sanitary napkin (1), longitudinal score lines (40, 41) applied to the core (5) and longitudinal glue lines located adjacent to the score lines (40, 41), cause controlled deformation of the sanitary napkin 's absorbent core (5) upon lateral compression and provide increased resiliency for the sanitary napkin (1) to return to its undefo rmed state when the compressive forces are removed.

Description

Sanitary napkin having shaping means Field of the Invention The invention relates to sanitary napkin comprising a liquid pervious topsheet, a liquid impervious backsheet and an absorbent core comprised between the topsheet and the backsheet, the absorbent core having a garment facing surface, a body facing surface, a longitudinal center line and two longitudinal sides generally parallel to the longitudinal center line, the absorbent core comprising shaping means for raising a central part of the core's body facing surface upon compression of the core trans-verse to the longitll~; n~l sides.

Such sanitary napkin is known from EP-A-0 355 252. In this patent application a sanitary napkin is described that has a flexure resistant deformation element that can be placed at the position of the backsheet. Upon deforma-tion of the element by compression by the user's thighs, the flexure resistant element causes the core to adopt a generally W-shaped configuration. This causes a good contact between the topsheet of the sanitary napkin, a central part of which is pushed upward, and the body of the wearer during use.
It is an object of an aspect of the invention to provide a sanitary napkin conforming closely to the body of the wearer during use and being comfortable.

It is an object of an aspect of the invention to provide a sanitary napkin in which undesirable bunching during use is reduced.

It is an object of an aspect of the invention to provide a sanitary napkin comprising shaping means of relatively simple nature, giving a well-defined deformation of the absorbent core during use.

T~
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It is an object of an aspect of the invention to provide a sanitary napkin that relaxes to a generally flattened state when pressure exerted by the user's thighs on the sanitary napkin is reduced.
Summary of the Invention An aspect of the invention is as follows:
Sanitary napkin comprising a liquid pervious top-sheet, a liquid impervious backsheet, and an absorbent core disposed between the topsheet and the backsheet, the absorbent core having a garment facing surface, a body facing surface, a longitudinal center line and two longitudinal sides generally parallel to the longitudinal center line, the absorbent core comprising an absorption layer, a fluid handling layer located between said absorption layer and said top sheet and shaping means for raising a central part of the core's body facing surface upon compression of the core transverse to the longitll~;n~l sides, characterized in that the shaping means comprises two axes of flexibility of the core, one axis of flexibility extending on each side of the longitudinal center line and generally parallel thereto, the stiffness of the core being reduced along each axis of flexibility, each axis of flexibility forming an axis of inflexion of the core's body facing side upon compression of the core transverse to the core's longitudinal sides, said shaping means further comprising a pair of bond lines, one bond line extending on either side of the longitudinal center line near the axes of flexibility, generally parallel thereto, or coincident with the axes of flexibility, the absorption layer and the fluid handling layer being bonded along the bond lines.

By way of added explanation, a sanitary napkin according to the invention is characterized in that the shaping means comprise two axes of flexibility of the core, one B

-2a- 2 1 4 4 9 5 ~
axis of flexibility extending on each side of the longitudinal center line and generally parallel thereto, the stiffness of the core being reduced along each axis of flexibility, each axis of flexibility forming an axis of inflexion of the core's body facing side upon compression of the core transverse to the core's longitll~; n~l sides.

By reducing the stiffness of the core along the axes of flexibility, for instance by scoring, embossing, perforating or cutting the core along these axes, the central area of the core located between the axes of flexibility will rise upward upon compression of the core in a direction transverse to the longitl~;n~l center line. The deformation of the core is controlled by the axes of flexibility so that undesired bunching and formation of longitl~;n~l channels, along which liquids can be transported to the perimeter of the sanitary napkin, are reduced.

Providing the core with axes of flexibility causes the central part of the core and the topsheet to remain closed to the loading point for efficient acquisition of liquids discharged for the user's vestibule, while the areas flanking the central region remain relatively flat for providing a m~;ml~m coverage of the undergarment.

The axes of flexibility also reduce the forces necessary for initial deformation (before the napkin is wetted) and hence increase the comfort of the sanitary napkin for the - wearer.

An embodiment of an absorbent article according to the invention, the core comprising an absorbent layer and a fluid handling layer located between the absorptive layer and the topsheet is characterized in that the shaping means comprise a pair of bond lines, one bond line extending on B

either side of the 1Q~;t~ ;ng1 center line near the a~ces of fle~cibility, ge~er~lly parallel lheleto, or coincid~n~ with the a~ces of fle~ibility, the absorption layer and the fluid hsn~lli~ layer being bonded along the bond lines.

The a~so~cnt core can co~plise a ~ ~r of layers, such as for in~t-qnce a ~hg.n;"~eH of two fibrous layers between which an a~~ol1,cnt gelling msteriql is col, plised, and a wipe vqc~l -;C ~;nn sheet o~e,l~ing the 1~ te for lateral distribution of the liquid across the 1~---h~G'S surface. Such a core is described in US-A~,950,264.

Joining to6ether of the lqminqtc and the wipe ac~luisilion sheet near the a~es of fle~cibiliq, couples the defoln~tion of the layers in the core, so that the well dermed dcfoill.ation of the lower layer is ~ to the upper layer. The bonAi~ of the layers can occur for i-~t~-ce by em~oss;~ only, so that the bond lines at the same time form the a~ces of fle~ibility. Other means of bon~1i~ are fusion l~--A;n~ under applic~tion of heat and p;esaure or ultr~onic fusion 1~ 1;nP. ~ef~,ably the layers are bonded by an adhesive in such a way that the liquid-h~ ning pro~c,lies of the layers are not s-lbs~-.t;~lly arrect~d Upon removal of the co~ ,ressive forces e~certed on the ~ napkin du~inL use, the elasdc forces in the central parts of each layer that has been raised, collectively act upon the bond lines to flatten the s~nit~ry naplcin. This l~S'llt~ in a increased resilicncy of the ~z-~ napkin and con~e~uently of a better cu~erage of the under~-...P,~It.

I?~efc,~.bly the adhesive of the bond lines is applied in a spiral pattern, which has a ~lali~ely low depth of ~netration into the layer onto which the spiral glue ~ is applied.

bl an em~li..-ert of a ss~ nqrlrin according to the m~e~ion, the bond lines e~ten~l along bctween 25% and 100% of the length of the absorbent core, ~referably along 30% and 85%, the width of each bond line bei~g l,ct~.-ee~ 2 and 16 mm, pref~Yably between 3 and 9 mm, the amount of r~heSive in each line being l~t~.~n 0.001 and 0.03 grams, pre~rably be~ween 0.02 and 0.029 grams, the ~list~nce of the bond lines 4_ 2 144958 from the longitudinal center line being between 7 and 23 mm, preferably between 10 and 20 mm, a spacing between two adjacent loops in each spiral being between 1 and 10 mm, preferably between 3 and 7 mm, the number of bond lines being between 2 and 8, preferably between 2 and 4.

In another embodiment of an absorbent article according to the invention, the absorbent core is at its garment facing surface connected to the backsheet, the backsheet being on its garment-facing side provided with a layer of adhesive, the adhesive not extending along the area of the backsheet located between a projection of the axes of flexibility onto the backsheet.
Bonding of the core to the backsheet prevents shifting of the core within the space between the topsheet and the backsheet. Preferably the garment facing side of the backsheet is glued to the inside of the garment using a pressure sensitive adhesive to keep the sanitary napkin in place during use. When the sanitary napkin is compressed during use, the backsheet is raised, together with the central part of the core. It is essential that the part of the backsheet that is raised together with the core, is not glued to the garment, so that it does not impair the deformation of the core.

Again another embodiment of an absorbent article according to the invention is characterized in that the core comprises a central acquisition zone comprising a lower amount of absorbent gelling material than the zones of the core surrounding the acquisition zone.

The omission of absorbent gelling material in the central zone of the sanitary napkin according to the invention, results in a better longitudinal distribution of liquids in the absorbent core and in faster acquisition. A
sanitary napkin having a central acquisition zone of -4a- 21 44958 reduced concentration of absorbent gelling material is known from Canadian patent application number 2,140,036 filed on June 30, 1993 in the name of The Procter &
Gamble Company. The reduction of absorbent gelling material in the central zone, reduces the stiffness of the central zone relative to the zones of the core that surround the central zone. This facilitates the . deformation of the central part of the core upon compression of the core transverse to WO 94/06386 ~ 1 4 4 9 5 8 PCI/US93/08848 s the lcngituclinql sides. The central zone of the core can be given an eml!os~ eY ~ for imparting Çullher fle~cibility.

Rrief ~ r~ption of thP ~rqwi~u,c Some em~i~ey~c of a sqnitpry naplcin accor~ing to the invention will bedescribed with re~rence to the acco~panying drawings. In the drawings:

Fig. 1 shows a top plan view of a ss~-it ~~ naplcin whc~c~n a part of the overlying layers have been cut away to e~cpose underlying structures, the sAn;tZry naplcin having a ge~e~ally straight core, Fig. 2 shows a top plan view of a sz..;~ n~rlri~ having a ~ ~pe~l core, Fig. 3 shows a cross section~l view of the sA..;I~ ~ n~plrin of Fig 1 along the t~s~erse center line 16, ~ig. 4 shows a sc-~ P-..~;C cross secticnql view of a ~rel~ eml~lin~ t of s~n;l~y -r~ accordillg to the invention along the ~ e~se center line 16.
Fig. S shows a top pl. n view of a sA~ r~ napl in having a central acquisition zone con~plising em~ss-..e~lts.
Fig. 6a and 6b show a sc~ t ~ cross sec1 cnql view of a s~ni~ napkin acco~ing to the invention before and after co~p~ssion lhereof.

net-q~ P~ n of thP ~ ,t;on The cml~1;A~e~lts of the al,soll/ent article as illusl,atcd in the drawings refcr to a ~ os~ble sqnitqq napl~n, i.e. an article which is worn by females adjacent to the p~ en~lql region and which is intf-nd~ to absorb and contain the ~ario~s e~ qtes which are ~lisch~g~ from the body (e.g. blood, .Af~r~s and urine) and which are intended to bc discarded after a single use. The i~ve.llion is however not l;...;t~ to sqnitqry naplcins only, but also covers other al,soll~ articles such as pqntiliner which ge~e~lly have a lower cap -city than S~;t ~ a~ .C, Although the e-~ t described in detail in the d~a~in~S has a so called nla~ -qte" core wherein the absorbent geltin~ ~tcnal is present as a Iaycr between two sheets, the hlvention is not l;...i~c~ ~her~to and also -6- 2 1 44~58 applies to Cores wherein the absorbent gelling material is mixed with fibers, such as described in the Canadian patent application No. 2,124,798, filed on November 6, 1992 in the name of The Procter & Gamble Company.

Figure 1 shows a sanitary napkin 1 comprising a liquid pervious topsheet 3, an absorbent core 5 underlying the topsheet and a liquid impervious backsheet 7. The core 5 has two longitudinal sides 9 and 11, which extend in a generally longit~ nal direction of a longitudinal center line 13 of the core 5. The longitudinal sides 9, 11 need not be straight but can also be curved towards the longitudinal center line, to provide a shaped core, as shown in figure 2. The absorbent core 5 can be covered by one or more acquisition layers for distributing fluids which have penetrated through the topsheet 3, across the absorbent core 5. The absorbent core 5 comprises a laminate wherein the absorbent gelling material is interposed between an upper tissue 24 and a lower tissue 25.

Parallel to the core's longitudinal center line 13 extend a pair of axes of flexibility 40 and 41, along which the core 5 has a reduced resistance against compression forces acting transverse to the longitudinal sides 9,-11.
The preferred axes of flexibility as shown in Figs. 1 and 2 are straight, but can be of inwardly concave or convex shape. Upon compression of the core transverse to the longitudinal sides 9, 11, the central part 15 of core that is located between the axes of flexibility 40, 41, that are preferably formed by scoring of the core, will raise in an upward direction so as to remain in close contact with the user's body. This is schematically illustrated in Figs. 6a and 6b.

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21 44~5~

In a preferred embodiment, the core 5 comprises at least two layers, that are bonded together along bond lines 51, 52 located adjacent to score lines 40, 41. Bonding of the layers of the core along the bond lines 51, 52 imparts an increased flexibility to the core, 5, 20 making it return to its undeformed shape when compression forces on the core are removed.

The core 5 can be provided with a central acquisition zone 18 that is flanked by two side zones 17 and 19. The central acquisition zone 18 comprises a lower concentration of absorbent gelling materials than the side zones, the concentration in the side zones 17, 19 being between 2 and 7.5 g./sq. foot, preferably about 5.5 g./sq. foot, for a relatively low gel strength absorbent gelling material and between 2 and 15 g./sq. foot, preferably about 10 g./sq. foot for relatively high gel strength absorbing gelling materials, and in the acqu~isition zone being preferably about 0 g./sq. foot. A
test method for measuring the gel strength is described in Canadian patent application No. 2,135,747, filed on May 1, 1993 in the name of The Procter & Gamble Company.

The concentration of absorbent gelling material need not change abruptly when going from the side zones to the acquisition zone, but can for instance decrease linearly from high to low, or according to any other desired profile.
The width, W, of the central part 15 of the core 5 preferably is narrow compared to the narrowest width, L, of the absorbent core 5. Preferably the distance W
between the score lines corresponds to the width of the central acquisition zone 18 of reduced concentration of absorbent gelling material, which in a preferred B

-7a-embodiment amounts to 3 mm. For sanitary napkins having a shaped core 5, as is shown in figure 2, the narrowest lateral dimension L of the sanitary napkin is located along the transverse center line 16 thereof and measures preferably about 70 mm. The sanitary napkin 1 is at its longitudinal perimeter provided with two lateral flaps or wings, which can during use be folded around the edge of the user's garment to position the sanitary napkin with respect to the garment and to reduce side soiling.

Looking at some of the elements of the sanitary napkin more specifically, the absorbent core 5 may be any means which is generally compressible, conformable, non-irritating to the wearer's skin and capable of absorbingand containing body exudates. The absorbent core 5 may be manufactured in a wide variety of sizes and shapes (e.g. rectangular, hour-glass, etc.). A preferred shape of the absorbent core 5 is the dogbone shape shown in FIG. 2. This preferred absorbent core 5 is about 22.0 centimeters long (longitudinal dimension along the longitudinal centerline 13), about 7.0 centimeters wide across its midportion (lateral B

WO 94/06386 2 1 4 ~g 5 8 PCI/US93/08848 ~i-n~Mcion) along the traverse center line 16. The abso~bent core S is fl~icqlly configured for ease of .~ r~-tllre and so that no conscious effort is re~llir~d by the ~.ea~cr to ~ropelly place the n,q,p~in 1 in the direction it should be worn. The midportion is confi~lred to b-qsic-q-lly conform to the wearer's thighs and to the ~h;~ r crotch portion of the wearer's p-q-nti~fs so as to pre~cnt eSceCc ~e bl~n~-hi~. The size of the alsorl,cnt core S may be varied to acco--~ ~qte wearers r-q-~inp in size and also r,q-~i~ in the e~pect~A amount of e~ qte fluid volume.
The absorbent core S may be -q-tt~c-h~ over the core's major top and bvtlbm surfaces respectively, to adjacent mPmhers such as the tops~eet 3 and bacl~ sheet 7 by any of the means well ~nown in the art, such as by spray-gluing or lines or spots of adhesive. Such qttS"~ n~ fS~ilitqteS
inte~ y and recoverability of the al,solL.ent ~ ials in use so as to mqintqin an o~ti~ deg~ce of abso.lJcncy. F~efe~dbly, the al,sol~ellt core S has a wet-ten~ile strength in the cross-direction of at least about 100.0 grams per cen~ eter. ~Wet tenci1e strength is ~ete~ blG by ASTM ~tqn~lqrd D 829-49. ,~ l ~ ~

The al.sGll~nt core S may be ~-rac~red from a wide ~ ic~r of liquid - absG~ nt .--~e~ i~ls cu.~.. only used in Aicpos~l-lG s~ y nar~inc, diapers, and other absoll,c.lt articles. F-s-q~rles of suitable absorbent mqteriqlc inClude co~ ~ wood pulp which is g~ne~lly rc~ i to as airfelt, crep~l celhllcse w-q~ i~, absol~t foqm~, absorbent sI~on~es, h- I;G staple fibers, polymeric fibers, hydrogel folllling polymer f~elling agents, or any equivalent .n~G~;~lc or co~ nations of materials.
A particularly pr~f~rred absoll,c~t l. ~tc.;~l are absorbent gelli-~
~9tC~l-S or pol~r~..e~ic gelling age~C. Pol~r~e~ic gel~ g agents are those u.atc~ials which, upon contact with fluids (i.e., liquids) such as water or body fluids, imbibe such fluids and tller~ form hydrogels. In this er, fluid ~i~ch~ged into the al,sGlbcnt core S can be ac~- ired and held by the polymeric ~elli~ agent, lLe~ providing the articles herein with çnk~c~l al.s~ nt capacity and/or im~ro~ed fluid reten~icn ,~e~ro~ e.

The polymeric gelli~g agent which is employed in the al)sG.l,cnt core S
will genc~lly complise particles of a s~ lly water-insoluble, slightly cross-lined, partially neutr~li7ed~ hydrogel f~ ing polymer 9 ~ ~ 44~8 t.; l Such p~l~c~ material~ ca~ bc p~par~i from pol~ G, ~tc~ h~r~; acit-co~ monomcrs. Suitablc l r~h ~atcd acitic s for usc i~ q~; ~ thc pol~c~;c ~llinr a~e~ts uscd m ~his i~vchtiGn inclt~e thosc listed in US-A~,6S4,039, entitled ~Hyd~o~l rG.~ Polymcr C~ tio~ for Usc i~ AbsorbeD~t S~uc~res", which issued to Bra~dt, Gol~m~n a~ ~ o~ March 31, 1987 .
l?~cf~Y~ O~ S inrlllde acrylic acit, .~ th~c.~lic acid, aDd 2-ac~rl~ito-2-u~ y.oya~c s~lfo~ic acid. Acrylic acit itsclf i~ c~pocially ~f~r~-for y,~ a~on of thc pol~rmc--c ge~ g agent ID thc hydrog~l f~.~g pol~u.c~;c ~llinl~ agent thc polymeric CQI~ O~
fol...cd from ~ ~c~ a~d, acid-coDtqinin~ monomcn may bc ~f~J~ onto other types of polymcr moieda such ~ starch or ccllulosc. Polyacrylatc grafted starch ~D~i~ls of thi~ typc arc apccially t,nf~l for u~c herein.

~cf~rr~i polymcr gelli~ ageDts which c~ bc ~pan~ from CG~ tiODal typc~ of moDomcr~ i~chde hytrolyzed acrylo~itrilc gra*et starch, polyacryl~e ~kl starch, poly~.~l~os, maleic a~hytrite-bascd copolymers a~d combiIIadoDs lhc.co~ P~pcislly pnf~ arc the polyac.~ d polyac.~ starch Wh~te~c. thc DatUrC of thc b~ic polymer compoDeD~ of thc hy~r~gel f~.~, polymcric ~eIli~ agcDts u~ed in the absorbe~t core S hcrei~, such matcrial~ al bc slightly cros~-lin~ Cross-lin~in~
sena to rc~der ttc h~d~g~ or~ polymer rl~inr age~ts used iD this i~c~tion sub~ally watcr-i~soluble, a~d cro~linlrin~ thus in part d~ cl ~olumc a~d e~tractablc polymcr charac~ cs of the h~rd~o~cl~ formed ~om thc polymeric ~lli-l~ a~eDts employet. Suitable cross-Iin~ a~cDts arc weU l~ow~ in the ut ~d inc}u~c, for c ~ .yle, thosc dcsc,ibcd i~ ~rcater detail i~ US-A~,076,663, which pateD~ issued to Masada et al on February 28, 1978 .
P~cfc..~t cro~li~ a~e~ts uc the di- or polyestc~ of ~A~ tcd mono- or polyca~l~: acits wit~ polyols, the bisac.~ ite~ and thc di- or triallyl amilles. P~C;9l1y prcf~,. cd cross-lin~ y a~en~ are N,N'-~ lenebisac~l&.,ide, ~ ylol propanc B

W094/06386 ~,~4~9S~ ~ PCI'/US93/08848 triacrylate and triallyl amine. The cross-linl~ing agent can ~e~e~ally co~plise from about 0.001 mole percent to 5.0 mole ~ercc~t of the rçs~lti~ hydrogel-foill.ing polymer ~ te~ . More ~eferably, the cross-lin~inP agent will co~iise from about 0.01 mole pcrcent to 3.0 mole percent of the hydrogel-fo~ ing polymeric gelli~ agent used herein.

The slightly cross-lin~l, hydrogel fo~g polymeric g~llin~ agents which may be used in the articles of the present iL.~enlion are ~enerally employed in their partially neutralized form. For p.~ ses of this invention, such m~teri~ls are considered partially neutralized when at least 25.0 mole ~ercent and prefe~ably at least 50.0 mole ~c~ce~t of monomers used to form the polymer are acid group-cont~ining monomers which have been neutralized with a salt-fol~ing cation. Suitable salt-fol~ ng C ~tiQn-~ ;nG1ll~e al~ali metal, ammo~ ~.., S~ S~ mm~nillm, and ~minGs. This p~rcen~e of the total mo-~ol..er lltili7~A which are neutrali_ed acid group-cont~ini~ monol~.els is r~f~rred to herein as the "degree of neutralizationn.

The polylllelic ~ellilu agent materials used in the al~soll,cnt ar~cles as shown in Figs 1 to 4 must have a relatively high c~p~~ity for imbibing fluids encv!~..tGrcd in such articles. The a~,~ll.cnt cap~city of these .nqtc~ can be ~lvz~';r.e~ by refere~c;-u the Hgel volume" of the polymeric ge~ g a~!ntc which are to be selecteA for use in the present invention.

For purposes of this inven~ion~ gel volume can be defined in terms of the amount of s~rl-~ ;~ unne ab~rl~ by any given polymeric gelli~ agent and is ~pccirled as grams of ~ t~G urine per gram of polymeric gelling agent. Gel volume in s~ ;c urine can be ~l&te~ ~ for f~ ing a S~C~n~ Qn of about 0.1~.2 parts of dried polymeric gelling agent to be tested with about 20 parts of S~.thP-liG urine. This s~ls~ -c;on is ...~;n~in~A at ambient te~ eldture under gentle s~ ~ for a time sufficient, e.g., about 1 hour, for swelling e~lnilibrium to be ~ inPA.
The gel volume of the polymeric gelling agent is then ~G~ teA from the weight fraction of the polymeric ~elling agent in grams of s~ l.el;c urine per gram of polymeric Pelli~P agent is then c~lr~ tP~ from the weight 2 ~ 4 ~ 9 5~8 fraction of the polymeric gelling agent in the suspension and the ratio of the liquid volume excluded from the formed hydrogel to the total volume of the suspension.

The gel volume of the gelling agents used in the absorbent core 5 herein will generally be at least about 20.0 grams of synthetic urine per gram of polymeric gelling agent. More preferably, the gel volume of the materials employed will range from about 20.0 to about 60.0, most preferably from about 22.0 to about 35.0 grams of synthetic urine per gram of polymeric gelling agent.

The absorbent gelling materials having an absorbent gel strength of more that 1.2 kPa after 5 minutes are classified as high gel strength absorbent gelling materials and can be used in higher concentrations in the side zones. Preferred absorbent gelling materials show a generally regular increase in gel strength from the value after 5 minutes exposure to the value after 30 minutes exposure.

In the preferred embodiments shown in Figs. 3-6, the absorbent core 5 is a laminate comprised of a layer of absorbent gelling material disposed between two air-laid tissues 24 and 25. A suitable laminate is the absorbent laminate WATER-LOCK L-535 available from the Grain Processing Corporation of Muscatin, Iowa (WATER-LOCK
registered TM by Grain Processing Corporation). Such superabsorbent laminates are disclosed in US-A-4,467,012, entitled "Composition for Absorbent Film and Method of Preparation", which patent issued to Pedersen et. al. on August 21, 1984, and US-A-4,260,443, entitled nT.~m;n~ted Absorbent Process n, which patent issued to Lindsay et.al.
on April 7, 1981. The WATER-LOCK L535 has a hydrogel B

-lla- 2 1 4 4 9 5 ~
polymer loading of 0.005 grams per square centimeter, however, loadings of 0.001-0.009 grams per square centimeter have been found acceptable. The first and S second tissue layers 24 and 25 provide containment of the absorbent polymer material, improve lateral wicking of the absorbent exudates throughout the absorbent core 5 and provide a degree of absorbency. In the case of non-particulate hydrogel-forming polymer gelling agents which can be formed into fibrous sheets, foams or films, the non-particulate gelling agent may T-12 214495~

c~ sc from about 15 % to about 100% by wei~ht of thc absorbc~t corc 5, more pr~fc~ably of from about 40% to about 100%, a~d most prcfc~ably of from about 60% to about 100%. Two suitable aDd c~crcially a~ailable non-pa~~ te absorbcnt ..utc.;als of ~ela~ely low gcl strc~h for usc i~ the absorben~ core S arc a doublc laycr acrylic fibrous ~atc.ial a~aillablc u~der thc tradc~9--le I qn~eal F from the Choli Co , LTD., of-~ig~ )sq~a, Ja~ a~t a c&l~ lcelh~losc fibrow matc~;al a~ailablc uDdcr thc tradc~c Aqualon C from Hercules, I~c. of Wilmin~Q~, Del.

Thc total abso,bc~t capacity of the absorb~t core 5 should bc co~p~ible w~h the ~eCiQn e~l~te loadi~g for thc intented u~e of thc ~qnitqry ~y~
1. ~lhcr, thc absorbcnt cap~~iq of thc absorbe~ core 5 may be ~rarie~
tO aCCO~ G v,-carc~s pn~in~ i~l tl~ eJ~ amount of e~ te fluit ~olume. For ;~ c, a ~ff~rc~t absor~e~t capacity may be ntili7~ for -s~ni~ry-napl~ i~tented for taytimc use a~ compared with those intcnted for ~ timc use, or for sa~ry ~1~ in~endet for use by tcena,Qç females as co- .y~tcd with those int~dcd for use by moro mature WG~-03et o~cr the absorbent core 5 a~ 3.0 milli~ ~t~.sbeyoDd the ed~u 9 ant 11 of thc absorbc~ corc S caII bc placed wct-laid tissuc 31 as shown in Fi,. 3. The wct-laid tissuc 31 is liquid pcY~cable.
A satisfactory wct-lait ~ssuc 31 has a basic wei~ht of about 15.8 grams pcr sq!~are mctcr a~d an air pe.~cabilit~ of about 30.S cubic ~ctus per mi~c pcr squ~rc mctcr at a ~c~e di~.c~tial of about 12.08 millime~r~ of water.

~.ubly, the wct-laid ~ssue 31 m~i~iDs ~tegrity whcn wc~ct, i~ usc.
The wet-l~id ~ssue 31 p~fc~ably has a wct te~ile ~l.c~ylh i~ the cross-dirccdon of at Icast about lS.0 ~m~ pcr ccnt;~ c~. Suitablc ~iss~cs 31 ant their mam~fac~rc arc tiscloset i~ U.S. Pate~t No. 3,301,746, c~titlet ~n~ for ro~n~ Absorbc~t Papcr by Imp.~ti~ a Fabric K~uc~lc P~n thcrcon prior to Dryi~ t Papcr thcrcof~, which patcnt issuct to ~fo.d a~d Si~son o~ Ja~uary 31, 1967. In a preferred embodiment, those parts of the wet-laid tissue 31 which extend beyond the longitudinal sides 9 and ~3 ' ~1~495~

11 of the al,so~l.cht core 5 are associated with the baclt sheet 7. The wet-laid tissue 31 may be associated with the back sheet 7 by qtt~chmerlt means as are well known in the art such as by spray-gluing on lines or spots of adhesive. The wet-laid tissue 31 serves a ~ bcr of ~u~l~oses.
The~tissue 31 serves to conrllle any loose su~e,absorl,cht material 29 bch.cen the tissue 31 and the back sheet 7 ther~r ~ ,c~ting the su~l~sollJcht ~te~ial 29 from Co~i~ in contact with the ~.earcY's sldn. Also, the tissue 31 Pmt,ro~cs lateral wicldng of the absorbed e~ud-q~es over the abs- ~bcnL core S thercby ~ro~idillg a more even distribution of the e~l~lqte~ throughout the al.sG~l,cnt core 5. I~ her, the tissue 31 l,~o~ u some degree of a~sG~l~hl~y and ~u~lher inhibits e~n~lq~es which have r~-~h~A and been absoll,el by the absoll,cnt core S
from rewetting the ~.earer's skin.

~--pe. ;..~osed over the- wet-laid tissue 31 can be a liquit pe~mcable wipe aG~ s;l;Q ~ sheet 33. In a l,ref~lo~l c~ ent, the wipe ac.l-~;sil;on sheet 33 is a nonwo~c~- sheet, such as a spulllaced 70%l30%
rayon/pol~ester fiber sheet. Spunlaced &brics of this type are n~n.lfactured by E.I. DuPont Nemours and Co~ .y of Wilmi~on, Delaw~e, and are made available under the tra~ --e "SONTARA"
(SONTARA reA;Lt~,rcd TM by E~.I. DuPont Nemours P Co~any).
These fabrics arc available in a number of suitable sqles, however, S~yle 8407 in its ape.t~ed form, having a basis weight of 0.005 grams per square centimeter and a thiclrness of about 0.04 mi~ ters, is ~-efe~le~.
The wipe acquisition sheet 33 e~le~ls beyond the edges of the wet-laid tissue 31 where it too is ~ S~'i~t~ with baclc sheet 7. The wipe aequisition sheet 33 gr~ll~ iml).o.es lateral wielcing of e~ es over the al,sG~l~nt eore S lhereby, in eombination with the eentral ae~ sit;Qn zone 15, l,r~ g a more even distribution of the e~vclstes thr~lghol~t the absorbent eore 5. The lateral wie~ng of the wipe aequisition sheet 33, in eombination with the lonP;~ spread of li~ l$ in the eentral aequisition zone 15, is important for the following reason. Many bul~y prior art s~ r~ napl in~ rely on a high degree of vertieal absorption at the point where elm~ es are initiqlly ~epos:lc~1. In other words,bec~l-se the abso~ t eores of these .-a~ s are fairly thiek, they ean absorb a high degree of e~ud~tes througl~ollt their th1eL~-Pss while lltili7iltg only a small degree of their surfaee area or lateral absorption eapability.

~.4 2 1 4495~

Howc~ er, thc rela~rcly thi~ ~apl~ 10 of thc presc~ c~lio~ have a comp~ ely small tc~ree of ~c~ l absorp~o~ Thaefore, for a rcla~ cly lar~c amount of e~ to bc absorbed, a w~c ~ Y;t;~o~
shcct 33, a~d a cc~ral acq~s;Lion zo ~e lS, which ca~ h~s~c~cly a~t IQn~ in~lly, dispc.sc thc c~ ovcr a br~c sur~cc arca of the absorbc~t corc S whcrc thc c~J~ c~bc~tcr a~ stcr bc ~crtically absorbet is hi~hly desirablc.

osed o~cr thc wipc acquisitio~ shcct 33 u thc liquid pe.~cablc topshcct 3. I~ a prcf~ i emb~li -~q~, thc topshect 3 is ~ssoc~,c~ with thc wipc acquisi~don shcet 33 by spray~ thc topsheet 3 to thc surfacc of thc wipc acq~silion shcct 33. Thc topshect 3 is cQ~!is~t, soft feelin~, a~d ~on~ tO the wca~'s slei~. r~ hcr, the tops~cct 3 is liquid pcniou~ , liquid to reatily lr~fc~ h its ~h;~L~ ~ss.
A suitablc topshcet 3 may be m~d from &.~VjdC ra~e of Q such as polymenc ~ fon ed thc~~plastic film~, ~ i plas~c film~, porou~ f~-m~ fibcrg (c.~., wood or cotto~ fibe~), s~rDt~ic fibe~ (e.~, polyestcr or pol~rop~ le~c fiber~) or fhm a combi~tio~ of ~ d s~ ~h~;c fibcr~, with apc.~rcd formed films bc~ prcf~.~i. Formct film~ arc cfc,~cd for the topshcct 3 ~c tl~cy are perviou~ iq~Ji-~ a~d yet ~o~absor~ Th~, the surface of t~ formed film which is m cG"~act witb the body f~ ' try, Ihcrc~ ro~ boty soilin~ a~d crca~ , a more comfortable fcel for the we rer. Suit~lc for~ film~ are des~ US-A-3,929,13S, e~ ~Ab80rp~c Sh..~ a~g ~aporod Capillarie~, which p~c~t i~od to Thompson on Decembcr 30, 19~5, US-~-4,324,246, cDdtled ~Dispo~ble ~bsorbe~t ~icle ha~i~g a St~i~ Skdst~ Topshcct-, which pat~ i~ to M~ e a~d Smith on April 13, 1982, US-A~,342,314, c~ed ~Railient ~stic Wc~
E~hibi~ ~cl lilce P~o~ , which p~t i~ to ~del a~d l'hompson Otl Au~t 3, 1982, a~d US~A ~,463,04S, estitlet ~M~croscopic~lly P~ ded l~Dimen~io~al Pl~c Wcb P~hi~
No~4lo~y Vis~lc Sur~ce a~ld Cloth-lilcc Tacdlc I~rcss~on~, which pateDt is~ued to ~hr, Loui~, M~ c~ u~d Oucllcttc Otl July 31, 1984 .

B

214495~

ID a prefe~.l embo~iment of the present inVçnti~nJ the body surface of the topsheet 3 is hydrophilic. The hyd~o~ c body surface helps liquid to transfer through the topsheet 3 faster than if the body surface was not hydrophilic. This ~iminiQlles the lilcelillood that mp~ al fluid will flow off the topsheet 3 rather than being al,sGl~ by the absorbent core 5. In a l,ief~Yred embo~1imPnt~ the body surface of the t~p~l~eet 3 is made hydrophilic by treati~g the body surface with a surf~ct~t It is preferred that the surfactant be s~lbs~n~ y evenly and completely distributed throughout the body surface of the tops~e~t 3. This can be accoml.lished by any of the co...n~on techniql~es well ~now to those s~ in the art.
For es~mrle~ the surfact~nt can be applied to the topsheet 3 by spraying, by p, ~1i~, or by the use of transfer rolls. Fullher, the surf~Gt~nt can be incolpo~ated into the polyme~ic .~ s of a folmed film topsheet or between or within the-fibers of a no..~v~.e~ to~s~ t.

The baclc sheet 7 is adjacent the al,so.l~nt core 5. In a p~felrc~
eml~;n~ , the absoll,~nt core may be ~ P~A to the baclc sheet 7. Any of the common techniqlles well known in the art, such as spray-gluing or lines or spots of adhesive may be used for this pu~pose. The back sheet 7 g~c~dlly tlefin~s the garment surface of the s ~ y ~apt~in The back sheet 7 m~ay be any means which is impervious to liqui~lc and which pr~en~s e~" l~s a~soll,ed and con~inPA in the absorbent core S from soiling articles, such as panties, which come in contact with Y~ulllcht surface of the s~ y "~pL ;~, 1. In the pief~rod embo~im~nt of the s5..;1~.y n~pt-in 1 illust~dtod in Figs. 1 and 6, the back sheet 7 is a barrier sheet ~ rrctvred from a thin plastic film. Other fle~cible liquid iou~ l.e may also be used. ~ef~,ably, the back sheet 7 is a polyethylene film having a thi~-css of from about 0.012 millimPter to about 0.051 milli...eter. As used herein, the term "fle~cible" refers to which are compliant and which will readily cGnfo~ to the ge.~al shape and CG~O ~'S of the h ~ .. body.

A suitable polyethylene film is .-~zn-~r~ctured by Mo..c~-.to ChPmical Co~ tion and m~rlreteA in the trade as Pilm No. 8020. The back sheet 7 is ~referdbly embossel and/or matte fini~lPA to provide a more clothlilce ~ear~ce. P~ulher, the baclc sheet 7 may permit vapours to esc~e from the abso-bc~lt core 5 which s~ll yre~c~ en~?tcs from p~-inp through the baclc sheet 7.

~cfcYably, the tops~t 3 a~d the baclc sheet 7 ha~re le~gth and width ,C;o~ c~ally larger tha~ the absorbent core S so that they est~n~
~oDd the lo~ 1 edgu 9 ~d 11 of the absorbe~ core 5 where they are ~s~ci~t~ tGyelhcr in a suitable ~ ~ .Gr. As used herein, the term "~CSQ~ t~ cy~ro ~u~ co~i~ whc~cb~ ~ first m~m~r is directly joiDed to a second member a~d cor~fi~tioDs whc~cby t first ...~-..'~r is iadir~ly joined to a second .--~ by ~rl;~;~ the first c~ to i~ c ~i~te ...~ which i~ turD are ~ ~ to the sCco m~mkr. L~ a~ e~ mc~lt, thc baclc sheet 7 and thc topsheet 3 have ellip~icql shape and c~ beyo~d the absorbe~t core S a A~ c of at least about 1.0 cenl;~ ter where thcy are joi~ed Lrc~Lly to e~ch other by ~ttM~k...~ ' mea~ a~ are well Ic~ow~ i~ the art. The at~k--.c-~t mea~
may be, for e~ample, a ~fo.~ con~uous layer of atheshe, ~t~c.-laycr of adhcsivc, or an array of separate li~es or spots of adhcsivc.

A prcfc.~c 1 em~ of a S~ Zr,~ l~apl has a cross-sct~o~
confi~uration as show~ in Fig~ 4. ~e core S is strai~ht-sided 1~ a Ic~th of 210 mm and a witth of 64 mm. The absorptio~ laycr (24, 25, 29) co.-~ ~ an air laid tis~ue (24, 25) as supplied by Wallc soft, havi~g a basis weight of 63~/m 2, whcsc~ 6.S~/square foot of absorbcnt gClli .-- ~, ;~1 of type L74 as supplied by Sholcubai are comprised. O~to the abso~pdon layer (24, 28, 29), a wipe acquisition sheet 71 bei~ a ~d~uqled ~nwoven of a basi~ wei~ht of S0.9 ~Im2, as supplied by Suo~, for bteral dis~ib~tio~ of liq~ across the laycn 24, 2S, is ~luod alOD~ the boDd linc Sl, S2, usi~ a spiral ~lue p~ The bond li~es Sl, S2 ha~e a len~ of 120 mm, a width of S mm, the ld;"'~'CG W
betwee~ the i~er ~uDtaria of the bo~ bei~ 3 mm. The amou~t of ~luc used in each spiral ~lue p~1te~ iS 0.007S ~m, a ~ cc betwee~ two adjace~t loop~ in the spiral ~t~.- bei~ S mm. O~ top of the wipe ac.~ ion shect 71, a tissue n of ~ y lowcr tensiq tha~
the shcet 71 is locq~. The shec~ 71 compnsa a~ air la;id tissue of basis wci~ht 6~ ~/m2 a~ supplied by WalldsoR. Thc shect 72 is conY~rctc~ to thc shcct 71 ~ria ~luc lincs S3 and S4, of ~;mil~- ~pe as ~lue li~es 51, 52.

B

W O 94/06386 ~ 1 4 4 9 5 8 P(~r/US93/08848 Thc glue used for ~ i~ the sheet 71, 72 and 24 is a hot-melt adhesive of type Findley 99~374.

The tops~ eet 3 is fixed to the sheet 73 by means of a cold glue, type Findley I 8Q8~ which is applied as a film.

The score lines 40, 41, 42, 43, 44 and 45 are 120 mm in Içn~th, 1 mm widc and have a depth of O.S mm. The ~ t~nce l/cl-.ee.. the score lines is 3 mm.
, ....
The garment facing surface 37 of the core S is glued to the bac~c~Pet 7 along two strips 57 and 58. The bac~c~ eet 7 is provided with a pressure se-~C;~;ve glue along two strips S9 and 60. The parts of the garl~ent facing surface 37 of tbe b~cl~c~lP,et 7 that are locst~P~ within a ~li$t~nce of 1.5 mm from the lonEitvdin~l center line 16 are free of adhesive.

As shown in Fig. S, the central ac~llisition zone 18, that is free of abso.l~,lt ~e~ te-- ;~1, is a closed CQ ~tO ~r~ which is at all sides fl~nL-~d by a~soll,en~ Pe~ tGl;~l. The length of tbe central acqlliciti~n zone 18 is 147 mm, the width being 3 mm. Within the central part lS of the core, the central part lS co...l,l;c;..P the central acquisition zone 18, tbe core 5 is provided with e~-~s~ s for imparting extra fle~cibili~r to that zone.

Upon colu~ression of the s ~r it~ naplcin along the sides 9, 11, the s~ naplcin of the cGnsl.uction as d~sc~ik l above, ~ss~ .es a generally W-st a~ configuration as shown in Figs. 6a and 6b, and rela~ces baclc to its original shape when comp~cs;.;~c forces are re~ioved, thus mainl~ good contact with the user's body and at the same time maintqinilU a sufficient covelage of the underg~e~t.

Claims

THE EMBODIMENTS OF THE lNVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Sanitary napkin comprising a liquid pervious topsheet, a liquid impervious backsheet, and an absorbent core disposed between the topsheet and the backsheet, the absorbent core having a garment facing surface, a body facing surface, a longitudinal center line and two longitudinal sides generally parallel to the longitudinal center line, the absorbent core comprising an absorption layer, a fluid handling layer located between said absorption layer and said top sheet and shaping means for raising a central part of the core's body facing surface upon compression of the core transverse to the longitudinal sides, characterized in that the shaping means comprises two axes of flexibility of the core, one axis of flexibility extending on each side of the longitudinal center line and generally parallel thereto, the stiffness of the core being reduced along each axis of flexibility, each axis of flexibility forming an axis of inflexion of the core's body facing side upon compression of the core transverse to the core's longitudinal sides, said shaping means further comprising a pair of bond lines, one bond line extending on either side of the longitudinal center line near the axes of flexibility, generally parallel thereto, or coincident with the axes of flexibility, the absorption layer and the fluid handling layer being bonded along the bond lines.

2. Sanitary napkin according to claim 1, characterized in that the axes of flexibility comprise score lines, embossments, perforations, cut lines or folds, or a combination thereof.

3. Sanitary napkin according to claim 2, the axes of flexibility comprising score lines, characterized in that the score lines extend between 25% and 100% of the core's length, the width of the score lines being between 0.25 mm and 3.0 mm, the distance of a score line from the longitudinal center line being between 23% and 70% of the central width, L, of the absorbent core, the number of score lines being between 2 and 12.

4. Sanitary napkin according to claim 3, the axes of flexibility comprising score lines, characterized in that the score lines extend between 30% and 80% of the core's length, the width of the score lines being between 0.5 mm and 1.5 mm, the distance of a score line from the longitudinal center line being between 31% and 63% of the central width, L, of the absorbent core, the number of score lines being between 2 and 6.

5. Sanitary napkin according to claim 1, characterized in that along the bond lines, the absorbent layer and the fluid handling layer are connected by an adhesive.

6. Sanitary napkin according to claim 5, characterized in that the adhesive is applied in a spiral pattern.

7. Sanitary napkin according to claim 6, characterized in that the bond lines extend along between 25% and 100%
of the length of the absorbent core, the width of each spiral being between 2 and 16 mm, the amount of adhesive in each bond line being between 0.001 and 0.03 grams, the distance of the bond lines from the longitudinal center line being between 7 and 23 mm, a spacing between two adjacent loops in each spiral pattern being between 1 and 10 mm, the number of bond lines being between 2 and 8.

8. Sanitary napkin according to claim 7, characterized in that the bond lines extend along between 30% and 85%
of the length of the absorbent core, the width of each spiral being between 3 and 9 mm, the amount of adhesive in each bond line being between 0.02 and 0.029 grams, the distance of the bond lines from the longitudinal center line being between 10 and 20 mm, a spacing between two adjacent loops in each spiral pattern being between 3 and 7 mm, the number of bond lines being between 2 and 4.

9. Sanitary napkin according to claim 1, the core comprising at least two liquid-handling layers adjacent liquid handling layers being bonded along bond lines, the bond lines that are located on the same side of the longitudinal center line being located at a generally uniform distance therefrom.

10. Sanitary napkin according to claim 1, characterized in that the core at its garment facing surface is connected to the backsheet, the backsheet being on its garment-facing side provided with a layer of adhesive, the adhesive not extending along the area of the backsheet located between a projection of the axes of flexibility onto the backsheet.

11. Sanitary napkin according to claim 1, characterized in that the sanitary napkin has a caliper smaller than 5 mm.

12. Sanitary napkin according to claim 11, characterized in that the absorption layer of the core comprises an upper layer and a lower layer and a layer of absorbent gelling material comprised between the upper layer and the lower layer.

13. Sanitary napkin according to claim 1, characterized in that the core comprises a central acquisition zone and a surrounding zone surrounding the central acquisition zone, the central acquisition zone comprising a lower amount of absorbent gelling material than the surrounding zone.

14. Sanitary napkin according to claim 13, characterized in that the core is embossed in the central acquisition zone.