CA2135747A1 - Catamenial device - Google Patents

Abstract

A catamenial device comprises a fluid permeable, body facing, topsheet (25), a liquid impermeable barrier layer and an absorbent body (34) disposed between the topsheet (25) and the barrier layer, the absorbent body (34) incorporating a water insoluble particular hydrogel material at a loading of at least 40 g/m2 of the plan area of the absorbent body, the water insoluble particulate hydrogel material having a gel strength of at least 0.38 kPa after 5 minutes exposure to synthetic urine solution in the modified AGEP test, a device incorporating insoluble particulate hydrogel material absorbing at least 40 g sheep's blood in the Total Capacity Storage Test.

Description

vo 93/2299~ ~ 1 3 ~ 7 4 7 PC~/US~3/04525 CA~TAME~NIAL DEVICE

This invention relates to disposable catamenial devices. More particularly it relates to disposab3e sanitary napkins and pantiliners designed to be located externally of the vaginal cavity and to be held in position adjacent the vaginal opening by the wearer's undergarment.

A major design objective of catamenial devices of this type is ~hat ~hey be non. bulky whilst providîng adequate menses absorption capability in order to be comfortable and non-obtrusive as w211 as effective in use.

The ~lse of water insoluble particulate hydrogel material as an absorbent material In disposable abso~bent ~.rticles such a~ disposable diapers, incontinence brief~ and cata~enial de~ioes has p~.~mitted significant reductions to be made in the bu~ of such articles without a sacrifice in absorbent capacity. Within the ~ield of catamenial devices, a categorv of thin flexible sanitary napkin products has been developed and introduced commercially that takes advantage of the high absorbency of particulate hydrogel material. The commonly assigned EP-A-0336578 discloses a sani~ary napkin of this general ~ype.

Nevertheless, in spite of the commercial ir~troductiorl of catamenial devices incorporating particulate hydrogel material as the, or thelmajo comlponent of the, absorbent medium, ~here remains a perception amongst users that thin sanitary napkins are only suitabie for ligh~ or low menstrual flows or as pantiliners. Attempts to change ~his perception by incre~sing the level o~ hydrogel material in ~he struc~ure have proved ineffective as such increases in level have re~ulted in a pronounced 'gel blockingl effect with a loss in ef~i~iency of usage of the hydrogel material and, under certain conditions, adverse ef~ects on overall absorbent capacit~

WO 93/2~998 ~ 1 ~ S 7 4 7 PCI/US93/0452~

When a hydrogel material absorbs aqueous liquids and swells, the ability of the resultant gel to maintain its integrity, particularly under pressure correlates'with the 'gel strength' of the material. 'Gel strength' is a composite of several properties, but for the purposes of the present invention can be expressed in terms of the modified A~bsorbent Gel Expansion Pressure test (hereinafter referred to as the modified AGEP test). References hereinafter to gel strength values are to the values obtained in this test.
-The particulate hydrogel materials used in current commerciallyavailable disposable absorbent products have been developed primarily for disposable diapers in which the major load is urine. Whilst such hydrogel materials provide a satisfactory balance between absorbency and other properties such as gel strength when exposed to liquids that are almost entirely aqueous, they appear not to be optimum for more complex liquid materials such as menses. Accordingly a need has been identified for a particulate hydrogel material that is menses specific i.e.
has the capability of ab~orbing blood and protein-containing liquids without gel blocking.

The Applicant has no~surprisingly found t}~t certain types of hydrogel material which have high gel strength but relatively low absorbent capacity and which also retain, or more preferably increase, their gel strength after absorbing a liquid load, provide enhanced performance in catamenial devices. This gel strength behaviour, when the hydrogel is subjected to a liquid load, minimises the gel blocking effect and permits the majority, if not all of the absorbent capacity to be utilised.

According to the present invention there is provided a catamenial device comprising a llquid permeable layer having a first body-facing surface and a second opposed surface, an absorbent body disposed adjacent the opposed surface said absorbent body comprising a water inso~uble particulate hydrogel material at a weight concentration of at least Sg/m2 of the plan area of th~ absorbent body, a liquid impermeable barrier layer disposed on the surface of said absor~ent body remote f~om said liquid permeable layer, and adhesive `:`; G

1' "'O 93~2299~S 2 1 3 5 7 ~ 7 P~/US93J04~2~

attachment means for securing said device tO a garment, said attachment means being disposed on the surface of said device opposed to said first body facing surface of said liquid permeable layer, wherein the water insoluble particulate hydrogel material has a gel strength of at least 0.38 kPa after S minutes and not less than 0.38 kPa after 30 minutes exposure tO a synthetic urine solution in a modified AGEP test and in that said device incorporating O.~g water insoluble particulate hydrogel material absorbs at least 40 g sheeps blood in the Total Stora~e Capacity Test.

Preferably the gel strength of the hydrogel after S minu~es is greater than 0~48 kPa and more preferably is greater than 0~S4 kPa. Preferably also the gel strength of the hydrogel after 30 minutes increases generally uniformly to a value greater by at least 25% of i~s value after S minutes and more preferably to a value greater by at least 50%.
Most prefera~ly the gel strength after 30 minutes is greater by at least 75~o of its value after 5 minutes.

In its broadest aspect the sanitary napkin structure comprises a fluid permeable layer, a fluid impermeable barrier layer and an absorbent means, comprising a water insolub~e particuÇate hydrogel material as defined above, disposed therebetween. The fluid permeable layer can constitute a single sheet of woven or non woven fibers which may be of natural or synthetic origin or a perfora~ed film of polymeric material.
Alternative~y the fluid permeable layer can itself comprise a composite of several sheets of the same or different materials, each of which has a distinct fu~ction. The fluid impermeable barrier layer is conventionally a film of polymeric plastics material but mfly itself form part of a co~nRosite in which sheets of other materials rnay be components. I The absorbent means may comprise the water insoluble parti~ula~e hydrogel material on its own, but is more commonly a composite .
structure in which the hydrogel material is held between or enveloped in a web or webs of fluid permeable fibrous material, or mixed with such fibrous material to form an absorbent web.
.
In one preferred embodiment, the sanitary napkin comprises, from the body surface down, an apertured formed film topsheet, an apertured :

wo 93/~2998 ~ 1 3 S 7 1 ;t P~/US93/04~2~

nonwoven wipe acquisition sheet, a wet-laid tissue, the superabsorbent core, and a barrier sheet. In a preferred embodiment, the napkin also has laterally extending ~laps which drape over the edges of the wearer's panties in the crotch and are attachable to the garment side of the wearer's panties.

BRIEF DESCRIPTION OF~THE DRAWINGS

The invention is illustrated in the drawings in which:-Figure 1 is a top plan view of a preferred ~anitary napkin embodimentof the present invention with portions being torn away to show underlying structure~

Figure 2 is a lateral cross-sectional view of the prefe~red sanitary napkin embodiment shown in Figure 1 taken along line 2-2 of Figure 1.

Figure 3 is a top plan view of a preferred topsheet and wipe acquisition sheet laminate with portions of ~he topsheet being torn away to show underlying stru~t~re.

Figure 4 is a top plan view of an al~ernatively preferred sanitary napkin embodiment of the presen~ invention with portions be:ing torn away to shown underlying~structure.

Figllre S is a top plan view of another alternatively preferred sanitary napkin embodiment of the present invention with portions being torn away to show underlying struc~ure. ~

DETAILED DESCRIPl~ON OF PREFERRED EMBODIMENTS

The present invention relates to female sanitaIy napkins and in particular to sanitary napkins which are thin and flexible and offer enhanced fit, comfort, and containment.

AS used herein, the term~"sanitary napkin" refers t~ an article which is worn by females ad3acent to the pudendal region and which is intended ; .

`VO 93/2299~ 2 1 3 ~ 7 ~ ~ PCl /US~3/0452~

to absorb and contain the various exudates which are discharged from the body (e.g. blood, menses and urine) and which is intended to be discarded after a single use (i.e. it is not intended to be laundered or otherwise restored or reused). Interlabial devices which reside partially within and partially external of the wearer's vestibule are also within the scope of this invention. As used herein, the term "pudendal"
re~ers to the externally visi~le female genitalia and is limited to the labia majora, the labia minora, the clitoris, and the vestibule~

A preferred embodirnent of a sanitaly napkin 10 of the present invention is shown in Figures 1 and 2. As can be seen in Figures 1 and ~, a preferred sanitary napkin 10 basically comprises an absorbent means 13 and a liquid impermeable barrier layer 16. The absorbent means 13 comprises a water-insoluble particulate hydrogel material of defined characteristics but otherwise may be any means which is generally compressible, conformable and non-irritating to the wearer's skin and which is capable of absorbing and containing body exudates such as menses, blood and urine. Preferably, the absorbent means 13 maintains integrity, when wetted, in use. The absorbent means 13 has a first surface 19 and a second major surface 22. The barrier~layer 16 is adjacent the second major surface 22 of the ~bsorbent means 13. The barrier layer 16 may be any means which is flexible and liquid impervious and which prevents the exudates absorbed and contairled in the absorbent means 13 from wetting articles such as panties which contact the sanitary nap.kin lO.

In the preferred embodiment shown in Figures 1 and 2, the absorbent means 13 comprises a liquid permeable lay$r comprising topsheet 25 togethçr with a wipe acquisition sheet 28 in combination with absorbent body 34. In the preferred embodiment shown in figures 1 and 2, the barrier means 16 is a barrier sheet, the absorbent body 34 is comprised of hydrogel-forming material 37 disposed between two layers of air-laid tissue 40 and 43~ The first and second ~issue layers 40 and 43 provide containment of the hydrogel-forming polymeric gelling agent 37, improve lateral wicking of ~he absorbed exudates throughout the absorbent body 34 and provide a degree of absorbency~ The s`anitary napkin 10 has side edges 11 and end edges 12 which together wo 93,22~9g ~ 1 3 5 ~ 4 7 Pcr/us93/~4s~ . ~

form the peripherv 15 of the sanitary napkin 10. The sanitary napkin 10 has a body surface ~6 which is generally defined by the topsheet 25, and a garment surface 17 which is generally defined by the barrier sheet 16.

The total absorbent capacity of the absorbent body 34 should be compatible with the design exudate loading ior the intended use of the sanitary napkin 10. Further, the absorbent capacity of the absorbent body 34 may be varied to aecommodate weare~s ranging in the expected amount of exudate fluid volume. For instance, a di~ferent absorbent capacity may be utilized for sanitary napkin intended for daytime use as compared with those intended for night-time use, or for sanitary napkin intended for use by teenage females as compared with those intended for use by more mature women. The absorbent body 34 may be manufactured in a wide variety of shapes (e.g. rectangular, hourglass, etc.). A preferred shape of the absorbent body 34 is the dogbone shape shown in Figllre 1, typically having a longi~udinal dimeIlsion along the longitudinal centerline 5~ of 22.0 cm.~ a lateral dimension along the lateral centerline 61 of 7.0 cms and a lateral dimension o~ 8.0 centimeters across its widest portion. Preferably, ~he central width of the absorbent is at least 7.0~entime~ers and the caliper of the n~pk;n as a whole is less than 3.0 millimeters more prefer~bly le~s than 2.5 millimeters.

In a preferred embodiment, the sanitary napkin 10 of the present invention will have a hydrogel-forming polymeric gelling agent distributed over at least 100 cm2 of the plan area of the absorbent body, more preferably over an area of at l~s~ 125 cm2, even more preferably over an area of ~t least 150 cm2, and most preferably over the entire plan area of the absorbent body 34. The hydrogel-forming polymeric gelling agent will be present in an amount of at least O.OO~S
g/cm2 up to about O.OO9g/cm2 Higher amounts per unit area can be used bu~ show a cor~espondingly less increased benefi~. More usually a loading of at least 0.002g/cm2 is employed, preferably at leas~
0.004g/cm2 and more preferably the loading lies in the range of from 0.0045g/cm2 to 0.008 g/cm2. Most preferably the amount of gelling ~ WO 93/2299~ ~ 1 3 5 7 1 7 PCr/US93/1)4~2 . 7 material per unit area lies in the range from O.OOSg/cm2 ~o 0.007g/cm2. Preferably, the absorbent body 34 will contain from 5.0%
to 85.0% by weight of hydrogel-forming polymeric gelling agent, more pref~rably from 10.0% to 70.0%, and most preferably from l5.0~o to 55.0%. In practice this corresponds to a weight of from 0.6g to 1.5g or more preferably of a weight from 0.7g to 1.25g and most preferably of a weight from 0.75g to 1.0g o~` polymeric gelling agent in the napkin.

In the illustrated embodiment, the absorbent body 34 is symmetrically configured for ease of manufacture and so that no conscious effort is requ;red by the wearer to properly place the napkin 10 in the direction it should be worn. However, the present inven~ion is not limited to - symmetrical structures and the basic re~uirement is merely that the midportion is shaped to conform to the wearer's thighs and to the edges of the thinner crotch portion of the wearer's panties so as to prevent excessive bunching.

Referring to Figure 2, the absorbent body 34 has a first major surface 46, a second major surface 49, a pair of erld edges S2 and a pair of side edges 55. The absorbent body 34 may also be attached over its first or second major surfaces 46 and 49, respectively, ~o adjacent members such as the topsheet 25 and barrier sheet 16 by any of the means well known in the art, such as by spray-glueing by spiral glueing or by lines or spots of adhesi~e. Such attachment provides integrity and facilitates recoverability of the absorbent materials irl use so as to maintain an optimum degree of absorbency. Preferably, the absorbent body 34 has a wet-tensile strength in the cross-direction of at least 1 Newton per centimeter. Wet tensile strength is determinable by ASTM Standard D 82g-4g.

In the preferred embodiment shown in Figure 2, the absorbent body 34 is a laminate comprised of a layer of superabsorbent polymer material 37 disposed between two layers of air laid tissue 40 and 43. This laminate is preferably formed as follows. A continuQus web of air Iaid cellulosic tissue 43 of slightly more than twice the desired width of the absorbent body is provided with a band of adhesive 31 on its upper surface, the adhesive band having a width slightly less than the width of ~3 WO 93~2299~ 3 5 7 ~ 7 p?~/US93/04?~i2 the tissue 43. A suitable adhesive is a hot melt adhesive such as HL
1222 supplied by H.B. Fuller GmbH, An der Roten, Bleiche, D-21210 '?
Luneberg, Germany. Superabsorbent polymeric gelling material is then fed to the web so as to form a layer 37 of the desired weight per unit area having a width corresponding to th?ie desired width of the absorbent body. The laye~ 37 o~ polymeric gelling ma~erial is thus held ` in position by the adhesive 31 on the tissue web 43 and does not migrate or sift through the absorbenc pad.

The side edge portions of the tissue web 43 are then folded inwardly over the adhered layer of polymeric gelling material 37 so as to form the upper tissue layer 40, and to adhere the side edge portions to an upper surface of the layer 37 of polymeric gelling material. The longitudinal edges of the side edge portions preferably overlap in the region of the longitudinal centre line of the web. The folded laminate is then severed into portions of the desired length to form individual absorbent cores. The cutter used to sever ~he individual portions is shaped so that the ends of the core are rounded. In the preferred embodiment shown in Figures 1 and 2, the cutter is shaped to follow the circumference of a circle of radius approximately 38 mm.

In the embodiment of Figure 2, the tissue layer 40 of absorbent body 34 forms the upper tissue layer of the laminate in the assembled napkin, such that the overlapped tissue side edge portions are disposed adjacent the wipe acquisition sheet. In an alternative embodiment the absorbent body 34 may be inverted during manufacture so that the layer 43 is disposed uppermost in the assembled napkin.

l'he pTimary absorbent material forming the core of the absorbent body is a wateriinsoluble particulate gelling agent capable of forrning a hydrogel when it absorbs aqueous liquids. In this connection, ;t particulate includes granules, ~lakes, rods, fibers, cubes, spheres and ~?
agglomerates of finer particles. ~?
?
Aqueous liquids, such as urine and body fluids, discharged into the ` ~ absorbent body 34 can be acquired and held by the polymeric gelling j?
agent, thereby providing the articles herein with enhanced absorbent ;~ ~ , ` '; ; ' ' ., . ,.'. , . ; ! ` i ,'`'O 93/22998 ~ 1 3 ~ 7 ~ 7 PCT/U593/04525 capacity and/or improved fluid retention performance. In principle, any material capable of forming a stable water-insoluble gel on absorption of.aqueous liquid can be used as the particulate gelling agent. Suitable materials of this type include chain entangled high molecular polymers cellulose derivatives such as carboxymethylcellulose, hydrophilic polymers grafted onto cellulose or starch backbones and cross.linked co-polymeric materials based on acrylic acid.

The polymeric gelling agent which is employed in the case of the absorbent body 34 will preferably comprise particles of a substantially water-insoluble, slightly cross-linked, partially neutralized, hydrogel-forming polymer material. Such polymer materials can be prepared from polymerizable, unsaturated, acid-containing monomers. Suitable unsaturated acidic monomers for use in preparing the polymeric gelling agents used in this invention include those listed in U~S~ Patent 5,6544,039, entitled "Hydrogel-Forming Polymer Compositions For Use In Absorbent Structures", whic~ issued to Brandt, Goldman and Inglin on March 31, 1987. Preferred monomers include acrylic acid, methacrylic acid, and 2-acrylamido-2-methyl propane sulfonic acid~
Ac~ylic acid itself is especially preferred: for preparation of the polymeric gelling agent material.

Preferred polymer gelling agents which can be prepared from conventional types of monomers include hydrolyzed acrylonitrile grafted starch, polyacIylate grafted starch, polyac~ylates, maleic anhydride-based copolymers and combinations thereof. Especially preferred are the polyacIylates and polyacrylate grafted starch.
Examples of such preferred gelling agents are Aquakeep 10 SH, a cross-linked sodium polyacrylate supplied by Atochem S~A.~ 4 Cours Michelet, La Defense, Paris, France, and Sanwet IM5600-S, a cross-linked starch grafted sodium polyacrylate supplied by Farbwerke Hoechst AG oi F~ank~urt, Germany.

l~he preferred.hydrogel-forming polymeric gelling agents used in the absorbent body 34 herein, will: in general be slightly cross-linked. E
Cross-linking serves to render such hydrogel-forming polymer gelling ~75 WO 93/2~998 Z 1 3 ~ 7 ~ 7 PCl /US93/04525 agents substanti~lly water-insoluble, and cross-linking thus in part determines the gel volume and extr~ctable polymer characteristics of the hydrogels formed from the polymeric gelling agents employed.
Suitable cross-linking agents are well known in the art and include, for example, those described in greater detail in U.S. Patent 4,076,663, which patent issued to Masuda et al. on February 28, 1987.

Preferred cross-linking agents are the di- or polyesters of unsatura~ed mono- or polycarboxylic acids with polyols, the bisacrylamides and the di- or triallyl amines. Especially preferred cross-linking agents arie N, N'-methylenebisacrylamide, trimethylol propane triacrylate and triallyl amine. The cross linking agent generally comprises from 0.001 mole - percent to 5.0 mole percent of the resulting hydrogel-forming polymer material. More preferably, the cross-linking agent will comprise from 0.01 mole percent to 3.0 mole percent of the hydrogel-forming polymeric gelling agent used herein.

The slightly cross-linked, hydrogel-forrning polymeric gelling agents ~i which are the preferred absorbent materials for use in the articles of the present invention are generally employed in their partially neutralized forrn. For the~ purposes of this in~ention, such materials are eonsidered partially neutralized when at least 25.0 mole percent, and preferably at least 50.0 mole percent of monomers used to form the polymer are acid group-containing monomers which have been neutralized with a salt-forming cation. ~Suitable salt-forming cations include alkali metal, ammonium, substituted ammonium, and amines.
I'his perce~tage of the total monomer utilized which are neutxalized acid group-containing monomers is referre~ to herein as the "degree of neutralization".

Irrespective of their c~mposition and nature, par~icula~e polymeric ; ~ gelling agents t`or use in catamenial devices in accordance with the present inventi~n must possess a gel strength above a defined minimum and must maintain ~gel strength above this minimum after absorption of aqueoùs liquid discharged by the wearer.
, vo g3,2299~ ~ 1 3 5 7 4 7 PCI/US93/0452:.

For the purpo~es of the present invention, the water insoluble particulate hydrogel material mu~t have a gel strength of at least 0.38 kPa after 5 minutes exposure to a synthetic urine solution in the modified Absorbent Gel Expansion Pressure Test (AGEP test) de~lned hereinafter. Further, the water insoluble hydrogel material must have a gel strength of at least 0.38 kPa after 30 minutes exposure to a synthetic urine solution in the AGEP test. Preferably the gel strength of the hydrogel after S minutes exposure should be at least 0.48 kPa and more preferably i~i at least 0.54 kPa. Mixtures of different polymeric gelling mater;als having different compositions may be used provided that each satisfies the above requirements.

A characteristic of hydrogel materials useful for the purposes of the present invention is that the gel strength of the fully saturated material (e.g. after 30 minutes exposure) should not be less than the minimurn value of 0.38 kPa required ~or unsaturated material ~i.e. after S
minutes exposure). However preferred hydrogel materials show a generally regular increase in gel strength from the value after S
minutes exposure to the value after 30 minutes exposure. Preferably this increase is at least ~$~o, more preferably is at least 505~o and most preferably is at least 75% of the value after ~ minutes exposure.

The modified AGEP test measures the force exerted by the gel as it expands following exposure absorption to a synthetic urine solution.
The force is measured by a circular pressure foot that fits closely within a 2 cm diameter sample cell of an Ametek Precision Stage Model C1395X av~ilable from Ametek Corporation, Mansfield & Brown Division, 8600 Somerset Drive, Largo, Florida 36543, USA. The Force gauge is an 'Accuforce' device available from Brown Tool & Supply Co, So~on, Ohio, USA.

The following procedure is used: r 1. Weigh out 0.179g+/- 0.001g polymeric gelling agent material into the absorption cell.
. Place the cell containing the sample in the sample alignment bracket on the precision stage of the Ametek, and line up the W093/22998 21~574~ Pcr/us93/04s2s ~ ~

sample holder so that the pressure foot will be centred when in the tube.
3. Add a 56 x load (10 ml) of Jayco svnurine (see note 1) to the sample.
4. Usirlg ~he lever on the Ametek stand, raise the sample until the foot is almost touching the fluid.
. Zero and clear the Ametelc Force Gauge and if using a chart recorder start it with the speed set to lcm/min.
6. Turn the illuminator on.
7. Using the coarse and fine adjustments on the precision stage, raise the sample until the level of the fluid is even with the top o~
the foot~ This is achieved by sighting across the foot. The fluid that is on the wall of the absorption all due to the surface tension will appear as a white band. As this band moves up the cell it will block the silver colour of the foo~. When the white band is above the top of the foot a silver band will ~eappear. At this point lower the sample using the fine adjuster until the silver ` band disappears.
8. Turn of~ the illuminator immediately.
. When the gel reaches the foo~, set the timer ~or 30 minutes and start it.
10. At the end of S, 10, 15, 20 and 30 minutes record the force in grams.

i : :

.' ~ ~

`:: :

~093/22998 ~3 PClJU593/1)4g2a Ca!culations Pressure = Reading of Machine (g) /area of foot (cm2) x 98.1 (IcPa~ :

Notes 1. Jayco Synurine The Jayco Synurine is made up with the following quantities of compounds per litre of solution.

Na~SO4 2.0 g/l KCI 2.0 g/l (NH4)2Hpo~ 0.1~ g/l (NH4)H2PO4 0.85 g/l MgC12: 6H~O o.s g/l CaC12: 2~20 0.25 g~l 2. Testing should be conducted with the equipment and sample a~ a stable temperature of 25C.

3. The tube internal diameter is 2 cm so that the surface area of the foot is 3.14 cm2.

The polymeric gelling agent materials usecl, in the absorbent articles herein must be ab~e to imbibe fluids encountered in such articles and more particularly must give the absorbent body a sufficiently high capacity ~or such fluids to permit absorption of medium to high menstrua} flows.

Absorption is a physical phenomenon and is determined by the physical characteristics of the liquid and the absorbent substrate.
Although menses is an aqueous-based body fluid its complex composi~ion comprising mineral salts, suspended proteinaceous s~lids .

;~135~
WO93~22998 . PCI/US93/0452~ r and partially solubilised liqui~ components makes standardisation of absorption determination difficult. This dif~iculty is compounded by differences between individuals so that reproducible ~uantitative results are, in practice, virtually impossible to obtain. Accordingly, screening tests have to be adopted in which model fluids are used to provide absorption data tha~ are correlatable with user experience.

One such screening tes~ that ha~s been found to be useful measures the Retention Capacity of polymeric gelling agent material under a centri~ugal load. This has been found to be more predictive of the absorption capacity of the material in a sanitary napkin than the equilibrium absorbent capaeity which represents the maximum weight of fluid that the polymeric gelling material is capable of retaining in the absence of any imposed load.

In the Retention Capacity test, a û.2g sample of polymeric gelling agent is placed in a heat sealable non woven pouch comprising a tea bag available as Dexter 1234 - Heat Sealable from Dexter Corporation, Windsor ~ocks, Connecticut 06096, USA. . The tea bag is sealed and immersed in a 0.9% saline solution at 20C for 20 minutes. The tea bag is then centrifuged for 3 minutes at 1400 RPM in a centrifuge drum of diameter 23 cm, providing a force of 250x gravity. A blank sample, i.e. an identical tea bag containing no polymeric gelling agent, is given the same treatment and the difference in weight be~ween the two samples, less the weight of the dry polymeric gelling agent, represents the fluid retained by the gelling agent. From this value the Retention Capacity can be calculated in g fluidl g dry polymeric gelling agent. For the purposes`of this test d~ pol~meric gelling agent is taken to be the material as supplied although this may incorporate up to 5~q by weight of moisture.
.
Polymeric gelling agent materials useful in the preserlt invention should preferably have a Retention Capacity as measured in the above described test of at least 10 g/g, more preferably at least 20g/g and most preferably at least 30g/g.

~0 93/Z299~ j Ft 4 7 PCr/U~i93/0452 Whilst the above defined Retentiorl Capacity values represent preferred minimum requirements for polymeric gelling agent materials to be useful in a sanitary napkin in accordance with the present invention, the Retention Capacity test is not by itself predictive of the suitability of such materials. One reason for this is the different physical characteristics of the saline solution used as a model for urine, and menses fluid.

Accordingly, the Applicant has found it desirable to employ an additional absorbency screening test to assess the suitability of polymeric gelling materials for the purposes of the present invention..
This test comprises a measurement of the total storage capacity of a - sanitar~ napkin incorporating the polymeric geliing agent, using sheeps blood as ~he liquid to be absorbed.

Sheeps blood is a l~bile material having a limited life even when stored under appropriate conditions. It comprises a heterogeneous mixture of approximate composition 15% by weight haemoglobin and 75-80%
by weight water with low leveis of ionic salts, lactic ac~d and urea.
.
For the purp~ses of absorbency testing for ~e present invention, fresh whole sheeps blood is employed. The blood may be stored at 4C + /-1C in a sealed container and is discarded after two wee~cs if not used.
Testing is carried cut at a liquid temperature of 22C ~ /~ 1C, and for this purpose a sealed container is removed from storage in advance of the testing, warmed in a water bath and shalcen to ensure uniform distribution of the components of the blood prior to the contents being poured into the vessel in which the testing ~akes place.

In the test, 1 litre of the sheeps blood is poured into a flat vessel of surface area greater than the area in plan of a sanitary napkin, and a napkin is weighed and then placed with the fluid permeable topsheet facing downwards on the surface of sheeps blood in ~he vessel. The napkin is left for 20 minutes after which the saturated napkin is removed and placed with its fluid-permeable topsheet su~face uppermost, on a slightly inclined Figid planar surface. The topsheet surface of the napkin is then subjected to a load of 17g/cm2 applaed .. .. .. .

WO 93~2~99~ 2 1 3 5 7 4 7 PCr/~JS93/0452:~ f via a plate of the s~me surf~ce are~ ~s the napkin. The plate is a composite structure comprising a rigid material with a layer of resilient foam on its lower surface and a fluid impermeable plastics film on the lower surface of the foam to prevent absorption of the blood by the foam. The load is maintained for two minutes and the napkin is th~n removed and weighed to obtain the quatltity of sheeps blood absorbed and retained under load. The difference between the dry and loaded weights of the napkin is taken to be the Total Storage Capacity of the napkin.

For the purposes of the test a model sanitary napkin is prepared comprising a non-absorbent fluid-permeable topsheet, a hydrophilic - fluid-permeable acquisition sheet underlying the topshee~, an absorbent core assembly composed of particulate gelling agent sandwiched between two layers of cellulosic tissue and a fluid impermeable backsheet underlying the core assembly.

The topsheet and backsheet extend outwardly of the edges of the core assembly and the acquisition sheet and are secured together around their periphery to envelop the core assembly and acquisiti~n sheet.

The air laid tissue component of the absorbent core assembly comprises an air laid wet-strength cellulosic web of basis weight 63g/rn2 having a length of 207 mm and a width of 150 mm. A hot melt adhesive (Fuller HL 12~2) is applied to one surface of the web to give a longitudinally extending band of width approximately 130 mm at an application rate of 4g/m2 (0.14g).

Particulate polymeric gellin'g material is deposited on the adhesiv~ly coated web surface at a loading of approximately 58.5g/m2 in the form of a longitudinally extending band of width 70 mm. The side edge portions of the web that are free of gelling material are then folded inwardly to cover the uppe~ sllrface of the band of polymeric gelling material, thus ~orming an upper tissue layer. The side edges of the web overlap to a small extent in the area of the longitudirlal centre line of ~he absorbent core assembly. The folded tissue - polymeric gelling material laminate is provided with rounded ends by the web with a ' :

`~O 93/2~99~ 213 ~ 7 4 7 PCT`/US93/0452 curved edge cutter of radius approximately 38 mm. This leaves a tissue laminate having a loaded surface area in plan of 136.5 cm2 containing 0.8g of polymeric gelling material.

A 70/30 rayon/polyester non woven spun laced fabric of basis weight 51g/m2 is used to form ~he fluid-permeable acquisition sheet. This sheet has a 'dog bone' sh~pe of overall length 207 mm, a minimum width at the centre of 76 mm and rounded ends of maximum width 86 mm. The sheet weight is 0.79g and the total weight of the acquisition sheet, tissue layers and gelling agent is 3.44g.

For the purposes of the present invention the Total Storage Capacity for a napkin incorporating 0.8g of polymeric gelling agent should be at least 40g, preferably at least 45g and most preferably at least SOg of sheeps blood in the above test.

Another important in~use characteristic of a polymeric gelling agen~
material is the rate at which it is capable of absorbing liquid when incorporated in a napkin up to the point a~ which the naplcin becomes completely saturated ~i.e. its Total Storage Capacity). This is a function of the susceptibility o~ the gelling zFgent material to gel blocking and hence, indirectly, a function of the gel strength of the gelling agent material. However different polymeric gelling ma~erials display different gel strength behaviour pateerns on absorption of liquid, even when the illitial (5 minute) g~l strength va~ues of the materials are simi~ar. In consequence, the time taken by di~ferent polymeric gelling agents to absorb a given volume of liquid, hereinafter referred to as the Acquisition Time, will v~ry. The Acquisition Time is also likely to be di~erent for any particular polymeric gelling material at different levèls of uptake of liquid. Nevertheless, sanitary napkins incorporating high gel s~rength materials are likely to display higher rates of absorption, i.e. Iower Acquisition Times, than materials of lower gel strength, because of the diminished effect of gel bloclcing.

The test to measure the A~quisi~io}l Time is carried out by applying successive 5ml aliquots of sh ep blood fluid to the topsheet surface of a sanitarv napkin containing a polyrneric gelling agen~ as the ~bsorbent -:

WO 93/22998 2 1 3 S 7 ~ 7` PCI /US93/04',25 ~

species, and recording the time taken for each successive aliquot ~o be absorbed by the gelling agent. This measurement is repeated for a similar sanitary napkin containing no polymeric gelling agent to provide a base-line value. A model sanitary napkin having a structure and composition as described above in connection with the Total Storage C~pacity Test is used to measure Acquisition Times.

Sanitary napkins containing the preferred polymeric gelling agents have Acquisition Times whose values are lower than those for sanitary napkins containing non-preferred polyrneric gelling agents. For polymeric acid based materials the Acquisition Time values are close to the base ~ine value for the aliquot eoncerned.

~or the purposes of the test, a model sanitary napkin is prepared, comprising a non absorbent, fluid permeable topsheet, a fluid permeable acquisition sheet, underlying the topsheet, a fluid impermeable backsheet and an absorbent core d;sposed be~ween the backsheet and the fluid acquisition sheet.

The absorbent core comprises t~Q layers of wet strength cellulosic tissue of basis weight 63glm2 bet~Neen whic~ a layer of particulate hydrogel material is disposed a~ a loading of 58~5g/m2 to give a total hydrogel weight of 0;8g and a total absorbent body weight of 3~44g.

The apparatus consists of a f}at horizontal plate upon which a napkin is placed in a flat configuration with the fluid permeable topsheet uppermost. A second flat plate overlies the first and is capable of being loaded so as to provide a pressure o~17g/cm2 based on ~he plan area of the napkin. The upper pla~e is formed with a recess at the intersection of its longitudinal and lateral axes, the recess being capable of holding at least 5 ml of liquid, and the recess is provided with a centrally located orifice in its base. a To carry out the test, a napkin ;s placed be~ween the ~wo plates, so that its central region underlies the orifice, the upper plate is loaded to provide a pressure o~ 17g/cm2 on the napkin and 5 ml of sheep blood :

.7~ 3~;~9L7 `~/0 93/2299~ PCr/US93/0452 at a temperature of 2~C +/- 1C is added to the central recess in the upper plate from a hand held container.

A stop watch is started as the sheep blood is added, and stopped when visual observation of the surface of the topsheet in the region of the orifice shows that all of the added liquid has passed through the topsheet. Successive Sml aliquots of liquid are added and the times for their absorption are measured in the same way until a total of 20 ml of sheep blood has been absorbed by the napkin.

The results are used to compare the rate of liquid uptake by various polymeric gelling materials. In principle, preferred polymeric gelling - materials have higher overall rates of uptake, i.e. take less time to absorb 20 ml of sheep blood. However, for two materials having the same overall rate of uptake, the material having the higher initial rate, i.e. for the uptake of the first 10 ml is preferred. Acquisition times of less than about 30 sec~nds are preferred for uptake of the S ml aliquot providing a total liquid uptake of 10 ml.

The rnean particle size and particle size distributIon of hydrogel materials useful in the presen~ invelltion ca,~, with advan~age di~fer from conventional practice. The mean particle size preferably lies within the range from 100 micrometers ~o 250 micrometers, w}th less than 1 ~o by weight being greater than 800 micrometers in size, 99% by weight Iying within the range 800 micrometers ~o S0 micrometers and less than 1% by weight being less than 50 micrometers in size.

Within the webs which form the layers of the absorben~ body 34, the particles of the polymeric gelling agent should be thoroughly dispersed but ~may or may not bè uniformly distributed. In particular, there may be regions or zones of the core layers which have higher concentrations of gelling agent particles than do o~her regions or zones of the layers.
However, it should be noted that the scope of the present invention is not intended to extend to sanitary napkins which are void of any superabsorbent material and which have a central absorbent member overlaid solely by nonwoven materials, wherein the nonwovell WO ~3/~299~ PC~/US93/04~25 ~
`~13~47 20 materials have caliper of less than 0.50 millimetres, as determined by the caliper tes~, as later defined.

Superimposed over the absorbent body 34 is a liquid permeable wipe acquisition sheet 28. In a preferred embodiment, the wipe acquisition sheet 28 is a nonwoven sheet. In the preferred embodiment shown in Figure 2, the sheet 28 is a spunlaced 70%/30% rayon/polyester fiber sheet. Spunlaced fabrics of this type are manufactured by E.I. DuPont Nemours & Company of W;lmington, Delaw~re, and are made available under the tradename''SONTARAI' (SONTARA registered TM by E.I. DuPont Nemours & Company). These ~abrics are available in a number of suitable styles, but, Style 8407 in its apertured form, having a basis weight of 0.005 grams per sqllare centimeter and a thickness of 0.55 millimeters, is preferred. The wipe acquisition sheet 28 extends beyond the edges of the wet-laid tissue 31 where it too is associated with the barrier sheet 16. The wipe acyuisition sheet 28 greatly improves lateral wicking of exudates over the absorbent body 34 thereby providing a more even distribution of the exudates throughout the absorbent body 34. The la~eral wiclcing of ~he wipe acquisition sheet ~8 is important for the f~llowing r~ason. Many bulky prior art sanitary napkins rely on a high degree o~ vertical absorption at the point where exudates are initially deposited. In o~her words, because the absorbent cores of these napkins are fairly thick, they can absorb a high degree of exudates throughout ~heir thickness while utilizing only a small degree of their surface area or lateral ~bsorption capability. However, the relatively thin napkin 10 of the present invention have a comparatively small degree of vert;cal absorption.
Therefore, for a relatively large amount of exudates to be absorbed~ a wipe ~cquisition sheet 28 which can laterally disperse the exudates over a large surface area of the absorbent body 34 where the exudates can better and faster be vertically absorbed is highly desirable. Further, the wipe acquisition sheet 28 provides a fairly high degree of initial absorption during the time interval between the time exudates are deposited onto the topsheet 25 and the time they are absorbed by the absorbent body 34. This property will be more specifically described later.

.
r . ~/0 93~2~99~ P~/US93/04525 7~7 ? 1 Superimposed over the wipe acquisition sheet ~8 is the liquid permeable topsheet 75. In a preferred embodiment, the topsheet 25 is associated with the wipe acquisition sheet ~8 by spray-gluing the topsheet ~5 to the surface of ~he wipe acquisition sheet 28. The topsheet 25 i~ compliant, ~oft feeling, and non-irritating to the wearer's skin. Further, the topsheet ~5 is liquid pervious, permitting liquid to readily tran~fer through it~s thickness. A suitable topsheet 25 may be manufactured from a wide range of materials such as polymeric materials, formed thermoplastic films, porous foams, reticulated foams, natural fibers ~e.g. wood or cotton fibers,), synthe~ic fibers ~e.g.
polyester or polypropylene fibers) or from a combination of natural and synthetic fibers, with apertured formed films being preferred.
Formed films are preferred for the topsheet 25 because they are pervious to liquids and yet non-absorbent. Thus, the surface of the formed film which 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. 3,929,135, entitled "Absorptive Structure Having Tapered Capillaries", which patent issued to Thompson on December 30, 197S, U.S. Patent 4,324 246, entitles "Disposable Absorbent Article Having A Stain Resistant Topsheet", wh;ch patent issued to Mullane a~d Smith on April 13, 15'82, U.S. Patent 4,342,314, entitled "Resilient Plastic Web Exhibiting ~iber-Like Properties", which patent issued to Radel and l~ompson on August 3, 1982, and U.S. Patent 4,463 ,045, entitled "Macroscopically Expanded Three-Dimenstonal Plastic Web Exhibiting Non-Glossy Visible Surface and Cloth-Like Tactile Impression", which pat~nt issues to Ahr, Louis, Mullane, and OuelleEe on July 31, 1984.

In a preferred embodiment' of the present invention, the body surf~ce 26 of ~he topsheet 25 is hydrophilic. The hydrophilic body surface 26 helps liq~id to transfer through the topsheet 25 faster ~ha~ if the body surface 26 was not hydrophil;c. This diminishe~ the likelihood that ;~
menstrual fluid will flow off the topsheet 2S rathe~ than being absorbed ~y the absorbent body 34.; In a preferred embodiment, the F~
body surface 26 of the topshe~et 25 is made hydrophilic by treating the body surface 26 with a; surfac~ant. It is preferred that the surfactanc be substantially evenly and completely dlstributed throughout the body ; ~

WO 93/22998 2 1 3 5 7 4 ~ PCr/US93/04525 surface 26 of the topsheet 25. This can be accomplished by any of the common techniques well known to those ~killed in the art. For example, the surfactant can be applied to the topsheet 25 by spraying, by p~dding, or by the use of transfer rolls. Further, the surfactant can be incorporated into the polymeric materials of a formed film topsheet or between or within the fibers of a nonwoven ~opsheet.

The barrier means 16 is disposed adjacent the secorld major su~face 22 of the absorbent means 13. In a preferred emb~diment, the absorbent means 13 may be affixed over the second major surface ~2 of the absorbent means 13 to the barrier means 16. Any of the common techniques well known in the art, such as spray-gluing or lines or spots of adhesive may be used for this purpose. The barrier means 16 generally defines the garment surface 17 of the sanitary napkin 10.
The barrier means 16 may be any means which is impervious to liquids and which prevents exudates absorbed and contained in the absorbent means 13 frnm soiling articles, such as panties, which come in contact with ~he garment surface 17 of the sanitary napkin 10. In the preferred embodiment of the sanitary napkin lG illustrated in Figures 1 and 2, the barrier means 16 is a barrier sheet manufactured rom a thin plastic film. Other flexible liquid impervio~; material~ may also be used. Preferably, the barrier sheet 16 is a polyethylene film having a thickness of from 0.012 millimeter to about 0.051 millimeter. As used herein, the term "flexible" refers to materials which are compliant and which will readily confarm to the general shape and contours of the human body.

A suitable po}yethylene film i~ manufactured by Monsanto Chemical Corporation and marketed'in the trade as Film No. 8020. The barrier shelet 16 is preferably embossed and/or matte finished to provide a more clothlike appearance. Further, the barrier sheet 16 may permit vapors to escape from the absorbent rneans 13 while s~ill preventing exudates ~rom passing through the barrier sheet 16.

Preferably, the ~opsheet 25 and the barrier she~t 16 have length and width dimensions generally larger than the absorbent body 34 so that they extend beyond the edges 52 and 55 of the absorbent body 34 ~0 93~2299~ PCI/U~;93/0452 ~3 where they are associated together in a suitable manner. As used herein, the term "associated" encompasses configurations whereby a first member is directly joined to a second member and configurations whereby a first member ~s indirectly joined ~o a second member by affixing the first member to intermediate members which in turn are affixed to the second member. The extension of the topsheet 25 and/or the b~rrier sheet 16 beyond the end edges 52 and the side edges 55 of the absorbent body 34 form the end edges 11 and the side edges 12, respectively, of the sanitary napkin 10. In a preferred embodiment, the barrier sheet 16 and the topsheet 25 have an elliptical shape and extend beyvnd the absorbent body 34 by a distance of at least 1.0 centimeter to form a peripheral margin where they are joined - directly to each other by attachment means as are well l~nown in the art. The attachment rneans may employ an adhesive in the form of a uniform continuous layer, a patterned layer or an aITay of separate lines or spots or may utilise heat and/or pressure to fuse the two sheets toge~her, or may crimp the sheets together mechanically.

The sanitary napkin 10 of the present invention preferably has a low flexure~resistance; Thus, the sanitary napkin 10 of the present invention is highly flexible and conforms ve~r well to the ~arious shapes of the fernale urogenital region. Preferably, the sanitary napkin 10 of ~he present invention has a flexure-resistance of less than 300.0 grams, more preferably less than 250.0 grams, and still more preferably less than about 175.0 grams and most preferably less than 130.0 grams.

The flexure-resistance of a sanitary napkin is measured by peak bending stiffness. Peak bending stiffness is determined by a test which is modelled after the ASTM I:) 4032-82 CIRCULAR BEND
PRC3CEDURE, the procedure being consid~erably modi~led and performed as follows. The CIRCULAR BEND PROCEDURE is a simultaneous multidirectional deformation of a ma~erial in which one face of a spscimen becomes concave and the other face becomes convex. The CIRCULAR~BEND PROCEDURE gives a force value related to flexure-resistance, simultaneously averaging stiffness in all directions.

213~7~7 WO 93J2299~ PCr/US93/0452 ~4 APPARATUS:

The apparatus necessary for the CIRCULAR BEND
PROCEI~)URE is a modified Circular Bend Stiffness Tester, having the following parts:

A smooth-polished steel plate platform which is 102.0 x 102.0 x 6.35 millimeters having ~n 18.75 millimeter diameter orifice.
The lap edge ot` the orifice should be at a 45 degree angle to a depth of 4.75 millimeters.

A plunger having an overal! length of 72.~ millimeters, a diameter of 6.~5 millimeters, a ball nose havillg a ~adius o~ 2.97 millimeters and a needle-pojnt extending 0.88 millimeter therefrom having a 0.33 millimeter base diameter and a point having a radius of less than 0.S millimeter, the plunger being mounted concentric with the orifice and having equal clearance on all sides. Note that the needle-point is merely to prevent lateral rnovement of the test specimen during testing. Therefore~
if the needle-point significantly adversely affects the test specimen (~or ex~mple, punctures an inflatable structure?, then the needle-point should not be used. The bottom of the plunger should be set well above the top of the orifice plate. From this position, the downw~rd stroke of the ball nose is to the exact bottom of the pla~e orifice.

A force-measurement gauge and more specifically an Instron inverted compression load cell. The,load cell has a load range of ~rom 0.0 to 2000.0 grams.
, ~
An actuator, and more spe~ifically the Instron Model No. 1122 having an inverted compression load cell. The Instron 1122 is made by the Instron Engineering Corporation, Canton, Massachusetts.

NUMBER AND PREPARATION OF SPECIMENS

~o 93,229~g ~ 1 3 S 7 ~ 7 P~/US93~4525 ~5 In ordier to perform the procedure for this test, as explained below, five representative sanitary napkins are necessary. From one of the five napkins to be tested, some number "Y" of 37.5 x 37.5 millimeter test specimens are cut. Specimens having portions in which a topsheet is joined directly to a barrier sheet or which are a laminate of a topsheet, two or less tissue sheets and a barrier sheet, should not be tested. The reason that these specimens are not tested is due to the reali~ation that prior ar~
napkins exi~t in which a topsheet is joined to a barrier sheet beyond the edges of an absorbent core in the periphery of the napkin, such portions of which are highly flexible. However, the present invention is more concerned with the overall flexibility of the sanitary napkin and not merely the peripheral portions thereof and, therefore, the ~lexibility of the present invention is more concerned with the flexibility of the significant absorbent portions of the sanita~y napkin. If any of these significant absorbent portions of the sanitary napkin meet the parameters of this test, then the sanitary napkin satisfies the test. Therefore, a number of different specimens should be tested from each sanitary napkin. Certainly, the structurally most flexible portion of the sanitary napkin should be tested, excluding ~}lose por~ions excluded above. The test specimens should not be folded or bent by the test person, and the handling of specimens must be ; kept to a minimum and to the edges to avoid af~ecting flexural-resistance properties. From the four remaining sanitary napkins, an equal number "Y" of 37.5 X 37.5 millimeter specimens, identical to the specimens cut from the first napkin, are cut.
Thus, the test person should ha~e "Y,' number of sets of five identical specimens.

PROCEDURE ~l The procedure for the CIRCULAR BEND PRO~EDURE is as follows.; The specimens are conditioned by leaving ~hem in a room which is 21 ~/- 1C and 50 +/- 2% relative humidity for a perlod of two hours. The test plate is levelled. The plunger i~
speed is set at 50.0 centimet rs per minute per full stroke length.

:`.: ~ `: i ' ` ~ :: : ~ :

W093/22998 æl3$747 PCl`/US93/U4525 '~6 A specimen is centered on the orifice platform below the plunger such tha~ the body surface 26 of the specimen is facing the plunger and the garment surface 17 of the specimen is facing the platform. The indicator zero i~s checked and adjusted, if necess~ry. The plunger is actuated. Touching the specimen during the testing should be avoided. l`he maximum force reading to the nearest gram is recorded. l he above steps are repeated until all five of the identical specimens have been tested.

CALCULATIONS

The peak bending stiffness for each specimen is the maximum force reading for that specimen. Remember that '.'Y" number of sets of five identical specimens were cut. Each set of ~lve identical specimens is tested and the five values received for that set are averaged. Thus, the test person now has an average value for each of the "Y" sets tested. Remember, if any of the significantly absorbent portions of the sanitary napkin have the requisite llexllre-resis~ance, then the napkin satisfies the parameters of this test. T}ierefore, the~lexure-resistance for a particularly designed sanitaIy napkin is the greatest of these average peak bending stiffnesses.

As alluded to earlier, the combination of topsheet 25 and wipe acquisition sheet 28 imparts sorne beneficial properties to the sani~ary napkin 10. . In particular, the combination of an apertured formed film topsheet 25 superimposed over an apertured nonwoven wipe acquisltion sheet 28 is bene~icial. A preferred wipe acquisition shelet 28;is` the previously descr;bed SONTARA 8407. An enlarged depiction of such an arrangement is shown in Figure 3. Such a combinatiorl is even more beneficial when the nonwoven wipe acquisition sheet 28 is formed or positions such that no fiber bundles 89 of the sheet 28 are beneath some of the apertures g3 of the formed ~llm topsheet 25 (i.e.
the apertures in the two shee~s 25 ~nd 28 are aligned) while beneath other apertures 83 o~ ~he formed film topsheet 25 fiber bundles 89 of the nonwoven sheet 28 are present (i.e. apertures in ~he two sheets 25 .. . . . . . . . , .. . . .. , . ~ .. .. .... ... .. . . . . , . ... . . .. . ~ .. . . . ....

j . .'VO 93/;22998 21 3 ~ 7 4 7` P~/US93~04:~2~

?7 and 28 are not aligned). Such an arrangement is readily apparent in Figure 3, wherein the apertures 86 of the nonwoven sheet 28 are larger than the apertures 83 of the formed film topsheet 25. Such an arrangement provides the sanitary napkin 10 at least two beneficial properties: enhanced gush acquisition and enhanced wipe acquisition.
Gush acquisition is enhanced in those areas whe~e the apertures 83 of the topsheet 25 are aligned with the apertures 86 of the nonwoven wipe acquisition sheet ~8. The aligned apertures 83 and 86 provide a direct route ~or e.Yudates to ~low from the body surface 26 of the topsheet 25 to the central ~bsorbent materials of the napkin 10.
Further, the apertures 83 and 86 themselves are able to contain a degree of fluid within their walls or boundaries until such fluid is absorbed. Wipe acquisition, which is the ability to pull liquid exudates from the wearer's skin into the absorbent material of the napkini 10, is enhanced in those areas where fiber bundles 89 of the nonwoven wipe acquisition sheet ~8 are aligned such that the fiber bundles 89 are beneath the openil~gs of the apertures 83 of the topsheet 25.

As just mentioned, wipe acquisition is critical in those regions where the topsheet 25 is in contact with exudates on the wearer's skin. In such areas, the sanitaly napkin 10 is likely utlder compressive forces from the wearer's body. When such is the case, the fiber bundles 89 of the nonwoven wipe ~acquisition sheet 28 beneath the apertures 83 of the topsheet 25 are forced somewhat up into the apertures 83 of the topsheet 25, closer to the wearer's skin. Obviously, the spaces between the fiber bundles 89 and the walls of the apertures 83 ar between the fibers of the fiber bundles 89 themselves will be less than the spaces which were between only the walls o~ the a~ertures 83. These spaces are capillaries. As is!wel! known in the art, as capil~ary spaces are~ `
decreased, capiilary or drawlng action is increase. Thus,.the capillary action in these apertures 83 where fibèr bundles 89 are present is increased~ and the sanitary napkin 10~is ~better able to draw exudates from the wearer's skin into these~ capillaries and eventually into the central absorbent materials of the sanitaly napkin 10.

Although all of the~ apertures 83 of ~he~ topsheet 25 are referenced by the numeral "83", for the following~teaching purposes, specific WO 93/~2998 ~rt PCI /US93/04~2 reference is directed to the aperture of Figure 3 s~ecifically labelled and designed "83". The specific aperture 83 referenced is an example in which an aperture 83 ot` the topsheet ~5 is aligned with an aperture 86 of the nonwoven wipe acquisition sheet 28. Theoretically, such an aperture is useful for gush acquisition since exudates have uninterrupted flow form the body surface ?6 of the topsheet ~S to the cen~ral absorbent material (not shown). Next, attention is directed to the aperture 83 immediately to the right of the specific aperture 83 just referenced. As seen, this aperture 83 will enter the capillaries of the fiber bundle 89. The exudates will then either be pulled or absorbed into the central absorbent materials or wicked to intersecting fiber bundles ~9, then wicked further to other intersecting fiber bundles 89, and so on, until the exudates are absorbed into a more laterally distant portion of the central absorbent materials. Hence, a large portion of the total absorbent capacity of the absorbent materials can be utilized.

As previously mentioned, the sanitary napkin 10 of the present invention has a liquid capacity great enough to absorb medium to high menstrual flows. As noted hereinbefore, measurement of ~he Total Storage Capacity of the sanitary napkin 10 is carried out using sheep blood as the liquid absorbate. Sanitary napk~ns in accordance with the inven~ion should have a Total Storage Capacity of at least 40g more preferably at least 45g and most preferably at least SOg The central absorbent ~idth 63 of the sanitary n~pkin 10 of the present invention is believed to be an important parameter for the following reason. The sanitary napkin 10 of ths present inventicn relies more on the lateral distribution of exudates over or,through a relatively large surface area of the absorbent core 34 rather than on a high degre~ of vertical absorption common to many prior art sanitary napkins. I
Therefore, because exudates which are distributed onto the topsheet 2S may not be quickly absorbed before ~hey migrate across ~he topsheet 25, it is important to contain such exudates pending absorption. The specified central absorbent width 63 of the sanitary napkin 10 of the present invention has been determined based on ~he width of a tlexible napkin which will cup around the labia in ~he region of the vaginal orifice such that at least the edges of the absorbent --.

,; ` ~0 93/2299~ 2 1 3 a 7 ~ 7 PCr/US~3/04~5 ~9 material are positioned in the uppPrmost part of the wearer;s legs at the crotch. Thus, the sanitary napkin 10 and the absorben~ material may be cupped shaped in the surrounding regions of the vaginal orifice and exudates deposited thereon will be contained until absorbed.

Determination of the central absorbent width o~ the sanitary napkin is carried ou~ as follows, reference being rnade to Figure S. A point 64 on the sanitary napkin 10 which is disposed beneath the center of the vaginal orifice, when worn, is located. A plane 65 parallel to the lateral centerline 61 and 3.75 centimeters forward frorn the point 64 in the direction of the wearer's mons pubis is located. Another plane 66 parallel to the lateral centerl;ne 61 and 5~0 centimeters rearward from the point 64 in the direc~ion o~ the wearer's bllttocks is also located.
The greatest flat-out, uncompressed, unmanipulated, la~eral dimension of absorbent material of the sanitary napkin 10 between the planes 65 and 66 is the central ansorbent width 63 of the sanitary napkin 10. l~he absorbent material m ~/ be a single sheet, etc., and the absorbent material may be in the orm of a nonwoven sheet, an absorbent topsheet, and- absorbent core, a tissue, synthetic s~aple fibers, etc. For example, a sanitary napkan 10 of the present invention might have a wipe acquisition sheet 28 having a width of ii.75 centimeters and an absorbent body 34 having a width of 7.0 centimeters. Thus, in this example, the sanitary napkln 10 has a central absorbent width 63 of 7.75 centimeters.

l'he sanitar~ napkin 10 should preferably be scaled to the widtb of the crotch of the underwear of the wearer. A sanitary napkin 10 having a centra~ absorbent width`63 which registers ~he absorbent 13 with ~he edges of the underwear crotch is particular3y prefe~red.~ For underwea~
ctot~hes having a width of 4.0 to 8.0 centimeters, a sanitary napkin having a central absorbent width~ 63 of 4.0~to 8.0~centimeters works~

The total width of the napkin 10 is scaled to the centra~ absorbent width 63, and should be from 1.2 to 2.0 centimeters greater than the centra! absorbent width 63, due to the additional margin necessary to join Ihe edges of the topsheet 25 and barrier sheet 16 together.

r~ = ~ D . 6 WO g3/2299X 2 1 3 ~ 7 ~ 7 PCI /US93/0452~ f Generally 0.3 tO 0.5 centimeters are necessary at each edge of the napkin 10 to join the topsheet ~5 to the barrier sheet 16~ Thus, a napkin having a central absorbent width 63 of 4.0 to 8.0 centimeters will h~ve a total width ranging from 5.~ ~o 6.0 centimeters to fiom 8.2 to 10.0 centimeters.

The sanitarv napkin lO of one embodiment of the present invention intended for underwe~r h~ving a relatively greater crotch width should have a central absorbent width 63 of at least 6.5 centimeters, more preferablv of ~t least 7.0 centimeters, more preferably o~ at least 7.75 centimeters, ~nd most pref~rably of at least 9.0 centimeters.

Preferred sanitary napkins in accordance with the present invention have low flex~re resistance and, in consequence are likely to be relatively thin. Thin ~anitary napkins are advantageous as they are unobtrusive and the user will have a low awareness of such sanitary napkîns during the period of wear. The sanitary napkin 10 shown in Figures 1 and 2 has a caliper of approx. 2.7 miilimeters~ The caliper of a sanitary napkin 10 is determined by the following test~

A comparator gauge, and specifically the A~es, Model 130 with dial indicator Model 482, available from the B~C~ Ames, Company of Waltharn, Massachusetts i~s needed. The comparator gauge should have a circul~r compar~tor t`oot made of aluminium and having a weight of lO~0 grams and a contact surface of 5.16 square centimeters~
The comparator gauge is zeroed. An 80.0 grams s~ainless steel weight is place don the spindle extending above the comparatQr dial. The comparator foot is raised and the napkin, ~ith any panty adhesive release paper being rernoved, is placed garment surface down onlthe base plate. The napkin is po~itioned on the base plate sot hat when the foot is lowered it is in the center of the napkin. Try to smooth out or avoid any wrinkles in the napkin. Gently lower the foot onto the napkin. De~errnine the napkin caliper by reading ~he compa~ator dial 30 seconds after the foot comes in contact with the napkin. Repeat the measurement 3.0 centimeters from each of the ends of the absorbent material along the longitudinal centerline 58 of the napkin.
The average of the three~ readings is the caliper of the sanitarv napkin.

213~7~7 ~-` W093/2~99~ ~; PCI/US93/0~2~

Pret`erably, the ~nit~lry nclpkin lO ot` the pre~ent invention has a caliper of less than 3.0 millimeters, more preferably less than 2.5 millimeters. Increases in the caliper of the sanitary napkin are generally less pret`erred ~nd are proportional to increases in the flexure-~esistence. Thus an incre~se in caliper to 4.5 or even 5.0 millimeter~, would be accompanied by ~n increase in ~lexure resistance to 400 grams. However an increase in caliper above 3.5 mm is not preferred.

An alternative embodiment o~` a sanitary napkin 10 of the present invention is shown in Figure 4. In this embodiment, a tissue layer 51 is irlserted between the absorbent body 34 and the topsheet 25 - and the sanitarv napkin 10 has two flaps 70 each of which are adjacent to ~nd extend laterally from a side edge 55 of the absorbent body 34. Thc ~lcaps 70 are configured to drape over the edges of the wearer's panties in the crotch region so that the flaps 70 are dispo~ed between the edges of the wearer's panties and the wearer's thighs. The flaps 70 serve at least two purposes.
First, the flaps 70 help serve to prevent soiling of the wearer's body and panties by menstrual fluid. Second, the flaps 70 are preferably provided with attachment means~71 on their garment surface 17 so that the flaps ~0 can be folded back under the panty and attached to the garrnent facing side of the panty. In this way, the ~laps 70 serve to keep the napkin lO properly positioned in the panty. A pre~erred.attachment means 71 is a pressure-sensitive adhesive, as is we31 known in the art. Alternatively, the flaps 70 may be attached to each other on the underside of ~he panty by the attachment means 71 being af,fixed to the panty.

In the embodiment shown, the flaps 70 are comprised of topsheet 25, tissue 51, and barrier sheet 16. Further, in ~he embodiment shownj the flaps 70 are unitary with the laminae of the napkin 10.
In other word, the topsheet ~5, tissue 51 and barrier sheet 16 simply extend laterally beyond the absorbent body 34 to form the flaps 70. However, the llaps 70 need not be unitary with the napkin 10 but can be separate elements which are affixed to the napkin 10~ Further, the flaps 70 can be comprised of a single 3 .~ i , ..

W093~7Z998 ~13S~ 4 i PCr/US93~04525 f`

3~
substrate or other lamin~e configuration~. However, it is preferred that the flaps 70 have a liquid impervious barrier sheet 16. The barrier sheet 16 prevents exudates which reach the flaps 70 from soiling the edges of the wearer's panties. Further, it is preferable that the flaps 70 be provided with an absorbent layer, at least to a point beyond the edges of the wearer's panties.
Theoretically, only ~ relatively small amount of menses should reach the tlaps 70, therefore, only a relatively small amount of absorbent material is desirable in the llaps 70. However, for sanitary napkins intended for medium or heavy menstrual ~lows, it is preferred that the f1aps 70 incorporate sorne absorbent material in order to prevent any exudates that reach the flaps from being able to flow further to unprotected areas. The absorbent material may be a tissue, or an extension of the absorbent body 34, such as the tissue-forming the layers 40 & 43. However, the absorbent material in the flaps 70 ~hould not s;gnificantly impair the flexibility of the flaps.

A number of sanitary napkins having flap designs suitable or adaptable for use with the sanitary napkins 10 of the present invention are known. Examples of sanitary~apkins with such flap designs are disclosed in U.S. Patent Nos. 4,687,478, 4,608,047 and 4,285,343.

For illustration purposcs, t~le central absorbent width 63 of the napkin 10 shown in Figure 4 would extend laterally ~rom the outer edge 52 of the tissue 51 in the one flap 70 to the outer edge 52 of the tissue 51 in the other flap 70.

Another alternative embodiment of a sanitary napkin 10 of the present invention is shown in Figure 5. Like the napkin 10 shown in Figure 4, this napkin lO also has flaps 70, only of a dif~erent configuration. In this embodiment, ~he flaps 70 are comprised ¦
only of the topsheet 25 and the barrier sheet 55 For illustrative purposes, the central absorbent width 63 of the napkin 10 shown in Figure S would extend laterally from one 21357~7 `JVO ~3/2299X PCl`~US93/0452:`

outer edge 52 of the tissue 51 to the other outer edge 52 of the tissue S l .

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Claims (19)

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

1. A catamenial device comprising a liquid permeable layer having a first body-facing surface and a second opposed surface, an absorbent body disposed adjacent the opposed surface, said absorbent body comprising a water insoluble particulate hydrogel material at a weight concentration of at least 5 g/m2 of the plan area of the absorbent body, a liquid impermeable barrier layer disposed on the surface of said absorbent body remote from said liquid permeable layer, and adhesive attachment means for securing said device to a garment, said attachment means being disposed on the surface of said device opposed to said first body facing surface of said liquid permeable layer, characterized in that the water insoluble particulate hydrogel material has a gel strength of at least 0.38 kPa after 5 minutes and not less than 0.38 kPa after 30 minutes exposure to synthetic urine solution in a modified AGEP test, and in that said device incorporating 0.8 g water insoluble particulate hydrogel material absorbs at least 40g sheeps blood in the Total Storage Capacity Test.

2. A catamenial device according to Claim 1 wherein the gel strength of the hydrogel after 5 minutes is greater than 0.54 kPa.

3. A catamenial device according to Claim 1 wherein the gel strength of the hydrogel after 30 minutes is greater by at least 25% of its value after 5 minutes.

4. A catamenial device according to Claim 1 wherein the gel strength after 30 minutes is greater by at least 75% of its value after 5 minutes.

5. A catamenial device according to Claim 1 wherein the particulate hydrogel material comprises a mixture of two or more hydrogels having different compositions.

6. A catamenial device according to Claim 1 wherein the hydrogel material is present at a loading of at least 60g/m2, the loading being based on the plan view area of the absorbent means.

7. A catamenial device according to Claim 1 wherein the hydrogel is deposited on an area of at least 150 cm2 of the plan area of the absorbent body.

8. A catamenial device according to Claim 1 wherein a device incorporating 0.8g polymeric gelling agent absorbs at least 50g sheeps blood in the Total Storage Capacity test.

9. A catamenial device according to Claim 1 wherein the Acquisition Time of the device for the absorption of the 5 ml aliquot to provide 10 ml total uptake is less than about 30 seconds.

10. A catamenial device according to Claim 1 wherein the absorbent means comprises particulate hydrogel material disposed between two layers of nonwoven fabric.

11. A catamenial device according to Claim 10 wherein the nonwoven fabric is a cellulosic tissue.

12. A catamenial device according to Claim 10 wherein the hydrogel material is adhesively bonded to at least one of the nonwoven fabric layers.

13. A catamenial device according to Claim 1 wherein said sanitary napkin has a caliper of less than 3 mm as measured under a load of 17.44 g/cm2.

14. A catamenial device according to Claim 13 wherein said sanitary napkin has a flexure resistance of less than 300 g as measured by a modified form of ASTM D 4032-82.

15. A catamenial device according to Claim 1 wherein the absorbent means comprises a mixture of fibers and particulate hydrogel material.

16. A catamenial device according to Claim 15 wherein the mixture is a homogeneous blend.

17. A catamenial device according to Claim 15 wherein the fibers comprise cellulosic fibers, microfibers or a mixture thereof.

18. A catamenial device according to Claim 1 wherein the fluid permeable layer comprises an apertured polymeric thermoplastic film, material that has been formed so as to have a three dimensional structure and a fiber like appearance.

19. A catamenial device according to Claim 1 wherein the device further comprises at least one laterally extending flap.