CA2672562A1 - Absorbent articles with an improved ventilation - Google Patents

Abstract

Absorbent article allowing for convective gas/air transport therethrough, especially by providing absorbent cores, which have sufficient basis capacity and air/gas permeability at the same time.
The absorbent core comprises a liquid storage region, and a liquid acquisition/distribution region positioned between the liquid storage region and the topsheets said acquisition/distribution region comprises an evaporation barrier layer/region.

Description

ABSORBENT ARTICLES WITH AN IMPROVED VENTILATION

The present invention relates to disposable absorbent articles, such as baby diapers, adult lncontinence artldes, and in particular to such arbdes providing improved aeration during use.

SaWround Disposable, absorbent arNdes such as diapers, incontinence artictes, sanitary towels, training pants and the like are well known In the arG Typically, disposable absorbent artlcles comprise a liquid pervious topsheet that faces the wearer's body, a liquid Impervious backsheet that faces the wearer's' clothing, an absorbent core interposed between the liquid previous topsheet and the badcsheek and means to keep the core in fixed relation to'the wearer's body.

Numerous attempts have been disclosed aiming at improving on the skin conditlon of the wearer by allowing the over-hydrated skin to dehydrate to an acceptable level by allowing either air to reach the skin thus minimizing potential ocdusion effects, and/or by water vapor being removed from the surface of the skin. Generally, such mechanisms are referred to as "breathability" or "vapor or moisture permeability".
A number of such applications aim at feminine hygiene products, such as catamenial products or so-called'panty-liner" as described in EP-A-0.104.906; EP A-0.171.041; EP-A-0.710.471. W097/23182 further disdoses an absorbent structure comprising fibrous superabsorbent material, combining such breathable materials with fibrous superabsorbent materiai in the absorbent oore. Such products generally have relatively low fluid storage capacity when compared for example to baby diapers or adult inconflnence products, often being designed for theoretical capacities signiflcantiy exceeding the ones for the feminine hygiene products.
Such breathabie materiais can be various kinds of webs, such as flinis which were rendered air and/or vapor pemieabie by aperturing as described In US-A-5.628.737, or by expioiting the "microporosity" property as descrtbed in EP-A-0.238.200; EP-A-0.288.021; EP-A-0.352.802; EP-A-0.515.501; US-A-4.713.068, whereby small voids are created within the flim similar to very small cracks. WO 94/23107; WO
94/28224; US-A-4.758.239; EP-A-0.315.013 all describe aitemative breathable materials which can be flbrous texHie or non-woven webs, with air or vapor easily penetrating through the reiaUveiy large pores of the structure. Such webs can be either untreated or treated with regard to improving their liquid impemieabiiity properties, such as described in EP-A-0.196.654. In WO 95/16562 a laminate of a non-woven with a breathable flim is disciosed. Further disclosures such as in WO 95/16746 relate to other materiais allowing water molecules to diffuse through. Also, combinations of various materials comprising various layers any of the above eienients are also well known.

in particufar for artlcies designed for receiving higher amounts of liquids, such as baby or adult Incontinence diapers, other approaches aimed at keeping only part of the artide breathable, such as by covering the liquid absorbing parts (often referred to as absorbent core) by a non-breathable materiai, but having other parts of the artcie made of breathable materiais, see e.g. EP-A-0.059.503 (Obenour).
There have been many attempts to improve the fluid handling properBes of absorbent articles or cores, In partlcuiar when further requirements were brought up such as a desired reduction of product bulkiness or thickness. Such effects are discussed in European Patent AppiicaUon 96105023.4 flied on March 29, 1996, but also in US-A-4.898.642; EP-A-0.640.330; EP-A-0.397.110; EP-A-0.312.118.

PCT publication WO 98/58609 disdoses a disposable absorbent artlcte sustaining low vapor phase moisture in the space as enclosed between the articie and the wearer In use, such as can be evaluated by measuring reiative humidity on a laboratory mannequin, such as can be achieved by combining high performance, low rewet absorbent cores with very breathable backsheet materials. Thus, the thrust of this disclosure aims at providing absorbent article with good liquid retention in the cores, combined with water vapor pemieable, liquid Impermeable barrier materials such as for the use as backsheets. The preferred, specific embodiment of this disdosure directs towards the use of a high amount of absorbent capacity so as to dry out the structures close to the skin of a wearer.

A series of related and co-flled PCT applications (WO 00/10497; WO 00/10498, WO
00/104099, WO 00/10500, WO 00110501) relates to breathable absorbent arHcles, induding when these are in the wet state. One approach described therein relates to creation of high permeability zones within an absorbent core, such as by aperturing the absorbent core, or by creatlng portions in the core containing substantially less high absorbency material than other portions of the core. Overall, the gas transfer mechanisms rely on gas diffusion mechanism, such as demonstrated by the preferred use of microporous film materials, as well as by the Tracer Gas Test. The approaches described therein can lead to relatively good relative humidity conditions while being wom, as long as the article Is not loaded such as with urine, but will exhibit signiflcandy increased relative humidity conditions upon loading.
Thus the prior art failed to provide satisfactory soiutlons for absorbent cores, wherein the ultimate storage capacity Is not too much exceeding the design capacity, i.e.
the capacity required to absorb the expected loading during the intended use. Thus, the ultimate storage capacity should preferably not be more than about twice the design capacity of the article.

The prior art also failed to provide structures which provide good convective transport without unduly complicating the manufacturing process, such as Is the case for strongly inhomogeneous structure, such as absorbent cores with apertures or ventilation openings Consequentiy, there Is still a need for absorbent arddes, wherein the micro climate and especially the relative humidity is kept within the ranges as generally accepted as being comfortabie, namely between 30 % to 50 %. There is further the need to provide arddes, wherein the reladve humidity is kept within this range even upon wetting of the articie.
There Is further still the need to achieve such goals without, unduly complicating the structure, i.e. by avoiding designs using high amounts of absorbent, and/or by creating strongly inhomogeneous structures, such as oores comprising apertures.
There is further stili a need for absorbent artides, wherein good microdimate conditions are achieved by carefully designing the chassis elements.

SUMMM
The present Invention provides an absorbent article with improved performance such as by providing arNdes with good "Wet Artlde - Relatlve Humidity differentiaP as being descriptive for the ciimate differences between the environment and the space between the arftde and the wearer. Preferably, the ardde comprises a backsheet which Is air or gas pemneable, but under normal use conditions not liquid permeable. The absorbent core can have a utdmate liquid storage capacity which is preferably not excessive when compared to the design capadty of the artide, though It preferably exhibits a basis capadty of more than about 0.7 mUcm". The core should further - espedaily when being loaded and wetted - allow convective gas or air transport therethrough, such as by exhibiting a permeance of at least 0.1 Darcy/mm, preferably of more than 1.0 Darcy/mm In a pardcular design, the absorbent core can comprise a liquid storage region and a liquid acquisition / distribution region positioned between this liquid storage region and said topsheet, whereby this atxluisitlon / distribu#ion region comprises an evaporation barrier layer / region, so as to reduce the evaporation tendency of the aracle from the core towards the space between the artide and the wearer during the intended use. The acquisition / distributjon region may contain material having a drip capadty of at least 5 g/g, which can comprise cellulosic fibrous materiai.

The arbde may comprise a bellows which is repeatedly deformable to force airflow through the absorbent artide in a controlled manner.

The artides according to the present invenUon are partlculariy suitable for being used as hygienic disposable absorbent artide, such as a baby diaper, an adult incontinence garment, thereby providing a comfortable microdimate in the space between the artide and the wearer.

Short descrintion of the drawinas 5 Fig. i- schematic diagram of the Dynamic Impact test method;
Fig. 2- sd7emat(c diagram of the Water Vapor Transmission method equipment;
Fig. 3- schematic drawing of the hamess;
Fig. 4- hamess on a mannequin;
Fig. 5- picture of the sensor box equipped with relative humidity sensor, Fig. 6- acquisition test set up Fig. 7- post acquisition collagen rewet test set up.
Detailed descrioflon General detiniflons As used herein, the term "absorbent arttdes" refers to devices which absorb and contain body exudates, and, more specifically, refers to devices which are placed against or In proximity to the body of the wearer to absorb and contain the vartous exudates discharged from the body. As used herein, the term "body ftuids" Includes, but is not limited to, urine, menses and vaginal discharges, sweat and feces.
The term "dtsposabte" ts used herein to describe absorbent articfes which are not intended to be laundered or otherwise restored or reused as an absorbent artlde (i.e., they are intended to be discarded after use and, preferably, to be recycled, composted or othennrise disposed of in an environmentally compatible manner).
As used herein, the term "Z-dimension" refers to the dimension orthogonai to the length and width of the member, core or artide. The Z-dimension usually corresponds to the thickness of the member, core or article. As used herein, the term "X-Y
dtmenslon" refers to the plane orthogonal to the thickness of the member, core or artide. The X-Y
dimension usually corresponds to the length and width, respedfveiy, of the member, core or ardde.

As used herein, the term ="absorbent core" refers to the component of the absorbent artide that is primarily responsible for fluid handling propertles of the artlde, Induding acquiring, transporting, distributlng and storing body fluids. As such, the absorbent core typically does not inciude the topsheet or backsheet of the absorbent artide.

As used herein, the term "absorbent member" refers to the components of the absorbent core that typicaNy provide one or more fluid handling funcdonailty, e.g., fluid acquisitlon, fluid distribution, fluid transportation, fluid storage. The absorbent member can consfltute the entlre absorbent core or only a portion of the absorbent core, i.e., the absorbent core can comprise one or more absorbent members. The "storage absorbent member" is the absorbent member component(s) of the absorbent core that function primarily to uitimateiy store absorbed fluids. As discussed above, the storage absorbent member may also distribute fluid as a result of its vertlcal wicking capability.

As use herein, the term "layer" refers to an absorbent member whose prlmary dimension Is X-Y, i.e., along its length and width. it should be understood that the term layer is not necessarily limited to single layers or sheets of material. Thus the layer can comprise iaminates or combinations of several sheets or webs of the requtsite type of materials.
Accordingly, the term "layer" Includes the temis "iayers" and "layered".
For purposes of this invention, it should also be understood that the term "upper" refers to absorbent members, such as layers, that are nearest to the wearer of the absorbent articie during use, and typically face the topsheet of an absorbent ardcle;
conversely, the term "Iower" refers to absorbent members that are furthermost away from the wearer of the absorbent article and typically face the backsheet.

All percentages, ratios and proportions used herein are calculated by weight unless otherwise specified.

Desian canacitv In order to be able to compare absorbent aracles for varying end use conditions, or differently sized ardcies, the "design capacity" has been found to be a suitable measure.
For example, babies are representing a typical usage group, but even within this group the amount of urine loading, frequency of loading, compostBon of the urine wilt vary widely from smaller babies (new-bom babies) to toddlers on one side, but also for example among various lndMdual toddlers.

Another user group may be larger children, stiA suffering from a certain form of incontinence.

Also, incontinent adults can use such artides, again with a wide range of loading conditions, generally referred to as light incontinence ranging up to severe incontlnence.
Henceforth, such artlcies being able to cope with such requirements should have the capability of picking up such amounts of urine, which wiil be referred to for the further discussion as "design capadty".

These amounts of fluids have to be absorbed by materials which can uitimateiy store the bodily fluids, or at least the aqueous parts of these, such that - if any -only little fluid is left on the surface of the article towards the wearers skin. The term "uitimate" refers in one respect to the situation as In the absorbent artide at long wearing times, In the other respect to absorbent materials which reach their "uitimate" capadty when being equilibrated with their environment. This can be In such an absorbent artide under real in-use conditions after long wearing times, or this also can be in a test procedure for pure materials or material composites. if the processes under consideratlon have asymptotlc kinetic behavior, one skilled In the art wiii readily consider "uttimato"
capacities to be reached when the actual capadty has reached a value suffidenfly close to the asymptotic endpoint, e.g. reiative to the equipment measurement accuracy.

As an absorbent artlde can comprise materials which are primariiy designed to uttimatety store fluids, and other materiais which are primarily designed to fuifiii other fundjons such as acquisitlon and/or distrfbutlon of the fluid, but may stiii have a certain ultimate storage capability, suitable core materials according to the present invention are described without attempting to artlfldally separate such functions. Nonetheless, the ultimate storage capacity can be determined for the total absorbent core, for regions thereof, for absorbent structures, or even sub-structures, but also for materials as being used in any of the previous.

in case of applying the present invention to other arficies requiring different end-uses, one skilled in the art wiil be able to readily adopt the appropHate design capacities for other intended user groups.

In order to determine or evaluate the Uitimate Design Storage Capacity of an absorbent artide, a number of methods have been proposed.

In the context of the present invention, it is assumed, that the Uitimate Storage Capacfty of an artlcie is the sum of the uitimate absorbent capacities of the individuai eiements or material. For these individual oomponents, various well established techniques can be applied as long as these are appifed consistenfly throughout the comparison.
For example, the Tea Bag Centrifuge Capadty as developed and well established for superabsorbent polymers can be used for such materials, but also for others.

Once the capacitles for the individuai materials are known, the total articte capacity can be calculated by muitipiying these values (in mi/g) with the weight of the material used in the arflcie.

For materials having a dedicated functionaiity other than ulflmate storage of fluids - such as acquisition layers and the like - the uitimate storage capadty can be neglected, either as such materials do In fact have only very low capadty values compared to the dedicated uitimate fluid storage materials, or as such materials are Intended to not be loaded with fluid, and thus should release their fluid to the other uitlmate storage materials.
With such deflnitions, for example a so-cailed `panty iiner' product exhibits very low Uitimate storage capacities of a few mi or less. Feminine Hygiene pads have often up to about 20 mi, light urinary inconttnence articies have for exampie 75 ml or about 90mi, medium urinary incontinence articies, or also smaller baby diaper can have about 165 ml, and toddler size baby diapers reaching 300 mi or more, and severe adult incontinence articie having 600 mi or more of uitlmate storage capacity.

Teabaa Centrifuoe Caaacitv Test (TCC testl Whilst the TCC test has been developed specificaily for superabsorbent matedals, it can readBy be applied to other absorbent rtiaterlals.
The Teabag Centrifuge Capadty test measures the Teabag Centrifuge Capacity values, which are a measure of the retention of liquids In the absorbent materials.
The absorbent materiai Is placed within a"teabag", Immersed In a 0.996 by weight sodium chkxide solutlon for 20 minutes, and then centrifuged for 3 minutes.
The ratio of the retained tiquid weight to the initiai weight of the dry material is the absorptfve capacity of the absorbent niateriai.
Two liters of 0.9% by weight sodium chloride in distilled water is poured into a tray having dimensions 24 cm x 30 cm x 5 cm. The liquid filling height should be about 3 cm.
The teabag pouch has dimensions 6.5 cm x 6.5 cm and is available from Teekanne In D4sseldorF, C3emnany. The pouch is heat sealable with a standard kitchen piastic bag seaf(ng device (e.g. VACUPACK2 PLUS from Krups, Germany).
I The teabag Is opened by carefully cuttlng It partiaily, and is then weighed.
About 0.200g of the sample of the absorbent material. accurately weighed to +/-0.005g. is placed In the teabag. The teabag Is then caosed with a heat sealer. This is called the sample teabag. An empty teabag is sealed and used as a blank.
The sample teabag and the blank teabag are then laid on the surface of the saline solution, and submerged for about 5 seconds using a spatuta to allow complete wetdng (the teabags w8l float on the surface of the saline soluflon but are then compieteiy wetted). The flmer is started immediately.

After 20 minutes soaking time the sample teabag and the blank teabag are removed from the saline sotution, and placed in a Bauknecht WS130, Bosch 772 TIZK096 or equivalent centrifuge (230 r(un diameter), so that each bag sticks to the outer waA af the centrifuge basket The centrifuge lid is closed, the centrifuge is started, and the speed increased quickly to 1,400 rpm. Once the centrifuge has been stabilized at 1,400 rpm the timer Is started. After 3 minutes, the centrifuge is stopped.
The sample teabag and the blank teabag are removed and weighed separately.
The Teabag Centrfiage Capacity (TCC) for the sample of absorbent material is calculated as follows:
TCC =[(sample teabag weight after centrifuging) -(biank teabag weight after centrifuging) - (dry absorbent matertai weight)] + (dry absorbent materiai weight).

Also, spedflc parts of the structures or the total absorbent artldes can be measured, such as "secttonaP' cut outs, i.e. looking at parts of the structure or the total articie, whereby the cxJtting is done across the full width of the artide at determined points of the longitudinal axis of the article. In partlcular, the definition of the "crotch region" as 5 described above allows to determine the "crotch region capacity". Other cut-outs can be used to determine a "basis capacity" (i.e. the amount of capacity contained in a unit area of the specific region of the artide. Depending on the size of the unit area (preferably 2 cm by 2 cm) the defines how much averaging Is taking place - naturally, the smaller the size, the less averaging will occur.
Uiflmate Storage Canacitv In order to determine or evaluate the UlUmate Design Storage Capacity of an absorbent article, a number of methods have been proposed.
In the context of the present Invention, it Is assumed, that the Ultimate Storage Capacity of an artide is the sum of the ultimate absorbent capadfles of the individual elements or material. For these individual components, various well established techniques can be applied as long as these are applied consistently throughout the comparison.
For example, the Tea Bag Cenirifuge Capacity as developed and well established for superabsorbent polyrners (SAP) can be used for such SAP materials, but also for others.
Once the capadties for the individual materials are known, the total article capacity can be calculated by multiplying these values (in mUg) with the weight of the materlal used in the ardcle.

For materials having a dedicated functionality other than ufUmate storage of fluids - such as acquis'dion layers and the like - the ultimate storage capacity can be neglected, either as such materials do In fact have only very low capacity values compared to the dedicated uitimate fluid storage materials, or as such materials are intended to not be loaded with fluid, and thus should release their fluid to the other ulflmate storage materials.

Basis capgcltles Each of the described capacities can also be expressed as a basis capacity, which is defined as the respective capacity per a unit area, expressed such as in mUcm2 or equivalents. This capacity can further be a local basis capadty, or an average over a certain area.

Microctimate The term miaroclimate as used herein refers to the conditions of the space between the artide and the wearer.

In this context, this spaos is confined by the body of the wearer, generally the skin of the wearer, and the hygienic artlde, comprising the core region of the arNde, and the chassis regions, the latter generally being tfi peripherai regions. Frequentiy, the ardcie comprises elastication elements, such as ieg ciffs, or barrier cuffs. Such sealing elements can, but do not need to, reduce the liquid and air exchange between the outside or environment and the space between the artide and the skin of the wearer.

Often, this space is a unitary, connected space, but It also can consist of sub-spaces, which can be connected to each other or which can be several spaces, which preferably all are designed and constructed according th the present Invention, as applicable.

The elements or the materiais of the absorbent artide are not considered to be part of this space, though such elements or materials may extend Into such a space.
Simiiary, body elements are not considered to be induded In the space. Also, liquid and/or solid body exudates, such as urine or feces, are not considered as part of this space.
ConsequentEy, the space can be described by the conditions of the gas. These conditions can have actual, local values (i.e. at one point In time at one iocation), or can be averaged over time or space or both.

The first element of the conditions for the gas space is the composition, and In particular the water content such as expressed as retative humldity, as defined by the ratio of the actual water vapor partial pressure to the corresponding water vapor partlal pressure at saturation. However, other components such as odorous vapors, or sidn attacking components can be contained in the space.

The temperature in the space is also of importance, as it is impacting on the relative humidity, but also because of Its Impact on the skin condition, and comfort of the wearer.

The temperature can be, but often wiU not be constant throughout the space. If the temperature of the skin of ft wearer and the environment are not constant, there wiii be a temperature gradient across the arflcie, across the space and versus the surface of the skin of the wearer.

It has been found, that In order to maintain comfortable and healthy skin, the mtaodimate within the space between the article and the wearer should be kept in the comfortable reiative humidity range, preferably of less than 50% RH, more preferably of less than 45% RH and even more preferably less than 40% RH. However, in order to prevent underhydratton of the skin of the wearer, the microdlmate should not have less than about 20% RH, preferably not less than about 30%.

TypicaUy, the temperature within the space wiii be between 30 C and 36 C, and temperatures of about 34 C are often perceived as comfortable.

In order to achieve such preferred microclimate conditions, it has been found, that the arUde should - when submitted to the In-Vivo microdimate testing - exhibit a Wet ArHde Reiative Humidity DifFerentiai of less than 20.0%, preferably less than 15.0%, and even more preferably less than 10.0%, as defined hereinafter.

A further important aspect of the gas space is the flow of the gas therein, in par4cuiar the convectivve transport in the gas phase. This flow Is connected with local pressure changes In the space - whilst there will generaiiy be no major pressure differentiai between the space and the environment (i.e. the region outside of the artlcte when wom), aiready small changes In pressure, such as can be created by movements of the wearer, or a temperature and/or compositlon dif'ferentiai can cause convecdve ftow such as through~ gaps beiween the artlcle, and the wearer. Preferably, it also can take place through the articie itself, such as through materials of the ar4de. For articies according to the present invention, this convec8on can occur through the arUde akug the z-direction of the artlde, though it may also indude x-y din3ctionai components.

The convective transport can be measured and expressed by the flow speed or velocity (in n-dsec), or by the flow rate (in g/sec), or by the area speciflc flux (in g/secJcm2).

Convedive transport should be distinguished from diffusive transport. The latter generally has much lower transport rates, and can - for example - be achieved by rrmoisture transport through a barrier layer, such as by using so-catied monolithic films as can be made from materials as Hytrei*m, as available from DuPont, or by slow migrafion of vapor through a microporous film materiai.

Known elements for aiiowing convecbve transport through certain elements of an articie are very open materials in the non-absorbent (chassis) parts of the article, such as nets, or scrims, or non-wovens with a sufficiently high permeability and pemieance for gas (as discussed hereinafter). Such transport mechanism Is also known to through an absorbent structure, such as when aperturing the core as described in the above mentioned series of PCT publications (WO 00/10497; WO 00/10498, WO 00/104099, WO 00/10500, WO
00110501), whereby the general teaching of these documents does not direct to convective transport through the artide, but on diffusive overall transport -such as implied by the preferred use of microporous backsheets.

In one asped; the present invenfion ainis at providing z-directionai convective transport through the complete absorbent artlde in the region of where the liquid is absorbed, I.e.
through the absorbent core, even when this Is loaded, and in pardcuiar not through special "venting means" as d)sdosed In the prior art but rather through the absorbent materiai itself. Henceforth, in additlon to highly permeable badcsheet and topsheet materials, the articie requires an absorbent core, which has a sufficiently high permeance in the absorbent material even when being loaded.
In another aspect, the present invention relates to parttcularly enhanced convection through gaps or the ar6cle such as described In more detail in co-filed patent application ABSORBENT ARTICLE HAVING A BELLOWS FOR CIRCULATING FRESH AIR
(Seitz/Krebs), disclosing enhanced circulation by means of bellows pumps.
The particularly useful absorbent structures for the present invention combine both fundJonaifty of the liquid absorbency with the convectivve gas transport through this structure and the remaining eiements forming the absorbent arGde at the same time.

Thus, the ability for convective fkriv through the structure should not be created by inhomogeneities In the strudure such as by providing apertures, or particuiar regions with enhanced ability for convective flow at reduced capacity.

The convectlve transport through dry and or loaded ar4des can be assessed by the Gas Permeabiiity methods, as described herein, whereby pemieability values for dry and wet artides can be determined. in combination with respecdve caliper measurements (on the dry and/or wet articie, respedivey), the permeance of the structure can be calculate, by dividing the permeabiiity by the thickness of the structure.
For inhomogeneous structures, the sample preparation or the test setup might require adaptation so as to not measure through the'venting channels" such as apertures and/or low basis weight, and/or low basis capacity regkms.

Preferably, an art'ide acoording to the present invention provides for wet permeance of more than about 0.1 Darcy/mm, preferably more than about 0.5 Darcy/mm, and even more preferably more than about 1.0 Darcy/mm. Typicaliy, the respect~re dry article permeance Is less than the one of the wetted article.

As the core of the artlde will typically provide an important resistance to the convective flow through the ardde, the core should exhibit a suffidently.high wet permeance of more than about 0.1 Darcy/mrn, preferably more than about 0.5 Darcy/mm, and even more preferably more than about 1.0 Darcy/mm. The respedive dry core permeance should not be less than the wet one, and Is typically more than I Darcy/mm or even more than 10 Darcy/mm.

Suitable core structures for such articles can be formed according to many known ways, and incorporate many known materials, such as comprising fibrous materlals, such as cellulose or synthetic fibers, or part<culate materials, such as superabsorbent partides, or foams, and especially faams fomied by the High intemal Phase Errwision polymerization process, or combinations thereof. The combinations can be homogeneous mixtures thereof, or segregated or separated materlais.

The openness of such structures can be achieved by seiecting particuiar arrangements of pemtieable materials.

It has been found, that superabsorbent materials are particularly suited to be used in 5 artlcies according to the present Invention, If they exhibit high Saline Flow Conductivvity performance (SFC), preferably of more than 30 * 10'' cm3 sec/g, when evaluated according to the disclosure of US-A-5.599.335.

10 Such materials can be arranged In a homogeneous mixing with fluff pulp, or can be layered between suitabiy open and permeabie layers of porous materiais, such as tissues, especially if these are a~r-laid, or nonwoven materials.

ParSculariy suitable materials are superabsorbent materiais as described In the above 15 referenced US-A-5.599.335, when arranged In a homogeneous blend with conventional fluff pulp, at aconcentratlon of 50% superabsorbent, preferably 80% and even more preferably more than 90% conoentratton based on the weight of the superabsorbent/fluff mixture. Suitable mixtures can further exhibit densities of between 0.1 g/ cmg and 0.3 cm3, preferably between 0.15 cm' and 0.2 cm3.
In particular embodiments, such mixtures can comprlse means which enhance the Integrity of the mixture, especially in the dry state. Thus, low amounts of adhesive may be added to the mixture, or other binders, such a tfiemiobondabie synthetic fibers.
In addition to the liquid storage elements in the core, the core may comprise other liquid handiing members, such as for enhancing fluid acquisition, or distribution.

Suitable cores are further described in EP-A-0.774.242; PCT applicatlons IB99/00739, 1B99/00741, IB99/00751, all flied on Apdi 23, 1999; PCT Application US98//05044. filed on March 18, 1998. The storage oore may further comprise poiymeric porous materials, preferably made by the High Intema! Phase Emulsion Polymerization process ("HIPE"
foams), such as described in PCT applications I899/00404 and IB99/00408, both filed March 12, 1999. Optionally, and often preferred, the storage core can be enveloped by a suitable web, such as a paper tissue or a suitabie non-woven materlal, such as described In WO
97/07761 and in PCT applicatlon 1B99/00888, flied on April 16, 1999.

A further suitable core structure comprises an acquisitlon/distribuUon member which indudes an evaporation barrier, such as an apertured formed flim, as described In more detail in co-filed PCT applicatlon "Disposabie absorbent arqdes having low rewet and reduced evaporatlon from the core through the topsheet", having publication No. WO/O1/97733.

The absorbent core may further comprise elements, which are particularly designed to handle non-urinary excretions, for example feces. At least as long as such elements are only loaded with liquid excretions, such as urine, these preferably satisfy the permeance requirements as descrlbed In the above.

This permeance of the absorbent core should preferably be achieved in the reglons of the artlde which at the same flme provide absorbent capacity. Whilst it is preferred for material usage effldency to not have artldes with an excessive overall capadty, the basis capacity (i.e. the amount of uitimate liquid storage capadty per unit area) should not be less than 0.3 n'd/cmZ, preferably not be less than 0.6 m!lcm2. This basis capacity and the corresponding permeance can be readily determined for structures, "where suffidentiy homogeneous regions are sufBdenfly large in dimension and size so as to allow testing.
In situations, where these areas are too small to allow direct measurement thereof, the materiai may be modifled so as to allow assessment thereof. For example, apertures my be blocked (i.e. filled with inert material, or structures may be rearranged close large apertures, (obviously with careful monitoring of the density and the caliper).

Other artlde elements In addidon to the described absorbent core, the absorbent artide compr'ises a backsheet to separate the core from the outside of the artide. The term backsheet refers to any material, or layer, or coating, posifloned between the core and the environment in the direction away from the wearer. Functionally, the badcsheet must on one side saflsfy the functlonal requirement of retaining the liquid as deposited onto and into the artide, as well as being capable of allowing gas or vapor flow rates therethrough which should preferably be not the rate-limitlng step of gas transfer from the inner space to the outside.

in addition, the backsheet may sattsfy further functlons, such as providing stability and integrity to the artlcte. or providing a pleasant feel or hand, or masking of exudates.
Preferably, the backsheet has a WVTR of at least 3000 g/24hrs/e , preferably of more than 2800 g/24hrs/mz, and even more preferably of more than 4000 g/24hrs/rrrz when submitted to the WVTR test as described hereinafter.

The backsheet should further prevent liquids from soiling the outside therethrough. and hence are designed to a leakthrough value of less than 100 g/0, preferably less than 50 g/me, and even more preferably of less than 10 g/0, when submitted to the Dynamic liquid Impact test, and a polyhole rewet performance of less than 0.10 mg, preferably less than 0.05 mg, and even more preferably less than 0.01 mg, when submitted to the polyhole rewet test, as described hereinafter.

The badcsheet material can be a single layer made of homogeneously or inhoniogeneousiy distributed phases, or a two- or muitilayer construction. The backsheet material can be a porous material, such as a fiim wfth a plurality of apertures, or It can be a porous web such as a non-woven or a foam material.

The backsheet thus may be constructed from a variety of materials and or composites.
For example, the badcsheet may be made of polyrneric film materials, suitably apertured to provide the required breathability without Jeopardizing the leak-through performance.
The backsheet may be made of non-woven materiais, or of multi-layer nonwavens, such as well known barrier webs, such as composites comprising a spun-bonded layer and a meitbiown layer.

Suitable materials are three-dimensionally formed apertured films, preferably comprising slanted cones, as described In PCT apptlcatlons US99/02395 or US99/02393, both filed on February 3, 1999 . Such films may be combined with non-wovens to form faminates. The backsheets or components thereof may be attached to each other or to other elements of the artlde. For example, when the backsheet is a composite made of an apertured film material with a non-woven web, the film material may be attached to the core components. The non-woven can also be attached to the film over the full area of the badcsheet, but preferably the layers are only attached to each other In the peripherai regions of the artlde.

Further, the backsheet can be a porous material comprising swellable substances, such as superabsorbent materials and the fike, as described in PCT publication WO
97/23182.
In yet a further embodiment, the backsheet material or at least parts thereof are rendered hydrophobic, such as by applying fluourocarbon treatments as described In PCT
publication WO 00/14229 (Palumbo).

Exemplary backsheet materials are as foliows:
Sample BS-1 is a nonwoven composite made of inelt bk)wn and spunbonded layers as provided by BBA -COROVIN, Peine, Germany, under the designation MD3000, and exhibits at a basis weight of about 12 gsm a WVTR of about 4670 [gimZ/24hr].
When testing a double layer of this materiai, the WVTR value Is about 4470 [g/mz/24hr].
Sample BS-2 is an apertured fomied film with slanted cones, available from Tredegar under the designation V174 LD40, exhibiting a WVTR value of about 2850 [g/m2/24hr].
Sample BS-3 is a combination of a layer of sample BS-1 with the film of Sample BS-2, providing a WVTR of about 2850 [gW/24hr], demonstrating, that the formed film resistance to flow dominates.

Further backsheet sarriples have been submitted to the permeability and caliper testing to determine their permeance. As none of the used methods was able to provide useful results over the fufi range of permeabiiities, dtfferent methods have been selected to provide the data, however, the resulfing pemieance values as expressed in Darcy /.mm are comparable across the whole range of selected niaterials.

Sample BS-4 (RR-1) Is a typical microporous films, e.g. as available from FinoTech under the designation BSB-X3-330, then mechanically acWated to provide a MVTR
value of about 1500 [g/rn2124hr]. When using the PMI pemneameter, the permeance was deterrrined to be 0.0003 Darcy / mm.

19 Sample BS-S (RR-2) is a further typical microporous film of the same type, but mechanically activated to then provide a MVTR value of about 3500 (,q/m'/24hr]. When using the PMI perrrueameter, the permeance was determined to be 0.0005 Darcy /
mm.

Sample BS-6 (MDO) as available from Tredegar Inc. under the designation X25498 or X25620 and exhibifing a MVTR of about 3500 [gJm2/24hrj was evaluated according to the PMi method, and gave a permeance of 0.0024 Darcylmm.

Sample BS-7 (CDO) as availabie from EXXON under the designation E)OXAIRE and exhibiting a MVTR of about 3800 [g/m2124hr] was evaluated according to the PMI
method, and gave a perrneance of 0.0029 Darcylmm.

Sample BS-1 provided - when submitted to a pemeabiiity test by using the "Textlluht nach Kretschmar" - a permeance result of about 375 Darcy / mm.
Sample BS-8, being an altemative composite PP-non-woven as available from BBA
COROVIN, Peine, Cemiany, under the designation MD2005, 5BSS8 gave upon testing according to the "Textiiuhr nach Kretschmar" test a permeance of about 125 Darcy /mm.

When submitting sample BS-2 to the Textiiuhr nach Kretschmar" testing, it provided a resuit of about 87 Darcy / mm.

Sample BS-9: A further apertured formed film with straight (i.e. non-slanted) cones, as available from Tredegar under the designation 515FP, gave upon testing according to the "Textiiuhr nach Kretscthmar" test a pemieance of about 275 Darcy /mm.
Similariy, the topsheet materfal must have a sufflcient pemneabiiity,,and should not impede liquid passage to the absorbent structure.

As can be seen from the above resuib for backsheets, non-woven materials generally exhibit high gas pemneance values, and thus conventtonai materiais, such as desaibed !n EP-A-0.774.242 (Palumbo), jo not exhibit a major resistance to gas flow Partlculariy preferred tospheet materials for applicatlons whereby more or less solid excretions can be deposited on the artlde, are nonwovens comprising apertures, at least in the por8ons thereof, which are aligned with the feces deposition region of the article, such as described in more detail in EP-A-0.714.272 or EP-A-0.702.543, and both of 5 which are incorporated herein by reference. Optionally, and preferably for feces handling artldes, such topsheets can be combined with feces handling members e.g.
underlying such topsheets, and further described In these appiicatlons.

The further elements of the artlcle should not limit the convecctive transport of the 10 discussed elements, but - as far as ftse are In the convective flow path -be at least as open as the flow limidng elements. This is parHcularly relevant for means to enhance the integrity of the structure, such as adhesive or other bonding means, or flxaSon means such as tapes and/or landing zone materials, which may be attached to the outside of the articie. This is also relevant for liquid barriers, such as the leg cuffs or so called barrier 15 cuffs. In a partlcular aspect, when such cuffs are longitudinally sealed liquid impemieably to the topsheet, and preferably therethrough, the underlying core structure should exhibit the describe permeance requirements at least across the width of the arflcle between these tack-down seals of the cuffs.

20 Beyond not limiting convective flow, further elements can be Included, which increase the convective flow. For example, bellows can be incorporated into the artide, such as described in the co-filed patent applicaflon "ABSORBENT ARTICLE HAVING A
BELLOWS FOR CIRCULATING FRESH AIR" (Seitz/Krebs) .

In addiUon to high permeance values, and to parHcular basis capacity requirements, preferred articles according to the present inventlon should be comfortably thin and soft, and thus should have a caliper of less than 9 mm at their thickest portion, and a bulk softness value of less than 10 N, preferably less than 5 N and even more preferably of less than 3 N, when tested according to the test method as disclosed in PCT
application, flied on March 10, 2000, published as Wo 01/68022 and titled "Absorbent Articles Exhibiting Improved Buckling and Bending Softness".

Methods and det rminati n General Conditions and SYOthe ic Urtne Unless otherwise noted, all tests are carried out at about 22 +/- 2 C and at 35+/-15% relathre humidity. The synthetic urine used In the test methods is 0.9%
solution of NaCt In distliied water.
Caiiner The caliper of the sample (dry or loaded) is measured (If necessary after a equillbration period) under the desired compression pressure for which the experiment will be run by using a conventional caliper gauge (such as supplied by AMES, Waitham, MASS, US) having a pressure foot diameter of 1 1/8 " (about 2.86 cm), exerting a pressure of 0.2 psi (about 1.4 kPa) on the sample, unless othennrise desired and notified.

PM(gas nermeabilitv A suitable permeability method for highly permeabie materiais or structures, especially for materials having a certain caliper of thickness, uses a Capiiiary Flow Porometer as supplied by Porous Materiais Inc., Ithaca, New York, US. under the designation CFP -120 AEXI, with approprtate manuals and software (Version 6.0, CapWin Version 6.54.25;
CapRep Version 6.56.15; CapGraph Version 1.5.1) or equivalent.

When foiiowing the operation instructlons for determining gas permeability as outlined in the user manual, the partlcuiar settlngs have been utilized:
The selected gas is air. The active sample diameter is set to 45 mm. The cylindrical sample can be dry or can be wetted. A spacing Insert (of 270.82 g) Is be applied without further compressing the sample. The resuitng permeability wiit be expressed in Darcy.
Kretschmar Te 7uhr The air permeability Is determined by measuring the time in which a standard volume of air Is drawn through the test specimen at a constant pressure and temperature.
This test is particularly suited to materials having relatively high permeability to gases, such as nonwovens, apertured fiinxs and the like.

The test Is operated in a temperature and humidity controlled environment, at 22 t 2 C
and 35% t 15 %reiative humidity. The test specirnen has to be conditioned for at least 2 hrs.

The test equipment as manufactured by Hoppe & Schneider GmbH, Heideiberg, Germany, under the desigrfation'Textltuhr nach Kretschmar", Is essentiaily a beitows in a verticai arrangement, with its upper end being mcwntsd in a fixed positbn, and the iower end being releasably hold at its upper positlon, which can be loosened by means of a release handle to slide under controiled conditbns to the kmrer positbn, thereby Increasing the voiume Inside the beikfws by puiHng air through the test specimen which Is covering the air entering opening at the upper end of the bellows. The test spedmen Is firmly hold to cover the air entering opening by means of a fastening ring of 5 cm2 or 10 cm~ to allow for different sampies sizes andlor different permeabiiity ranges.
If the 10 cm2 ring Is used, the sample should be at least 55 mm wide, for the 5 rM2 ring at least 35 mm.
For both, the samples should have a iength of about 150 mm, In case of very high permeabitity materials, the opening can be further reduced, with appropriate adJustments to the equipment and calculation.

The equipment comprises a stopwatch (1/100 sec) which automatically measures the 5rne between the operation of the release handle thus starting the sliding of the bellows, and the bottom of the beikyws reaching its lower end posMon.
The air permeabiiity k of the material can then be calculated as follows:
k=(V* *d)/(t*A*Ap) wherein V is the volume of the bladder, here 1900 cm';
is the viscosity of the air, here 1.86*1V Pa sec;
d is the test specimen caliper in mm;
t Is time required for the expansion of the bellows, in sec;
A is the air entering opening, here 4.155 cm2 ;
Ap is the pressure differentiat, here 160 Pa.
The resuit<ng unit of k is cm?, whereby I Darcy corresponds to 9.889* 10'0 cm2.
The test Is repeated once fbr each test specimen, and should be repeated on 10 specimen to provide a representative basis for a matenai.

As discussed in the above, the present Invention aims at providing pemieable materials without necessite5ng the need for creating partlcuiar conventison channels.
Consequently, the above menNoned pentreability test (and the respective permeance measurement as described below) should aim at determining the peimeability of these structures, and henceforth, the above tests may need certain modiflcatlons so as to measure the storage materiai rather than the apertures, such as by reduang the test spectmen opening, or - if readily achievable - by blocking some of the apertures.

Permeance Perrrs3ance Is deflned as the pemneabiiity (as determined in the above) per unit thickness of the material, expressed In Darcy/mm.
PQM4te test One piece of 10 cm by 10 cm of Filterpaper such as Grade Medium White W/S
available from Schleicher & SchOll, Germany Is weighed to the nearest 0.001g.

On a suitable flat surfaoe, such as a lab bench, an absorbent artlde is placed fiat over the fliterpaper, such that the loading point on the topsheet of the ardde faces upwards, and the fliterpaper is centered under this loading point, in direct contact with the backsheet of the artide, or the materiai.to be tested.

The sample Is loaded at the loading point for its Intended use with an appropriate volume of liquid, preferably 0.9% by weight saline soiution, generaily.about 80% of its theoretical capacity. if this is not determined, folloving values can be used, exemplifying the loading for various, broadly used baby diaper sizes:
Mini/Mini plus (size 1, 2) 175 mi Midi (size 3 250 mi Maxi (size 4) 300 mi Maxi plus / larger (size 5, 6) 350 mi The loading of the ardde is executed by pouring it through a funnel, whereby the outlet is positioned 20 mm above the loading point of the absorbent artlcle. A suitable funnei for baby diaper applica8ons has funnel diameter of about 82 mm (about 3.1 Inch), a funnel height of about 132 mm (about 3.5 inch), and an outiet tube of about 70 mm (about 2.7 inch) fength, and about 6.7 nvn (about 0.25 inch) inner diameter. The flow rate of liquid into the funnel should be fast, but It should be adjusted by controlied pouring of liquid so as to avoid excessive pooling or run-off outside of the ardcie during the loading.

After addition of the Iiqual, and a further a waiting period of 60 secs (+/ 3 seca), a rectangular weight (10 cm' 10 cm; each +/- 3mm) of 3.65 kg +1- 0.5%. After 120 sec (+/-3 secs), as can be measured by any suitable timer, the weight is removed and the fliterpaper is re-weighed to determine the liquid-pick up.

The weight pick up Is reported to the nearest 1 mg, and then converted into and expressed as fluid absorption In M.

Dynamic JUguid Imoact Test Dynamic fluid transmission is measunad with the apparatus 9100 shown In Figure 1.
According to this test, an absorption material 9102 weighed to the nearest 0.0001 gram is placed directly on top of the energy absorbing impact pad 9103. The absorption material 9102 may comprise a No. 2 fllter paper available from Whatman Laboratory DMsion, Distributed by VWR Sdentific of Cleveland, OH. The absorption material should be able to absorb and retain simulated urine which passes through the sheet material being tested. The energy absorbing impact pad 9103 Is a carbon black fliled cross linked rubber foam. The 12.7 cm by 12.7 cm (5 inch by 5 inch) square impact pad has a density of 0.1132 glcm9 and a thickness of 0.79 cm (0.3125 inches). The impact pad 9103 has a Durometer Vaiue of A/30/15 according to ASTM 2240-91. A circular absorbent core materiai 9104 measuring 0.0635 meters (2.5 inches) in diameter is weighed. The absorbent core materiai may comprise Individualized, crosslihked wood pulp cellulosic fibers as described in U.S. Pat. No. 5,137,537 issued to Herron et al. on Aug.

11, 1992.
The absorbent core material should be able to hold a sufficient amount of simulated urine, e.g., at least about ten times its dry weight.
Other absorbent materials that can be used indude airfelt, tissue, cellulose wadding, as long as these exhibit the required absorbent capacity of at least 10 g/g. If the materiais have a capadty below 10 g!g then they should be wetted to at least 80% of their saturation capacity. Also, the absorbent materials should be essentially free of "superabsorbent materials' which might bind the liquid too tightly and thus affect the results.

The absorbent core has a basis weight of about 228 g/m'. The absorbent core materiai Is then Is loaded wi#i shtwiated urhm b about ten (10) times its dry weight.
The simulated urine Is an aqueous 0.9 % by weight satine solutlon, exhibiting a surface energy value as conventlonally determined of 72.5 rnf+Vm.
5 A section of the backsheet material 9105 to be tested Is pWW face down with the outside surface on a ciean and dry tabletop. The toaded core materia19104 is piaced directfy In the center of the backsheet material 9105. The backsheet/core anrangement Is tiw secuned to the Impact portlon 9107 of the impact arm 9108 with a rubber band 9109.
The backsheetlcore arrangement is posiHoned such that the core 9104 is adjacent the 10 bottom surface 9110 of the tnpact portfon 9407. The impact ann 9108 is raised to a desinei Mnpact angle to pmvide the desired impact energy. The Impact arm 9108 is dropped and the impact arm 9108 Is then atlowed to njst on the sample for about two minutes after impaot The arm Is then raised and the fliter paper 9102 Is removed and placed on a digitat scale. The mass of the wet fBter paper Is then reoorded at the three 15 minute mark. The dynamic fluid transrMssion value (DFTV) is calculated and expressed In g/ cmP using the foliowing Ãormula:

DF?V = {mass of the wet filter paper (grams) - mass of the dry filter paper (grams)) I {impact area (m2)}
The Impact area, expressed In e, is the area of the bottom surface 9110 of the Impact portlon 9107. The impact area Is 0.00317 nf. The absorbent tore material 9104 should have an area slightly larger than that of the Impact area of the surface 9110.

Water Vanor?ransmission Rate When referring to Fig. 2, ihe test specirrren (210) having a diameter of about 120 mm is posifloned centered in a flat out conditbn over a 75 mm deep cylindricai cup (220) with a circular opening (222) of 50 mm Inner diameter, which has been fiiled up to about 10 mm below the upper end with distiiled water (228). The sample is supported by a cyiindrtcal rim (224) at the tap of the cup, of about 120 mm dianaeter. T'he sample is covered by a oover lid (230) of a Inner diameter to flt the outer diameter of the rim. The lid has a centered opening (232) corresponding to the opening 222 of the cup opening, andd a fiange (240) to aNow fixation of sample and o minimize evaporatian losses at the side, extending approyJmately 70 mm. The lid has a weight of approximately 238.5 g.

The assembly is weighed and positioned into a dimate chartber, such as available from WTB Binder, Tutttingen, Germany, type 377200990031.00 at 33 C 20% RH, with high air circulation rate of about 15cmisec air veiocity.
After 5 hrs, the assembly is removed from the chamber, and reweighed. TtIe Water Vapor Transmission Rate Is catcufated from the loss per time unit and opening area (the latter being 1963.5mm'), and expressed in units of g/e/24hrs.
For very different rates, the evaporation tlme In the chamber can be adjusted, such as to 2hrs for very permeable materials, or to 24 hrs for matertals with low permeability.

VV-VM of full nroduct The equipment described above can also be used to detemiine WVTR of samples having higher caliper such as dry or wet diapers. In this case, a dreuiar sample having a diameter of 109 mm Is applied at the cup rim surface. To avoid exchange with the environment, a glass ring having an outer dianieter of 120mm, an inner diameter of 110mm, and a height of sample caliper minus 1 mm is put around the sample.

When evaiuating dry artlcies, it has to be taken into account that a dry arGde acts as a desiccant, that is, absorbs water vapor until reaching saturation. This effect can be minimized by equilibrating the sample prior to determining WVTR.

For equiiibration, a circular 109 mm diameter cut out piece of the ardcie Is placed in a suitable box, backsheet facing the environment. This equipment is placed for about 48 hrs inside a climate chamber of the type as described In the above, at 33 C, 90%RH, maximum ventilation (15 crnJs). When removing the sample from the chamber, the starting weight of equilibrated arhde Is recorded. As described in the above, the equilibrated piece Is then placed on the surface of the cup fified with water with badmhest fadng down to the water, topsheet fadng to the environment. The glass ring is placed around the sample.
The equipment is placed In the dimate chamber as above, and after removing it therefrom, the weight of complete equipment is recorded, as well as the end weight of the test specimen, to account for further absorption of vapor or evaporation from equilibrated articie through the topsheet to environment When evaiuating wet artldes, it has to be taken into account that wet artides can show additionally significant evaporation from ioaded core through topsheet to envinsnment.
Thus, weight loss of equipment Is not only due to diNusion of water vapor from cup through the product to the environnient, but also due to evaporadon from loaded artide through topsheet to environment. instead of the equiiibration as for the dry arhide, the cut-out piece Is now evenly loaded with 10g Saline per g of the test specimen.
The stardng weight of the test specimen is recorded accardingiy, and so Is the startlng weight of the filled cup with water only (i.e. no sample).
The loaded test specimen Is placed on the surface of the filled cup filled, the backsheet fadng down to the water, topsheet facing to the environment, and the protedlve ring is added to surround the sample.
The equipment is placed in the dimate chamber as above, and after removing it therefrom, the weight of complete equtpment is recorded, as well as the end weight of the test spedmen, to account for further absorption of vapor or evaporatian from equilibrated ardde through the topsheet to environment.

There are two equivalent possibiliHes how to calculate WVTR from the above-measurements for wet diapers:
= (start weight of cup with water only - end weight of cup with water oniy}/(Time x opening area);
=((start weight of complete equipment - end weight of complete equipment) -(start weight of wet diaper - end weight of wet diaper)) /(Time x opening area).

Wet Artide _ el tive HumidityOftrentai Temperature and relative humidity vary between body sites under the diaper due to loading pattem, babies activvity and emotionai state, and environment, such as room conditions. A muiti point measurement provides the opportunity to monitor simultaneously conditions at several locations underneath the diaper.
Partlcuiar interest iles in the understanding of change In conditions between iocations corresponding to the loaded and non-ioaded areas of the diaper. Typical diaper users change the diaper between 3 to 12 hours. Wtthin this period on average the baby has baded the diaper with 3-4 gushes of u-ine. Therefore, a partlaiiy loaded diaper may be worn for several hours before being changed. Thus, the conditions under the artlcie when wom, i.e. in the space between the ardde and the skin of the wearer, are monitored at predefiermitied bcaGions of the sensora in this space.

The microddimate as a functJon of body temperature and water evaporation may also change in response to babies activit<es and emotional state. To correlate potentiai mtcrodimate changes babies can be supervised during the measurement period by their parent(s)/guardian(s) who record spedflc events, acivities and times in a diary.

Further, the micro-ciimate within the article Is dependent on the room conditions.
Henceforth, it has been found partjcuiarly useful to indude a reference measurement point on the wearer, but not covered by the article which is evaluated, but only by nomiai dothing, e.g. conventional underwear.

The present method and the pardcuiar equipment used herein should be set up with particuiar considera~tion of safety and hygienic conditions, such as the Dedaratfon of Helsinki Recommendations gukiing physicians In bioniedicai research involving human subjects, as adopted by the 18th Waid Medical Assembty, Heisinki, Finland, June 1964 and its further amendments.
The Temperature and relative Humidity sensoring device consists of temperature (T) and relative humidity (RH) sensors, data-loggers to store data and a harness carrying the sensors and the data-logger.

Fitting the Temperature and Relative Humidity Monitoring System as described in more detail hereinafter, and changing diapers wiii preferably take place in a separate room.
Before fitting the Monitoring System to the baby the sensors and cables wiii be fixed onto the hamess with medicat tape. The cables will be connected to the data-logger.
Excess cables and the data loggers will be stored and fixed in the data-lagger bag at the back of the hamess.

The complete hamess will be fitted on the baby with the help of the parent andlor guardian during the change of the diaper. The Monitoring System is fitted onto the baby such that all sensors on the hamess face the diaper side. The eiastics of the hamess will be carefully adjusted to the baby to avoid skin marks. Foitowing the adjustment of the hamess a diaper is fitted over the Temperature and Relative Humidity Monitoring System carefully avoiding disk>catlon of the sensors. After fltting and diaper change the baby wiN
be taken to a separate room for the wear perlod. The babtes may not wear underwear over the diaper, if ciimratic conditions allow.

Monitor9na Sy,ftm Wearincr Period The Monitoring System wearing period may last up to 12 hours. During the wearing period of the Monitoring System and the diaper the babies can be entertained by their parent and/or guardian. Babies may be encouraged by parents or guardians perform playTui tasks (i.e. like in play groups) and/or to act as they like. A diary of the actlvities can be kept by the parent and/or guardian as appropriate for the specific study objective.
Aifemativeiy, the activities can be recorded on video for evatuation of activittes at a later time.
Controlled Diaoer Loadina Depending on the specific study objective diapers may be loaded with cumulative gushes of "artificiai urine" (i.e. physiological saline) up to the desired representative loading in view of the design and intended use of the artlcie. For example, to represent an ovemight usage of a MAXI size diaper (i.e. intended for an about 9 to 18kg baby) a total volume of 300 mi has been found suitable. The "araflciai urine" wiil be prepared as described herein and warmed up to 37 C prior to loading. Diapers may be pre-loaded immediately to fitting or loaded In-use. Loading In-use wili be performed using soft flexible tube with rounded tip at a controlled ioading rate and voiume.
StudLsiz@
It Is esttmated that tn total approximately 5 babies will need to be recruited to provide a meaningfiui basis. Selection criteria may be set, such as relatlng to generaity healthy babies of both sexes, weighing more than 7 kg and being elder than 6 months (corresponds to Maxi- or larger size users).

Iemoerature & Reiative Humiditv MoniWng Svstem Information 30' The monitoring system comprises three essenfiai elements, nameiy a hamess for fbdng the system on the wearer, the sensors for measuring temperature and reiative humidity, and the data logging system.

The hamess Is designed to allow accurate positioning and fixing of the sensors on the wearer, and to provide means for carrying the data logging system. The hamess needs to be made of skin friendiy materiai. Materials described below are combined as in the following configuration.

A suitabfe design for the hamess has been found by comprising a waist belt to be fitted around the waist of the wearer, and further comprising fixation elements fitted between the legs of the wearer.

A typicai hamess can be seen in Fig.3 as a schematic diagram, and in Fig.4 as a photograph fitted on a baby mannequin.

Sensorboxes and cables are fixed on the hamess with an adhesive tape, such as LEUKOSlLKTM'. The bag for the data loggers is made out of cotton. It Is equipped with 4 snap-fasteners to be able to remove the data loggers. The bag is tightened to the hamess via mechanical fasteners. Data loggers are additionaiiy coated by PU
foam to achieve more comfort.

Further particuiariy suitable materials have been found as useful as foiiows.
The skilled person wiil be readily enabled to replace materials by equivalent ones, or to adjust sizes to other sizes of the wearer, except tor the sensors locatlon, which Is an essential element of the present Invention.

An athieNc supporter ("Jock-strap" or 'Ttefschutz") (320)such as available from Adidas, AG, Germany, is sewn together with Rubber straps (330) such as available from Wenco Service Marketing, Duesseidorf, Gemrany, as "Baby Eiastic" and convenUonai "popper buttons" to the described hamess. Medical tapes, such as available form i3etersdorf AG, Hamburg, Germany, and Vekxo TM type hook and loop closure systems (340) are used to close the harness and to fix it at the wearers body. Conventionai cotton fabric can be used as bag for the data logger (310).

The harness can be replaced by other means to fix the sensors, and the logger appropriatefy, such as by stretch-pants, or topical adhesives applied to fix the sensors directly on the skin of the wearer, as long as this fixation means does not impede the functlonality of the artide, and it should further have a minimai effect on the climate within the articte, and on the skin.

Data Acaulsition The climate data as generated by the sensors as described herein are gathered by a data logging system wom by the wearer, or a data transmission system connected to a data logging system physically located away from the wearer. The connectlon between the transmission system and the data logging system Is preferably not executed by flxed cables, but rather by cable-less systems, such as radio signals or infra-red data transmission systems.
A particulariy suited system indudes a data-logging system to be wom by the tested person, wherein the data are recorded during the test period, and from where these data can be read into a data processing unit after the testlng.

A specific example is Smart Reader Plus, available from Status Instruments Ltd, Tewkesbury, United Kingdom, connected via an Insulated flat four wire cable such I.D.C.
Flachbandkabel, form RS Components GmbH MtSrFeiden-WalldorF, Germany.

Sensors and Sensor box The sensors are parNculariy designed to measure both temperature and reiative humidity at small dimensions, and compatibie with hygienic and safety requirements during the resting.

The sensors used for the Monitortng System should have the following accuracy, which should be maintained during data logging, transmission, and/or processing.
Temperature: 0.2 C
Reiative Humidity: t 2 %

A suitabie temperature sensor Is a precision thermistor, as from Omega Precision Thermistor Resistance Omega Engineering Inc., Stanfoni, USA.

As suitable relative humidity sensor Is Capacitive Humidity Sensor, such as available from OHMIC Instruments Co., Maryland. USA, under the designation HC 700.

The sensors can be afflxed to the hamess by conventional, such as dispersion adhesives, shrinking tubes, and/or casting polymers, such as of the ABS type.

All relative humidity sensors are cast into a plastic box (17x11x4 mm, see Figure 5, hereafter called sensor box). Six out of seven temperature sensors are also lnciuded In these sensor boxes. The remalning temperature sensor Is lsolated with a shrinking tube and wiil be placed Inside the absorbent part of the diaper. The sensor boxes are connected with the data loggers via a 4-wire isolated cable.
Cleanina Aaents Before usage, all sensor boxes will be disinfected by 15 minutes incubation in a 6%
solution of Gigasept FF in distilled water. Afterwards, they will be washed by Immersion for 5 minutes in distiiled water and reused when they are dry again. If there is any contamination of baby's excrement, sensors will either be cleaned before disinfecting or discarded.

The hamess can washed In a regular washing machine with conventional washing powder at a temperature of 95 C.
Electrical parts:
Two coupled data loggers are stored In the data logger bag at the rear side of the harness. Data loggers do not come in direct contact with the skin. For Improved wearing comfort the data loggers are wrapped in a soft PU foam material.
Each data logger unit Is powered by one 3 V battery of about 24 mm diameter.
The batteries are secured inside the data loggers with a flrm clip. Furthermore, the four point clip button closure system of the data logger bags provides additional protection from accidental access to batterigs. Constant supervision of parents or guardians witf further ensure that babies have no access to the batteries.

The cables connectlng the data loggers with the sensor boxes are as small in wkith as the hamess etastics and are fixed via the medical tape to that side of the eiastic which is not in contact with the skin. The cable insulation consists of flexibie PVC.
PVC Is an inert polymer with a good safety profile and used in commencial and medical applications (e.g.
urine bags, flexible catheters).

The sensor boxes contain the temperature and relative humidity sensor. The relative humidity sensor lies protected under a cover made of a coated nickel alloy.
The sensor boxes are fixed to the hamess on that side which Is not In contact with the skin.

The foliowing describes a typical set up for carrying out the test, though of course partiaalar elements such as of the babies activities, dotlhing etc. can be varied.
Preferabiy, babies should be heaithy, and the number of babies In one group should be kept small, such as 5 babies. Normal hygienic precautbns should be taken, such as washing equipment and dothing used on the babies anJ using hand disinfectants.
Equipment vulnerable to damage in machine washing (e.g. electrical parts such as sensor boxes and wires) wiil be disinfected by immersion In a solution of a disinfectant.
Po oning of the sensors The Temperature and Relattve Humidity monitoring system consists of Hamess with temperature (T-) and relattve humidity (RH-) sensorboxes and/or pure RH
sensor, to be wom undemeath the articie. Preferably, five T/RH sensors and one RH
sensors are used. A further T-sensor is further placed inside the artide. A
further reference sensor Is applied outside the artlde.

The T-sensor is applied from the outside after the arflde is applied on the wearer. and the sensor Is applied through the badcsheet to be positioned closety in the loading region of the artide, affixed e.g. by adhesive tape.

The reference sensor fs appiied outside the article in the rear waist part at the right hip such as by mechanical fastener. Slnce the part is not underneath the hygienic artide, the reference sensor Is located on the hamess towards the outside of the hamess (i.e. on the opposite side to the one oriented towards the skin of the wearer) and is covered by the cotton clothing.

For the determinaflon of the result of the measurement, the stgnals of the sensors covered by the absorbent ardde are averaged, expressed and calculated to a tenth a percent.
To detemdne the Wet Articie Relative Humidity Differentiai, the relative humidity value of the reference sensor (i.e. the one not covered by the articie, but by terry cloth only) is deducted from the average relative humidity values.
Under most circumstance, the result wiil be a positive value. In case that the coverage by the arUcle will result In a reduced relative humidity, the result will be negative.
Evaooratlon Rate from Loaded Absorbent Artlcle This test method relates to an absorbent arflcie. A rectangular test specimen of TO mm (in transverse direction of the article) by 100 mm (in longitudinal direcdon of the article) Is cut by suitable scissors or a cut6ng blade from a representative part of the absorbent core, such as transversely centered, and from about 6 cm from front core edge.

The dry weight is recorded, and the specimen is placed in a glass box of about 72 mm by 102 mm, and about 40 mm high without lid, with backsheet down, and the topsheet facing to environment.

The specimen Is loaded with 10 g of 0.9% saiine sotution per gram weight of the specimen, whereby the liquid is evenly distributed over the area, thereby avoiding the weti3ng of the glass box.

The complete weight of the glass box with the loaded specimen Is recorded.
The equipment Is placed into a ciimate chamber such as available from 1NTB
Binder, Tuttlingen, Germany, type 37720099003100 at 33 C +/- 211, at 50% relative humidity (RH) +/- 3%. The ventilation is adjusted to provide an air flow velocity of about 15 crn/sec over the opening of the glass box.
After two hours evaporation time, the end weight of the complete glass box with the specimen is recorded.

The area speciflc evaporadon rate is determined Evaporat'wn Rate =(Start weight - End weight}1(Time x sample area).
whereby the start and end welght is the total weight of the glass box with the spedmen.

5 The above loading values have been found useful for baby diapers, espedalfy for baby diapers for babies of the size of about 9 to 18 kg, often referred to as MAXI
size. In case of very different absorbent capacities of the absorbent artide under consideration, the amount of liquid load should be adjusted to about 50 % of the theoretical basis capadty 10 as defined herein.

Acouisition Test This test should be carried out at about 22 +/- 2 C and at 35+/- 15% relative humidity.
15 The synthetic urine used in these test methods is 0.9 % Saline solution.

Referring to Figure 6, an absorbent structure (410) is loaded with a 75 ml gush of synthetjc urine at a rate of 15 mUs using a pump (Model 7520-00, supplied by Cole Parmer Instruments., Chicago, U.S.A.), from a height of 5 cm above the sample surface.
20 The time to absorb the urine Is recorded by a timer. The gush Is repeated at precisely 5 minute gush intervais until the ar8de is sufflcientiy loaded. Current test data are generated by loading four times.

The test sample, which can be a complete absorbent article or an absorbent structure 25 comprising an absorbent core, a topsheet, and a backsheet, is arranged to lie flat on a foam platform 411 within a perspex box (only base 412 of which Is shown). A
perspex plate 413 having a 5 cm diameter opening In its middle is placed on top of the sample on the loading zone of the structure. Synthetic urine is introduced to the sample through a cylinder 414 fitted, and glued inth the opening. Electrodes 415 are located on the lowest 30 surface of the plate, in oontact with the surface of the absorbent structure 410. The electrodes are connected to the tinw. Loads 416 are placed on top of the plate to simulate, for example a baby's weight. A pressure of about 50g cm-2 (0.7psi) is achieved by positioning weights 416, e.g. fix the commonly available MAXI size 20 kg.

As test fluid is introduced into the cylinder It typically builds up on top of the absorbent structure thereby complettng an electrical dreuit between the eledrodes. The test fluid Is transported from the pump to the test assembly by means of a tubing of about 8 mm diameter, which is kept filled wvith test fluid. Thus the fluid starts to leave the tubing essen8aliy at the same time the pump starts operatfng. At this tlme, also the timer Is started, and the timer is stopped when the absorbent structure has absorbed the gush of urine, and the efectricai contact between the electrodes is broken.

The acquisition rate is defined as the gush volunie absorbed (ml) per unit time(s). The acquisition rate is calculated for each gush inhWuced into the sample. Of particular interest In view of the current lnvention are the first and the last of the four gushes.

This test Is primarily designed to evaluate products generally referred to as MAXI size products for a design capacity of about 300 mi, and having a respective Ulflmate Storage Capacity of about 300 ml to 400 mt. tf products with signitkantty different capacities should be evaluated (such as can be envisaged for adult inconflnence products or for smaller babies), the setHngs In par6cuiar of the fluid volume per gush should be adjusted appropriately to about 20% of the total arttcle design capacity, and the deviation from the standard test protocai should be recorded.
Post uisition Coliaõaen Rewet Method (refer to Fig. 7) Before executing the test, the collagen film as purchased from NATURIN GmbH, Weinhein, Germany, under the designatfon of COFFI and at a basis weight of about 28g/m2 is prepared by being cut into sheets of 90 mm diameter e.g. by using a sample cutter device, and by equilibradng the film in the controlled environment of the test room (see above) for at least 12 hours (tweezers are to be used for all handling of the coliagen film).

At least 5 minutes, but not more than 6 minutes after the last gush of the above acquisitiat test is absorbed, the cover plate and weights are removed, and the test sample (520) is carefully placed flat on a lab bench.

4 sheets of the precut and equilibrated collagen material (510) are weighed with at least one mitligram accuracy, and then positioned oentered onto the loading point of the artlde, and covered by perspex plate (530) of 90 nwn diameter, and about 20 mm thickness. A

weight (540) of 15 kg is carefully added (also centered). After 30 +/- 2 seconds the weight and perspex plate are carefully removed again, and the coiiagen films are reweighed.

The Post Acquisitlon Collagen Rewet Method result Is the moisture pick up of the coiiagen film, expressed in mg.
It should be noted further, that this testing protocol can be adjusted easiiy acoording to specific product types, such as different baby diaper sizes, or adult incontinence artlcies, or catamenial articies, or by the variation in the type and amount of loading fluid, the amount and size of the absorbent material, or by variadons In the applicable pressure.
Having once defined these relevant parameters, such modifications will be obvious to one skilled in the ark When considering the results from the adjusted test protocol the products can easily be optimizing these identified relevant parameter such as In a designed experiment according to standard statisticai methods with reaiistic in use boundary condiHons.

Urin caoacitv The drip capa<~ty test described here Is based on a standard and Industry wide applied raw material test for airfett (fluff) pulp. The test was initiaity developed to evaluate the degree to which a fibers can acquire, transport (distribute) away from the loading point and retain a load of synthetic urine in a fiber web. A slight modification of the test is used to simulate more in-use conditions.

in the acquisition-drip test a 75mi gush of synthetic urine (0.9 % saiine) is appited to a fiber web supported on a wire mesh (porous) at a rate 15 mi/sec. The (saturated) drip capacity Is then determined from the fluid that is retained in the fibrous materiai after the gush.

To execute the test, a sample pad 7.5 cm x 25 cm is weighed and placed on a large mesh wire screen positioned on a drip tray (like in the diagram) which is then mounted on a weight bafance.

75mi of Synthetlc urine is introduced via a pump (the same pump used and detailed in the acquisition test) into the center of the sample at a rate of 15t 0.25 mUsec.

By suspending the mesh screen on a balance one can detenrine closely the amount of urine retained by the sample and urine passed into the drip tray. This helps to minimize variations of the pump delivering the urine.

Note the pump deiivery rate Is conflrmed prior to each run.
The drip capacity Is then given as the rato:
- Urine retained on saturation (nil) - Dry Weight of sample (g) Optionally, the "drip time" can be recorded, i.e. the time difference between the start of ioading the structure and the time when the first drop falls out of the sample.

Claims (6)

1. Absorbent article, comprising an absorbent core, a topsheet, a backsheet, wherein said core provides a basis capacity of at least 0.7 ml/cm2 and said backsheet provides a Dynamic liquid impact performance of less than 20g/m2.

2. Absorbent article according to claim 1, wherein said backsheet is selected to provide a polyhole rewet of less than 10 mg.

3. Absorbent article according to any one of claims 1 and 2, wherein said absorbent core has a ultimate storage capacity of less than 1.5 time the design capacity.

4. Absorbent article according to any one of claims 1 to 3, further comprising a bellows which is repeatable deformable to force airflow through the absorbent article in a controlled manner.

5. Absorbent article according to any one of claims 1 to 4, wherein said article provides a Poyhole rewet of less than 0.10 mg.

6. Use of absorbent article according to any one of claims 1 to 5 on a wearer, thereby defining a space between the article and the wearer, said space exhibiting an micro climate having a Relative Humidity of less than 50% RH.