CN103946685A - Absorbent articles with improved absorbent properties - Google Patents

Abstract

An absorbent article such as a disposable diaper, training pant and adult incontinence undergarment comprising an absorbent structure having superabsorbent polymer particles, said article being capable of absorbing and containing body exudates and having improved absorption properties and thus being capable of reducing leakage, especially at the first gush, i.e. when the article starts to be wetted.

Description

Absorbent articles with improved absorbent properties

technical field

The present invention relates to absorbent articles comprising superabsorbent polymer particles, such as disposable diapers, training pants and adult incontinence underwear.

Background technique

Absorbent articles such as disposable diapers, training pants, and adult incontinence underwear absorb and contain body exudates. Many absorbent articles such as diapers contain superabsorbent polymer materials. Superabsorbent polymers are usually present in the core of absorbent articles in particulate form. The superabsorbent polymer particles are capable of absorbing liquid and swelling upon contact with liquid exudates. However, it has been shown in the past that not all superabsorbent polymer particle types are equally suitable for use in absorbent articles.

It is known that in order for absorbent articles comprising superabsorbent polymer particles to exhibit good absorption and containment functions, certain technical requirements need to be fulfilled by the superabsorbent polymer particles. Superabsorbent polymer particles first need to be able to quickly absorb liquid exudates. In the prior art, the absorption rate of superabsorbent polymer particles is generally characterized by measuring the free swelling rate (FSR) of the particles.

In addition to having a high rate of absorption, the superabsorbent polymer particles present in the core need to be highly permeable to liquids. Poor permeability of superabsorbent polymer particles can trigger penetration of absorbent articles due to gel blocking. Gel blocking can occur in the absorbent core when swollen superabsorbent polymer particles block the interstitial spaces between the particles. In such cases, the liquid exudates cannot or only slowly reach the underlying layer of superabsorbent polymer particles disposed in the core. Liquid exudates remain on the surface of the absorbent core and can thus leak from the diaper.

In the prior art, the permeability of superabsorbent polymer particles is usually characterized by measuring the SFC (Saline Flow Conductivity) of the particles. The parameters are measured at equilibrium, ie the measurements are made on a fully pre-swelled gel bed of superabsorbent polymer particles.

However, the inventors have now surprisingly found that absorbent cores comprising superabsorbent polymer particles having high FSR and high SFC values do not automatically direct liquid exudates into the absorbent article with a fast acquisition time, especially during the first gush , that is, when the absorbent core comes into contact with liquid for the first time.

Accordingly, the present invention provides absorbent articles which have improved absorbent properties and thus reduce leakage, especially at the first gush, ie when the article starts to be wetted.

Contents of the invention

The present invention relates to an absorbent article comprising an absorbent structure. The absorbent article is divided into three parts: a front part, a back part and a crotch part arranged between the front part and the back part. The absorbent structure includes an absorbent core. The absorbent core has a dry thickness of 0.2 to 5 mm at the crotch point of the article. One or more parts of the absorbent structure comprise at least 90% by weight of superabsorbent polymer particles and require a time to reach an uptake of 20 g/g (T20) of less than 440 s, said uptake being measured according to the K(t) test method .

Description of drawings

Fig. 1 is a plan view of a diaper according to one embodiment of the present invention.

Figure 2 is a cross-sectional view of the diaper shown in Figure 1 taken along section line 2-2 of Figure 1 .

Figure 3 is a partial cross-sectional view of an absorbent core according to one embodiment of the present invention.

Figure 4 is a partial cross-sectional view of an absorbent core according to another embodiment of the present invention.

Figure 5a is a partial cross-sectional view of an absorbent core comprising the combination of the first and second absorbent core layers shown in Figures 3 and 4 .

Figure 5b is a partial cross-sectional view of an absorbent core comprising the combination of the first and second absorbent core layers shown in Figures 3 and 4 .

Figure 6 is a schematic diagram of a rheometer.

Figure 7 is a partial cross-sectional side view of a suitable permeability measurement system for performing dynamic effective permeability and uptake kinetics measurement tests.

Figure 8 is a cross-sectional side view of the piston/roller assembly used for dynamic effective permeability and uptake kinetics measurement tests.

FIG. 9 is a top view of a piston head suitable for use in the piston/drum assembly shown in FIG. 8 .

Figure 10 is a partial cross-sectional side view of a suitable permeability measurement system for performing a urine permeability measurement test.

Figure 11 is a cross-sectional side view of a piston/drum assembly for performing a urine permeability measurement test.

FIG. 12 is a top view of a piston head suitable for use in the piston/drum assembly shown in FIG. 11 .

Figure 13 is a cross-sectional side view of the piston/roller assembly of Figure 11 placed on a sintered disk for the swollen phase.

Figure 14 is a cross-sectional view of a flat acquisition measurement system suitable for performing flat acquisition tests.

Figure 15 is a cross-sectional view of an absorbent structure to be tested according to the K(t) test method from which a layer of material that is not part of the absorbent structure has been removed by means of "cold spray".

Figure 16 is a cross-sectional view of an absorbent structure to be tested according to the K(t) test method, wherein the upper layer of the absorbent structure is perforated using a perforating tip.

Figure 17 is a top view of an aperture pattern according to which the upper or lower layer of the absorbent structure may be apertured.

Figure 18A is a graph representing the uptake (in g/g) of the absorbent structures of Comparative Examples 1 and 2 and Example 1 as a function of time as measured according to the K(t) test method.

Figure 18B is a graph representing the uptake (in g/g) of the absorbent structures of Comparative Examples 1 and 2 and Example 2 as a function of time as measured according to the K(t) test method.

Detailed ways

The term "absorbent article" as used herein refers to devices that absorb and contain bodily exudates, and more specifically, devices that are placed against or adjacent to the body of a wearer to absorb and contain various bodily exudates. Absorbent articles include diapers, training pants, adult incontinence underwear, feminine hygiene products, and the like. As used herein, the term "body fluid" or "body exudate" includes, but is not limited to, urine, blood, vaginal discharge, breast milk, sweat, and fecal matter. In some embodiments of the invention, the absorbent article is a diaper or training pants.

As used herein, "absorbent core" refers to a structure disposed between the topsheet and backsheet of an absorbent article for absorbing and containing liquid received by the absorbent article. The core comprises superabsorbent polymer particles. The core may comprise one or more substrate layers, superabsorbent polymer particles disposed on the one or more substrate layers, and typically a thermoplastic composition disposed on the superabsorbent polymer particles. Typically the thermoplastic composition is a thermoplastic adhesive material. The thermoplastic binder material may form a fibrous layer at least partially in contact with the superabsorbent polymer particles on the one or more substrate layers and partially in contact with the one or more substrate layers. In order to enhance the adhesion of the superabsorbent polymer particles and/or the thermoplastic adhesive material to the respective substrate layers, an auxiliary adhesive may be deposited on the one or more substrate layers prior to the application of the superabsorbent polymer particles. The absorbent core may also include one or more cover layers such that superabsorbent polymer particles are disposed between one or more substrate layers and one or more cover layers. The one or more substrate or cover layers may comprise or consist of a nonwoven, tissue or film, or combinations thereof. The absorbent core may also contain odor control compounds.

The absorbent core may consist essentially of one or more substrate layers, superabsorbent polymer particles, thermoplastic composition, optionally secondary adhesive, optionally cover layer, and optionally odor control compound.

The absorbent core may comprise superabsorbent polymer particles sandwiched between two layers, an upper layer and a lower layer, wherein there are no superabsorbent polymer particles above and below the upper layer. The upper layer corresponds to the substrate or cover layer of the absorbent core closest to the topsheet of the article, and the lower layer corresponds to the substrate or cover layer of the absorbent core closest to the backsheet of the absorbent article. Alternatively, in the absence of an upper layer, the absorbent core may correspond to a structure disposed between the topsheet and the lower layer; or in the absence of a lower layer, the absorbent core may correspond to the structure disposed between the upper layer and the backsheet. structure between. In the absence of upper and lower layers, the absorbent core may correspond to the entire structure arranged between the topsheet and the backsheet of the absorbent article. The substrate or cover layer may comprise or consist of a nonwoven, tissue or film, or combinations thereof.

As used herein, "absorbent structure" means one of the following structures:

a. An absorbent core of an absorbent article, wherein the absorbent core comprises superabsorbent polymer particles sandwiched between two layers, an upper layer and a lower layer, with no superabsorbent polymer particles above and below the upper layer. The upper layer corresponds to the substrate or cover layer of the absorbent core closest to the topsheet of the article, and the lower layer corresponds to the substrate or cover layer of the absorbent core closest to the backsheet of the absorbent article.

b. An absorbent core of an absorbent article in combination with a topsheet of an absorbent article, wherein the absorbent core does not comprise an upper layer as previously defined.

c. An absorbent core of an absorbent article in combination with a backsheet of an absorbent article, wherein the absorbent core does not comprise a lower layer as previously defined.

A "portion of an absorbent structure" as used herein refers to a portion of an absorbent structure passing through the thickness of the absorbent structure, ie a portion of the absorbent structure comprising in the corresponding portion all the different layers from which the absorbent structure is made.

As used herein, "front" and "back" refer to the front and back waist regions of an absorbent article. The lengths of the front and back portions are each one-third of the overall length of the article from the respective front and back waist edges. For embodiments in which the front waist edge and/or the rear waist edge are not configured as a straight line extending parallel to the transverse centerline of the absorbent article, the length of the absorbent article passes from the point at the front waist edge closest to the transverse centerline and ends at Terminate at the rear waist edge point closest to the transverse centerline and be measured on or parallel to the longitudinal centerline.

As used herein, "crotch" refers to the region of the article positioned in the center of the article between the front and back of the article. The length of the crotch is one-third of the overall length of the article.

"Crotch point" as used herein refers to the point of the article which is located at the intersection of the longitudinal and transverse centerlines of the article, the center of the absorbent article. It should be understood that, for the present invention, the crotch point of the article need not be positioned at the center of the absorbent core, i.e. at the intersection of the longitudinal and transverse centerlines of the absorbent core, especially if the absorbent core is not centered on the transverse centerline of the article Down, ie where the absorbent core is offset to the front and/or rear of the article.

As used herein, "the center of the front" refers to the point of an absorbent article that is located at the intersection of the longitudinal centerline of the article and a line parallel to the transverse centerline of the article and is located at a distance from the transverse centerline of the absorbent article a distance of one-third of the overall length. For embodiments in which the front waist edge and/or the rear waist edge are not configured as a straight line extending parallel to the transverse centerline of the absorbent article, the length of the absorbent article passes from the point at the front waist edge closest to the transverse centerline and ends at Terminate at the rear waist edge point closest to the transverse centerline and be measured on or parallel to the longitudinal centerline.

"Comprising", "comprising" and "containing" are open-ended terms that also encompass "consisting of" or "consisting of" which are closed-ended terms.

As used herein, "airfelt" refers to comminuted wood pulp, which is a form of cellulosic fibers.

"Superabsorbent polymer particles" as used herein refers to cross-linked polymeric materials that can absorb at least 10 times their own weight in Aqueous 0.9% saline solution. The superabsorbent polymer particles are in granular form so as to be flowable in the dry state. Preferred superabsorbent polymer particles of the present invention are made from poly(meth)acrylic acid polymers. However, superabsorbent polymer particles, eg based on starch, are also within the scope of the present invention.

As used herein, "thermoplastic binder material" means a polymer composition from which fibers can be formed and applied to superabsorbent polymer particles to immobilize the superabsorbent polymer particles in both the dry and wet state. The thermoplastic binder material of the present invention preferably forms a fibrous network on superabsorbent polymer particles.

As used herein, "nonwoven" means a man-made sheet, web or batt of oriented or randomly oriented fibers bonded by friction and/or bonding and/or adhesion, or felted by wet milling , excluding paper and products of yarn or filament bound in combination by weaving, weaving, tufting, stitchbonding, whether or not additionally sewn. These fibers may be of natural or man-made origin and may be staple or continuous filament or be formed in situ. Commercially available fibers have diameters ranging from less than about 0.001 mm to greater than about 0.2 mm, and they come in a variety of different forms: staple fibers (called chemical staple or chopped fibers), continuous monofilaments ( filaments or monofilaments), bundles of untwisted continuous filaments (tows), and bundles of twisted continuous filaments (yarns). Nonwoven fabrics can be formed by a number of methods such as meltblowing, spunbonding, solution spinning, electrospinning, and carding. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (gsm).

As used herein, the term "attached" refers to a configuration in which a first element is fixed directly to another element by directly attaching the first element to a second element, or by attaching the first element to one or more A formation of a third intermediate element which in turn is attached to the second element thereby indirectly securing the first element to the second element. Attachment means may include adhesive bonding, thermal bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other suitable attachment means or combinations of these attachment means known in the art.

Figure 1 is a plan view of an absorbent article 10 of some embodiments of the present invention. The absorbent article 10 is shown in its flat, uncontracted state (ie, without elastic-induced shrinkage), with portions of the absorbent article 10 cut away to more clearly show the underlying structure of the diaper 10 . In Figure 1, the portion of the absorbent article 10 that contacts the wearer faces the viewer. The absorbent article 10 generally includes a chassis 12 and an absorbent core 14 disposed within the chassis 12 .

The chassis 12 of the absorbent article 10 in FIG. 1 may comprise the main body of the absorbent article 10 . Chassis 12 may include an outer cover 16 that includes a topsheet 18 that may be liquid pervious and/or a backsheet 20 that may be liquid impermeable. The absorbent core 14 may be enclosed between a topsheet 18 and a backsheet 20 . The chassis 12 may also include side panels 22 , elasticized leg cuffs 24 and an elastic waist structure 26 .

Leg cuffs 24 and elastic waist structure 26 may each generally include elastic members 28 . One end of the absorbent article 10 is configured as the front portion 30 and the other end is configured as the rear portion 32 of the absorbent article 10 . The central portion of the absorbent article 10 is configured as a crotch portion 34 extending longitudinally between the front portion 30 and the rear portion 32 .

The absorbent article 10 is depicted in FIG. 1 with its longitudinal centerline 36 and its transverse centerline 38 . The perimeter 40 of the absorbent article 10 is defined by the outer edges of the absorbent article 10, wherein the longitudinal edge 42 extends approximately parallel to the longitudinal centerline 36 of the absorbent article 10, and the front waist edge 43 and the rear waist edge 44 extend approximately parallel to the transverse direction of the absorbent article 10. Centerline 38 extends between longitudinal edges 42 . The chassis 12 may also include a fastening system, which may include at least one fastening member 46 and at least one platform region 48 .

The absorbent article 10 may also include such other structures known in the art, including front and back ears, waist cap structures, elastics, etc., to provide better fit, containment, and aesthetic properties. Such additional structures are well known in the art and are described, for example, in US Patent 3,860,003 and US Patent 5,151,092.

To hold the absorbent article 10 in place about the wearer, at least a portion of the front portion 30 can be attached to at least a portion of the rear portion 32 by fastening members 46 to form one or more leg openings and an article waist. When fastened, the fastening system bears a tensile load around the waist of the article. The fastening system may allow a user of the article to grasp an element of the fastening system, such as fastening member 46, and connect the front portion 30 to the rear portion 32 in at least two locations. This can be accomplished by manipulating the strength of the bond between the elements of the fastening device.

According to certain embodiments, the absorbent article 10 may be provided with a reclosable fastening system, or may alternatively be provided in the form of a pant diaper. When the absorbent article is a diaper, it may include a reclosable fastening system joined to the chassis for securing the diaper to the wearer. When the absorbent article is a pant diaper, the article may comprise at least two side panels joined to each other to form a pant.

absorbent structure

The absorbent structure includes superabsorbent polymer particles.

The one or more parts of the absorbent structure comprise at least 90% by weight of superabsorbent polymer particles based on the weight of the part of the absorbent structure, excluding any substrate and/or cover layer and /or the weight of the topsheet and/or the backsheet. The one or more substrate or cover layers may comprise or consist of a nonwoven, tissue or film, or combinations thereof.

One of the one or more portions of the absorbent structure may be centered on the front of the article, and/or one of the one or more portions of the absorbent structure may be centered on the crotch point of the article.

At least one of the one or more portions of the absorbent structure may have a surface area of 30 ^cm2 or greater. Alternatively, each of the one or more portions may have a surface area of 30 cm ² or greater.

At least one of the one or more portions of the absorbent structure having a surface area of 30 cm ² or greater may encompass a circular area. Alternatively, each of the one or more portions of the absorbent structure having a surface area of 30 cm ² or greater may encompass a circular area.

One or more portions of the absorbent structure may comprise at least 95% by weight superabsorbent polymer particles.

One or more portions of the absorbent structure may comprise at least 98% by weight superabsorbent polymer particles.

One or more portions of the absorbent structure may comprise at least 99% by weight superabsorbent polymer particles.

The entire absorbent structure may comprise at least 90%, preferably at least 95%, more preferably at least 98%, even more preferably at least 99% by weight of superabsorbent polymer particles.

These embodiments are especially preferred because absorbents comprising a high percentage of superabsorbent polymer particles are absorbent compared to the thickness of conventional absorbent articles having a higher amount of conventional absorbent materials such as airfelt or the like in addition to superabsorbent polymer particles. The article typically has a reduced thickness when dry. The reduced thickness helps improve fit and comfort when positioning the article on the wearer.

One or more parts of the absorbent structure require a time to reach an uptake of 20 g/g (T20) of less than 440 s, or less than 400 s, or less than 350 s, or less than 300 s, or less than 250 s, according to the following K(t ) measured by the test method.

The time to 20 g/g uptake (T20) may be from 50 s to 440 s, or from 100 s to 350 s, or from 150 s to 300 s, as measured according to the K(t) test method described below.

One or more portions of the absorbent structure may have an effective permeability at 20 minutes (K20), measured according to the K(t) test method, of at least 2.9·10 ⁻⁸ cm ² .

One or more portions of the absorbent structure may have a mass of at least 2.95·10 ⁻⁸ cm ² , or at least 3·10 ⁻⁸ cm ² , or 2.95·10 ⁻⁸ cm as measured according to the K(t) test method described below Effective permeability at 20 minutes from ² to 1.0·10 ^-6 cm ² , or from 2.95·10 ^-8 cm ² to 1.0·10 ^-7 cm ² , or from 3.0·10 ^-8 to 1.0·10 ^-7 cm ² ( K20).

One or more portions of the absorbent structure may have a ratio between a minimum effective permeability and a permeability at 20 minutes of greater than 0.75, or greater than 0.8, or greater than 0.9, as measured according to the K(t) test method described below ( Kmin/K20 ratio). In such embodiments, transient gel blocking is minimized and throughout the entire swelling process, especially in the initial part of the swelling phase that is most important for the first gush, the liquid effluent can travel rapidly through the interstices between the particles space.

The uptake (U20) of one or more portions of the absorbent structure at 20 min is at least 24 g/g or at least 24.5 g/g, or 24 g/gt to 60 g/g, as measured according to the K(t) test method described below , or 24.5g/g to 50g/g, or 24.5g/g to 40g/g.

In some embodiments, the entire absorbent structure complies with the aforementioned T20, K20 and U20 values.

Absorbent articles comprising such an absorbent structure have improved absorbent properties, especially at the first gush, and thus exhibit reduced leakage, compared to absorbent articles of the prior art. Such absorbent structures are especially suitable for use in absorbent articles.

absorbent core

In some embodiments, the absorbent core comprises an average ^amount of superabsorbent polymer particles per area of 50 to 2200 g/ ^m2 , or 100 to 1500 g/ ^m2 , or 200 to 1000 g/m2.

In some ^embodiments , in the crotch portion of the ^{article ,} the absorbent ^core comprises an average amount of ultra- Absorbent polymer particles/area. The absorbent article includes a sufficient amount of superabsorbent polymer particles to have good absorbent properties, and is thin enough to provide fit and comfort to the wearer. However, superabsorbent polymer particles are also present in the front and back, although the amount especially in the back may be lower (or even zero). In some embodiments, in the rear of the article, the absorbent core comprises less than 300 g/m ² , or less than 200 g/m ² , or 25 to 300 g/m ² , or 50 to 200 g/m ² , or 50 to 100 g/m 2 ^m Average amount of superabsorbent polymer particles per surface area.

In some embodiments, the absorbent core may also contain traces of absorbent material other than superabsorbent polymer particles, such as airfelt.

In some embodiments, the absorbent core generally comprises less than 5% by weight airfelt, preferably less than 2%, and more preferably no airfelt. In some embodiments, the absorbent structure may also be free of airfelt.

The absorbent core has a thickness at the crotch point of the article of less than 10 mm, preferably less than 5 mm, more preferably less than 3 mm, even more preferably less than 1.5 mm, or 0.1 to 10 mm, preferably 0.2 to 5 mm, more preferably A dry thickness of 0.3 to 3 mm, even more preferably 0.5 to 1.5 mm. Thus, the absorbent core is sufficiently thin compared to absorbent cores comprising conventional airfelt. As a result, fit and comfort are significantly improved.

superabsorbent polymer particles

The superabsorbent polymer particles useful in the present invention can be in a wide variety of shapes. The term "particle" refers to particles, fibers, flakes, spheres, powders, platelets and other shapes and forms known to those skilled in the art of superabsorbent polymer particles. In some embodiments, the superabsorbent polymer particles may be in the shape of fibers, ie, elongated needle-shaped superabsorbent polymer particles. In those embodiments, the superabsorbent polymer particle fibers have a small dimension (ie, the diameter of the fiber) of less than about 1 mm, typically less than about 500 μm, and preferably less than 250 μm down to 50 μm. The length of the fibers is preferably from about 3 mm to about 100 mm. Fibers can also be in the form of filaments that can be woven.

Alternatively, in some preferred embodiments, the superabsorbent polymer particles of the present invention are spherical particles. According to the invention, and in contrast to fibers, "spherical particles" have a longest and shortest dimension, where the ratio of the longest to shortest particle size of the particles is in the range 1-5, where a value of 1 would equal a perfectly spherical particles, and a value of 5 will give some deviation from such spherical particles. In such embodiments, the superabsorbent polymer particles may have a particle size of less than 850 μm, or 50 to 850 μm, preferably 100 to 500 μm, more preferably 150 to 300 μm, as measured according to EDANA method WSP220.2-05. Superabsorbent polymer particles having a relatively low particle size help to increase the surface area of the absorbent material in contact with the liquid exudates and thus support rapid absorption of the liquid exudates.

Superabsorbent polymer particles useful in the present invention include a variety of water-insoluble, but water-swellable polymers capable of absorbing large quantities of fluids. Such polymeric materials are generally known in the art.

Suitable superabsorbent polymer particles may for example be obtained by inverse suspension polymerization as described in US Patent 4,340,706 and US Patent 5,849,816, or by spraying as described in US Patent Applications 2009/0192035, 2009/0258994 and 2010/0068520 Or other gas phase dispersion polymerization. In some embodiments, suitable superabsorbent polymer particles are obtainable by state-of-the-art production processes, as described more particularly in WO2006/083584, page 12, line 23 to page 20, line 27.

In some embodiments, the surface of the superabsorbent polymer particles may be coated. In such embodiments, the coating makes the surface sticky so that the superabsorbent polymer particles cannot easily rearrange when wetted (so they cannot block the voids).

In some embodiments, superabsorbent polymer particles may be coated with cationic polymers. Preferred cationic polymers may include polyamine or polyimine materials which are reactive with at least one component contained in bodily fluids, especially urine. Preferred polyamine materials are selected from: (1) polymers with primary amine groups (e.g., polyvinylamine, polyallylamine); (2) polymers with secondary amine groups (e.g., polyvinylamine; amines); and (3) polymers having tertiary amine groups (for example, polyN,N-dimethylalkylamines). Practical examples of cationic polymers are e.g. polyethyleneimines, modified polyethyleneimines crosslinked by epihalohydrin, polyamines, polyimides modified by grafting ethyleneimines to the extent soluble in water Aminoamines, polyetheramines, polyvinylamines, polyalkylamines, polyamidopolyamines, and polyallylamines.

In preferred embodiments, the cationic polymer has a weight average molecular weight of at least 500, more preferably 5,000, most preferably 10,000 or greater. The cationic polymer having a weight average molecular weight of 500 or more is not limited to a polymer showing a single maximum value (peak) in molecular weight analysis by gel permeation chromatography, and even if it exhibits multiple maximum values (peaks), Polymers having a weight average molecular weight of 500 or more can also be used.

Preferable amounts of cationic polymer are in the range of about 0.05 to 20 parts by weight, more preferably about 0.3 to 10 parts by weight, and most preferably about 0.5 to 5 parts by weight, relative to 100 parts by weight of superabsorbent polymer particles.

In some embodiments, the superabsorbent polymer particles may be coated with a chitosan material, as disclosed in US 7 537 832 B2.

In some other embodiments the superabsorbent polymer particles may comprise mixed bed ion exchange absorbent polymers as disclosed in WO99/34841 and WO99/34842.

As already mentioned above, absorbent structures comprising superabsorbent polymer particles with high SFC and FSR values do not automatically lead to fast acquisition times of liquid exudates, especially at the first gush, i.e. when the dry absorbent structure comes into contact with the liquid. on contact. Without being bound by theory, it is believed that dry superabsorbent polymer particles are generally less absorbent of water than wet superabsorbent polymer particles because water diffuses less into dry superabsorbent polymer particles than into wet ones. Diffusion of superabsorbent polymer particles.

The absorption properties of dry absorbent structures comprising superabsorbent polymer particles in relation to initial uptake have hitherto been studied. More precisely, the study focused on the "Saline Flow Conductivity" (SFC) of the superabsorbent polymer particles, which is measured at equilibrium and thus at a stage away from the initial fluid intake. For absorbent structures comprising a significant amount of airfelt in addition to superabsorbent polymer particles, temporary storage of liquid entering the absorbent core is provided by the airfelt such that the superabsorbent polymer particles absorb, with some delay, liquid from the surrounding airfelt. liquid. But even for absorbent articles without airfelt disclosed in the prior art, the permeability of the superabsorbent polymer particles is always measured at equilibrium, thus not taking into account the initial exposure of the dry superabsorbent polymer particles to liquids. time performance. The inventors of the present invention have carefully studied the performance of absorbent structures comprising superabsorbent polymer particles upon initial exposure to liquid. They have found that certain, but not publicly available, absorbent structures comprising superabsorbent polymer particles and comprising no or very low amounts of airfelt exhibit superior performance. Excellent performance results in improved fluid acquisition, thereby reducing the risk of leakage. It has been found that excellent absorbent structures comprising superabsorbent polymer particles can be described in terms of the time required for a dry absorbent structure comprising superabsorbent polymer particles to achieve a certain liquid uptake when absorbed against a certain confining pressure. Thus, it is now possible to deliberately and easily select these newly developed absorbent structures without additional extensive research and testing.

In some embodiments, the absorbent structure comprises particles of superabsorbent polymer having a mass of greater than 50, preferably greater than 60, or 50 to 500, or 55 to 200, or 60 to 150 UPM units expressed as UPM (urine Permeability measurement) the permeability at equilibrium, where 1 UPM unit is 1×10 ⁻⁷ (cm ³ .s)/g.

UPM values are measured according to the UPM test method listed below. This method is closely related to the prior art SFC test method. The UPM test method generally measures the flow resistance of a pre-swelled layer of superabsorbent polymer particles, ie the flow resistance is measured at equilibrium. Such superabsorbent polymer particles having a high UPM value thus exhibit high permeability when a substantial volume of the absorbent article has been wetted by liquid exudates. Absorbent structures comprising such superabsorbent polymer particles exhibit good absorption properties not only in the first gush but also in subsequent gushes.

In some embodiments, the absorbent structure may comprise superabsorbent polymer particles having an 0.6 g/g/s, or FSR (Free Swell Rate) of 0.4 to 0.6 g/g/s.

The free swelling rate of superabsorbent polymer particles is measured according to the FSR test method listed below. Absorbent structures comprising superabsorbent polymer particles having a high free swell rate value will be able to quickly absorb liquid without confining pressure. In contrast to the K(t) test method, no external pressure is applied to the gel bed in order to measure the free swelling rate. Absorbent structures comprising superabsorbent polymer particles having too low a FSR value may not require less than 440 s to achieve an uptake of 20 g/g, as measured according to the K(t) test method of the present invention, and will therefore not be able to absorb liquid as rapidly as possible effluent. However, as mentioned above, absorbent structures comprising superabsorbent polymer particles having high FSR values do not automatically lead to high uptake values as measured according to the K(t) test method.

In some embodiments, the absorbent structure may comprise superabsorbent polymer particles having a mass of greater than 20 g/g, or greater than 24 g/g, or 20 to 50 g/g, as measured according to EDANA method WSP241.2-05. , or a CRC (centrifuge retention capacity) value of 20 to 40 g/g, or 24 to 30 g/g. CRC measures the liquid absorbed by superabsorbent polymer particles that freely swell in excess liquid.

Absorbent structures comprising superabsorbent polymer particles having a high CRC value are preferred since fewer superabsorbent polymer particles are required to facilitate the overall capacity required for liquid absorption.

In some embodiments, the absorbent article may have a first gush acquisition time of less than 30 seconds, preferably less than 27 seconds, as measured according to the Flat Acquisition Test Method described below. Infant diapers (such as Pampers Active Fit Size 4 or other Pampers Infant Diapers Size 4, Huggies Infant Diapers Size 4 or most other trade names) intended for a wearer with a body weight in the range of 8 to 13 kg ± 20% Diaper size 4) for collection time measurements. As shown in the "Examples" section of this patent application, compared to absorbent articles of the prior art, comprising an absorbent structure (which comprises superabsorbent polymer particles, and measured according to the K(t) test method, up to 20 g/g Absorbent articles whose uptake requires less than 440 s) can provide faster acquisition times, especially at the first gush, and thus reduce leakage.

Absorbent core structure

In the following, examples of the absorbent core of the present invention are given. However, the present invention is not limited to such absorbent cores.

In some embodiments, the absorbent core 14 includes an absorbent layer 60, as shown in FIGS. 3 and 4 . The substrate layer 64 of the absorbent layer 60 may be referred to as a dusting layer and has a first surface 78 facing the backsheet 20 of the diaper 10 and a second surface 80 facing the superabsorbent polymer particles 66 . According to some embodiments, substrate layer 64 is a nonwoven material, such as a multi-layer nonwoven material having a spunbond layer as an outer layer and one or more meltblown layers interposed between the spunbond layers, including but not limited to An SMS material comprising a spunbond layer, a meltblown layer and another spunbond layer. The absorbent layer 60 may include a cover layer 70, as shown in FIG. 4 . The cover layer 70 may be a nonwoven material, such as a multilayer nonwoven material having a spunbond layer as an outer layer and one or more meltblown layers interposed between the spunbond layers, including but not limited to SMS material, so The SMS material includes a spunbond layer, a meltblown layer and another spunbond layer. In some embodiments, base layer 64 and cover layer 70 are made of the same material.

As shown in FIGS. 3 and 4 , superabsorbent polymer particles 66 may be deposited on substrate layer 64 in particle clusters 90 including land areas 94 and junction areas 96 between land areas 94 . As defined herein, the landing zone 94 is the area where the thermoplastic adhesive material does not directly contact the nonwoven substrate or the secondary adhesive; the land zone 96 is the area where the thermoplastic adhesive material does directly contact the nonwoven substrate or the secondary adhesive. Area. The bonding region 96 contains few or no superabsorbent polymer particles 66 . Landing area 94 and engagement area 96 may have a variety of shapes including, but not limited to, circular, oval, square, rectangular, triangular, and the like.

Thus, the thermoplastic adhesive material 68 provides cavities that hold the superabsorbent polymer particles 66 and thereby secure the material. In another aspect, the thermoplastic adhesive material 68 bonds to the base layer 64 and thus attaches the superabsorbent polymer particles 66 to the base layer 64 . In some other embodiments, the thermoplastic adhesive material 68 will also at least partially penetrate both the superabsorbent polymer particles 66 and the substrate layer 64, thus providing further fixation and attachment.

In some other embodiments, the absorbent core 14 may include two absorbent layers, a first absorbent layer 60 and a second absorbent layer 62 . As best shown in FIGS. 5A and 5B , the first absorbent layer 60 of the absorbent core 14 includes a substrate layer 64, superabsorbent polymer particles 66 on the substrate layer 64, and a thermoplastic adhesive on the superabsorbent polymer particles 66. Material 68. Although not shown, the first absorbent layer 60 may also include a cover layer such as the cover layer 70 shown in FIG. 4 .

Likewise, as best shown in Figures 5A and 5B, the second absorbent layer 62 of the absorbent core 14 may also include a substrate layer 72, superabsorbent polymer particles 74 on the second substrate layer 72, and superabsorbent polymer particles 74 The thermoplastic adhesive material 76 on. Although not shown, the second absorbent layer 62 may also include a cover layer such as the cover layer 70 shown in FIG. 4 . As noted above, the substrate 64 of the first absorbent layer 60 may be referred to as the dusting layer and has a first surface 78 facing the backsheet 20 of the diaper 10 and a second surface 80 facing the superabsorbent polymer particles 66 . Likewise, the substrate layer 72 of the second absorbent layer 62 may be referred to as a core cover and has a first surface 82 facing the topsheet 18 of the diaper 10 and a second surface 84 facing the superabsorbent polymer particles 74 . The first substrate layer 64 and the second substrate layer 72 may be adhered to each other with an adhesive around the perimeter to form a wrap around the superabsorbent polymer particles 66 and 74 to retain the superabsorbent polymer particles 66 and 74 in the absorbent core 14. Inside.

Depending on the desired application of the absorbent core 14 and the particular absorbent article 10 in which the absorbent core may be incorporated, the area of the absorbent core 14 comprising superabsorbent polymer particles may vary. However, in some embodiments, the region of superabsorbent polymer particles may extend substantially completely across the absorbent core 14 . In some alternative embodiments, the region of superabsorbent polymer particles extends completely across the absorbent core 14 in the crotch portion 34 of the absorbent article 10, whereas the region of superabsorbent polymer particles does not extend completely across the front of the absorbent article 10. And the absorbent core 14 in the rear part is extended.

Combining the first and second absorbent layers 60 and 62 together to form the absorbent core 14 allows the layers to be offset such that the superabsorbent polymer particles 66 on the substrate layer 64 and the superabsorbent polymer particles on the substrate layer 72 The particles 74 are distributed substantially continuously across the superabsorbent polymer particle region, as shown in Figures 5A and 5B. In some embodiments, although the superabsorbent polymer particles 66 and 74 are discontinuously distributed across the first substrate layer 64 and the second substrate layer 72 in clusters 90, the superabsorbent polymer particles 66 and 74 span the superabsorbent The polymer particle domains are distributed substantially continuously. In some embodiments, the absorbent layers may be offset such that the landing area 94 of the first absorbent layer 60 faces the junction area 96 of the second absorbent layer 62, and the landing area of the second absorbent layer 62 faces the first absorbent layer. 60 of the junction region 96, as shown in Figures 5A and 5B. When the land area 94 and the junction area 96 are suitably sized and arranged, the resulting combination of superabsorbent polymer particles 66 and 74 is a substantial matrix of superabsorbent polymer particles spanning the superabsorbent polymer particle region of the absorbent core 14. The upper continuous layer (that is, the first substrate layer 64 and the second substrate layer 72 do not form a plurality of depressions, each of which contains a cluster 90 of superabsorbent polymer particles 66 and 74 therebetween), as in FIG. 5A shown.

The amount of superabsorbent polymer particles may or may not vary along the length of the core, usually the core is profiled in its longitudinal direction. It has been found that for most absorbent articles such as diapers, liquid discharge occurs primarily in the front half of the diaper. Therefore, the front half of the absorbent core 14 should contain most of the absorbent capacity of the core. Thus, according to certain embodiments, the front half of the absorbent core 14 may comprise greater than about 60% superabsorbent polymer particles, or greater than about 65%, 70%, 75%, 80%, 85%, or 90% of superabsorbent polymer particles.

Typically, a thermoplastic binder material can be used to at least partially immobilize the superabsorbent polymer particles in both dry and wet states. The thermoplastic binder material can be disposed substantially uniformly between the superabsorbent polymer particles. Typically, however, the thermoplastic binder material may be provided as a fibrous layer at least partially in contact with the superabsorbent polymer particles and partially in contact with the one or more substrate layers. Typically, the thermoplastic binder material of the present invention forms a fibrous network over the superabsorbent polymer particles. Typically, as in the example shown in Figures 5A and 5B, the superabsorbent polymer particles 66 and 74 are provided as discrete layers, and a layer of fibrous thermoplastic adhesive material 68 and 76 is laid over the superabsorbent polymer particles 66 and 74. layer, such that the thermoplastic adhesive material 68 and 76 is in direct contact with the superabsorbent polymer particles 66 and 74, but is also in direct contact with the second surfaces 80 and 84 of the substrate layers 64 and 72, which are not superabsorbent polymerized Matter particles 66 and 74 cover. This imparts a substantially three-dimensional structure to the fibrous layers of thermoplastic adhesive material 68 and 76, which is itself a substantially two-dimensional structure of relatively small thickness compared to the lengthwise and widthwise dimensions. In other words, the thermoplastic adhesive material 68 and 76 undulates between the superabsorbent polymer particles 68 and 76 and the second surface of the substrate layers 64 and 72 .

The thermoplastic binder material can provide cavities to wrap around the superabsorbent polymer particles and thereby immobilize these particles. In another aspect, the thermoplastic adhesive material bonds to the one or more substrate layers, and thus attaches the superabsorbent polymer particles to the one or more substrate layers. Some thermoplastic adhesive material will also penetrate into both the superabsorbent polymer particles and the one or more substrate layers, thus providing further fixation and attachment. Of course, while the thermoplastic adhesive materials disclosed herein provide improved wet fixation (i.e., fixation of the absorbent material when the article is at least partially loaded), these thermoplastic adhesive materials can also provide improved wet fixation to the absorbent material when the absorbent core is dry. Provides excellent fixation. Thermoplastic adhesive materials may also be referred to as hot melt adhesives.

Without wishing to be bound by theory, it has been found that those thermoplastic adhesive materials most suitable for immobilizing superabsorbent polymer particles combine good cohesion and good adhesive properties. Good adhesion promotes good contact between the thermoplastic adhesive material and the superabsorbent polymer particles and the substrate layer. Good cohesion reduces the likelihood of the adhesive breaking, especially in response to external forces, ie in response to strain. When the absorbent core absorbs liquid, the superabsorbent polymer particles swell and subject the thermoplastic binder material to external forces. The thermoplastic binder material can allow such swelling without interruption and without imparting too much compressive force that would inhibit swelling of the superabsorbent polymer particles.

The thermoplastic adhesive material may collectively comprise a single thermoplastic polymer or a blend of thermoplastic polymers having a temperature between 50°C and 300°C when measured by ASTM method D-36-95 "Ring and Ball". A softening point in the range between °C; or alternatively, the thermoplastic adhesive material may be a hot melt adhesive comprising at least one compound with other thermoplastic diluents such as tackifying resins, plasticizers and additives such as Antioxidant Combination Thermoplastic Polymers. In some embodiments, thermoplastic polymers generally have a molecular weight (Mw) greater than 10,000 and a glass transition temperature (Tg) generally below room temperature or -6°C<Tg<16°C. In some embodiments, typical concentrations of hot melt polymers range from about 20% to about 40% by weight. In some embodiments, thermoplastic polymers may be water insensitive. Exemplary polymers are (styrene) block copolymers comprising A-B-A triblock structures, A-B diblock structures, and (A-B)n radial block copolymer structures, where the A block is a Non-elastomeric polymer blocks, and the B block is an unsaturated conjugated diene or a (partially) hydrogenated version of this type. The B blocks are typically isoprene, butadiene, ethylene/butene (hydrogenated butadiene), ethylene/propylene (hydrogenated isoprene), or mixtures thereof.

Other suitable thermoplastic polymers that may be employed are metallocene polyolefins, which are polymers of ethylene prepared using single site or metallocene catalysts. Among other things, at least one comonomer can be polymerized with ethylene to produce copolymers, terpolymers or higher polymers. Also suitable are amorphous polyolefins or amorphous polyalphaolefins (APAO), which are homopolymers, copolymers or terpolymers of C2 to C8 alpha olefins.

In some embodiments, the thermoplastic binder material is in the form of fibers. In some of these embodiments, the fibers will have an average thickness of about 1 micron to about 50 microns, or about 1 micron to about 35 microns, and an average length of about 5 mm to about 50 mm, or about 5 mm to about 30 mm. In order to improve the adhesion of the thermoplastic adhesive material to the substrate layer or any other layer, especially any other nonwoven layer, such layers may be pretreated with a secondary adhesive.

In certain embodiments, the thermoplastic adhesive material is between 0.5 and 30 g/m ² , between 1 and 15 g/m ² , between 1 and 10 g/m ² or even Amounts between 1.5 and 5 g/ ^m2 are applied on the base layer.

An exemplary thermoplastic adhesive material 68 and 76 may have a pressure measured at 20° C. of at least 30,000 Pa, and less than 300,000 Pa, or less than 200,000 Pa, or between 140,000 Pa and 200,000 Pa, or less than 100,000 Pa. Storage modulus G'. In another aspect, the storage modulus G' measured at 35°C may be greater than 80,000 Pa. In another aspect, the storage modulus G' measured at 60°C can be less than 300,000 Pa and greater than 18,000 Pa, or greater than 24,000 Pa, or greater than 30,000 Pa, or greater than 90,000 Pa. In another aspect, the storage modulus G' measured at 90°C can be less than 200,000 Pa and greater than 10,000 Pa, or greater than 20,000 Pa, or greater than 30,000 Pa. The storage modulus measured at 60°C and 90°C can be a measure of the form stability of a thermoplastic adhesive material at elevated ambient temperatures. This value is especially important if the absorbent product is used in hot climates where the thermoplastic adhesive material will lose its its integrity.

G' is measured using a rheometer as schematically shown in Figure 6; this figure is for general illustration purposes only. The rheometer 627 is capable of applying shear stress to the adhesive and measuring the resulting strain (shear deformation) response at a constant temperature. Adhesive was placed between a Peltier element serving as a lower fixing plate 628 and an upper plate 629 with a radius R of 10 mm connected to the drive shaft of the motor to create shear stress. The gap between the two plates has a height H of 1500 microns. The Peltier element enables control of the temperature of the material (+0.5°C). The strain amplitude was set to 0.05%, the strain frequency was set to 1 Hz and the cooling rate was set to 2°C/min (wherein the start temperature was set to 150°C or higher and the end temperature was set to -5°C).

The absorbent core may also include secondary adhesives not shown in the figures. In order to enhance the adhesion of the superabsorbent polymer particles and the thermoplastic adhesive material to the corresponding substrate layer, an auxiliary adhesive can be deposited on the substrate layer prior to the application of the superabsorbent polymer particles on the substrate layer. Secondary adhesives may also assist in securing the superabsorbent polymer particles and may include the same thermoplastic adhesive materials as described above, or other adhesives including, but not limited to, sprayable hot melt adhesives agent. An example of a commercially available secondary binder is H.B. Fuller Co. (St. Paul, MN) product number HL-1620-B. The secondary adhesive may be applied to the base layer by any suitable method, but according to some embodiments it may be applied in slots about 0.5 to about 1 mm wide spaced about 0.5 to about 2 mm apart.

top sheet

The absorbent article 10 can include a topsheet 18 which can be liquid permeable. The topsheet 18 can be made of a wide variety of materials, such as woven and nonwoven materials; polymeric materials, such as apertured formed thermoplastic films, apertured plastic films, and hydroformed thermoplastic films; porous foams; cellular foams ; a cellular thermoplastic film; and a thermoplastic scrim. Suitable woven and nonwoven materials may include natural fibers (e.g., wood fibers or cotton fibers), synthetic fibers (e.g., polymer fibers such as polyester, polypropylene, or polyethylene fibers), or blends derived from natural and synthetic fibers. combination.

In some embodiments, the topsheet 18 may be made of a hydrophobic material to isolate the wearer's skin from liquids that have penetrated the topsheet 18 . In such embodiments, at least a portion of the upper surface of the topsheet 18 is treated to be hydrophilic so that liquids will penetrate the topsheet 18 more rapidly. This will reduce the likelihood that bodily exudates will flow off the topsheet 18 instead of being drawn through the topsheet 18 and absorbed by the absorbent core. The topsheet 18 may be rendered hydrophilic by treating it with a surfactant. Suitable methods of treating the topsheet 18 with the surfactant include spraying the topsheet material with the surfactant and dipping the material into the surfactant.

In some embodiments, the topsheet comprises an apertured formed film. Apertured formed films are permeable to bodily exudates but not absorbent, and have a reduced tendency for liquids to recede through and rewet the wearer's skin. Thus, the surface of the formed film that is in contact with the body remains dry, thereby reducing the likelihood of body soiling and providing a more comfortable feel to the wearer. Suitable formed film topsheets are described in the following patents: U.S. Patent 3,929,135, issued December 30, 1975 to Thompson entitled "Absorbtive Structures Having Tapered Capillaries"; issued April 13, 1982 to Mullane et al. US Patent 4,324,246 to Article Having A Stain Resistant Topsheet"; US Patent 4,342,314 to Radel et al. entitled "Resilient Plastic Web Exhibiting Fiber-Like Properties" on August 3, 1982; to Ahr et al. on July 31, 1984 US Patent 4,463,045 entitled "Macroscopically Expanded Three-Dimensional Plastic Web Exhibiting Non-Glossy Visible Surface and Cloth-Like Tactile Impression"; and US Patent 5,006,394 "Multilayer Polymeric Film" issued April 9, 1991 to Baird.

Alternatively, the topsheet comprises an apertured nonwoven material. Suitable apertured nonwoven materials are described in US Patent 5,342,338 and PCT Application WO 93/19715.

Negative

The absorbent article may include a backsheet 20 attachable to the topsheet. The backsheet prevents exudates absorbed by the absorbent core and contained within the diaper from soiling other external articles that may contact the diaper, such as bed sheets and undergarments. In some embodiments, the backsheet may be substantially impermeable to liquids (e.g., urine) and comprise a laminate of a nonwoven and a thin plastic film, such as having a thickness of about 0.012 mm (0.5 mil) Thermoplastic film to a thickness of about 0.051 mm (2.0 mils). Suitable backsheet films include those manufactured by Tredegar Industries Inc. (Terre Haute, Ind.) and sold under the trade designations X15306, X10962 and X10964. Other suitable backsheet materials may include breathable materials that allow vapors to escape from the diaper while still preventing liquid exudates from passing through the backsheet. Exemplary breathable materials may include materials such as woven webs, nonwoven webs, composite materials such as film-coated nonwoven webs, and materials such as ESPOIR NO and EXXON Chemical Co. manufactured by Mitsui Toatsu Co. of Japan. A microporous membrane named EXXAIRE manufactured by .(Bay City, Tex). A suitable breathable composite comprising polymer blends is available from Clopay Corporation of Cincinnati, Ohio under the designation HYTREL blend P18-3097. Such breathable composite materials are described in more detail in PCT Patent Application WO 95/16746, published June 22, 1995 in the name of E.I. DuPont. Other breathable backsheets including nonwoven webs and apertured formed films are described in US Patent 5,571,096, issued November 5,1996 to Dobrin et al.

Test Methods

· K(t) test method (dynamic effective permeability and uptake kinetics measurement test method)

The method measures the time-dependent effective permeability (K(t)) and uptake kinetics of absorbent structures comprising superabsorbent polymer particles under confining pressure. The purpose of this method is to evaluate the ability of an absorbent structure comprising superabsorbent polymer particles to acquire and distribute body fluids when the polymer is present in high concentrations in the absorbent article and exposed to the mechanical stresses normally occurring during the use of the absorbent article. Darcy's law and steady-state flow methods were used to calculate effective permeability (see below). (See also, e.g., "Absorbency" edited by P.K. Chatterjee, Elsevier, 1982, pp. 42-43, and "Chemical Engineering", Vol. II, Third Edition, J.M. Coulson and J.F. Richardson, Pergamon Press, 1978, pp. 122-127).

Contrary to previously published methods, the samples were not preswelled, so instead of forming hydrogels by preswelling the hydrogel-forming superabsorbent polymer particles in synthetic urine, the measurements were started with a dry structure.

The equipment used for this method is called " " or "Time-Dependent Permeability Tester", equipment number 03-080578 and commercially available at BRAUNGmbH, Frankfurter Str. 145, 61476 Kronberg, Germany, and as described below. Operating instructions, wiring diagrams are also available upon request and detailed technical drawings.

Dynamic Effective Permeability and Uptake Kinetics Measurement System

Figure 7 shows a dynamic effective permeability and uptake kinetics measurement system, referred to herein as a "time-dependent permeability tester".

The device consists of the following main components:

- Digital laser sensor 701 for M11 thickness measurement (MEL Mikroelektronik GmbH, 85386 Eching, Germany

-Fiber 702 for liquid level detection (FU95, Keyence Corp., Japan)

-Digital Fiber Sensor 703 (FS-N10, Keyence Corp., Japan)

- Precision Balance 704 (XP6002MDR, Mettler Toledo AG, 8606 Greifensee, Switzerland)

- Power unit logo! Power supply (C98130-A7560-A1-5-7519, Siemens AG)

-Labview Software License 706 (National Instruments, Austin, Tx, USA)

- Accept container 707 (5L Glass Beaker, Roth)

-Reservoir 708 (5L glass bottle, VWR) with connection 709 and open tube 723 for air intake

- Operating unit and console 705 (Conrad Electronics)

-Computerized data acquisition system 710

- Piston/roller assembly 713 as described herein

- control valve 714 (Bürkert)

FIG. 8 shows a piston/drum assembly 713 comprising a piston guide cover 801 , a piston 802 and a drum 803 . Roller 803 is made of transparent polycarbonate (such as ) and have an inner diameter p of 6.00 cm (area = 28.27 cm ² ). The inner drum wall 850 is smooth; the height r of the drum is about 7.50 cm. The bottom 804 side of the drum 803 is lined with US Standard 400 mesh stainless steel mesh (not shown) (eg, available from Weisse and Eschrich) which is bi-stretched to taut prior to attachment to the bottom 804 of the drum 803 . The piston 802 consists of a stainless steel piston body 805 and a stainless steel head 806 . The diameter q of the piston head 806 is slightly less than 6 cm in order to slide freely into the drum 803 without leaving any gaps for the gel forming particles to pass through. The piston body 805 is firmly attached vertically in the center of the piston head 806 . The piston body diameter t is about 2.2 cm. The piston body 805 is then inserted into the piston guide cover 801 . The guide cover 801 has a POM (polyoxymethylene) ring 809 which has a feature that allows the piston 802 to slide freely but keeps the piston body 805 completely vertical once the piston 802 with the guide cover 801 is positioned on top of the drum 803 and parallel to the diameter of the drum wall 850 . A top view of piston head 806 is shown in FIG. 9 . Piston head 806 is designed to apply pressure evenly to sample 718 . It is also highly permeable to hydrophilic liquids so as not to restrict liquid flow during measurements. Piston head 806 consists of US Standard 400 mesh stainless steel mesh 903 (eg, available from Weisse and Eschrich) which is bi-stretched to taut and secured at piston head stainless steel outer ring 901 . The entire bottom surface of the piston is flat. The stainless steel radial spokes 902 then ensure structural integrity and resistance to bending of the screen. The height of the piston body 805 is chosen such that the weight of the piston 802 consisting of the piston body 805 and the piston head 806 is 596 g (± 6 g), which divided by the area of the drum 803 corresponds to 0.30 psi. The piston guide cover 801 is an oblate stainless steel with a diameter s of about 7.5 cm held perpendicular to the piston body 805 by a POM ring 809 in its center. There are two inlets (810 and 812) in the boot cover.

A first inlet 812, allowing the level sensing fiber 702 to be positioned just above the top surface of a screen (not shown) attached to the bottom (804) of the drum 803 once the piston 802 is assembled with the drum 803 for measurement 5cm above. The second inlet 810 allows connection to a liquid tube 721 that supplies liquid to the experiment.

To ensure that the assembly of the piston 802 with the drum 803 proceeds consistently, slots 814 are made on the drum 803 to match the piston markings 813 in the guide cover 801 . In this way, the angle of rotation of the drum and of the guide cover is always the same.

Before each use, the piston head 806 and the stainless steel screen cloth 903 of the drum 803 should be inspected for clogging, holes or overstretching and replaced if necessary. A K(t) device with a damaged screen can provide erroneous K(t) and uptake kinetics results and must not be used until the screen is replaced.

A 5 cm mark 808 is scored on the drum at a height k of 5.00 cm (±0.02 cm) above the top surface of the screen attached to the bottom 804 of the drum 803 . This identifies the fluid content to be maintained during analysis. Position the level sensing fiber 702 exactly at the 5 cm mark 808 . Maintaining correct and constant fluid content (hydrostatic pressure) is critical to measurement accuracy.

Reservoir 708 connected via tubing to piston/drum assembly 713 holding samples and control valve 714 were used to deliver saline solution to drum 803 and maintain saline solution at 5.00 Å above the top surface of the screen attached to the bottom of drum 804 The level at height k in cm. The valve 714 , the fiber 702 for liquid level detection and the digital fiber sensor 703 are connected to the computerized acquisition system 710 through the operation unit 705 . This enables the dynamic effective permeability and uptake kinetics measurement system to control the valve 714 and ultimately maintain the fluid level at the 5 cm mark 808 using information from the fluid level sensing fiber 702 and the digital fiber sensor 703 .

The reservoir 708 was placed over the piston/roller assembly 713 in such a way that a 5 cm static head developed within 15 seconds of starting the test and remained in the roller throughout the test procedure. The piston/roller assembly 713 is positioned on the support ring 717 of the cover plate 716 and the first inlet 812 is held in place by the docking support 719 . This allows only one location for the boot cover 801 . Furthermore, due to the positioning marks 813, there is only one location for the drum 803 as well. The screen attached to the bottom of the drum 804 must be perfectly level and lying. The support ring 717 must have an inner diameter small enough to firmly support the drum 803, but larger than 6.0 cm to lay outside the inner diameter of the drum once positioned on the support ring 717. This is important in order to avoid any interference of the support ring 717 with the liquid flow.

Saline solution applied to sample 718 under a constant static head of 5 cm can now flow freely from piston/roller assembly 713 into receiving vessel 707 positioned on balance 704 accurate to within ±0.01 g. Connect the digital output of the balance to a computerized data acquisition system.

The thickness (thickness) of the sample is continuously measured by the digital laser sensor 701 for thickness measurement. The laser beam 720 of the digital laser sensor 701 is aimed at the center of the POM cover plate 811 of the piston body. The precise positioning of all components of the piston/roller assembly 713 allows the piston body 805 to be perfectly parallel to the laser beam 720 and thus obtain an accurate measurement of thickness.

test preparation

Reservoir 708 is filled with test solution. The test solution was an aqueous solution containing 9.00 grams of sodium chloride and 1.00 grams of surfactant per liter of solution. The preparation of the test solutions is described below. The receiving container 707 is placed on a balance 704 connected to a computerized data acquisition system 710 . Reset the balance to zero before starting the measurement.

Preparation of test liquid :

Chemical reagents required:

- Sodium Chloride (CAS No. 7647-14-5, eg: Merck, Cat. No. 1.06404.1000)

- linear C ₁₂ -C ₁₄ alcohol ethoxylates (CAS No. 68439-50-9, e.g. , Sasol, Italy)

- deionized H ₂ O

Ten liters of a deionized water solution containing 9.00 g/L NaCl and 1.00 g/L linear C12-C14 alcohol ethoxylate was prepared and equilibrated at 23°C ± 1°C for 1 hour. The surface tension was measured on 3 separate aliquots and should be 28 ± 0.5 mN/m. If the surface tension of the solution differs from 28 ± 0.5 mN/m, discard the solution and prepare a new test solution. Test solutions must be used within 36 hours of their preparation and are considered expired thereafter.

K(t) sample preparation

A representative circular section of a 6.00 cm diameter absorbent structure was obtained. This portion of the absorbent article may be obtained with a suitable circular die and hydraulic molding knife (eg Electro-Hydraulic Alfa Cutter 240-10 from Thwing-Albert Equipment Company, 14 W. Collings Ave. West Berlin, NJ 08091).

The circular sample 118 is carefully positioned flat on a screen (not shown) attached to the bottom 204 of the drum 203, occupying all available surface on the screen. It is important to orient the side of the circular sample 118 that is in direct contact with the screen to be the side that in use is generally further away from the liquid source in order to reproduce a common direction of flow in use. For example for samples related to absorbent articles such as diapers, typically the side facing the wearer should be positioned on top, while the side facing the garment should be positioned in contact with the screen at the bottom of the drum. Careful positioning of the sample is critical to the accuracy of the measurement. If the dimensions of the absorbent structure are so small that a 6.0 cm diameter sample cannot be obtained from it, it is possible to join two absorbent structures of equal size in order to obtain the minimum sample size required. The two samples need to be taken from the same location on two identical absorbent structures. The two absorbent structures should be joined by straight edges and, if necessary, they are cut to obtain such straight edges. The purpose of this is to recreate a flat homogeneous layer with no or only very small gaps at the joined edges. The bond layer was then processed according to the standard sample preparation described above, taking extra care to center the bond line in the cutting die so as to obtain two semicircles of the same shape. It is important to carefully position the two semicircles within the sample holder so as to reproduce the full circle and occupy the entire available surface on the screen with no or only minimal gaps. The two halves must be positioned with the sides facing the screen as described above. However, in most embodiments the sample will consist of an integral circular portion of the absorbent structure.

Method for extracting an absorbent structure from an absorbent article

Position the absorbent article on a flat surface. If the product contains structures that prevent it from flattening (such as hoop elastics), cut them at suitable intervals to allow the product to flatten.

The portion of the absorbent structure to be tested according to the K(t) test method which comprises at least 90% by weight of superabsorbent polymer particles is first identified and should be isolated as described below.

All material that is not a part of the absorbent structure is removed from the absorbent structure, taking care not to unduly damage the absorbent structure.

If the materials to be removed are attached to the absorbent structure, for example by means of an adhesive material such as a thermoplastic adhesive material, in order to avoid damaging the structure, it can be applied with a cooling temperature of -50 to -60°C by means of cold spraying. (such as "IT Icer" or "PRF101 Cold Spray" from Taerosol, Kangasala Finland) to remove them, as shown for example in Figure 15.

Figure 15 shows an absorbent structure 151 comprising superabsorbent polymer particles 152 sandwiched between two substrate layers 153,154. The material layer 156 is attached to one of the substrate layers 153 , 154 and thus is not part of the absorbent structure 151 . This layer needs to be removed from the absorbent structure 151 . To avoid excessive damage to the absorbent structure 151 , the material layer 156 to be removed from the absorbent structure 151 is pulled off the absorbent structure 151 with a 180° peel geometry while cooling the adhesive material 155 with cold spray 157 . The spraying should last at least 1 second but no longer than 5 seconds for each single portion of material layer 156 .

After each material was removed, the remainder of the absorbent structure was maintained at a pressure of 0.3 psi until the temperature returned to the original value (TAPPI laboratory conditions).

The upper and/or lower layer of the absorbent structure may be suitably perforated to allow liquid to flow through, as shown for example in Figure 16, which shows an absorbent structure 161 comprising superabsorbent polymer particles 162 sandwiched between two Between the base layer 163,164. Perforation is performed using a hot metal tip (also referred to as perforating tip 165 ), which comprises a steel rod 166 with a diameter H of 0.7 ± 0.2 mm. A standard paper clip bent around a solder tip 167 such as CT60/621 from ERSA GmbH, Wertheim, Germany can be used for this purpose. The punch tip 165 should be set at a temperature of 310±20°C. The perforating tip 165 is positioned in brief contact with the layers to be perforated at low pressure in order to perforate the layers, for example by melting without affecting any other material of the absorbent structure 161 . The holes were produced using the same protocol in a regularly arranged square hole pattern with a hole edge-to-edge distance D of 1 ± 0.2 mm, as shown for example in FIG. 17 .

The integrity of each absorbent structure was visually inspected with the aid of a backlight, and damaged absorbent structures were discarded. Examples of damage are eg cuts, holes, wrinkles which were not present before the absorbent structure was removed from the absorbent article. Perforations made in these layers with the punching tip are not considered damage unless they affect other layers. Substantial migration of superabsorbent polymer particles and fibers within the absorbent structure is also considered damage.

The absorbent structures thus produced were then cut according to the K(t) test method.

K(t) program

The measurements are carried out under Tappi laboratory conditions: 23°C ± 1°C/50% RH ± 2%.

An empty piston/roller assembly 713 is mounted in the circular opening of cover plate 716 and supported around its lower periphery by support ring 717 . Docking supports 719 are used to hold the piston/roller assembly 713 in place with the roller 803 and piston 802 aligned at the proper angle. The reference thickness reading (r _r ) is measured by a digital laser sensor. Thereafter, the empty piston/drum assembly 713 is removed from the cover plate 716 and the support ring 717 and piston 802 are removed from the drum 803 .

Sample 718 is positioned (absorbent structure) on the trommel screen as described above. Thereafter, the piston 802 combined with the guide cover 801 is carefully set in the drum 803 by matching the positioning mark 813 of the guide cover 801 with the slit 814 prepared in the drum 803 .

The piston/roller assembly is held in place with the butt support 719, with the roller and piston aligned at the proper angle.

This can be done in only one way. Connect liquid tube 721 to reservoir 708 and insert digital fiber sensor 703 into piston/drum assembly 713 via two inlets 810 and 812 in guide cover 801 .

A computerized data acquisition system 710 is connected to the balance 704 and to the digital laser sensor 701 for thickness measurement. The flow of liquid from the reservoir 708 to the drum 803 is initiated by the computer program opening the valve 714 . The drum is filled until the 5 cm mark 808 is reached within 5 to 15 seconds, after which the computer program adjusts the flow to maintain a constant 5 cm static head. The amount of solution passing through the sample 718 was measured by a balance 704 and the thickness increase was measured by a laser caliper. Data collection began when fluid flow was initiated, specifically when valve 714 was first opened, and continued for 21 minutes or until the reservoir ran dry such that the 5 cm static head was no longer maintained. The duration of one measurement is 21 minutes, the laser caliper and balance readings are recorded periodically at intervals that can vary from 2 to 10 seconds depending on the measurement range, and the measurement is repeated 3 times.

After 21 minutes, the measurement of the 1st replicate was successfully completed and the control valve 714 was automatically closed. The piston/roller assembly 713 was removed, and therefore the measurements of the 2nd and 3rd replicates were always performed according to the same procedure. At the end of the measurement of the 3rd replicate, the control valve 714 stops the liquid flow and closes the piston 722 of the reservoir 708 . The collected raw data is stored in the form of a simple spreadsheet, which can then be easily imported into programs for further analysis, such as Excel2003, SP3.

In the datasheet, the following information about each reading is reported:

· Time from start of experiment

The weight of the liquid collected by the receiving container 707 on the scale 704

·Thickness of sample 718

Data from 30 seconds to the end of the experiment were used in the K(t) and uptake kinetics calculations. Data collected during the first 30 seconds were not included in the calculation. The effective permeability K(t) and uptake kinetics of the absorbent structure were then determined using the following set of formulas.

The formula used :

The following table describes the symbols used in the formulas.

The drive pressure is calculated from the static head as follows:

Δp=h·G·ρ=4929.31g/(cm·s ² )

The thickness at each time t _i is calculated as the difference between the thickness sensor reading at time t _i and the reference reading without sample:

For samples of superabsorbent particles, the thickness of the sample at time t _i =0 (d ₀ ) was used to evaluate the amount of particles sprayed on.

The apparent sample density inside the drum can in fact be calculated as follows:

If the apparent density inside the drum differs by more than ±40% from that of the powder, the measurement must be considered invalid and eliminated.

Apparent density can be measured according to EDANA method 406.2–02 (“Superabsorbent materials-Polyacrylate superabsorbent powders-GRAVIMETRIC DETERMINATION OF DENSITY”)

The rate of change of the balance reading with time at time t _i is calculated as follows:

The rate of change of the thickness reading with time at time t _i is calculated as follows:

Uptake kinetics were calculated as follows:

The so-called dry sample volume (V _s ) represents the skeleton volume of the sample, so V _s is the actual volume occupied by the solid material in the dry sample, excluding possible pores and gaps.

_V can be calculated or measured by different methods known to those skilled in the art, for example, knowing the correct composition and skeletal density of the components, it can be determined as follows:

Alternatively, for an unknown material composition, _V can be easily calculated as follows:

The average density _ps can be determined by pycnometry using a suitable non-swelling liquid of known density. This technique cannot be performed on the same samples that are subsequently used for K(t) measurements, therefore, appropriate additional representative sample sets should be prepared for this experimental measurement.

From U(t) at different time periods calculated as described above, uptake at any particular time can be determined by linear interpolation. For example one of the important outputs is the uptake at 20 minutes, also known as U20 (in g/g).

From U(t) at different time periods, the time required to achieve certain uptakes can also be determined by linear interpolation. The time when the intake of 20 g/g was reached for the first time was called T20. Similarly, the time to reach any other uptake (eg T5 or T10) can be calculated accordingly. Knowing U20, the time to reach 80% of U20 can also be measured from U(t) at different time stages, and this performance is called T80%.

The effective permeability is calculated from the mass change rate and thickness change rate as follows:

The effective viscosity of the liquid depends on the temperature and was calculated during the experimental interval (23 °C ± 1 °C) according to the following empirical formula:

η＝A+B·T [g/(cm.s)]

where A = 1,479.10 ^-2 [g/(cm.s)], and B = -2.36.10 ^-4 [g/(cm.s.°C)]

From K(t _i ), the effective permeability at certain times can be calculated by linear interpolation. For example one of the important outputs is the uptake at 20 minutes, also known as K20( ^m2 ). Similarly, permeability at any other time (eg K5 or K10) can be calculated accordingly.

A further parameter derived from the data is Kmin, which is the smallest K(t) value measured over the entire curve in the interval _ti = 30s to _ti = 1200s. This value can be used to calculate Kmin/K20, which is the ratio between the minimum effective permeability and the permeability at 20 minutes. This parameter indicates that transient gel blocking may occur in some samples. If the value is close to 1, there is no transient gel blocking, and if the value is close to 0, it is an indication that the material underwent a strong drop in effective permeability when initially loaded with liquid.

The mean values of T20, T80%, K20, U20 and Kmin/K20 are reported from triplicate determinations according to the required precision known to those skilled in the art.

· Thickness measurement test method .

This method is intended to provide a procedure for determining the thickness of an absorbent core at the crotch point of an absorbent article. The test can be performed with a conventional caliper, such as the EG-225 type, which is purchased from ONO SOKKI Technology Inc., 2171 Executive Drive, Suite400, Addison, IL60101, USA, with a suitable meter stand, a 41mm diameter aluminum circular sample foot, made of The foot exerts a force of 10 gf. Add additional weights to achieve a total of 160gf, adjusting the pressure to 1.18kPa (0.173psi).

After determining the exact position of the absorbent core in the absorbent article when assembled, the thickness of the absorbent core is measured before assembling the absorbent core in the absorbent article. However, the thickness can also be measured after the absorbent core has been removed from the finished product by any suitable method known to those skilled in the art.

The crotch point of an absorbent article is measured at the intersection of the longitudinal and transverse centerlines of the article.

basic plan

1. All tests are carried out at 23±1°C and 50±2% relative humidity.

2. Allow the absorbent core to equilibrate for 8 hours at 23±1°C and 50±2% relative humidity.

3. Measure the crotch point as described above and mark on the wearer's surface of the absorbent core.

4. Position the absorbent core under the caliper with the surface of the wearer facing the sample contacting the foot and the center of the crotch point under said foot.

5. Gently lower the sample contact foot into contact with the surface of the absorbent core.

6. A reading is taken 5 seconds after the foot makes contact with the absorbent core.

· Urine Permeability Measurement (UPM) Test Method

Urine Permeability Measurement System

This method measures the permeability of a swollen hydrogel layer 1318 . The equipment used for this method is described below. This method is closely related to the prior art SFC (saline flow conductivity) test method.

Figure 10 shows a permeability measurement system 1000 equipped with a constant static head reservoir 1014, an open ended tube 1010 to admit air, a plug for refilling 1012, a test stand 1016, a transfer tube 1018, a piston 1020 , ring support frame 1022, receiving container 1024, balance 1026 and piston/roller assembly 1028.

FIG. 11 shows piston/roller assembly 1028 including metal weight 1112 , piston shaft 1114 , piston head 1118 , cover 1116 , and roller 1120 . Roller 1120 is made of transparent polycarbonate (such as ) and has an inner diameter p of 6.00cm, (area = 28.27cm2), wherein the inner drum wall 1150 is smooth. The bottom 1148 of the drum 1120 is covered with a US Standard 400 mesh stainless steel mesh (not shown) that is biaxially stretched to taut prior to attachment to the bottom 1148 of the drum 1120 . Piston shaft 1114 is made of transparent polycarbonate (such as ) made and has a total length q of approximately 127mm. The central portion 1126 of the piston shaft 1114 has a diameter r of 21.15 mm. The upper part 1128 of the piston shaft 1114 has a diameter s of 15.8 mm, forming the shoulder 1124 . The lower portion 1146 of the piston shaft 1114 has a diameter t of approximately 5/8 inches and is threaded to screw tightly into the central bore 1218 of the piston head 1118 (see FIG. 12 ). Piston head 1118 is perforated and made of clear polycarbonate (eg ) and was also fitted with stretched American Standard 400 mesh stainless steel mesh (not shown). The weight 1112 is stainless steel, has a central hole 1130 , slides onto the upper portion 1128 of the piston shaft 1114 and rests on the shoulder 1124 . The combined weight of piston head 1118 , piston shaft 1114 and weight 1112 is 596g (±6g), which is equivalent to 0.30psi on the area of drum 1120 . The combined weight can be adjusted by drilling a blind hole down the central axis 1132 of the piston shaft 1114 to remove material and/or provide a cavity to add weight. The drum cover 1116 has a first cover opening 1134 in its center for vertical alignment of the piston shaft 1114 and a second cover opening 1136 near the edge 1138 for introducing fluid from the constant static head reservoir 1014 into the drum 1120 .

A first linear indicator mark (not shown) is marked radially along the upper surface 1152 of the weight 1112 , transverse to the central axis 1132 of the piston shaft 1114 . A corresponding second linear indicator mark (not shown) is marked radially along the top surface 1160 of the piston shaft 1114 transverse to the central axis 1132 of the piston shaft 1114 . A corresponding third linear indicator mark (not shown) parallel to the central axis 1132 of the piston shaft 1114 is marked along the central portion 1126 of the piston shaft 1114 . A corresponding fourth linear indicator mark (not shown) is marked radially along the upper surface 1140 of the drum cover 1116 , transverse to the central axis 1132 of the piston shaft 1114 . Furthermore, along the lip 1154 of the drum cover 1116 a corresponding fifth linear indicator mark (not shown) parallel to the central axis 1132 of the piston shaft 1114 is scored. A corresponding sixth linear indicator mark (not shown) parallel to the central axis 1132 of the piston shaft 1114 is marked along the outer drum wall 1142 . Aligning the first, second, third, fourth, fifth, and sixth linear indicators so that the weight 1112, piston shaft 1114, drum cover 1116, and drum 1120 are in the same orientation relative to each other for each measurement re-locate.

The specification details of drum 1120 are:

The outer diameter u of the drum 1120: 70.35mm

Inner diameter p of the drum 1120: 60.0mm

Height v of roller 1120: 60.5mm

The specification details of drum cover 1116 are:

Outer diameter w of drum cover 1116: 76.05mm

Inner diameter x of drum cover 1116: 70.5mm

Thickness y of drum cover 1116 including lip 1154: 12.7mm

Thickness z of drum cover 1116 without lip 1154: 6.35 mm

Diameter a of the first cover opening 1134: 22.25 mm

Diameter b of the second cover opening 1136: 12.7mm

Distance between centers of first and second cover openings 1134 and 1136: 23.5mm

Weight 1112 specification details are:

Outer diameter c: 50.0mm

Diameter d of center bore 1130: 16.0mm

Height e: 39.0mm

The specification details of piston head 1118 are:

Diameter f: 59.7mm

Height g: 16.5mm

The outer holes 1214 (14 in total) have a diameter h of 9.65mm, and the outer holes 1214 are equidistant

Spaced apart, where the center is 47.8mm from the center of the center hole 1218

The inner holes 1216 (7 in total) have a diameter i of 9.65 mm, and the inner holes 1216 are equally spaced

Spaced apart, its center is 26.7mm from the center of the center hole 1218

The central bore 1218 has a diameter j of 5/8 inch and is threaded to accommodate the piston shaft

Lower portion 1146 of 1114 .

Prior to use, the piston head 1118 and the stainless steel mesh (not shown) of the drum 1120 should be inspected for clogging, holes or overstretched and replaced if necessary. Urine permeability measurement devices with damaged screens can output false UPM results and must not be used until the screen has been replaced.

A 5.00 cm mark 1156 is scored on the drum 1120 at a height k of 5.00 cm (±0.05 cm) above a screen (not shown) attached to the bottom 1148 of the drum 1120 . This identifies the fluid content to be maintained during analysis. Maintaining correct and constant fluid content (hydrostatic pressure) is critical to measurement accuracy.

A constant static head reservoir 1014 is used to deliver the saline solution 1032 to the drum 1120 and maintain the level of the saline solution 1032 at a height k of 5.00 cm above a screen (not shown) attached to the bottom 1148 of the drum 1120 . Position the bottom 1034 of the inlet tube 1010 so as to maintain the level of the saline solution 1032 in the drum 1120 at the desired height k of 5.00 cm during the measurement, i.e. when the drum 1120 is positioned on the support screen on the ring frame 1040 above the receiving vessel 1024 (not shown) the bottom 1034 of the intake tube 1010 lies in substantially the same plane 1038 as the 5.00 cm mark 1156 on the drum 1120 . Proper height alignment of the intake tube 1010 with the 5.00 cm mark 1156 on the drum 1120 is critical to the analysis. One suitable reservoir 1014 consists of a jar 1030 containing: a horizontally oriented L-shaped transfer tube 1018 for liquid transfer, a fixed cap for allowing air to be within the constant static head reservoir 1014 A vertically oriented open-ended tube 1010 at height, and a bung 1012 for refilling a constant static head reservoir 1014. Tube 1010 has an inner diameter of 12.5 mm ± 0.5 mm. A delivery tube 1018 located near the bottom 1042 of the constant static head reservoir 1014 contains a piston 1020 for starting/stopping saline solution 1032 delivery. The outlet 1044 of the transfer tube 1018 is sized to pass through the second cover opening 1136 on the drum cover 1116, the end of which is positioned below the surface of the saline solution 1032 in the drum 1120 (after the saline solution 1032 reaches 5.00 in the drum 1120 cm height). The intake tube 1010 is held in place with an O-ring retainer (not shown). The constant static head reservoir 1014 can be positioned on a laboratory crane 1016 so that its height is adjusted relative to the height of the drum 1120 . The components of the constant static head reservoir 1014 are sized to quickly fill the cylinder 1120 to a desired height (ie, static head) and maintain that height throughout the measurement period. The constant static head reservoir 1014 must be able to deliver saline solution 1032 at a flow rate of at least 3 g/s for at least 10 minutes.

The piston/roller assembly 1028 is positioned on a 16 mesh rigid stainless steel support screen (not shown) (or equivalent) supported on ring frame 1040 or a suitable alternative rigid frame. The support screen (not shown) is sufficiently permeable so as not to impede the flow of the saline solution 1032, and sufficiently rigid to support the stainless steel mesh (not shown) from being stretched. The support screen (not shown) should be flat and level to avoid tipping of the piston/roller assembly 1028 during testing. Saline solution 1032 that passes through the support screen (not shown) is collected within a receiving container 1024, which is positioned below (but not supported by) the support screen (not shown). The receiving container 1024 is placed on a balance 1026 with an accuracy of at least 0.01 g. The digital output of the balance 1026 is connected to a computerized data acquisition system (not shown).

Preparation of reagents (not shown)

Jayco synthetic urine (JSU) 1312 (see Figure 13) was used as the swelling phase (see UPM procedure below), while 0.118M sodium chloride (NaCl) solution was used as mobile phase (see UPM procedure below). The following preparations are based on a standard 1 liter volume. If volumes other than 1 liter are prepared, all quantities are therefore weighed proportionally.

JSU : Fill a 1 L volumetric flask to 80% of its volume with distilled water and place a magnetic stirring bar in the volumetric flask. Weigh the following dry ingredients (accurate to ±0.01 g) with weighing paper or a beaker using an analytical balance, and quantitatively add them to a volumetric flask in the same order listed below. Stir the solution on a suitable stir plate until all solids are dissolved, remove the stir bar, and dilute the solution to a volume of 1 L with distilled water. Place the stir bar again and stir the solution on the stir bar for an additional few minutes.

Amount of salt to prepare 1 liter of Jayco synthetic urine:

Potassium chloride (KCl) 2.00g

Sodium sulfate ( _Na2SO4 ) 2.00g

Ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) 0.85g

Diammonium hydrogen phosphate ((NH ₄ ) ₂ HPO ₄ ) 0.15g

Calcium chloride (CaCl ₂ ) 0.19g–[or hydrated calcium chloride (CaCl ₂ 2H ₂ O) 0.25g]

Magnesium chloride (MgCl ₂ ) 0.23g–[or hydrated magnesium chloride (MgCl ₂ 6H ₂ O) 0.50g]

To make preparation quicker, each salt is completely dissolved before adding the next. Jayco Synthetic Urine can be stored in a clean glass container for 2 weeks. If the solution becomes cloudy, the solution should not be used again. Shelf life in a clean plastic container is 10 days.

0.118M sodium chloride (NaCl) solution : 0.118M sodium chloride was used as the saline solution 1032 . Weigh out 6.90 g (±0.01 g) of sodium chloride using weighing paper or a beaker and quantitatively transfer it to a 1 L volumetric flask; and fill the volumetric flask with distilled water. Add a stir bar and stir the solution on a stir plate until all solids are dissolved.

test preparation

A thickness gauge (not shown) (eg, Mitotoyo Digimatic Height Gage) is set to a reading of zero using a solid reference cylindrical weight (not shown) (40 mm diameter; 140 mm height). This operation is conveniently performed on a smooth and level bench 1046 . Place the piston/roller assembly 1028 without superabsorbent polymer particles under a caliper (not shown) and record the reading _L1 to the nearest 0.01 mm.

The constant static head reservoir 1014 is filled with saline solution 1032 . The bottom 1034 of the inlet tube 1010 was positioned so as to maintain the top (not shown) of the liquid meniscus (not shown) in the cylinder 1120 at the 5.00 cm mark 1156 during the measurement. Proper height alignment of the intake tube 1010 at the 5.00 cm mark 1156 on the drum 1120 is critical to the analysis.

The receiving container 1024 is placed on a balance 1026, and the digital output of the balance 1026 is connected to a computer-processed data acquisition system (not shown). A ring stand 1040 with a 16 mesh rigid stainless steel support screen (not shown) is placed over the receiving vessel 1024 . The 16 mesh screen (not shown) should be rigid enough to support the piston/drum assembly 1028 during measurement. The support screen (not shown) must be flat and level.

UPM program

Using an analytical balance, weigh 1.5 g (±0.05 g) of superabsorbent polymer particles onto a suitable weighing paper or weighing aid. The moisture content of the superabsorbent polymer particles is measured according to Edana Moisture Content Test Method 430.1-99 ("Superabsorbent materials - Polyacrylate superabsorbent powders - Moisture Content - weight loss upon heating" (February 99)). If the moisture content of the superabsorbent polymer particles is greater than 5%, the superabsorbent polymer particle weight should be corrected for moisture (ie in this particular case the added superabsorbent polymer particles should be 1.5 g on a dry weight basis).

An empty drum 1120 is placed on a horizontal table 1046 and superabsorbent polymer particles are quantitatively transferred into the drum 1120 . The superabsorbent polymer particles are evenly dispersed over a screen (not shown) attached to the bottom 1148 of the drum 1120 by gently shaking, rotating, and/or tapping the drum 1120 . Even distribution of particles on a screen (not shown) attached to the bottom 1148 of the drum 1120 is critical to obtaining the highest precision results. After the superabsorbent polymer particles have been evenly distributed on a screen (not shown) attached to the bottom 1148 of the drum 1120, the particles must not adhere to the inner drum wall 1150. The piston shaft 1114 is inserted through the first cover opening 1134 with the lip 1154 of the cover 1116 facing towards the piston head 1118 . The piston head 1118 is carefully inserted into the drum 1120 to a depth of a few centimeters. The cover 1116 is then placed onto the upper edge 1144 of the drum 1120 while being careful to keep the piston head 1118 away from the superabsorbent polymer particles. The cover 1116 and piston shaft 1126 are then carefully rotated so that the third, fourth, fifth and sixth linear index marks are aligned and then aligned. The piston head 1118 is then lowered slightly (through the piston shaft 1114) to rest on the dry superabsorbent polymer particles. The weight 1112 is placed on the upper portion 1128 of the piston shaft 1114 so that it rests on the shoulder 1124 such that the first and second linear index marks are aligned. The proper placement of the cover 1116 prevents adhesion of the weights on the hydrogel layer 1318 and ensures even distribution.

Swelling phase : Saturate an 8 cm diameter sintered disk (7 mm thick; eg Chemglass Inc. #CG201-51, large porosity) 1310 by adding excess JSU 1312 to the sintered disk 1310 until the sintered disk 1310 is saturated. The saturated frit 1310 was placed in a wide flat bottom Petri dish 1314 and JSU 1312 was added until it reached the top surface 1316 of the frit 1310 . The height of the JSU must not be greater than the height of the sintering tray 1310 .

A screen (not shown) attached to the bottom 1148 of the drum 1120 stretches easily. To prevent stretching, apply lateral pressure on the piston shaft 1114 with the index finger just above the cover 1116 while grasping the roller 1120 of the piston/roller assembly 1028 . This "locks" the piston shaft 1114 in place against the cover 1116 so that the piston/drum assembly 1028 can be lifted without exerting undue force on the screen (not shown).

The entire piston/roller assembly 1028 is lifted in this manner and placed on a sintering disc 1310 in a petri dish 1314 . JSU 1312 from Petri dish 1314 passes through sintered disc 1310 and is absorbed by superabsorbent polymer particles (not shown) to form hydrogel layer 1318 . The JSU1312 available in the Petri dish 1314 should be sufficient for all swelling phases. If desired, more JSU 1312 can be added to the Petri dish 1314 during hydration to keep the JSU 1312 level at the top surface 1316 of the sintering tray 1310 . After a period of 60 minutes, the piston/roller assembly 1028 was removed from the sintering disc 1310, taking care to lock the piston shaft 1114 against the cover 1116 as described above and ensure that the hydrogel layer 1318 did not lose JSU 1312 or Inhale air. Place the piston/roller assembly 1028 under a caliper (not shown) and record the reading _L2 to the nearest 0.01mm. If the reading changes over time, only the initial value is recorded. The thickness L ₀ of the hydrogel layer 1318 is determined by L ₂ −L ₁ to the nearest 0.1 mm.

The piston/roller assembly 1028 is transferred to a support screen (not shown) attached to the ring support frame 1040, taking care to lock the piston shaft 1114 in place against the cover 1116. The constant static head reservoir 1014 is positioned such that the transfer tube 1018 is placed through the second cover opening 1136 . Initiate measurements in the following order:

a) Open the piston 1020 of the constant static head reservoir 1014 to allow the saline solution 1032 to reach the 5.00 cm mark 1156 on the drum 1120 . This saline solution 1032 level should be obtained within 10 seconds of opening the plunger 1020 .

b) Once 5.00 cm of saline solution 1032 is obtained, the data collection procedure is initiated.

The mass of the saline solution 1032 passing through the hydrogel layer 1318 was recorded at 20 second intervals for 10 minutes by means of a computer (not shown) attached to the balance 1026 . At the end of 10 minutes, the piston 1020 on the constant static head reservoir 1014 was closed.

Data from 60 seconds to the end of the experiment were used in the UPM calculations. Data collected before 60 seconds are not included in the calculation. Flow F _s (in g/s) is the slope of a linear least squares fit to a plot of weight (in grams) of saline solution 1032 collected as a function of time (in seconds) from 60 seconds to 600 seconds.

The urine permeability measurement (Q) of the hydrogel layer 1318 is calculated using the following formula:

Q=[F _g ×L ₀ ]/[ρ×A×ΔP],

where F _g is the flow rate determined by the regression analysis of the flow results in g/s, _L0 is ^the initial thickness of the hydrogel layer 1318 in cm, and ρ is the density of the saline solution 1032 in gm/cm . A (from the formula above) is the area of the hydrogel layer 1318 in cm ² , ΔP is the hydrostatic pressure in dyne/cm ² , and the urine permeability measurement Q is in cm ³ s/gm . The average of three determinations should be reported.

· FSR test method

This method determines the swelling rate of superabsorbent polymer particles, especially polymer hydrogel particles such as crosslinked polyacrylates, in a 0.9% saline solution (0.9 mass % NaCl aqueous solution). The measurement principle is to allow superabsorbent polymer particles to absorb a known amount of fluid and to measure the time it takes to absorb the fluid. The results are then expressed as grams of absorbed fluid in grams of material/second. All tests were performed at 23±2°C.

A representative sample of four grams of superabsorbent polymer particles was dried in an uncovered 5 cm diameter petri dish at 23±2°C and 0.01 Torr or less in a vacuum chamber for 48 hours prior to measurement.

About 1 g (+/- 0.1 g) of the test sample was removed from the vacuum chamber and immediately weighed (to the nearest 0.001 g) into a 25 mL beaker having an inner diameter of 32 to 34 mm and a height of 50 mm. Spread the material evenly over the bottom. 20 g of 0.9% saline was weighed (to the nearest +/- 0.01 g) into a 50 mL beaker and then carefully but quickly poured into the beaker containing the test material. Start the timer as soon as the liquid touches the material. The beaker was not moved or stirred during swelling.

When the last portion of undisturbed fluid is touched by the swelling particle, stop the timer and record the time to the nearest second (or more precise if appropriate). To increase the reproducibility of the endpoint assay, the liquid surface can be illuminated with a small lamp without heating the surface with the lamp. Weigh the beaker again to determine the actual liquid drawn up to within ±0.1 g.

The free swell rate is calculated by dividing the weight of the superabsorbent polymer particle by the amount of liquid actually picked up and dividing the result by the time required for this uptake, and is expressed as "g/g/s". Three measurements were taken and the results averaged to obtain the FSR value in g/g/s, reported to 3 significant figures.

· Flat Acquisition Test Method

This method determines the wearer's designed baby diapers (such as Pampers Active Fit in size 4 or other Pampers baby diapers in size 4, Huggies baby diapers in size 4 or most other branded baby diapers) usually having a weight in the range of 8 to 13 kg ± 20%. collection time for baby diapers of size 4).

equipment

The test equipment is shown in Figure 14 and consists of polycarbonate (e.g. ), groove 1411 with a nominal thickness of 12.5 mm (0.5 inches). The slot 1411 comprises a straight horizontal base 1412 having a length of 508 mm (20.0 inches) and a width of 152 mm (6.0 inches). Two straight vertical sides 1413 of 64 mm (2.5 inches) high by 508 mm (20 inches) in length are attached to the long edge of the base 1412 to form a U-shaped slot 1411 having a length of 508 mm (20.0 inches) , 152mm (6.0 inches) internal width, and 51mm (2.0 inches) internal depth. The front and rear ends of the groove 1411 are not closed.

Wrap an open-cell polyurethane foam block 1414 with dimensions of 508×152×25 mm in polyethylene film, and place the foam 1414 at the bottom of the groove 1411 in a way that the edge of the groove 1411 is aligned, and the upper surface of the polyethylene film film is Smooth with no seams, wrinkles or blemishes. Polyurethane foam 1414 has a compressive modulus of 0.48 psi. Using an indelible marker, draw a reference line parallel to the transverse centerline 152 mm (6.0 inches) across the width of the upper surface of the polyethylene cover from one end (front edge).

The straight polycarbonate top plate 1415 has a nominal thickness of 12.5 mm (0.5 inches), a length of 508 mm (20.0 inches), and a width of 146 mm (5.75 inches). A 51 mm (2.0 inch) diameter hole was drilled in the center of the top plate 1415 (ie, the hole was centered at the intersection of the longitudinal and transverse axes of the upper surface of the top plate 1415). A polycarbonate roller 1416 having an outer diameter of 51 mm (2.0 inches), an inner diameter of 37.5 mm (1.5 inches), and a height of 102 mm (4.0 inches) was glued into the hole in the top plate 1415 such that the bottom edge of the roller 1416 was in contact with the bottom edge of the top plate 1415. The lower surface is flush and the roller 1416 protrudes 89mm (3.5 inches) vertically above the upper surface of the top plate 1415, and the seam between the roller 1416 and the top plate 1415 is watertight. An annular groove 1417 having a height of 2 mm and a diameter of 44.5 mm (1.75 inches) is machined into the bottom inner edge of the drum 1416 . Two 1 mm diameter holes were drilled on the upper surface of the top plate 1415 at a 45° angle such that the holes intersected the inner surface of the drum 1416 directly above the groove 1417 and at opposite sides of the drum 1416 (i.e. 180° apart). Two stainless steel wires 1418 with a diameter of 1 mm were glued into the holes in a watertight manner so that one end of each wire was flush with the inner drum wall and the other end protruded from the upper surface of the top plate 1415. These wires are hereinafter referred to as electrodes. Across the width 152 mm (6.0 inches) of the top panel 1415, draw a reference line from the front edge parallel to the transverse centerline. The top plate 1415/drum 1416 assembly has a weight of approximately 1180 grams.

Two steel weights are also required, each weighing 9.0 Kg and measuring 146 mm (5.75 inches) wide, 76 mm (3.0 inches) deep, and approximately 100 mm (4 inches high).

procedure :

All tests were performed at 23±2°C and 35±15% relative humidity.

The polycarbonate tank 1411 containing the wrapped foam block 1414 is placed on a suitable flat level surface. Remove the disposable absorbent product from its packaging, and cut the cuff elastic at appropriate intervals so that the product lays flat. The product is weighed to within ±0.1 grams on a suitable top loading balance and then placed on the covered foam block 1414 in the collection device with the front waist edge of the product aligned with the fiducial marks on the polyethylene cover. Center the product along the longitudinal centerline of the device with the topsheet (body side) of the product facing up and the rear waist edge toward the rear end of the foam block 1414. Place the top plate 1415 on top of the product with the raised rollers facing up. The drawn reference line is aligned with the front waist edge of the product and the rear end of the top panel 1415 is aligned with the rear edge of the foam block 1414 . The two 9.0 Kg weights were then gently placed on the top plate 1415 so that the width of each weight was parallel to the transverse centerline of the top plate, and each weight was 83mm (83 mm) from the front or rear edge of the top plate 1415. 3.25 inches).

Appropriate electrical circuitry is connected to the two electrodes to detect the presence of conductive fluid between them.

A suitable pump such as model 7520-00 supplied by Cole Parmer Instruments (Chicago, USA) or equivalent is set to discharge up to a 0.9 mass % aqueous solution of sodium chloride through a flexible plastic tube having a diameter of 4.8 mm (3/16 inch) inside diameter, such as R-3603 or equivalent. The end portion of the tube was clamped vertically so that it was centered within a drum 1416 attached to a top plate 1415 with the discharge end of the tube facing down and 50 mm (2 inches) below the upper edge of the drum 1416. The pump was operated via a timer and pre-calibrated to discharge a 75.0 mL gush of 0.9% saline solution at a rate of 15 mL/s.

The pump is activated and a timer is started immediately upon activation. The pump delivers 75 mL of 0,9% NaCl solution to the drum 1416 at a rate of 15 mL/s and then stops. As the test fluid is introduced into the drum 1416, it typically accumulates to some extent on top of the absorbent structure. This fluid completes the electrical circuit between the two electrodes in the drum. After the gush has been delivered, the meniscus of the fluidic solution droplet is absorbed into the structure. The time was noted when the circuit was interrupted due to the absence of free fluid between the electrodes in the drum.

The acquisition time for a particular inrush is the time interval between the point at which the pump for that inrush was activated and when the circuit was interrupted.

Four gushes were delivered to the product in this manner; each gush was 75 mL and delivered at 15 mL/s. The time interval between the initiation of each gush is 300 seconds.

Record the acquisition time of the four surges. Three products were tested in this manner, and the average inrush time for each corresponding inrush (first to fourth) was calculated.

example

Absorbent structures according to the present disclosure have been prepared to compare their performance with that of prior art absorbent structures. All tested absorbent structures included superabsorbent polymer particles sandwiched between two substrate layers made of nonwoven material. For the data given in Table 1, all samples have been taken from the absorbent core. The sample corresponds to the portion of the absorbent core of an absorbent article (size 4) centered on the longitudinal centerline of the article at a distance of 152 mm from the front waist edge of the article. In the portion of the absorbent core where the samples were taken, the absorbent structures of Examples 1 and 2 and Comparative Examples 1 and 2 had the same structure. They differ only in the superabsorbent polymer particles used. For the data given in Table 2, the overall absorbent structures of Example 2 and Comparative Examples 1 and 2 have the same structure and differ only in the superabsorbent polymer particles used.

·Comparative example 1

An absorbent structure comprising the same superabsorbent polymer particles as used in Pampers Active Fit diapers commercially available in the UK in August 2010 has been prepared. These superabsorbent polymer particles are generally prepared according to US2009/0275470A1. It should be noted that the superabsorbent polymer particles can be separated from commercially available Pampers Active Fit diapers as described in European patent application n° 10154618.2 entitled "Method of separating superabsorbent polymer particles from a solidified thermoplastic composition comprising polymers" .

The standard particle size distribution of the superabsorbent polymer particles is from 45 to 710 μm, with a maximum of 1% below 45 μm and a maximum of 1% above 710 μm.

·Comparative example 2

300 g of superabsorbent polymer particles have been prepared according to Comparative Example 11 disclosed in PCT patent application WO2010/095427A1 entitled "Polyacrylic acid-based water-absorbing resin powder and method for producing the same". An absorbent structure comprising such superabsorbent polymer particles has been prepared.

·Instance 1

4000 kg of the superabsorbent polymer particles of Comparative Example 1 have been sieved over an AISI 304 standard 300 μm stainless steel wire mesh in a trommel sieve plant having a capacity of about 100-150 kg/hour, resulting in 750 kg having a median diameter of about 180-200 μm ( D50) and a particle size distribution of 45 to 300 μm, with a maximum of 3% of superabsorbent polymer particles below 45 μm and a maximum of 3% above 300 μm. An absorbent structure comprising such superabsorbent polymer particles has been prepared.

·Instance 2

300 g of superabsorbent polymer particles have been prepared according to Example 9 disclosed in PCT patent application WO2010/095427A1 entitled "Polyacrylic acid-based water-absorbing resin powder and method for producing the same". An absorbent structure comprising such superabsorbent polymer particles has been prepared.

Several parameters of the absorbent structures of Examples 1 and 2 and Comparative Examples 1 and 2 have been measured: time to reach an uptake of 20 g/g (T20), uptake at 20 min (U20) have been measured according to the above K(t) test method , time to uptake of 80% of U20 (T80%), effective permeability at 20 minutes (K20) and instantaneous gel blocking index (Kmin/K20). The UPM (urine permeability measurement) of the superabsorbent polymer particles of the absorbent structures of Examples 1 and 2 and Comparative Examples 1 and 2 have been measured according to the UPM test method described above. The CRC (centrifuge retention capacity) of superabsorbent polymer particles has been measured according to EDANA method WSP241.2-05.

Figures 18A and 18B show the uptake in g/g of Comparative Examples 1 and 2 versus the absorbent structures of Examples 1 and 2 as a function of time measured according to the K(t) test method described above.

The differences in the measured parameters are summarized in Table 1 below.

Table 1

As can be seen from Figures 18A and 18B and from Table 1, the time to 20 g/g uptake (T20) of the absorbent structures prepared according to Examples 1 and 2, as measured according to the K(t) test method, was significantly lower than that according to Comparative Example 1 and 2 prepared absorbent structures. Thus, these absorbent structures are capable of rapidly absorbing liquid even during the dry phase, ie upon initial exposure to liquid.

As can also be seen from Table 1, superabsorbent polymer particles having a high equilibrium permeability (high UPM value) such as the superabsorbent polymer particles of the absorbent structures of Comparative Examples 1 and 2 do not automatically lead to the inclusion of such superabsorbent polymer particles A high T20 value of an absorbent structure, which means that the equilibrium permeability of superabsorbent polymer particles is not a reliable criterion for selecting an absorbent structure capable of rapidly absorbing liquid upon initial exposure to liquid.

• Acquisition time for diapers with absorbent structures comprising superabsorbent polymer particles of Comparative Example 1 or 2 versus diapers with absorbent structures comprising superabsorbent polymer particles according to the present disclosure.

The acquisition time of Pampers Active Fit size 4 diapers commercially available in the UK in August 2010 was measured according to the "Flat Acquisition Test Method" described above. These diapers included an absorbent core comprising the superabsorbent polymer particles of Comparative Example 1. Acquisition time has been measured for the same diaper where the absorbent core has been replaced by an absorbent core of the same construction but in which the superabsorbent polymer particles have been replaced by superabsorbent polymer particles of Comparative Example 2 or Example 2 according to the Flat Acquisition Test Method described above . The absorbent cores of all diapers had a dry caliper at the diaper crotch point of 1.7 mm as measured according to the Thickness Measurement Test Method listed above. The values obtained for the acquisition times of all samples are summarized in Table 2 below.

Table 2

sample Comparative example 1 Comparative example 2 Example 2 Acquisition time of the first surge (75mL), unit is s 30 28 26

As can be seen from Table 2 above, the first gush acquisition time of diapers having an absorbent core comprising superabsorbent polymer particles according to Comparative Example 1 or 2 is higher than that of the superabsorbent polymer particles in which the superabsorbent polymer particles have been replaced by Example 2. Time to first gush collection of the same diaper replaced.

Accordingly, absorbent articles according to the present invention, i.e. absorbent articles comprising an absorbent structure comprising an absorbent structure in which one or more parts of the absorbent structure comprise At least 90% superabsorbent polymer particles and require a time to reach 20 g/g uptake (T20) of less than 440 s as measured according to the K(t) test method.

The dimensions and values disclosed herein are not to be understood as being strictly limited to the precise numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and a functionally equivalent range surrounding that value. For example, a dimension disclosed as "40mm" is intended to mean "about 40mm".

Claims (15)

1. An absorbent article comprising an absorbent structure, said absorbent article being divided into three parts: a front, a rear and a crotch disposed between said front and said rear, said absorbent structure comprising an absorbent A core having a dry thickness of 0.2 to 5 mm at the crotch point of the article, wherein one or more portions of the absorbent structure comprise at least 90% by weight superabsorbent polymer particles and require less than 440 s to reach Time to 20 g/g uptake (T20) measured according to the K(t) test method. 2. The absorbent article according to claim 1, wherein the center of one of the one or more parts of the absorbent structure is located on the center of the front of the article, and/or one or more of the absorbent structure One of the sections is centered at the crotch point of the article. 3. The absorbent article according to any one of the preceding claims, wherein the absorbent article further comprises a topsheet and a backsheet, wherein the absorbent core is interposed between the topsheet and the backsheet. 4. The absorbent article according to any one of the preceding claims, wherein one or more portions of the absorbent structure have an effective permeability at 20 minutes (K20) of at least 2.9·10 ⁻⁸ cm ² , said Effective permeability is measured according to the K(t) test method. 5. Absorbent article according to any one of the preceding claims, wherein one or more parts of the absorbent structure have an uptake (U20) at 20 min of at least 24 g/g, said uptake according to K(t) Measured by the test method. 6. The absorbent article according to any one of the preceding claims, wherein the absorbent core is free of airfelt. 7. Absorbent article according to any one of the preceding claims, wherein in the crotch portion of the article, the absorbent core comprises superabsorbent polymer particles in an average amount of 200 to 900 g/ ^{m2 per} the absorbent core surface area. 8. The absorbent article according to any one of the preceding claims, wherein the absorbent article has a first gush acquisition time of less than 27s, the acquisition time measured according to the flat acquisition test method. 9. The absorbent article according to any one of the preceding claims, wherein the superabsorbent polymer particles are contained in the absorbent core such that the superabsorbent polymer particles are deposited on the first substrate layer and the second substrate layer. Between the bottom layers, wherein said first substrate layer faces said backsheet, and said second substrate layer faces said topsheet. 10. The absorbent article of claim 9, wherein the superabsorbent polymer particles are secured by a thermoplastic adhesive material. 11. The absorbent article of claims 1-8, wherein the absorbent core comprises a first substrate layer, at least a portion of the superabsorbent polymer particles deposited on the first substrate layer, and Thermoplastic binder material that absorbs polymer particles. 12. The absorbent article of claim 11 , wherein the absorbent core further comprises a second substrate layer, at least a portion of the superabsorbent polymer particles deposited on the second substrate layer, and the superabsorbent polymer particles immobilized on the second substrate layer. a thermoplastic adhesive material of polymeric particles, the first substrate layer and the second substrate layer being brought together such that at least a portion of the thermoplastic adhesive material of the first substrate layer contacts a portion of the second substrate layer At least a portion of a thermoplastic adhesive material. 13. The absorbent article of claims 10 to 12, wherein the thermoplastic binder material forms a fibrous network over the superabsorbent polymer particles. 14. The absorbent article according to any one of the preceding claims, wherein at least one of the one or more portions of the absorbent structure has a surface area of 30 ^cm2 or greater. 15. The absorbent article of claim 14, wherein at least one of the one or more portions of the absorbent structure having a surface area of 30 ^cm2 or greater encompasses a circular area.