MX2014005627A

MX2014005627A - Absorbent articles with improved absorption properties.

Info

Publication number: MX2014005627A
Application number: MX2014005627A
Authority: MX
Inventors: Maike Thomann; Bruno Johannes Ehrnsperger; Marc Jennewein; Marion Lutsche; Andrea Peri
Original assignee: Procter & Gamble
Priority date: 2011-11-21
Filing date: 2012-11-19
Publication date: 2014-07-11
Also published as: IN2014DN03302A; RU2573344C1; BR112014012193A2; RU2014118637A; GB201407172D0; CN107080619A; CA2856581A1; WO2013078109A1; CA2856581C; JP2015501684A; CN103946685A; ZA201403490B; GB2510285A; CL2014001318A1; GB2510285B; DE112012004845T5; JP6054409B2; SG11201401933SA

Abstract

An absorbent article such as disposable diaper, training pant, and adult incontinence undergarment comprising an absorbent structure comprising superabsorbent polymer particles, the article being able to absorb and contain body exudates and having improved absorption properties and therefore being able to reduce leakage, especially at the first gush, i.e. when the article starts to be wetted.

Description

ABSORBENT ITEMS WITH IMPROVED ABSORPTION PROPERTIES FIELD OF THE INVENTION The present invention is directed to absorbent articles, such as disposable diapers, training pants and incontinence underwear in adults, comprising particles of superabsorbent polymers.

BACKGROUND OF THE INVENTION Absorbent articles, such as disposable diapers, training pants and incontinence underwear in adults, absorb and contain body exudates. Many absorbent articles, such as diapers, contain superabsorbent polymeric material. The superabsorbent polymers are typically present in the core of the absorbent articles in the particulate form. The particles of superabsorbent polymers have the ability to absorb liquids and swell when they come in contact with liquid exudates. However, in the past it has been shown that not all categories of superabsorbent polymer particles are equally suitable for use in an absorbent article.

It is known that to have absorbent articles comprising superabsorbent polymer particles that exhibit good absorption and containment functions, the superabsorbent polymer particles must meet specific technical requirements.

First, the superabsorbent polymer particles must be able to rapidly absorb liquid exudates. Generally, on the subject above, the absorption rate of the superabsorbent polymer particles has been characterized by measuring the free swell velocity (FSR) of the particles.

In addition to having a high absorption rate, the superabsorbent polymer particles present in the core must also be very permeable to liquids. Poor permeability of the superabsorbent polymer particles can induce leakage of the absorbent article due to blockage of the gel. Blocking of the gel can take place in the absorbent core when swelling superabsorbent polymer particles block the voids between the particles. In such a case, the liquid exudates can not reach, or can only reach slowly, the underlying layers of superabsorbent polymer particles disposed in the core. The liquid exudates remain on the surface of the absorbent core and can therefore leak out of the diaper.

Typically, in the prior art, the permeability of the superabsorbent polymer particles has been characterized by measuring the SFC (Conductivity of the saline flux) of the particles. This parameter is measured in equilibrium, that is, the measurement is made on a gel bed of fully swollen superabsorbent polymer particles.

However, the inventors have surprisingly discovered that absorbent cores comprising particles of superabsorbent polymers having high values of FSR and SFC do not automatically lead to rapid collection times of liquid exudates in the absorbent article, especially, in the first discharge, that is, when the absorbent cores come into contact with liquid for the first time.

The present invention therefore provides an absorbent article having improved absorption properties and, therefore, reduced leakage, especially, in the first discharge, that is, when the article begins to get wet.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to an absorbent article comprising an absorbent structure. The absorbent article is divided into three portions: a front portion, a rear portion and a crotch portion disposed between the front portion and the rear portion. The absorbent structure comprises an absorbent core. The absorbent core has a dry thickness at the crotch point of the article of 0.2 to 5 mm. One or more portions of the absorbent structure comprise at least 90% by weight of superabsorbent polymer particles and require a time to reach a pick-up of 20 g / g (T20) of less than 440 s as measured in accordance with the method of test K (t).

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a plan view of a diaper in accordance with an embodiment of the present invention.

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

Figure 3 is a partial cross-sectional view of an absorbent core layer in accordance with one embodiment of the present invention.

Figure 4 is a partial cross-sectional view of an absorbent core layer in accordance with another embodiment of the present invention.

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

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

Figure 6 is a schematic representation of a rheometer.

Figure 7 is a side view in partial cross-section of a suitable permeability measuring system when performing the test to determine the kinetics of uptake and effective dynamic permeability.

Figure 8 is a cross-sectional side view of a piston / cylinder unit for use in carrying out the test to determine the kinetics of uptake and effective dynamic permeability.

Figure 9 is a top view of a piston head suitable for use in the piston / cylinder unit shown in Figure 8.

Figure 10 is a side view in partial cross-section of a permeability measuring system suitable for carrying out the urine permeability measurement test.

Figure 1 1 is a cross-sectional side view of a piston / cylinder unit for use in carrying out the urine permeability measurement test.

Figure 12 is a top view of a piston head suitable for use in the piston / cylinder unit shown in Figure 11.

Figure 13 is a cross-sectional side view of the piston / cylinder unit of Figure 1 1 placed on a fritted glass disk for the phase of swelling Figure 14 is a cross-sectional view of a flat-state pick-up measurement system for carrying out the pick-up test in the flat state.

Figure 15 is a cross-sectional view of an absorbent structure to be tested in accordance with the test method K (t), wherein a layer of material that is not part of the absorbent structure is removed from the absorbent structure with the help of a cold spray.

Figure 16 is a cross-sectional view of an absorbent structure to be tested in accordance with the test method K (t) wherein the upper layer of the absorbent structure is perforated with a piercing tip.

Figure 17 is a top view of the perforation pattern according to which the upper or lower layer of an absorbent structure can be perforated.

Figure 18A is a graph depicting the g / g uptake as a time function for the absorbent structures of Comparative Examples 1 and 2 and Example 1, as measured in accordance with the test method K (t).

Figure 18B is a graph depicting the g / g uptake as a time function for the absorbent structures of Comparative Examples 1 and 2 and Example 2, as measured in accordance with the test method K (t).

DETAILED DESCRIPTION OF THE INVENTION As used in the present description, "absorbent article" refers to devices that absorb and contain body exudates and, more specifically, refers to devices that are placed against or close to the body of the user to absorb and contain the various exudates expelled from the body. Absorbent articles include diapers, training pants, incontinence underwear in adults, feminine hygiene products, and the like. As used in the present description, the terms "body fluids" or "body exudates" include, but are not limited to, urine, blood, vaginal discharges, breast milk, sweat and fecal matter. In some embodiments of the present invention, the absorbent article is a training diaper or brief.

In the present description, "absorbent core" is used to refer to a structure disposed between an upper canvas and a lower canvas 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 in one or more of the substrate layers and a thermoplastic composition typically disposed on the superabsorbent polymer particles. Typically, the thermoplastic composition is an adhesive thermoplastic material. The adhesive thermoplastic material can form a fibrous layer that is at least partially in contact with the superabsorbent polymer particles in one or more of the substrate layers and partially in contact with one or more of the substrate layers. The auxiliary adhesive may be deposited on one or more of the substrate layers prior to the application of the superabsorbent polymer particles to increase the adhesion of the superabsorbent polymer particles and / or the adhesive thermoplastic material to the respective (s) substrate layer (s). The absorbent core may further include one or more cover layers so that the superabsorbent polymer particles are disposed between one or more of the substrate layers and one or more of the cover layers. One or more of the substrate layers or cover layers may comprise or consist of a non-woven fabric, a tissue paper or a film, or combinations thereof. The absorbent core may further comprise compounds for controlling odors.

The absorbent core may consist essentially of one or more substrate layers, the superabsorbent polymer particles, the thermoplastic composition, optionally, the auxiliary adhesive, optionally, the cover layer (s) and, optionally, odor control compounds. .

The absorbent core may comprise superabsorbent polymer particles which are sandwiched between two layers, specifically, an upper layer and a lower layer without superabsorbent polymer particles on top of the upper layer and below the lower layer. The top layer corresponds to the substrate layer or cover layer of the absorbent core that is closest to the top canvas of the article, and the bottom layer corresponds to the substrate layer or cover layer of the absorbent core that is closest to the bottom canvas of the absorbent article. Alternatively, in the absence of an upper layer, the absorbent core may correspond to the structure that is disposed between the upper canvas and the lower layer or, in the absence of a lower layer, the absorbent core may correspond to the structure that is disposed between the upper layer and the lower canvas. In the absence of an upper layer and a lower layer, the absorbent core may correspond to the entire structure that is disposed between the upper canvas and the lower canvas of the absorbent article. The substrate layer (s) or cover layer (s) may comprise or consist of a nonwoven fabric, a tissue paper or a film or combinations thereof.

"Absorbent structure" is used in the present description to refer to one of the following structures: to. the absorbent core of the absorbent article in case the absorbent core comprises superabsorbent polymer particles that they are sandwiched between two layers, that is, an upper layer and a lower layer without superabsorbent polymer particles on top of the upper layer and below the lower layer. The top layer corresponds to the substrate layer or cover layer of the absorbent core that is closest to the top canvas of the article, and the bottom layer corresponds to the substrate layer or cover layer of the absorbent core that is closest to the bottom canvas of the absorbent article. b. The absorbent core of the absorbent article in combination with the upper canvas of the absorbent article in case the absorbent core does not comprise an upper layer as defined above; c. the absorbent core of the absorbent article in combination with the bottom canvas of the absorbent article in the event that the absorbent core does not comprise a bottom layer as defined above.

"Absorbent structure portion" is used in the present description to refer to a portion of the absorbent structure through the thickness of the absorbent structure, i.e., a portion of the absorbent structure comprising all the different layers that make up the structure absorbent in the respective portion.

"Front portion" and "back portion" are used in the present description to refer to the front and rear waist regions of the absorbent article. The length of the front portion and the rear portion is one third of the total length of the article starting from the respective front and rear waist edges. For embodiments wherein the front and / or rear waist edge is not configured as a straight line extending parallel to the transverse center line of the absorbent article, the length of the absorbent article is determined on or parallel to the longitudinal center line starting from the point of the front waist edge that is closest to the transverse center line and ending at the point of the posterior waist edge that is closest to the transverse center line.

"Crotch portion" is used in the present description to refer to the region of the article located in the center of the article between the front portion and the posterior portion of the article. The length of the crotch portion is one third of the total length of the article.

"Crotch point" is used in the present description to refer to the point of the article that is located in the center of the absorbent article at the intersection of the longitudinal center line and the transverse center line of the article. For purposes of the invention, it should be understood that the crotch point of the article is not necessarily located in the center of the absorbent core, ie, at the intersection of the longitudinal center line and the transverse center line of the absorbent core, especially , in the case that the absorbent core is not centered on the transverse center line of the article, that is, in the case that the absorbent core is displaced towards the front and / or rear of the article.

"Center of the front portion" is used in the present description to refer to the point of the absorbent article located at the intersection of the longitudinal center line of the article and the line that is parallel to the transverse center line of the article and which is located at a distance from the transverse centerline of one third of the total length of the absorbent article. For modalities where the front and / or rear waist edge is not configured as a straight line extending parallel to the line transverse center of the absorbent article, the length of the absorbent article is determined on or parallel to the longitudinal center line starting from the point of the leading waist edge that is closest to the transverse center line and ending at the point of the posterior waist edge that is closer to the transverse centerline.

"Understand", "understand" and "understand" are open terms that encompass, in addition, the terms "consist of", "consist of" "consist of" which are closed terms.

"Air felt" is used in the present description to refer to ground wood pulp, which is a form of cellulosic fiber.

"Super absorbent polymer particle" is used in the present disclosure to refer to crosslinked polymeric materials that can absorb at least 10 times their weight of a 0.9% aqueous saline solution as measured with the Centrifugal Holding Capacity test (EDANA, WSP 241 .2-05). The superabsorbent polymer particles are in particulate form to be fluid in the dry state. The preferred superabsorbent polymer particles of the present invention are made with poly (meta) acrylic acid polymers. However, for example, starch-based superabsorbent polymer particles are, moreover, within the scope of the present invention.

"Adhesive thermoplastic material" is used in the present disclosure to refer to a polymeric composition from which fibers can be formed and applied to the superabsorbent polymer particles with the intention of immobilizing the superabsorbent polymer particles both in the dry state and in the the wet state. The adhesive thermoplastic material of the present invention preferably forms a fibrous web on the superabsorbent polymer particles.

A "nonwoven fabric" is used in the present description to refer to a canvas, weft or wadding made with directionally or randomly oriented fibers, joined by friction and / or cohesion and / or adhesion, to the exclusion of paper and the products that they are woven, knitted, plush, joined by stitches that incorporate threads or filaments of union, or felted in wet, whether they are punched or not additionally. The fibers may be natural or artificial and be shortened or continuous filaments or formed in situ. Commercially available fibers have diameters ranging from less than 0.001 mm to more than 0.2 mm, approximately, and come in several different forms: Short fibers (known as staple or cut fibers), single continuous fibers (filaments or monofilaments), bundles non-woven continuous filaments (tow) and braided strands of continuous filaments (yarn). Non-woven fabrics can be formed by various processes, such as meltblowing, spunbonding, solvent-formed, electroforming and carding. The basis weight of the non-woven fabrics is usually expressed in grams per square meter (gm2).

"United" is used in the present description to refer to configurations by which a first element is directly secured to another element by fixing the first element directly to a second element or by means of which a first element is indirectly secured to a second element by fixing the first element to a third or more intermediate members that, in turn, are fixed to the second element. The joining means may comprise adhesive bonds, thermal bonds, pressure bonds, ultrasonic bonds, dynamic mechanical joints or any other suitable joining means or combinations of these joining means as is known in the art.

Figure 1 is a plan view of an absorbent article 10 in accordance with some embodiments of the present invention. The absorbent article 10 it is shown in its flat extended state without contracting (ie, without the elastic-induced contraction), and the portions of the absorbent article 10 are cut out to more clearly show the underlying structure of the diaper 10. A portion of the absorbent article 10 that contacting a user is directed towards the observer in Figure 1. The absorbent article 10 generally comprises a frame 12 and an absorbent core 14 disposed in the frame 12.

The frame 12 of the absorbent article 10 in Figure 1 may comprise the main body of the absorbent article 10. The frame 12 may comprise an outer cover 16 which includes an upper canvas 18, which may be liquid permeable, and / or a lower canvas 20, which can be impermeable to liquids. The absorbent core 14 may be enclosed between the upper canvas 18 and the lower canvas 20. The structure 12 may also include side panels 22, leg cuffs with elastic 24 and an elasticized waist 26.

The leg cuffs 24 and the elasticized waist 26 may generally comprise elastic elements 28. An end portion of the absorbent article 10 is configured as the front portion 30, and the other end portion is configured as the back portion 32. of the absorbent article 10. The intermediate portion of the absorbent article 10 is configured as the crotch portion 34, which extends longitudinally between the front and rear portions 30 and 32.

The absorbent article 10 is illustrated in Figure 1 with its longitudinal centerline 36 and its transverse centerline 38. The periphery 40 of the absorbent article 10 is defined by the outer edges of the absorbent article 10 in which the longitudinal edges 42 run, generally , parallel to the longitudinal center line 36 of the absorbent article 10, and the leading and trailing waist edges 43 and 44 run between the longitudinal edges 42 generally parallel to the transverse centerline 38 of the 1 absorbent article 10. The structure 12 may further comprise a fastening system which may include at least one fastening element 46 and at least one positioning area 48.

The absorbent article 10 may also include other features such as those known in the art, including front and back ear ps, waist cap features, elastics, and the like, to provide better aesthetic, fit and containment. These additional features are well known in the art and are described, for example, in U.S. Pat. UU num. 3,860,003 and 5,151,092.

For the purpose of keeping the absorbent article 10 in place around the user, at least a portion of the front portion 30 may be attached by the fastening member 46 to at least a portion of the rear portion 32 to form one or more openings for the legs and an article waist. When clamped, the clamping system carries a tension load around the waist of the article. The fastening system may allow a user of the article to take an element of the fastening system, such as the fastening member 46, and connect the front portion 30 to the rear portion 32 in at least two places. This can be achieved by manipulating the bonding forces between the elements of the fastening device.

According to certain embodiments, the absorbent article 10 can be provided with a resilient fastening system or alternatively can be provided in the form of a brief-type diaper. When the absorbent article is a diaper, it can comprise a fastening system which, in turn, can be re-closed together with the structure to secure the diaper to a wearer. When it is a brief type diaper, the absorbent article may comprise at least two side ps joined together to form a brief.

Absorbent structure The absorbent structure comprises superabsorbent polymer particles.

One or more portions of the absorbent structure comprise at least 90% by weight of superabsorbent polymer particles, based on the weight of the portion of the absorbent structure, which excludes the weight of any substrate layer and / or cover layer and / or upper canvas and / or lower canvas that could be included in the portion of the absorbent structure. One or more of the substrate layers or cover layers may comprise or consist of a nonwoven fabric, a tissue paper or a film, or combinations thereof.

One of one or more of the portions of the absorbent structure may be centered over the center of the front portion of the article and / or one of one or more of the portions of the absorbent structure may be centered over the crotch point of the article.

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

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

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

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

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

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

These embodiments are particularly preferred since absorbent articles comprising a high percentage of superabsorbent polymer particles typically have a reduced dry thickness compared to the thickness of conventional absorbent articles having a higher amount of conventional absorbent materials, such as as an air felt and the like in addition to the superabsorbent polymer particles. The reduced thickness helps to improve the fit and comfort when the article is placed on the user.

One or more of the portions of the absorbent structure require a time to reach a catch 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, as measured in accordance with the test method K (t) described below.

The time to reach a catch of 20 g / g (T20) can be 50 s to 440 s, or 100 s to 350 s, or 150 s to 300 s, as measured in accordance with the K (t) test method described later.

One or more of the portions of the absorbent structure can have an effective permeability in 20 minutes (K20) of at least 2.9-10"8 cm2 as measured in accordance with the test method K (t).

One or more of the portions of the absorbent structure can have an effective permeability in 20 minutes (K20) of at least 2.95- 10"8 cm2, or at least 3-10" 8 cm2, or 2.95- 10"8 cm2 a 1 .0- 10"6 cm2, or from 2.95- 10" 8 cm2 to 1 .0-10"7 cm2, or from 3.0-10-8 at 1.0- 107 cm2 as measured in accordance with the test method K (t) described below.

One or more of the portions of the absorbent structure may have a ratio between the minimum effective permeability and the permeability in 20 minutes (ratio of Kmin / K20) greater than 0.75, or greater than 0.8 or greater than 0.9, as measured in accordance with with the test method K (t) described later. In these modalities, the transient blockage of the gel is minimal, and the liquid exudates can quickly move through the empty spaces present between the particles during the entire swelling process and, especially, in the initial part of the swelling phase, which It is the most critical for the first download.

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

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

The absorbent articles comprising an absorbent structure have improved absorption properties and, therefore, exhibit reduced leaks compared to the absorbent articles of the previous material, especially, in the first discharge. These absorbent structures are particularly 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, the absorbent core comprises an average amount of superabsorbent polymer particles per area of 100 to 1500 g / m2, or 150 to 1000 g / m2., or from 200 to 900 g / m2, or from 400 to 700 g / m2 in the crotch portion of the article. The absorbent article comprises a sufficient amount of superabsorbent polymer particles to have good absorption properties as well as to be sufficiently thin and provide adjustment and comfort to the user. However, the superabsorbent polymer particles are present, in addition, in the front and rear portions, although especially, in the rear portion, the amount may be low (or even nil). In some embodiments, the absorbent core comprises an average amount of superabsorbent polymer particles per surface area of less than 300 g / m2, or less than 200 g / m2, alternatively, from 25 to 300 g / m2, or from 50 to 200 g / m2 or 50 to 100 g / m2 in the posterior portion of the article.

In some embodiments, the absorbent core may also comprise minor amounts of an absorbent material other than superabsorbent polymer particles, for example, air felt.

In some embodiments, the absorbent core typically comprises less than 5% by weight of air felt, preferably less than 2% and, most preferably, is free of air felt. In some embodiments, the absorbent structure may also be free of air felt.

The absorbent core has a dry thickness at the crotch point of the article of less than 10 mm, preferably, less than 5 mm, more preferably, less than 3 mm, still more preferably, less than 1.5 mm, alternatively, of 0.1 to 10 mm, preferably 0.2 to 5 mm, more preferably 0.3 to 3 mm, even more preferably 0.5 to 1.5 mm, as measured in accordance with the test method described later. The absorbent core is, therefore, sufficiently thin compared to conventional absorbent cores that contain air felt. Thus, adjustment and comfort are substantially improved.

Particles of superabsorbent polymer The superabsorbent polymer particles useful for the present invention can have various forms. The term "particles" refers to granules, fibers, flakes, spheres, powders, platelets and other shapes and forms known to persons skilled in the art of superabsorbent polymer particles. In some embodiments, the superabsorbent polymer particles may be in the form of fibers, ie, elongated acicular superabsorbent polymer particles. In those embodiments, the fibers of superabsorbent polymer particles have a smaller dimension (ie, fiber diameter) that is less than about 1 mm, usually less than 500 μ? T? and, preferably, less than 250 μ? up to 50 μ? t ?. The length of the fibers is preferably from about 3 mm to about 100 mm. The fibers may also be in the form of a long filament that can be woven.

Alternatively, in some preferred embodiments, the superabsorbent polymer particles of the present invention are spherical type particles. In accordance with the present invention and in contrast to the fibers, the "spherical-type particles" have a longer dimension and a smaller dimension, with a particulate ratio between the longest and the smallest dimension of the particle in the range of 1-5, wherein a value of 1 is equivalent to a perfectly spherical particle and a value of 5 allows some deviation of a spherical particle of this type. In these embodiments, the superabsorbent polymer particles may have a size of particle smaller than 850 μ? t ?, or 50 to 850 μ? t ?, preferably, 100 to 500 μ? and, more preferably, from 150 to 300 μp ?, as measured in accordance with the WSP 220.2-05 method of EDANA. The superabsorbent polymer particles having a relatively low particle size help to increase the surface area of the absorbent material that is in contact with liquid exudates and, therefore, support rapid absorption of the liquid exudates.

The superabsorbent polymer particles useful in the present invention include a variety of water insoluble, but swollen polymers in water, capable of absorbing large amounts of fluids. These polymeric materials are generally known in the art.

Suitable superabsorbent polymer particles can be obtained, for example, from reverse phase suspension polymerizations, as described in US Pat. UU num. 4,340,706 and 5,849,816, or from other spray dispersions or gaseous phase polymerizations, as described in the US patent applications. UU num. 2009/0192035, 2009/0258994 and 2010/0068520. In some embodiments, suitable superabsorbent polymer particles can be obtained by production processes of the current state of the art, as described more particularly from page 12, line 23, to page 20, line 27 of WO 2006/083584 .

In some embodiments, the surface of the superabsorbent polymer particles may be coated. In these embodiments, the coating causes the surface to be tacky so that the superabsorbent polymer particles can not be rearranged (and, therefore, can not block the empty spaces) easily upon wetting.

In some embodiments, the superabsorbent polymer particles may be coated with a cationic polymer. Preferred cationic polymers may include polyamine or polyimine materials that are reactive with at least one component included in bodily fluids, especially urine. Preferred polyamine materials can be selected from the group consisting of (1) polymers having primary amine groups (eg, polyvinylamine, polyallylamine); (2) polymers having secondary amine groups (e.g., polyethyleneimine); and (3) polymers having tertiary amine groups (e.g., poly N, N-dimethylalkylamine).

Practical examples of the cationic polymers are, for example, polyethyleneimine, a modified polyethylenimine which is crosslinked with epihalohydrin in a water-soluble range, polyamine, a polyamine-modified polyaminoamine, ethyleneimine, polyetheramine, polyvinylamine, polyalkylamine, polyamidopolyamine and polyallylamine.

In preferred embodiments, a cationic polymer has a weight average molecular weight of at least 500, more preferably 5,000, most preferably 10,000 or more. Cationic polymers having a weight average molecular weight of greater than 500 or greater are not limited to polymers exhibiting a single maximum value (peak) in a molecular weight analysis by gel permeation chromatography, and polymers having a Weighted average molecular weight of 500 or greater even when they exhibit several maximum values (peaks).

A preferable amount of the cationic polymer is in the range of about 0.05 to 20 parts by weight against 100 parts by weight of the superabsorbent polymer particle, more preferably, from about 0.3 to 10 parts by weight and, most preferably, from about 0.5 to 5 parts by weight.

In some embodiments, the superabsorbent polymer particles may be coated with chitosan materials, such as that described in US patent UU no. 7 537 832 B2.

In some other embodiments, the superabsorbent polymer particles may comprise mixed bed ion exchange absorbent polymers, such as that described in WO 99/34841 and WO 99/34842.

As already mentioned above, absorbent structures comprising particles of superabsorbent polymer having high values of SFC and FSR do not automatically lead to rapid collection times of liquid exudates, especially at the first discharge, ie when the dry absorbent structures come into contact with liquid for the first time. Without being limited by theory, it is thought that dried superabsorbent polymer particles are typically more reluctant to absorb water than wetted superabsorbent polymer particles, since the diffusivity of water in the dried superabsorbent polymer particles is lower. that the diffusion capacity of the water in the wetted superabsorbent polymer particles.

Heretofore, the absorption properties of dry absorbent structures comprising superabsorbent polymer particles relative to initial uptake have not been investigated. Instead, the focus has been on the conductivity of the saline flux (SFC) of the superabsorbent polymer particles, which is determined in equilibrium and, therefore, in a remote stage of the initial uptake of liquid. For absorbent structures that contain a significant amount of air felt in addition to superabsorbent polymer particles, temporary storage of liquid entering the absorbent core is provided by the air felt which allows the superabsorbent polymer particles to absorb liquid from the absorbent core. surrounding air with a certain delay. But even for air felt-free absorbent articles described in the previous material, the permeability of the superabsorbent polymer particles is always has measured in equilibrium, therefore, the behavior of dried superabsorbent polymer particles after an initial exposure to liquids is not taken into account. The inventors of the present invention have thoroughly investigated the performance of absorbent structures comprising particles of superabsorbent polymer after initial exposure to liquids. They have discovered that certain absorbent structures that are not yet publicly available that comprise superabsorbent polymer particles and very low or zero amounts of air felt exhibit superior performance. Superior performance has led to improved liquid uptake and thus reduces the risk of leaks. It has been found that higher performance absorbent structures comprising superabsorbent polymer particles can be described in terms of the time it takes for these dry absorbent structures comprising particles of superabsorbent polymer to achieve some uptake of liquids when absorbing against a confining pressure. In this way, it is now possible to select easily and intentionally these newly developed absorbent structures without the need for exhaustive research and additional tests.

In some embodiments, the absorbent structure comprises superabsorbent polymer particles with an equilibrium permeability expressed as UPM (Urine Permeability Measurement) value greater than 50, preferably, greater than 60, or 50 to 500, or 55 to 200 , or from 60 to 150 units of UPM, where 1 unit of UPM is 1 x 10 ~ 7 (cm3.s) / g.

The UPM value is determined in accordance with the UPM test method described below. This method is closely related to the CFS test method of the previous subject. The UPM test method typically measures the resistance to flow of a previously swollen layer of particles of superabsorbent polymer, that is, the resistance to flow is determined in equilibrium. Therefore, superabsorbent polymer particles having a high UPM value exhibit high permeability when a significant volume of the absorbent article has already been wetted with the liquid exudates. The absorbent structures comprising these superabsorbent polymer particles exhibit good absorption properties not only at the first discharge but also at subsequent discharges.

In some embodiments, the absorbent structure may comprise superabsorbent polymer particles having an FSR (free swell rate) value greater than 0.1 g / g / s, or from 0.1 to 2 g / g / s, or from 0.3 to 1 g / g / s, or from 0.3 to 0.6 g / g / s, or from 0.4 to 0.6 g / g / s.

The free swelling velocity of the superabsorbent polymer particles is determined in accordance with the FSR test method described below. Absorbent structures comprising superabsorbent polymer particles having high values for the rate of free swelling will be able to absorb liquid rapidly without any confining pressure. Contrary to the test method K (t), no external pressure is applied to the gel bed in order to measure the rate of free swelling. Absorbent structures comprising superabsorbent polymer particles having too low a FSR value may not require less than 440 s to achieve uptake of 20 g / g, as measured in accordance with the test method K (t) of the present invention and, therefore, will not be able to absorb liquid exudates with the necessary speed. However, as mentioned above, absorbent structures comprising superabsorbent polymer particles having a high FSR value do not automatically lead to high uptake values as measured in accordance with the test method K (t).

In some embodiments, the absorbent structure may comprise superabsorbent polymer particles having a CRC value (centrifugal holding capacity) greater than 20 g / g, or greater than 24 g / g, or 20 to 50 g / g, or from 20 to 40 g / g, or from 24 to 30 g / g, as measured in accordance with the WSP method 241 .2-05 of EDANA. The CRC measures the liquid absorbed by the superabsorbent polymer particles for free swelling in excess liquid.

Absorbent structures comprising superabsorbent polymer particles having a high CRC value are preferred since fewer particles of superabsorbent polymer are needed to provide a general capacity required for liquid absorption.

In some embodiments, the absorbent article may have a capture time for the first discharge of less than 30 s, preferably, less than 27 s, as measured in accordance with the flat-state acquisition test method described below. This collection time is measured in a baby diaper that is designed for users who weigh in the range of 8 to 13 kg ± 20% (such as Pampers Active Fit, size 4, or other Pampers baby diapers, size 4 , Huggies baby diapers, size 4, or baby diapers, size 4, of many other commercial brands). An absorbent article comprising an absorbent structure comprising particles of superabsorbent polymer and requiring less than 440 s to achieve uptake of 20 g / g, as measured in accordance with the K (t) test method, can provide uptake times faster, especially, in the first discharge and, therefore, reduced leaks compared to the absorbent articles of the previous material, as shown in the Examples section of the present application. 5 Structure of the absorbent core An example of an absorbent core of the present invention is given below. However, the present invention is not limited to these absorbent cores.

In some embodiments, the absorbent core 14 comprises an absorbent layer 60, as illustrated in Figures 3 and 4. The substrate layer 64 of the absorbent layer 60 can be referred to as a powder layer, and has a first surface 78 that is oriented to the lower canvas 20 of the diaper 10 and a second surface 80 that is oriented to the superabsorbent polymer particles 66. According to some embodiments, the substrate layer 64 is a nonwoven fabric material, such as a fabric material non-woven multilayer having thermally bonded filament layers as outer layers and one or more melt-blow layers between the thermally bonded filament layers, including, but not limited to, SMS material, comprising a layer of filaments thermally bonded, one melt-blown layer and one other layer of thermally bonded filaments. The absorbent layer 60 may include a cover layer 70, as illustrated in Figure 4. The cover layer 70 may be a nonwoven fabric material, such as a multilayer nonwoven fabric material having layers of filaments thermally bonded as outer layers and one or more melt-blown layers between the thermally bonded filament layers, including, but not limited to, SMS material, comprising a thermally bonded filament layer, a meltblown layer and another layer of thermally bonded filaments. In some embodiments, the substrate layer 64 and the cover layer 70 are made of the same material.

As illustrated in Figures 3 and 4, the superabsorbent polymer particles 66 can be deposited on the substrate layer 64 in groups 90 of particles comprising raised areas 94 and bonding areas 96 between raised areas 94. As defined in the present disclosure, raised areas 94 are areas where the thermoplastic adhesive material does not come into contact with the non-woven fabric substrate or the auxiliary adhesive directly; The bonding areas 96 are areas where the thermoplastic adhesive material comes into contact with the nonwoven fabric substrate or with the auxiliary adhesive directly. The bonding areas 96 contain very few or no superabsorbent polymer particles 66. The raised areas 94 and bonding areas 96 can have a variety of shapes including, but not limited to, circular, oval, square, rectangular, triangular and the similar.

In this way, the adhesive thermoplastic material 68 provides cavities for containing the superabsorbent polymer particles 66 and, thereby, immobilizes this material. In another aspect, the adhesive thermoplastic material 68 is bonded to the substrate layer 64 and thereby fixes the superabsorbent polymer particles 66 to the substrate layer 64. In some other embodiments, the adhesive thermoplastic material 68 penetrates, in addition , at least partially, in the superabsorbent polymer particles 66 and in the substrate layer 64, and thus provides immobilization and additional fixation.

In some other embodiments, the absorbent core 14 may comprise two absorbent layers, a first absorbent layer 60 and a second absorbent layer 62. As best illustrated in Figures 5A and 5B, the first absorbent layer 60 of the absorbent core 14 comprises a substrate layer 64, superabsorbent polymer particles 66 in the substrate layer 64, and an adhesive thermoplastic material 68 in the superabsorbent polymer particles 66. Although not illustrated, the first absorbent layer 60 may further include a layer of an absorbent layer. cover, such as the cover layer 70 illustrated in Figure 4.

Similarly, as best illustrated in Figures 5A and 5B, the second Absorbent layer 62 of absorbent core 14 may further include a substrate layer 72, superabsorbent polymer particles 74 in the second substrate layer 72, and an adhesive thermoplastic material 76 in the superabsorbent polymer particles 74. Although not illustrated, the second absorbent layer 62 may further include a cover layer, such as the cover layer 70 illustrated in Figure 4. As mentioned above, reference may be made to the substrate layer 64 of the first absorbent layer 60 as a layer of powder and has a first surface 78 that faces the lower canvas 20 of the diaper 10 and a second surface 80 that faces the superabsorbent polymer particles 66. Similarly, reference can be made to the substrate layer 72 of the second absorbent layer 62 as a core cover and has a first surface 82 facing the upper canvas 18 of the diaper 10 and a second surface 84 facing the parts. superabsorbent polymer 74. The first and second substrate layers 64 and 72 can adhere to each other with adhesive around the periphery to form a wrap around the superabsorbent polymer particles 66 and 74 and maintain the superabsorbent polymer particles 66 and 74 inside the absorbent core 14.

The area of the absorbent core 14 comprising particles of superabsorbent polymer can vary depending on the desired application of the absorbent core 14 and the particular absorbent article 10 into which it can be incorporated. In some embodiments, however, the area of the superabsorbent polymer particles extends substantially through the entire absorbent core 14. In some alternative embodiments, the superabsorbent polymer particle area extends fully through the absorbent core 14 in the crotch portion 34 of absorbent article 10 as long as the superabsorbent polymer particle area does not fully extend through the absorbent core 14 at the front and rear portions of the absorbent article 10.

The first and second absorbent layers 60 and 62 can be combined together to form the absorbent core 14 so that the layers can be moved so that the superabsorbent polymer particles 66 in the substrate layer 64 and the superabsorbent polymer particles 74 in the layer of substrate 72 are distributed substantially continuously through the superabsorbent polymer particle area, as illustrated in Figures 5A and 5B. In some embodiments, the superabsorbent polymer particles 66 and 74 are distributed substantially continuously through the superabsorbent polymer particle area although the superabsorbent polymer particles 66 and 74 are discontinuously distributed through the first and second polymeric particles. second layers of substrate 64 and 72 in groups 90. In some embodiments, the absorbent layers may be offset so that the raised areas 94 of the first absorbent layer 60 are oriented towards the bonding areas 96 of the second absorbent layer 62, and the raised areas of the second absorbent layer 62 are oriented towards the areas of union 96 of the first absorbent layer 60, as illustrated in Figures 5A and 5B. When the raised areas 94 and the bonding areas 96 are appropriately sized and sized, the resulting combination of superabsorbent polymer particles 66 and 74 is a substantially continuous layer of superabsorbent polymer particles through the superabsorbent polymer particle area of the absorbent core. 14 (i.e., the first and second substrate layers 64 and 72 do not form a plurality of cavities, each with a group 90 of superabsorbent polymer particles 66 and 74 therebetween), as shown in Figure 5A.

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

Typically, the adhesive thermoplastic material can serve to immobilize, at least partially, the superabsorbent polymer particles in both the dry and the wet state. The adhesive thermoplastic material can be arranged substantially uniformly between the superabsorbent polymer particles. However, typically, the adhesive thermoplastic material can be provided as a fibrous layer that is at least partially in contact with the superabsorbent polymer particles and partially in contact with the substrate layer (s). Typically, the adhesive thermoplastic material of the present invention forms a fibrous web on the superabsorbent polymer particles. Typically, as illustrated, for example, in Figures 5A and 5B, the superabsorbent polymer particles 66 and 74 are provided as a discontinuous layer, and a layer of fibrous adhesive thermoplastic material 68 and 76 is placed on the particle layer of superabsorbent polymer 66 and 74 such that the adhesive thermoplastic material 68 and 76 is in direct contact with the superabsorbent polymer particles 66 and 74, but also in direct contact with the second surfaces 80 and 84 of the substrate layers 64 and 72, wherein the substrate layers are not covered by the superabsorbent polymer particles 66 and 74. This imparts a substantially three-dimensional structure to the fibrous layer of adhesive thermoplastic material 68 and 76 which, for it is, practically, a two-dimensional structure of relatively small thickness in comparison with the dimension in the longitudinal and wide directions. In other words, the adhesive thermoplastic material 68 and 76 is crimped between the superabsorbent polymer particles 68 and 76 and the second surfaces of the substrate layers 64 and 72.

The adhesive thermoplastic material can provide cavities for bonding the superabsorbent polymer particles and thereby immobilize these particles. In another aspect, the adhesive thermoplastic material is bonded to the substrate layer (s) and, thereby, fixes the superabsorbent polymer particles to the substrate layer (s). Some adhesive thermoplastic materials also penetrate the superabsorbent polymer particles and the substrate layer (s) and thus provide immobilization and additional fixation. Of course, while the adhesive thermoplastic materials described in the present disclosure provide improved wet immobilization (ie, immobilization of the absorbent material when the article is at least partially loaded), these adhesive thermoplastic materials can also provide a very good immobilization of the absorbent material when the absorbent core is dry. The adhesive thermoplastic material can also be referred to as a hot-melt adhesive.

Without intending to be limited by theory, it has been discovered that these adhesive thermoplastic materials which are most useful for immobilizing the superabsorbent polymer particles combine a good cohesion and adhesion behavior. Good adhesion can promote adequate contact between the adhesive thermoplastic material and the superabsorbent polymer particles and the substrate layer (s). Proper cohesion reduces the likelihood that the adhesive will break, particularly in response to external forces and, specifically, in response to tension. When the absorbent core absorbs liquid, the superabsorbent polymer particles swell and subject the adhesive thermoplastic material to external forces. The adhesive thermoplastic material must allow such swelling without breaking or imparting too much compression forces, which would prevent the superabsorbent polymer particles from swelling.

The adhesive thermoplastic material may comprise, in its entirety, a single thermoplastic polymer or a blend of thermoplastic polymers, with a softening temperature, as determined by the ASTM D-36-95"Ring and Ball" method (ring and balloon). ), in the range between 50 ° C and 300 ° C or, alternatively, the adhesive thermoplastic material can be a hot melt adhesive comprising at least one thermoplastic polymer in combination with other thermoplastic diluents, such as tackifying resins, plasticizers and additives, as antioxidants. In some embodiments, the thermoplastic polymer typically has a molecular weight (MW) greater than 10,000 and a glass transition temperature (Tg), usually, lower than room temperature or -6 ° C < Tg < 16 ° C. In some embodiments, typical concentrations of the polymer in a hot melt are in the range of about 20 to about 40% by weight. In some embodiments, the thermoplastic polymers may be insensitive to water. Exemplary polymers are block copolymers (styrenics) which include ABA triblock structures, AB diblock structures and radial block (AB) n copolymer structures wherein the A blocks are non-elastomeric block polymers typically comprising polystyrene, and the B blocks are unsaturated conjugated diene or (partially) hydrogenated versions of them. Block B is typically isoprene, butadiene, ethylene / butylene (hydrogenated butadiene), ethylene / propylene (hydrogenated isoprene), or a mixture thereof.

Other suitable thermoplastic polymers that can be used are the metallocene polyolefins, which are ethylene polymers prepared by the use of single-center or metallocene catalysts. Also, at least one comonomer can be polymerized with ethylene to make a higher order copolymer, terpolymer or polymer. Also applicable are amorphous polyolefins or amorphous polyalphaolefins (APAOs), which are homopolymers, copolymers or terpolymers of C2 to C8 alpha olefins.

In some embodiments, the adhesive thermoplastic material is present in the form of fibers. In some of these embodiments, the fibers have an average thickness of from about 1 to about 50 microns or from about 1 to about 35 microns, and an average length from about 5 mm to about 50 mm or from about 5 mm to about 30 mm. To improve the adhesion of the adhesive thermoplastic material to the substrate layer (s) or to any other layer, particularly any other layer of non-woven fabric, these layers can be pre-treated with an auxiliary adhesive.

In certain embodiments, the adhesive thermoplastic material is applied on the substrate layer in an amount of between 0.5 and 30 g / m2, from 1 to 15 g / m2, between 1 and 10 g / m2 or even between 1.5 and 5 g / m2. g / m2 per substrate layer.

An illustrative adhesive thermoplastic material 68 and 76 may have a storage modulus G 'measured at 20 ° C of at least 30,000 Pa and less than 300,000 Pa, or less than 200,000 Pa, or from 140,000 Pa to 200,000 Pa, or less than 100,000 In a further aspect, the storage module G 'measured at 35 ° C may be greater than 80,000 Pa. In a further aspect, the storage module G' measured at 60 ° C may 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 module G 'measured at 90 ° C may be less than 200,000 Pa and greater than 10,000 Pa, greater than 20,000 Pa or greater than 30,000 Pa. The storage module measured at 60 ° C and 90 ° C can be a measure of the stability of the shape of the adhesive thermoplastic material at high ambient temperatures. This value is particularly important if the absorbent product is used in a warm climate, where the adhesive thermoplastic material would lose its integrity if the storage module G 'at 60 ° C and 90 ° C was not sufficiently high.

G 'is measured with a rheometer, as schematically illustrated in Figure 6 for illustrative purposes only. The rheometer 627 can apply a shear stress to the adhesive and measure the response to the resulting stress (the shear strain) at constant temperature. The adhesive is placed between a Peltier element, acting as a lower fixed plate 628, and an upper plate 629 with a radius R of 10 mm, which is connected to the stem of the drive unit of a motor to generate the shear stress. The space between both plates has a height H of 1500 microns. The Peltier element allows temperature control of the material (+0.5 ° C). The deformation amplitude is fixed at 0.05%, the deformation frequency at 1 Hz and the cooling rate at 2 ° C / min (with an initial temperature at 150 ° C or higher and a final temperature at -5 ° C) .

The absorbent core may further comprise an auxiliary adhesive which is not illustrated in the figures. The auxiliary adhesive may be deposited on the substrate layer (s) prior to the application of the superabsorbent polymer particles in the substrate layer (s) to increase the adhesion of the superabsorbent polymer particles and the material adhesive thermoplastic to the respective substrate layer. The auxiliary adhesive may further assist in immobilizing the superabsorbent polymer particles and may comprise the same adhesive thermoplastic material as described above or may further comprise other adhesives including, but they are not limited to, sprayable hot melt adhesives. An example of a commercially available auxiliary adhesive is the H.B adhesive. Fuller Co. (St. Paul, MN), product no. HL-1620-B. The auxiliary adhesive can be applied to the substrate layer (s) by any suitable method, but, in accordance with some embodiments, can be applied in slots with a width of about 0.5 to about 1 mm separated by a distance of about 0.5. to approximately 2 mm.

The upper canvas The absorbent article 10 may comprise an upper canvas 18 which may be liquid permeable. The upper canvas 18 can be manufactured with a wide variety of materials, such as woven fabric and non-woven fabric materials; polymeric materials, such as thermoplastic films formed with holes, perforated plastic films and hydroformed thermoplastic films; porous foams; cross-linked foams; crosslinked thermoplastic films; and thermoplastic canvases. Suitable woven and non-woven fabric materials may be composed of natural fibers (eg, wood or cotton fibers), synthetic fibers (eg, polymer fibers such as polyester, polypropylene or polyethylene fibers) or a combination of natural and synthetic fibers.

In some embodiments, the upper canvas 18 can be fabricated with a hydrophobic material to isolate the user's skin from liquids that have passed through the upper canvas 18. In these embodiments, at least a portion of the upper surface of the upper canvas 18 is it tries to be hydrophilic so that liquids are transferred through the upper canvas 18 more quickly. This decreases the likelihood that the body exudates will flow out of the upper canvas 18 instead of being drawn through the upper canvas 18 to be absorbed by the absorbent core. The upper canvas 18 can become hydrophilic when treated with a surfactant. Suitable methods for treating the upper canvas 18 with a surfactant include spraying the upper canvas material with the surfactant and immersing the material in the surfactant.

In some embodiments, the upper canvas includes a film formed with holes. Orifice-formed films are permeable to bodily exudates, but non-absorbent, and exhibit a reduced tendency to allow liquids to pass back through them and rewet the user's skin. In this way, the surface of the formed film that is in contact with the body remains dry, thereby reducing the possibility of the body becoming dirty and creating a more comfortable feeling for the wearer. Suitable formed films are described in U.S. Pat. UU no. 3,929,135, entitled "Absorptive Structures Having Tapered Capillaries," issued to Thompson on December 30, 1975; the US patent UU no. 4,324,246, entitled "Disposable Absorbent Article Having A Stain Resistant Topsheet", issued to Mullane, et al. on April 13, 1982; the US patent UU no. 4,342,314 entitled "Resilient Plástic Web Exhibiting Fiber-Like Properties", granted to Radel, et al. on August 3, 1982; the US patent UU no. 4,463,045 entitled "Macroscopically Expanded Three-Dimensional Plástic Web Exhibiting Non-Glossy Visible Suríace and Cloth-Like Tactile Impression", issued to Ahr, et al. on July 31, 1984; and the US patent. UU no. 5,006,394"Multilayer Polymeric Film", awarded to Baird on April 9, 1991.

Alternatively, the upper canvas includes nonwoven fabric materials with holes. Suitable materials of non-woven fabric with holes are described in US Pat. UU no. 5,342,338 and in the PCT patent application WO 93/19715.

The lower canvas The absorbent article may comprise a lower canvas 20 which may be attached to the upper canvas. The lower canvas can prevent the exudates absorbed by the absorbent core and contained within the diaper from fouling other external articles that may come into contact with the diaper, such as sheets and underwear. In some embodiments, the bottom sheet may be substantially impermeable to liquids (eg, urine) and comprise a sheet of a non-woven fabric and a thin plastic film, such as a thermoplastic film having a thickness of about 0.012 mm (0.5 mil) to approximately 0.051 mm (2.0 mil). Suitable lower canvases include those manufactured by Tredegar Industries Inc. of Terre Haute, Ind. And sold under the trade names of X15306, X10962 and X10964. Other suitable bottom sheet materials may include permeable materials that allow steam to escape from the diaper while preventing liquid exudates from passing through the bottom sheet. Illustrative permeable materials may include materials such as woven wefts, non-woven fabric webs, composite materials such as non-woven webs with coating film and microporous films such as those made by Mitsui Toatsu Co. of Japan under the designation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex., Under the designation EXXAIRE. Suitable permeable composites comprising polymer blends are available from Clopay Corporation, Cincinnati, Ohio under the name HYTREL, blend P18-3097. Such permeable composite materials are described in greater detail in PCT application no. WO 95/16746, published June 22, 1995 under the name E. I. DuPont. Other permeable bottom liners including nonwoven webs and perforated shaped films are described in US Pat. UU no. 5,571,096 issued to Dobrín et al. on November 5, 1996.

Test methods • Test method K (t) (Test method to determine the kinetics of uptake and effective dynamic permeability) This method determines the time-dependent effective permeability (K (t)) and the uptake kinetics of an absorbent structure containing superabsorbent polymer particles under a confining pressure. The objective of this method is to evaluate the ability of the absorbent structure containing superabsorbent polymer particles to capture and distribute bodily fluids when the polymer is present in high concentrations in an absorbent article and is exposed to mechanical pressures as they occur, typically, during the use of the absorbent article. Darcy's law and flow methods are used under conditions of stability to calculate effective permeability (see below). (See also, for example, "Absorbency," ed by PK Chatterjee, Elsevier, 1982, pp. 42-43 and "Chemical Engineering Vol. II, 3rd edition, JM Coulson and JF Richardson, Pergamon Press, 1978, pp. 122-127.) In contrast to previously published methods, the sample does not pre-swell, therefore, the hydrogel is not formed by previously swelling the hydrogel-forming superabsorbent polymer particles in synthetic urine, but the measurement starts from a dry structure.

The equipment used in this method is called 'Zeitabhángiger Durchlássigkeitsprüfstand' or 'Device for tests of permeability dependent of the time', Equipment no. 03-080578, which is commercially available from BRAUN GmbH, Frankfurter Str. 145, 61476 Kronberg, Germany and is described below. Upon request, operating instructions, wiring diagrams and detailed technical drawings are also available.

System to determine the kinetics of uptake and effective dynamic permeability Figure 7 shows the system for determining the kinetics of uptake and effective dynamic permeability, called, in the present description, 'Apparatus for time-dependent permeability tests'.

The team consists of the following main parts: M1 1 digital laser sensor for 701 caliber measurement (MEL Mikroelektronik GmbH, 85386 Eching, Germany) Fiber for detection of liquid level 702 (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 (C98130-A7560-A1 -5-7519, Siemens AG) Labview 706 software license (National Instruments, Austin, Tx, USA) Receiving vessel 707 (5-liter glass beaker, Roth) Receptacle 708 (5-liter glass bottle, VWR) with gasket 709 and open end tube for air inlet 723 Operating unit and console 705 (Conrad Electronics) Computerized data collection system 710 A piston / cylinder unit 713 as described in the present description A control valve 714 (Bürkert) Figure 8 shows the piston / cylinder unit 713 comprising a cover piston guide 801, piston 802 and cylinder 803. Cylinder 803 is made of transparent polycarbonate (eg, Lexan®) and has an internal diameter p of 6.00 cm (area = 28.27 cm2). The internal cylinder walls 850 are smooth; the height of the cylinder r is approximately 7.50 cm. The lower part 804 of cylinder 803 faces a stainless steel screen with standard 400 mesh from the USA. UU (not shown), (eg, from Weisse and Eschrich) which is stretched biaxially until tensioned before joining the bottom 804 of the cylinder 803. The piston 802 is composed of a piston body 805 of stainless steel and a head 806 stainless steel. The diameter q of the piston head 806 is slightly less than 6 cm so as to slide freely inside the cylinder 803 without leaving any space for the hydrogel-forming particle to pass through. The piston body 805 is firmly attached perpendicular to the center of the piston head 806. The diameter t of the piston body is approximately 2.2 cm. Then, the piston body 805 is inserted into a piston guide cap 801. The guide cap 801 has a POM (polyoxymethylene) ring 809 with a diameter that allows free sliding of the piston 802, but still maintains the body of the piston 802. piston 805 perfectly vertical and parallel to the cylinder walls 850 when the piston 802 with the guide cap 801 is placed on top of the cylinder 803. The top view of the piston head 806 is shown in Figure 9. The piston head 806 is provided for to apply the pressure homogeneously to the sample 718. It is also very permeable to the hydrophilic liquid so as not to limit the liquid flow during the measurement. The 806 piston head consists of a 903 stainless steel screen with standard 400 mesh from the USA. UU (eg from Weisse and Eschrich) that is stretched biaxially until tensioned and secured in the stainless steel outer ring 901 of the piston head. The entire surface of the bottom of the piston is flat. The structural integrity and the flexural strength of the mesh fabric is then ensured by the radial spokes 902 of stainless steel. The height of the piston body 805 is selected so that the weight of the piston 802 composed of the piston body 805 and the Piston head 806 be 596 g (± 6 g 6 g), this corresponds to 2.07 kPa (0.30 psi) on the cylinder area 803.

The piston guide cap 801 is a flat stainless steel circle with a diameter s of approximately 7.5 cm which is held perpendicular to the piston body 805 with the POM 809 ring at its center. There are two entries in the guide cover (810 and 812).

The first inlet 812 allows the liquid level sensing fiber 702 to be placed exactly 5 cm above the upper surface of the fabric (not shown) attached to the lower part (804) of the cylinder 803 when the piston 802 assembles with cylinder 803 for measurement.

The second inlet 810 allows to connect a liquid tube 721 that provides the liquid to the experiment.

To make sure that the piston assembly 802 with the cylinder 803 is made consistently, a slit 814 is made in the cylinder 803 that coincides with a position marker 813 in the guide cap 801. In this way, the rotation angle of the cylinder and the cover is always the same.

Before each use, the 903 stainless steel screen of the 806 piston head and cylinder 803 should be examined to determine binding, holes or overstretching and replace it when necessary. An apparatus of K (t) with the damaged sieve can give wrong kinetics of capture and K (t) and should not be used until the sieve has been replaced.

A mark of 5 cm 808 is drawn on the cylinder 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 cylinder 803. This marks the level of fluid that must Stay during the analysis. The fiber for detection of liquid level 702 is placed exactly in the 5 cm mark 808. The maintenance of a correct and constant fluid level (hydrostatic pressure) is crucial for the accuracy of the measurement.

A receptacle 708 connected by a pipe to the piston / cylinder unit 713 containing the sample and a control valve 714 is used to supply saline solution to cylinder 803 and maintain the saline level at a height k of 5.00 cm above the top surface of the screen attached to the bottom of the cylinder 804. The valve 714, the fiber for liquid level detection 702 and the digital fiber sensor 703 are connected to the computerized pick-up system 710 through the operating unit 705. This allows the system for measuring the kinetics of capture and the effective dynamic permeability to use the information of the fiber for liquid level detection 702 and the digital fiber sensor 703 to control the valve 714 and to maintain, finally, the liquid level at the 808 mark of 5 cm.

The receptacle 708 is placed on the piston / cylinder unit 713 in such a way as to allow a 5 cm hydrohead to be formed 15 seconds after the start of the test and which will remain in the cylinder during the entire test procedure. The piston / cylinder unit 713 is placed in the support ring 717 of the cover plate 716, and the first entry 812 is held in place by the fixing support 719. This allows a single position of the guide cover 801. In addition, due to the position marker 813, there is only one position for the cylinder 803. The screen attached to the bottom of the cylinder 804 must be perfectly level and horizontal. The support ring 717 must have an internal diameter small enough to firmly support the cylinder 803, but greater than 6.0 cm so as to remain outside the internal diameter of the cylinder when the cylinder is placed on the support ring 717. This is important to avoid any interference of the support ring 717 with the liquid flow.

The saline solution, applied to the sample 718 with a constant hydro head of 5 cm, can flow freely from the piston / cylinder unit 713 to a receiving vessel 707 placed on the balance 704 having an accuracy within ± 0.01 g. The digital output of the balance is connected to a computerized data collection system.

The caliber (thickness) of the sample is constantly measured with a digital laser sensor for 701 caliber measurement. The laser beam 720 of the digital laser sensor 701 is directed to the center of the POM cover plate 81 1 of the piston body. The precise positioning of all parts of the piston / cylinder unit 713 allows the piston body 805 to be perfectly parallel to the laser beam 720 and, as a result, an accurate measurement of the thickness is obtained.

Preparation of the test The receptacle 708 is filled with test solution. The test solution is 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 solution is described below. The receiver vessel 707 is placed on the balance 704 which is connected to a computerized data collection system 710. Before starting the measurement, the balance is tared.

Preparation of the test liquid: Necessary chemical substances: Sodium Chloride (CAS No. 7647-14-5, eg: Merck, catalog number 1.06404.1000) C12-C14 linear alcohol ethoxylate (CAS No. 8439-50-9, eg, Lorodac ®, Sasol, Italy) Deionized H20 Ten liters of a solution containing 9.00 grams per liter of NaCl and 1.00 grams per liter of linear C12-C14 alcohol ethoxylate in distilled water are prepared and equilibrated at 23 ° C ± 1 ° C for 1 hour. The surface tension is measured in 3 individual aliquots and should be 28 ± 0.5 mN / m. If the surface tension of the solution is different from 28 ± 0.5 mN / m, the test solution is discarded and a new one is prepared. The test solution must be used within 36 hours of its preparation and is considered expired after this period.

Preparation of the sample for K (t) A representative circular portion of the absorbent structure of 6.00 cm in diameter is obtained. The portion of the absorbent article can be obtained with a suitable circular die and a hydraulic cutting press (such as, eg, Electro-Hydraulic Alfa Cutter 240-10 distributed by the Thwing-Albert instrument company, 14 W. Collings Ave. West Berlin, NJ 08091).

The circular sample 1 18 is carefully placed flat on the screen (not shown) adhered to the lower part 204 of the cylinder 203 that occupies the entire available surface of the screen. It is important to place the circular sample 1 18 so that the side in direct contact with the screen is that which during use is usually farthest from the liquid source so as to reproduce the common direction of flow during use. For example, for samples related to absorbent articles, such as diapers, the side usually oriented to the user should be placed on the top while the side facing the garment should be placed in contact with the screen on the bottom of the cylinder. Careful placement of the sample is vital to the accuracy of the measurement. In case the dimension of the absorbent structure is small and a sample of 6.00 cm in diameter can not be obtained from this, it is possible to join two absorbent structures of equal size to obtain the minimum sample size needed. The two samples should be taken in the same position of two identical absorbent structures. The two absorbent structures must be joined through a straight edge and, if necessary, cut to obtain that straight edge. The objective is that the joined edges recreate a flat homogeneous layer without any separation or only with a minimum separation. Then, this bonded layer is handled in accordance with the standard sample preparation described above with the additional precaution of centering the bond line in the cutting die to obtain two semicircles of identical shape. It is important that both semicircles are placed carefully inside the sample holder to recreate a complete circle and occupy all the available surface in the screen without any separation or only with a minimum separation. Both halves should be placed with the side facing the screen as explained above. However, in most embodiments, the sample will consist of a unitary circular portion of the absorbent structure.

Method for extracting an absorbent structure from an absorbent article The absorbent article is placed on a flat surface. In case the product contains characteristics that prevent it from being spread flat (such as folds), these are cut at appropriate intervals to allow the product to lie flat.

First, the portion (s) of the absorbent structure comprising (n) at least 90% by weight of superabsorbent polymer particles that will be tested in accordance with test method K (t) is identified. and must be isolated as explained below.

All materials that are not part of the absorbent structure are removed from the absorbent structure and care is taken not to excessively damage the absorbent structure.

If the materials to be removed are adhered to the absorbent structure, for example, with adhesive material, such as a thermoplastic adhesive material, to avoid damage to the structure, they could be removed with the help of cold sprays with a cooling temperature of -50. at -60 ° C (such as the cold spray "IT read" or "PRF 101" distributed by Taerosol, Kangasala, Finland) as shown, for example, in Figure 15.

Figure 15 shows an absorbent structure 151 comprising superabsorbent polymer particles 152 that are sandwiched between two substrate layers 153, 154. A layer of material 156 is adhered to one of the substrate layers 153, 154 and, therefore, it is not part of the absorbent structure 151. This layer should be removed from the absorbent structure 151. To prevent undue damage to the absorbent structure 151, the layer of material 156 that will be removed from the absorbent structure 151 is pulled from the absorbent structure 151 in a 180 ° peel geometry while the adhesive material 155 is cooled with cold spray 157. Spraying should last at least 1 second, but not more than 5 seconds for each individual portion of material layer 156.

After removing each of the materials, the remaining part of the absorbent structure is maintained under a pressure of 2.07 kPa (0.3 psi) until the temperature returns to the initial value (TAPPI laboratory conditions).

The upper layer and / or the lower layer of the absorbent structure can be adequately perforated to allow the liquid to flow through them as they are. shows, for example, in Figure 16 which depicts an absorbent structure 161 comprising superabsorbent polymer particles 162 that are sandwiched between two layers of substrate 163, 164. The perforation is made with a hot metal tip, also called perforating tip 165 comprising a steel rod 166 with a diameter H of 0.7 ± 0.2 mm. A standard paper fastener, folded around a welder tip 167 such as CT 60/621 distributed by ERSA GmbH, Wertheim, Germany, can be used for this purpose. The drill bit 165 should be at a temperature of 310 ± 20 ° C. The piercing tip 165 is placed in contact with the layers that will be perforated for a short period of time with low pressure in order to pierce the layers, for example, by melting without affecting any of the other materials of the absorbent structure 161. The holes are created with the same procedure in a regular square hole pattern with a hole D edge to edge distance of 1 ± 0.2 mm, as shown, for example, in Figure 17.

Each absorbent structure is visually controlled to determine integrity and if damaged it is discarded with the help of backlighting. Examples of damage are, for example: cuts, holes or wrinkles that were not present before removing the absorbent structure of the absorbent article. The perforations in the layers made with the piercing tip are not considered damage unless they affect other layers. In addition, the substantial migration of superabsorbent polymer particles and fibers within the absorbent structure is considered as damage.

The absorbent structures prepared in this way are then cut in accordance with the test method K (t).

Procedure K (t) The measurement is carried out under standardized laboratory conditions Tappi: 23 ° C ± 1 ° C / 50% RH ± 2%.

The empty piston / cylinder unit 713 is mounted in the circular opening of the cover plate 716 and is supported around the lower perimeter by the support ring 717. The piston / cylinder unit 713 is held in place with the support fastening 719, and the cylinder 803 and the piston 802 are aligned at the correct angle. The reading of the reference caliber (rr) is measured with the digital laser sensor. After this, the empty piston / cylinder 713 unit is removed from the cover plate 716 and the support ring 717 and the piston 802 is removed from the cylinder 803.

The sample 718 is placed (absorbent structure) on the cylinder screen as explained above. After this, the piston 802 mounted with the guide cap 801 is carefully placed inside the cylinder 803 by matching the position marker 813 of the guide cap 801 with the slit 814 made in the cylinder 803.

The piston / cylinder unit is held in place with the fixing bracket 719, with the cylinder and piston aligned at the correct angle.

This can be done only in one direction. The liquid tube 721 connected to the receptacle 708 and the digital fiber sensor 703 are inserted into the piston / cylinder unit 713 via the two inlets 810 and 812 in the guide cap 801.

The computerized data acquisition system 710 is connected to the balance 704 and the digital laser sensor for caliber measurement 701. The computer program initiates the flow of fluids from the receptacle 708 to the cylinder 803 when valve 714 is opened. cylinder until the 808 mark of 5 cm is reached in a period of 5-15 seconds, after which, the computer program regulates the flow rate to maintain a constant hydro head of 5 cm. The amount of solution passing through the sample 718 is measured with the scale 704, and the increase in the gauge is measured with The laser gauge meter. The data collection starts when the fluid flow begins, specifically, when the valve 714 is first opened, and continues for 21 minutes or until the receptacle is emptied so that the 5 cm hydro head is no longer maintained. The duration of a measurement is 21 min, the readings of the balance and the laser caliber are recorded regularly with an interval that can vary according to the measurement range from 2 to 10 s, and 3 replicas are measured.

After 21 min, the measurement of the 1st replication finishes satisfactorily, and the controlled valve 714 closes automatically. The piston / cylinder unit 713 is removed, and the measurements of the 2nd and 3rd replications are made accordingly, always following the same procedure. At the end of the measurement of the 3rd replica, the controlled valve 714 stops the flow of liquid, and the stop valve 722 of the receptacle 708 is closed. The collected raw data is stored in the form of a simple data table which, afterwards, can easily be imported into another program for further analysis, for example, Excel 2003, SP3.

The following information is reported in the data table for each reading: • Time since the beginning of the experiment • Weight of the liquid collected by receiver vessel 707 on balance 704 • Caliber of the sample 718 The data are used from 30 seconds until the end of the experiment in the calculation of uptake kinetics and K (t). The data collected in the first 30 seconds are not included in the calculation. Then, the effective permeability K (t) and the kinetics of uptake of the absorbent structure with the following set of equations are determined.

Equations used: The table below describes the notation used in the equations.

The transmission pressure is calculated from the hydro head as follows: ?? =? · 0 ·? = 4929.3 lg / (cm-s2) The caliber at each time t, is calculated as the difference between the gauge sensor reading at time t, and the reference reading without the sample: d, = - rr [cm] For samples of superabsorbent particles, the size of the sample at time t, = 0 (d0) is used to evaluate the quality when spreading the particles.

A bulk density of the sample inside the cylinder can be calculated, in fact, as: P: = -T- [g / cm3] If this bulk density within the cylinder differs from the bulk density of the powder by more than ± 40%, the measurement should be considered invalid and eliminated.

The bulk density can be determined in accordance with the method 406.2 - 02 ("Super absorbent materials - Polyacrylate superabsorbent powders -GRAVIMETRIC DETERMINARON OF DENSITY", (superabsorbent materials: superabsorbent powders of polyacrylate - GRAVYMETRIC DETERMINATION OF DENSITY)) of EDANA.

The rate of change over time of the reading of the balance in time t, is calculated as follows: The rate of change with the time of reading the caliber at time t, is calculated as follows: ¾ = _½_ Í ___ ± [cm / s] dt t, + l - t The uptake kinetics is calculated as follows: u (1 |) - (A -d '- v-> -' [g / g] m By volume of dry sample (Vs) is meant the structural volume of the sample, therefore, Vs is the actual volume occupied by the solid material in the dry sample that excludes pores and interstices that may be present.

The Vs can be calculated or measured by using different methods known to an experienced person, for example, by knowing the exact composition and structural density of the components, it can be determined as follows: Alternatively, for a composition of unknown material, Vs can be easily calculated as follows: V = ^ - [cm3] Ps The apparent density ps can be determined by pycnometry with a suitable non-inflatable liquid of known density. This technique can not be performed on the same samples used later for the measurement of K (t), therefore, an additional representative set of samples suitable for this measurement experiment should be prepared.

From U (t) in the different stages of times calculated as explained above, the uptake can be determined at any specific time by linear interpolation. For example, one of the important results is 20-minute uptake, also called U20 (in g / g).

From U (t) in the different stages of time, the time required to reach a certain uptake by linear interpolation can also be determined. The time in which the uptake of 20 g / g is first reached is called T20. Similarly, the time to reach any other feedback can be calculated accordingly (eg, T5 or T10). In addition, when knowing U20, it is possible to determine from U (t) in the different stages of time, the time to reach 80% of U20, property called T80%.

The effective permeability is calculated as follows from the rates of change of mass and change of caliber: The effective viscosity of the liquid depends on the temperature and, in the experiment interval (23 ° C ± 1 ° C), it is calculated according to the following empirical equation: ? =? +? ·? [g / (cm.s)] where A = 1, 479.10"2 [g / (cm.s) J and B = -2.36.10" 4 [g / (cm.s.C)] From K (tj) the effective permeability can be determined in a specific time by linear interpolation. For example, one of the important results is the uptake at 20 minutes or K20 (m2). Similarly, permeability can be calculated at any other time (eg, K5 or K10).

Another parameter that can be derived from the data is Kmin, which is the minimum value K (t) measured on the total curve in the interval from t¡ = 30 s to t¡ = 1 00 s. This value is useful for calculating Kmin / K20, which is the ratio between the minimum effective permeability and the permeability at 20 minutes. This parameter expresses the temporary blocking of the gel that could occur in some of the samples. If the value is close to 1, there is no temporary blocking of the gel; if the value is close to 0, this is an indication that the material experiences a marked drop in effective permeability when initially loaded with liquid.

The average values for T20, T80%, K20, U20 and Kmin / K20 are reported from 3 replicates in accordance with the required accuracy, as is known to an experienced person.

• Calibration test method, The purpose of this method is to provide a method for determining the thickness of the absorbent core at the crotch point of an absorbent article. The test can be performed with a conventional gauge meter, such as the EG-225 type distributed by ONO SOKKI Technology Inc., 2171 Executive Drive, Suite 400, Addison, IL 60101, USA. UU., With an appropriate meter holder, that has a circular sample foot of 41 mm diameter aluminum, with a force exerted by the foot of 0.1 Newton (10 gf). An additional weight is added in order to achieve a total of 1.6 Newton (160 gf) to adjust the pressure to 1.18 kPa (0.173 psi).

The thickness of the absorbent core is determined before assembling the absorbent core in the absorbent article after having decided the exact position that the absorbent core will have in the absorbent article once assembled. However, the thickness can be further determined after removal of the absorbent core from a finished product by any suitable method known to one skilled in the art.

The crotch point of an absorbent article is determined at the intersection of the longitudinal centerline and the transverse centerline of the article.

Basic protocol 1. All tests are performed at 23 ± 1 ° C and 50 + 2% relative humidity. 2. The absorbent core is allowed to equilibrate at 23 ± 1 ° C and 50 ± 2% relative humidity for 8 hours. 3. The crotch point is determined as described above and marked on the surface of the absorbent core oriented to the user. 4. The absorbent core is placed below the gauge with the surface facing the user towards the foot of contact with the sample and with the crotch point centered under the foot. 5. The contact foot is lowered with the sample carefully so that it comes into contact with the surface of the absorbent core. 6. The gauge reading is taken 5 seconds after the foot comes into contact with the absorbent core.

• Test method to determine urine permeability (UPM) Urine permeability measuring system This method determined the permeability of a swollen hydrogel layer 1318. The equipment used in this method is described below. This method is intimately related to the test method of SFC (Conductivity of saline flow) of the previous matter.

Figure 10 shows the permeation measurement system 1000 configured with the constant hydrostatic head receptacle 1014, open end tube for air inlet 1010, vent with plug for recharge 1012, laboratory platform 1016, supply tube 1018, tap wrench step 1020, annular support support 1022, receiving container 1024, balance 1026 and piston / cylinder unit 1028.

Figure 1 1 shows the piston / cylinder unit 1028 comprising a metal weight 1 12, piston rod 1 1 14, piston head 1 1 18, cover 1 1 16 and cylinder 1 120. The cylinder 1 120 is made of transparent polycarbonate (eg, Lexan®) and has an internal diameter p of 6.00 cm (area = 28.27 cm2) with internal cylinder walls 1 150 that are smooth. The lower part 1 148 of the cylinder 1 120 is faced with a stainless steel screen with standard 400 mesh from the USA. UU (not shown) that is stretched biaxially until it is tensioned before it is joined to the lower part 1 148 of the cylinder 1 120. The piston rod 1 1 14 is made of transparent polycarbonate (e.g., Lexan®) and has a general length q of approximately 127 mm. A portion of the 1126 center of Piston rod 1114 has a diameter r of 21.15 mm. An upper portion 1128 of the piston rod 1114 has a diameter s of 15.8 mm, which forms a shoulder 1124. A lower portion 1146 of the piston rod 1114 has a diameter f of approximately 1.6 cm (5/8 inch) and is threaded to be screwed firmly into the center hole 1218 (see Figure 12) of the piston head 1118. The piston head 1118 is perforated, made of transparent polycarbonate (eg, Lexan®) and is also covered with a a stainless steel screen with standard 400 mesh from the USA UU (not shown). The weight 1112 is made of stainless steel, has a central hole 1130, slides over the upper portion 1128 of the piston rod 1114 and rests on the shoulder 1124. The combined weight of the piston head 1118, piston rod 1114 and the weight 1112 is 596 g (± 6 g), which corresponds to 2.07 kPa (0.30 psi) over the area of the cylinder 1120. The combined weight can be adjusted by drilling a blind hole in a central shaft 1132 of the piston rod 1114 to remove material and / or provide a cavity for adding weight. The cylinder cover 1116 has a first lid opening 1134 at its center to vertically align the piston rod 1114 and a second lid opening 1136 near the rim 1138 to introduce fluid from the constant hydrostatic head receptacle 1014 to the cylinder 1120.

A first linear index mark (not shown) is drawn radially along the upper surface 1152 of the weight 1112; the first linear index mark is transverse to the central axis 1132 of the piston rod 1114. A second corresponding linear index mark (not shown) is drawn radially along the upper surface 1160 of the piston rod 1114; the second linear index mark is transverse to the central axis 1132 of the piston rod 1114. A third corresponding linear index mark (not shown) is drawn along the central portion 1126 of the piston rod 1114; the third linear index mark is parallel to the central axis 1132 of the piston rod 1 1 14. A fourth corresponding linear index mark (not shown) is drawn radially along the upper surface 1 140 of the cylinder cover 1 1 16; the fourth linear index mark is transverse to the central axis 1 132 of the piston rod 1 114. In addition, a fifth corresponding linear index mark (not shown) is drawn along a rim 1 154 of the cylinder cover 11. 16; the fifth linear index mark is parallel to the central axis 132 of the piston rod 1 1 14. A sixth corresponding linear index mark (not shown) is drawn along the outer cylinder wall 1 142; the sixth linear index mark is parallel to the central axis 1 132 of the piston rod 1 1 14. The alignment of the first, second, third, fourth, fifth and sixth linear index marks allows the weight 11 12, the piston rod piston 1 1 14, cylinder cover 11 16 and cylinder 1 120 are replaced with the same orientation with respect to each other in each measurement.

The specification details of cylinder 1 120 are: Outer diameter u of cylinder 1 120: 70.35 mm Internal diameter p of cylinder 1 120: 60.0 mm Height v of cylinder 1 120: 60.5 mm The specification details of the cylinder cover 1 1 16 are: Outer diameter w of the cylinder cover 1 1 16: 76.05 mm Internal diameter x of the cylinder cover 1 1 16: 70.5 mm Thickness and cylinder cover 1 116 including flange 1154: 12. 7 mm Thickness z of the cylinder cover 1 1 16 without the flange 1 154: 6.35 mm Diameter a of the first cover opening 134: 22.25 mm Diameter b of the second lid opening 1 136: 12.7 mm Distance between the centers of the first and second lid openings 1 134 and 1 136: 23.5 mm The specification details of the 1 1 12 weight are: External diameter c: 50.0 mm Diameter d of the central hole 1 130: 16.0 mm Height e: 39.0 mm The specification details of the piston head 1 1 18 are Diameter f. 59.7 mm Height g. 16.5 mm External holes 1214 (14 in total) with a diameter h of 9.65 mm, outer holes 1214 spaced equidistantly with the centers at a distance of 47.8 mm from the center of the central hole 1218 Inner holes 1216 (7 in total) with a diameter of 9.65 mm diameter / ', inner holes 1216 spaced apart equidistantly with centers at a distance of 26.7 mm from the center of the central hole 1218 The central hole 1218 has a diameter j of 1 .6 cm (5/8 inch) and is threaded to accept a lower portion 1 146 of the piston rod 1 1 14.

Before use, stainless steel screens (not shown) of piston head 1 1 18 and cylinder 1 120 should be examined to determine blockages, holes or overstretching and replaced when necessary. A urine permeability measuring device with a damaged screen may provide erroneous UPM results and should not be used until the screen has been replaced.

A mark of 5.00 cm 1 156 is drawn on cylinder 1 120 at a height k of 5 5. 00 cm (± 0.05 cm) above the screen (not shown) attached to the lower part 1 148 of the cylinder 1 120. This marks the level of fluid that must be maintained during the analysis. Maintaining the correct and constant fluid level (hydrostatic pressure) is critical to the accuracy of the measurement.

A receptacle with constant hydrostatic head 1014 is used to supply saline solution 1032 to the cylinder 1 120 and to maintain the level of saline 1032 at a height of 5.00 cm above the screen (not shown) attached to the lower part 1 148 of the cylinder 1 120. The lower part 1034 of the air intake tube 1010 is positioned so as to maintain the level of the saline solution 1032 in the cylinder 1120 at the required height k of 5.00 cm during the measurement, ie the part lower 1034 of the air tube 1010 is approximately in the same plane 1038 as the 5.00 cm mark 1156 in the cylinder 1 120 when this is supported on the support mesh (not shown) in the annular support 1040 above the receiving container 1024. The correct alignment of the height of the air intake tube 1010 and the marking of 5.0 cm 1 156 on the cylinder 1120 is crucial for the analysis. A suitable receptacle 1014 consists of a container 1030 which contains: a horizontally oriented L-shaped supply tube 1018 for supplying fluid, a tube with an open end oriented vertically to allow the entry of air at a fixed height into the receptacle with hydrostatic head constant 1014, and plugged vent 1012 for recharging the receptacle with constant hydrostatic head 1014. Pipe 1010 has an internal diameter of 12.5 mm ± 0.5 mm. The delivery tube 1018, located near the bottom portion 1042 of the constant hydrostatic head receptacle 1014, contains a stopcock 1020 for starting / stopping the delivery of saline solution 1032. The outlet 1044 of the delivery tube 1018 is sized to be inserted through the second lid opening 1 136 in the cylinder lid 1 1 16, with the end placed below the surface of the saline solution 1032 in the cylinder 1 120 (after the height is reached 5.00 cm of saline solution 1032 in cylinder 1 120). The air intake tube 1010 is held in place with an O-ring (not shown). The receptacle with constant hydrostatic head 1014 can be placed on a laboratory platform 1016 in order to adjust its height with respect to that of the cylinder 1 120. The components of the receptacle with constant hydrostatic head 1014 are sized to quickly fill the cylinder 1 120 a the required height (ie, hydrostatic head) and maintain this height for the duration of the measurement. The constant hydrostatic head receptacle 1014 should be capable of delivering the saline solution 1032 at a flow rate of at least 3 g / s for at least 10 minutes.

The piston / cylinder unit 1028 is placed on a rigid mesh stainless steel support fabric 16 (or equivalent) (not shown), which rests on annular support 1040 or a suitable alternative rigid support. This support fabric (not shown) is sufficiently permeable so as not to impede the flow of saline 1032 and sufficiently rigid to support the stainless steel mesh screen (not shown) and to prevent stretching. The support fabric (not shown) should be flat and level to avoid tilting the piston / cylinder unit 1028 during the test. Saline solution 1032 passing through the support fabric (not shown) is collected in a receiving container 1024 placed below (without supporting) the support fabric (not shown). The receiving container 1024 is placed on the balance 1026, which has an accuracy of at least 0.01 g. The digital output of balance 1026 is connected to a computerized data capture system (not shown).

Preparation of reagents (not illustrated) Jayco synthetic urine (JSU) 1312 (see Figure 13) is used for a swelling phase (see the UPM procedure below), and a solution of sodium chloride (NaCl) 0.1 8 M for a flow phase (see the UPM procedure below). The following preparations are brought to a standard volume of one liter. For preparations of volumes other than one liter, all quantities are suitably graded.

JSU: Fill a 1 L volumetric flask with distilled water to 80% volume and place a magnetic stir bar in the flask. Separately, with a weighing paper or a flask, the following amounts of dry ingredients are weighed to an accuracy of ± 0.01 g using an analytical balance and added quantitatively to the volumetric flask in the same order as listed below. The solution is stirred on a suitable stir plate until all the solids are dissolved, the stir bar is removed and the solution is diluted to a volume of 1 L with distilled water. A stir bar is again introduced and the solution is stirred on a stir plate for a few more minutes.

Amounts of salts to make 1 liter of Jayco synthetic urine: Potassium Chloride (KCI) 2.00 g Sodium sulphate (Na2S04) 2.00 g Dihydrogenized ammonium phosphate (NH4H2P0) 0.85 g Ammonium phosphate, dibasic ((NH4) 2HP04) 0.15 g Calcium chloride (CaCl2) 0.19 g - [or hydrated calcium chloride (CaCl2-2H20) 0.25 g] Magnesium chloride (MgCl2) 0.23 g - [or hydrous magnesium chloride (MgCl2 6H20) 0.50 g] To make the preparation faster, each salt dissolves completely before adding the next one. Jayco synthetic urine can be stored in a clean glass container for two weeks. The solution should not use if it becomes cloudy. Shelf life in a clean plastic container is 10 days.

Sodium chloride solution (NaCl): 0.1 18 M: 0.1 M sodium chloride is used as 1032 saline solution. With a weighing paper or a beaker, 6.90 g (± 0.01 g) of sodium chloride are weighed and transfer quantitatively to a 1 liter volumetric flask; and the flask is filled to volume with distilled water. A stir bar is added and the solution is mixed on a stir plate until all solids are dissolved.

Preparation of the test With a solid cylindrical reference weight (not shown) (40 mm in diameter, 140 mm in height), a gauge is set (not shown) (eg, Mitotoyo Digimatic Height Gage) for a reading of zero. This operation is carried out, conveniently, on a smooth and level 1046 laboratory table. The piston / cylinder unit 1028 without superabsorbent polymer particles is placed below the gauge (not shown) and a reading is recorded, L ^ with an accuracy of 0.01 mm.

The constant hydrostatic head receptacle 1014 is filled with saline 1032. The lower part 1034 of the air intake tube 1010 is positioned so as to maintain the upper part (not shown) of the meniscus of the liquid (not shown) in the cylinder 1 120 at the 5.00 cm mark 1156 during the measurement. Correct alignment of the height of the air intake tube 1010 at the 5.0 cm mark 1 156 on the cylinder 120 is crucial for the analysis.

The receiving container 1024 is placed on the balance 1026, and the digital output of the balance 1026 is connected to a computerized data collection system (not shown). sample). The annular support 1040 with a rigid mesh stainless steel support fabric 16 (not shown) is placed above the receiving container 1024. The mesh 16 fabric (not shown) must be sufficiently rigid to support the piston unit / cylinder 1028 during the measurement. The support screen (not shown) must be flat and level.

UPM procedure 1.5 g (± 0.05 g) of superabsorbent polymer particles are weighed on a suitable weighing or auxiliary weighing paper on an analytical balance. The moisture content of the superabsorbent polymer particles is determined in accordance with the moisture content test method 430.1 -99 of EDANA ("Superabsorbent materials - Polyacrylate superabsorbent powders - Moisture Content - weight loss upon heating" polyacrylate superabsorbents - Moisture content - Weight loss after heating) (February 99)). If the moisture content of the superabsorbent polymer particles is greater than 5%, then the weight of the superabsorbent polymer particles must be corrected with respect to moisture (i.e., in that particular case, the superabsorbent polymer particles added must be 1.5 g on the basis of dry weight).

The empty cylinder 1 120 is placed on a leveled laboratory table 1046, and the superabsorbent polymer particles are transferred quantitatively to the cylinder 1120. The superabsorbent polymer particles are uniformly dispersed on the screen (not shown) attached to the bottom 1148 of the cylinder 1120 when shaking, turning and / or gently tapping the cylinder 1 120. It is important to have a homogeneous distribution of particles on the screen (not shown) attached to the lower part 1 148 of the cylinder 1120 to obtain a result with the most high accuracy. After the superabsorbent polymer particles have been evenly distributed over the screen (not shown) attached to the lower part 1 148 of the cylinder 1120, the particles should not adhere to the inner walls of cylinder 150. The piston rod 1 1 14 is inserted through the first opening 1 134, with the flange 1 154 of the cover 1 116 facing the piston head 1 118. The piston head 1 1 18 is inserted carefully into the cylinder 1 120 a few centimeters deep. Then, the lid 1 1 16 is placed on the edge 1 144 of the cylinder 1 120, while care is taken to keep the piston head 11 18 away from the superabsorbent polymer particles. The cover 1 1 16 and the piston rod 1126 are carefully rotated to align the third, fourth, fifth and sixth linear index marks. Then, the piston head 1 1 18 is lowered smoothly (via the piston rod 11 14) to rest on the dry superabsorbent polymer particles. The weight 11 12 is placed on the upper portion 1 128 of the piston rod 1 1 14 so that it rests on the shoulder 1 124 so that the first and second linear index marks are aligned. Proper settlement of the lid 1 116 prevents clumping and ensures even distribution of the weight on the hydrogel layer 13 8.

Swelling phase: A fritted disk 8 cm in diameter (7 mm thick) is saturated; p. eg, Chemglass Inc., no. GC 201-51, thick porosity) 1310 by adding an excess of JSU 1312 synthetic urine to the fritted glass disk 1310 until the fritted glass disk 1310 is saturated. The saturated fritted glass disk 1310 is placed in a wide petri dish with flat bottom 1314, and the synthetic urine JSU 1312 is added until it reaches the upper surface 1316 of the fritted glass disk 1310. The height of the JSU must not exceed the height of the fritted glass disk 1310.

The screen (not shown) adhered to the lower part 1 148 of the cylinder 1 120 is easily stretched. To prevent stretching, a lateral pressure is applied on the piston rod 1 1 14, just above the lid 1 1 16, with the index finger while the cylinder 1 120 of the piston / cylinder unit 1028 is clamped. This "locks" the piston rod 1 1 14 in place against the cover 1 1 16 so that the piston / cylinder unit 1028 can be lifted without exerting a excessive force on the screen (not shown).

The entire piston / cylinder unit 1028 is lifted in this manner and placed on the fritted disk 1310 in the Petri dish 1314. The synthetic urine JSU 1312 of the Petri dish 1314 passes through the fritted disk 1310 and is absorbed by the particles of superabsorbent polymer (not shown) to form a hydrogel layer 1318. The synthetic urine JSU 1312 available in Petri dish 1314 should be sufficient for the entire swelling phase. If necessary, more synthetic JSU 1312 urine can be added to Petri dish 1314 during the hydration period to maintain the level of the synthetic urine JSU 1312 on the upper surface 1316 of the fritted disk 1310. After a period of 60 minutes, remove the piston / cylinder unit 1028 from the fritted glass disk 1310, taking care to immobilize the piston rod 1 1 14 against the cover 1 1 16 as described above and making sure that the hydrogel layer 1318 does not lose JSU 1312 or Incorporate air during this procedure. The piston / cylinder unit 1028 is placed below the gauge (not shown) and a reading L2 is recorded, at the value closest to 0.01 mm. If the reading changes over time, only the initial value is recorded. The thickness of hydrogel layer 1318, L0 is determined from L2-Li to an accuracy of 0.1 mm.

The piston / cylinder unit 1028 is transferred to the support fabric (not shown) attached to the annular support bracket 1040 taking care to lock the piston rod 1 1 14 in place against the cover 1 1 16. The receptacle with Constant hydrostatic head 1014 is located so that the supply tube 1018 is placed through the second lid opening 1 136. The measurement starts with the following sequence: a) The stop valve 1020 of the constant hydrostatic head receptacle 1014 is opened to allow the saline solution 1032 to reach the 5.00 cm 1156 mark on the 1 120 cylinder. This level of saline solution 1032 must be obtained within 10 seconds after to open the stopcock 1020. b) When the 5.00 cm of saline solution 1032 has been reached, the data collection program begins.

With the help of a computer (not shown) connected to balance 1026, the amount of saline solution 1032 passing through hydrogel layer 1318 is recorded at 20 second intervals for a period of 10 minutes. At the end of 10 minutes, the stop valve 1020 is closed in the receptacle with constant hydrostatic head 1014.

The data is used from 60 seconds until the end of the experiment in the calculation of the UPM. Data collected before 60 seconds are not included in the calculation. The flow regime Fs (in g / s) is the slope of a least-squares linear fit for a graph of the weight of saline solution 1032 collected (in grams) as a function of time (in seconds) from 60 seconds to 600 seconds.

The measurement of urine permeability (Q) of the hydrogel layer 1318 is calculated with the following equation: Q = [Fgx L0] / [p x A x ??], where Fg is the flow regime in g / s determined from the regression analysis of the results of the flow regime, L0 is the initial thickness of the hydrogel layer 1318 in 6 cm, p is the density of the saline solution 1032 in gm / cm3. A (from the above equation) is the area of the hydrogel layer 1318 in cm2, ?? is the hydrostatic pressure in dynes / cm2, and the measurement of the permeability to urine, Q, is expressed in units of cm3 s / g. The average of the three determinations must be recorded.

• FSR test method This method determines the velocity of the superabsorbent polymer particles, especially the hydrogel-forming polymer particles, such as cross-linked polyacrylates, to swell in 0.9% saline (0.9% aqueous NaCl solution). The principle of measurement is to allow the superabsorbent polymer particles to absorb a known quantity of fluids, and the time it takes to absorb the fluids is measured. Then, the result is expressed in grams of fluid absorbed per gram of material per second. The entire test is performed at 23 ± 2 ° C.

Four grams of a representative sample of the superabsorbent polymer particles are dried in an uncovered Petri dish of 5 cm diameter in a vacuum chamber at 23 ± 2 ° C and 1.33 Pa (0.01 torr), or less, during 48 hours before the measurement.

Approximately 1 g (+/- 0.1 g) of the test sample is removed from the vacuum chamber and weighed immediately to an accuracy of 0.001 g in a 25 ml beaker, which has 32 to 34 mm internal diameter and 50 mm in height. The material is evenly distributed over the bottom. We weigh 20 g of 0.9% saline with an accuracy of +/- 0.01 g in a 50 ml beaker, and then pour it carefully, but quickly, into the beaker containing the test material. A timer is turned on immediately after the liquid comes into contact with the material. The glass does not move or shake during swelling.

The timer is stopped, and the time is recorded to the nearest second (or more accurately if appropriate) when the last part of the fluid at rest is reached by the particles that swell. In order to increase the reproducibility of the determination of the end point, the surface of the liquid can be illuminated with a small lamp without that lamp warming the surface. The vessel is weighed again to determine the liquid actually absorbed, with an accuracy within ± 0.1 g.

The free swelling rate is calculated by dividing the weight of the superabsorbent polymer particles by the amount of liquid actually absorbed and dividing the result by the time required for this absorption, and is expressed in "g / g / s". Three measurements are made, and the results are averaged to obtain the FSR value in g / g / s, reported with 3 significant figures.

• Flat test method of acquisition This method determines the collection times of a baby diaper designed, typically, for users who weigh in the range of 8 to 13 kg ± 20% (such as Pampers Active Fit, size 4, or other Pampers baby diapers, size 4, baby diapers Huggies, size 4 or diapers for babies of size 4 of many other commercial brands).

Apparatus The apparatus for the test is shown in Figure 14 and comprises a 141 1 pan made of polycarbonate (e.g., Lexan®) with a nominal thickness of 0.5 inches. The trough 141 1 comprises a rectilinear horizontal base 1412 having a length of 508 mm (20.0 inches) and a width of 152 mm (6.0 inches). Two sides rectilinear verticals 1413 of 64 mm (2.5 inches) high and x 508 mm (20 inches) in length are attached to the long edges of the base 1412 to form a U-shaped 141 1 pan having a length of 508 mm (20.0 inches), an internal width of 152 mm (6.0 inches) and an internal depth of 51 mm (2.0 inches). The front and rear ends of the 141 1 pan are not closed.

An open cell polyurethane foam sheet 1414 with dimensions of 508 x 152 x 25 mm is wrapped in a polyethylene film and placed on the bottom of the tray 141 1 in such a way that the edges of the foam 414 and the pan 141 1 are aligned, and the top surface of the polyethylene film is smooth and free of seams, wrinkles or imperfections. The polyurethane foam 1414 has a compression modulus of 3.31 kPa (0.48 psi). With an indelible marker, a reference line is drawn across the width of the top surface of the polyethylene cover to 152 mm (6.0 inches) from one end (the front end), parallel to the transverse center line.

A 1415 rectilinear polycarbonate top plate 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 hole 51 mm (2.0 inches) in diameter is drilled in the center of the top plate 1415 (ie, the center of the hole is located at the intersection of the longitudinal and transverse axes of the upper surface of the top plate 1415) . A polycarbonate cylinder 1416 with an outside diameter of 51 mm (2.0 inches), an internal diameter of 37.5 mm (1.5 inches) and a height of 102 mm (4.0 inches) is glued in the hole of the top plate 1415 so that the lower edge of the cylinder 1416 is at the same level as the lower surface of the upper plate 1415 and the cylinder 1416 protrudes vertically 89 mm (3.5 inches) above the upper surface of the upper plate 1415, and the junction between the cylinder 1416 and the upper plate 1415 is impermeable. An annular recess 1417 with a height of 2 mm and a diameter of 44.5 mm (1.75 inches) is mechanically made on the lower inner edge of the cylinder 1416. Two holes of 1 mm diameter are drilled at an angle of 45 ° with the upper surface of the upper plate 1415 so that the holes intersect the inner surface of the cylinder 1416 immediately above the recess 1417 and are on opposite sides of the cylinder 1416 (i.e., separated by 180 °). Two 1418 stainless steel wires having a diameter of 1 mm in the holes are glued in a waterproof manner so that one end of each wire is flush with the inner wall of the cylinder and the other end protrudes from the upper surface of the upper plate 1415. Hereinafter, these wires will be referred to as "electrodes". A reference line is drawn across the width of the top plate 1415 of 152 mm (6.0 inches) from the leading edge parallel to the transverse center line. The upper plate unit 1415 / cylinder 1416 has a weight of approximately 180 grams.

Two steel dumbbells are also needed, 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.

Process: All tests are carried out at 23 ± 2 ° C and relative humidity of 35 ± fifteen %.

The polycarbonate tray 141 1 containing the wrapped foam board 1414 is placed on a suitable flat horizontal surface. A disposable absorbent product is removed from its packaging and the elastics of the fold are cut at suitable intervals to allow the product to lie flat. The product is weighed with an accuracy within ± 0. 1 gram on a suitable supenor loading scale and then placed on the covered foam sheet 1414 in the pickup apparatus with the front waist edge of the product aligned with the reference mark on the polyethylene cover. The product is centered along the longitudinal center line of the apparatus with the top canvas (body side) of the product facing upward and the rear waist edge towards the rear end of the foam sheet 1414. The top plate 1415 is Place on the product with the cylinder projecting upward. The drawn reference line is aligned with the front waist edge of the product and the rear end of the top plate 1415 is aligned with the trailing edge of the foam board 1414. Afterwards, the two 9.0 kg weights are placed gently on the upper plate 1415 so that the width of each weight is parallel to the transverse center line of the upper plate, and that each weight is 83 mm (3.25 inches) from the leading or trailing edge of the upper plate 1415.

A suitable electrical circuit is connected to the two electrodes to detect the presence of an electrically conductive fluid between them.

A suitable pump is configured, for example, model 7520-00 by Colé Parmer Instruments, Chicago, USA. US, or equivalent, to discharge a mass of 0.9% aqueous sodium chloride solution through a flexible plastic tube having an inside diameter of 3/8 inch (4.8 mm), for example, Tygon® R-3603 or the equivalent. The end portion of the tube is held vertically so that it is centered within the cylinder 1416 attached to the top plate 1415 with the discharge end of the tube facing down and located 50 mm (2 inches) below the top edge of the cylinder 1416. The pump is operated with a timer and pre-calibrated to discharge a 75.0 ml jet of 0.9% saline at a rate of 15 ml / s.

The pump is activated and a timer is operated immediately after activation. The pump delivers 75 ml of 0.9% NaCl solution to cylinder 1416 at a rate of 15 ml / s and then stops. As it is introduced into the cylinder 1416, the test fluid typically accumulates in the upper part of the absorbent structure to a certain extent. This fluid completes an electrical circuit between the two electrodes of the cylinder. After the supply of the jet, the meniscus of the solution descends as the liquid is absorbed into the structure. When the electrical circuit is interrupted due to the absence of free fluid between the electrodes of the cylinder, time is recorded.

The pickup time for a particular jet is the time interval between the activation of the pump for that jet and the point at which the electrical circuit is interrupted.

In this way, four jets are supplied to the product; Each discharge is 75 ml and is delivered at 15 ml / s. The time interval between the start of each download is 300 seconds.

The capture time for four downloads is recorded. Three products are tested in this way, and the average download time is calculated for each of the respective downloads (first to fourth inclusive).

Examples Absorbent structures were prepared in accordance with the present disclosure to compare their properties with the properties of the absorbent structures of the previous material. All the absorbent structures evaluated comprise superabsorbent polymer particles which are sandwiched between two substrate layers made of non-woven fabric material. For the data given in Table 1, all the Samples were taken from an absorbent core. Samples correspond to the absorbent core portion of an absorbent article (size 4) centered on the longitudinal center line 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 are taken, the absorbent structures of Examples 1 and 2 and Comparative Examples 1 and 2 have the same structure. They differ only with respect to the superabsorbent polymer particles that have been used. For the data given in Table 2, all the absorbent structures of Example 2 and Comparative Examples 1 and 2 have the same structure and differ only with respect to the superabsorbent polymer particles that have been used.

• Comparative example 1 An absorbent structure was prepared comprising the same superabsorbent polymer particles as those used in the Pampers Active Fit diapers commercially available in the United Kingdom in August 2010. These superabsorbent polymer particles are generally manufactured in accordance with the patent from the USA UU no. 2009 / 0275470A1. It should be noted that superabsorbent polymer particles can be isolated from commercially available Pampers Active Fit diapers as described in European Patent Application no. 10154618.2 entitled "Method of separating superabsorbent polymer particles from a solidified thermoplastic composition comprising polymers" (Method for 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 pm with a maximum of 1% less than 45 pm and a maximum of 1% greater than 7 0 pm.

• Comparative example 2 300 g of superabsorbent polymer particles were prepared according to Comparative Example 1 1 described in PCT patent application WO 2010/095427 A1 entitled "Polyacrylic acid-based water-absorbing resin powder and method for producing the same". An absorbent structure comprising these superabsorbent polymer particles was prepared.

• Example 1 4000 kg of superabsorbent polymer particles from Comparative Example 1 were sieved onto a standard 300 μ stainless steel wire mesh. AISI 304 in a screening equipment with a capacity of approximately 100-150 kg per hour to obtain 750 kg of superabsorbent polymer particles with a mean diameter (D50) of approximately 180-200 μ? and a particle size distribution of 45 to 300 μ? with a maximum of 3% less than 45 μ ?? and a maximum of 3% greater than 300 μ ??. An absorbent structure comprising these superabsorbent polymer particles was prepared.

• Example 2 300 g of superabsorbent polymer particles were prepared in accordance with Example 9 described in PCT patent application WO 2010/095427 A1 entitled "Polyacrylic acid-based water-absorbing resin powder and method for producing the same". An absorbent structure comprising these superabsorbent polymer particles was prepared.

Several parameters of the absorbent structures of the Examples 1 and 2 and of Comparative Examples 1 and 2: the time to reach a capture of 20 g / g (T20), the uptake at 20 min (U20), the time to reach an uptake of 80% of U20 (T80) %), the effective permeability in 20 minutes (K20) and the transient blocking rate of the gel (Kmin / K20) were determined in accordance with the K (t) test method described above. The UPM (Measurement of urine permeability) of the superabsorbent polymer particles of the absorbent structures of Examples 1 and 2 and of Comparative Examples 1 and 2 was determined in accordance with the UPM test method described above. The CRC (centrifugal holding capacity) of the superabsorbent polymer particles was determined in accordance with the WSP 241.2-05 method of EDANA.

Figures 18A and 18B depict the uptake in g / g as a function of time for the absorbent structures of Comparative Examples 1 and 2 as compared to Examples 1 and 2, as measured in accordance with test method K (t ) previously described.

The different values for the measured parameters are summarized in Table 1 below.

Table 1 As can be seen in Figures 18A and 18B and in Table 1, the times to achieve a pick-up of 20 g / g (T20) as measured in accordance with the test method K (t) for the absorbent structures manufactured in accordance with Examples 1 and 2 are significantly lower than for the absorbent structures prepared in accordance with Comparative Examples 1 and 2. Therefore, these absorbent structures are capable of rapidly absorbing liquid even in the dry stage, i.e., after initial exposure to the liquid.

In addition, as can be seen in Table 1, the superabsorbent polymer particles having a high permeability at equilibrium (a high UPM value), such as the superabsorbent polymer particles of the absorbent structures of Comparative Examples 1 and 2, do not they automatically lead to a high T20 value for the absorbent structure comprising these superabsorbent polymer particles, which means that the equilibrium permeability of the superabsorbent polymer particles does not constitute a reliable criterion in order to select the absorbent structures that are able to quickly absorb liquids after initial exposure to these.

• Diaper collection times comprising an absorbent structure comprising the superabsorbent polymer particles of Comparative Examples 1 or 2 versus diapers comprising an absorbent structure comprising the superabsorbent polymer particles according to the present disclosure.

The collection times of the Pampers Active Fit diapers, size 4, commercially distributed in the United Kingdom in August 2010, have been determined in accordance with the flat state capture test method described above. These diapers comprise an absorbent core comprising the superabsorbent polymer particles of Comparative Example 1. The collection times of the same diapers wherein the absorbent core has been replaced by an absorbent core with the same structure, but where the superabsorbent polymer particles have been replaced by the superabsorbent polymer particles of Comparative Example 2 or Example 2 , have been determined in accordance with the flat-state acquisition test method described above. The absorbent cores of all diapers have a dry thickness at the diaper crotch point of 1.7 mm, as measured in accordance with the gauge measurement test method described above. The values obtained for the capture times of all the samples are summarized in Table 2 below.

Table 2 As can be seen in Table 2 above, the capture times of the first discharge for diapers comprising an absorbent core comprising the superabsorbent polymer particles according to Comparative Examples 1 or 2 are higher than the collection time of the first discharge of the same diaper wherein the superabsorbent polymer particles have been replaced by the superabsorbent polymer particles of Example 2.

Therefore, the absorbent articles according to the present invention, specifically, absorbent articles comprising a structure Absorbent wherein one or more portions of the absorbent structure comprise at least 90% superabsorbent polymer particles and require a time to achieve a pick-up of 20 g / g (T20) of less than 440 s as measured in accordance with the method of K (t) test have improved absorption properties, especially in the first discharge, that is, when the article begins to get wet.

The dimensions and values described in the present description should not be understood as strictly limited to the exact numerical values mentioned. Instead, unless otherwise specified, each of these dimensions will refer to both the aforementioned value and a functionally equivalent range comprising that value. For example, a dimension expressed as "40 mm" will be understood as "approximately 40 mm".

Claims

CLAIMS 1 . An absorbent article comprising an absorbent structure; the absorbent article is divided into three portions: a front portion, a rear portion and a crotch portion disposed between the front portion and the rear portion; the absorbent structure comprises an absorbent core; the absorbent core has a dry thickness at the crotch point of the article of 0.2 to 5 mm, characterized in that one or more portions of the absorbent structure comprise at least 90% by weight of superabsorbent polymer particles and require a time to reach a uptake of 20 g / g (T20) less than 440 s as measured in accordance with the test method K (t). 2. The absorbent article according to claim 1, further characterized in that one of one or more of the portions of the absorbent structure is centered in the center of the front portion of the article and / or one of one or more of the portions of the structure. Absorbent is centered on the crotch point of the article. 3. The absorbent article according to any of the preceding claims, further characterized in that the absorbent article further comprises an upper canvas and a lower canvas, wherein the absorbent core is sandwiched between the upper canvas and the lower canvas. 4. The absorbent article according to any of the preceding claims, further characterized in that one or more of the portions of the absorbent structure have an effective permeability in 20 minutes (K20) of at least 2.9 · 10 to cm2 as measured in accordance with test method K (t). 5. The absorbent article in accordance with any of the previous claims, further characterized in that the pickup of one or more of the portions of the absorbent structure in 20 min (U20) is at least 24 g / g as measured in accordance with the test method K (t). 6. The absorbent article according to any of the preceding claims, further characterized in that the absorbent core is free of air felt. 7. The absorbent article according to any of the preceding claims, further characterized in that the absorbent core comprises an average amount of superabsorbent polymer particles per surface area of the absorbent core of 200 to 900 g / m2 in the crotch portion of the article. 8. The absorbent article according to any of the preceding claims, further characterized in that the absorbent article has a collection time for the first discharge of less than 27 s, as measured in accordance with the method of test in the flat state. 9. The absorbent article according to any of the preceding claims, further characterized in that the superabsorbent polymer particles are comprised in the absorbent core so that the superabsorbent polymer particles are deposited between a first and a second substrate layer, with the first layer of substrate oriented towards the lower canvas and the second layer of substrate oriented towards the upper canvas. 10. The absorbent article according to claim 9, further characterized in that the superabsorbent polymer particles are immobilized by adhesive thermoplastic material. eleven . The absorbent article according to claims 1 to 8, further characterized in that the absorbent core comprises a first substrate layer, at least a portion of the superabsorbent polymer particles are deposited on the first substrate layer, and the adhesive thermoplastic material immobilizes the superabsorbent polymer particles. 12. The absorbent article according to claim 1, further characterized in that the absorbent core further comprises a second substrate layer, at least a portion of the superabsorbent polymer particles are deposited on the second substrate layer, and the thermoplastic material adhesive immobilizes the superabsorbent polymer particles; the first and second substrate layers are combined together so that at least a portion of the adhesive thermoplastic material of the first substrate layer comes into contact with at least a portion of the adhesive thermoplastic material of the second substrate layer. 13. The absorbent article according to claims 10 to 12, further characterized in that the adhesive thermoplastic material forms a fibrous web on the superabsorbent polymer particles. 14. The absorbent article according to any of the preceding claims, further characterized in that at least one or more of the portions of the absorbent structure have a surface area of 30 cm 2 or more. 15. The absorbent article according to claim 14, further characterized in that at least one of one or more of the portions of the absorbent structure having a surface area of 30 cm 2 or more comprises a circular area.