Absorbent core comprising highly bulky intermediate layer and two different superabsorbent polymers

Abstract

An absorbent core (28) for an absorbent article (20), the absorbent core comprising a high loft intermediate layer (43) having a first superabsorbent polymer SAP1 (60) and a second superabsorbent polymer SAP2 (62) in the form of particles deposited on two different surfaces thereof, the SAP1 particles and the SAP2 particles being at least partially distributed within the high loft layer wherein the SAP1 has a higher capacity than the SAP2, and wherein the SAP2 has a higher capacity than the SAP2. And wherein the permeability of SAP2 is greater than 5 x 10-7 cm3. S / g.

Description

[0001] This application is a divisional application of patent application filed on December 10, 2020, with application number 202080107679.8 (PCT / CN2020 / 135174) and invention title: "Absorbent Core comprising a high-fluffy intermediate layer and two different superabsorbent polymers". Technical Field

[0002] This invention relates to absorbent cores and their use in personal hygiene absorbent articles. Absorbent cores are particularly useful in baby diapers. Background Technology

[0003] Absorbent products used for personal hygiene, such as disposable baby diapers, training pants for toddlers, or incontinence underwear for adults, are designed to absorb and contain bodily waste, particularly urine. These absorbent products consist of several layers that provide different functions, typically including a top sheet, a bottom sheet, an absorbent core between them, and other layers.

[0004] Absorbent cores should be able to absorb and retain effluent for extended periods (e.g., overnight for diapers), minimizing backflow to keep the wearer dry and prevent staining clothes or sheets. Absorbent cores typically consist of a blend of pulverized wood pulp cellulose fibers and superabsorbent polymer (SAP) particles (also known as absorbent gelling material (AGM)) as the absorbent material.

[0005] Recently, absorbent cores made of non-fluffed cellulose fibers (also known as "non-breathable felt" cores) have been proposed. SAP particles can be encapsulated, for example, in discrete sacs formed between two substrates (see, for example, WO95 / 11654, Tanzer et al.). It has also been proposed to attach SAP particles with a microfiber adhesive network to a nonwoven substrate by means of an adhesive (see, for example, WO2008 / 155699A1, Hundorf et al.).

[0006] Recently, a non-breathable felt core has been disclosed, comprising a high-loft fiber interlayer in which SAP is at least partially distributed (see, for example, WO2016 / 106,021A1, Bianchi et al.). SAP particles are applied to each side of the high-loft nonwoven fabric, wherein the SAP particles deposited on the surface of the high-loft layer are at least partially distributed and fixed within the pores of the high-loft layer. A tissue or nonwoven fabric is further adhesively attached to each of the high-loft interlayers to further secure the particles within the high-loft interlayers. At least a top cover layer, oriented towards the top sheet on the absorbent article, should be fluid-permeable. Additional wrapping layers are typically used to further stabilize these layers and form the absorbent core. These absorbent cores are typically produced continuously as a single stream that can be collected into rolls. The roll can be transported to a diaper production line, where the absorbent cores are individually cut and continuously assembled with other components of the absorbent article.

[0007] Publications of this type of absorber core include WO2020 / 025401 (BASF, Ge et al.), WO2020 / 032280, WO2020 / 032281, WO2020 / 032282, WO2020 / 032283, and WO2020 / 032284 (Nippon SHOKUBAI). Different types of SAPs have been proposed for use on the top and bottom sides of the high-loft layer: a high-permeability SAP in the top layer and a high-retention-capacity SAP in the bottom layer.

[0008] There is a ongoing need to improve the performance of absorbent cores, particularly in terms of absorption rate, capacity, low rewetting, and wearing comfort, while keeping the total manufacturing cost as low as possible. Summary of the Invention

[0009] This invention relates to an absorbent core extending in both transverse and longitudinal directions, having a thickness in the vertical direction, and comprising a liquid-permeable top cover layer, a bottom cover layer, and an intermediate layer sandwiched between the top and bottom cover layers. The intermediate layer is a high-loft porous layer, such as a carded nonwoven fabric, having a top surface oriented toward the top cover layer and a bottom surface oriented toward the bottom cover layer. The absorbent core contains two different types of superabsorbent polymer (SAP) particles deposited on corresponding sides of the high-loft core and at least partially distributed within the intermediate layer. According to the invention, the absorbent core comprises:

[0010] - The first superabsorbent polymer (“SAP1”) in particle form deposited on the top surface of the high-fluffy intermediate layer;

[0011] - A second superabsorbent polymer (“SAP2”) in particulate form deposited on the bottom surface of the high-fluffy intermediate layer.

[0012] While it has been previously suggested to deposit high-permeability SAPs on the top side of a high-loft layer and high-retention-capacity SAPs on the bottom surface of a high-loft layer, this invention has found that when the first SAP has a higher capacity (e.g., as measured by the CRC method) than the second SAP and the second SAP has a permeability greater than 5 UPM units (e.g., as measured by the UPM method), an absorber core with a generally good balance between acquisition rate and backflow is obtained. Preferably, SAP2 has higher permeability than SAP1.

[0013] The absorbent core may contain at least 60% by weight of SAP (all combined), and particularly at least 70% by weight, relative to the total weight of the core. The high-loft interlayer may be formed entirely of synthetic fibers and may be substantially free of fluffy cellulose fibers, but fibers of natural or naturally derived origin, such as cellulose, cotton, or viscose, may also be present in the interlayer and / or top and / or bottom cover layers.

[0014] The top and bottom cover layers are typically nonwovens or tissue paper. For example, low-basic-weight tissue paper is readily available and relatively inexpensive. The absorbent core may also include a wrapping layer that completely covers the bottom or top cover layer, typically forming a C-shaped wrap around the longitudinally extending side edges of these layers, and thus better securing the SAP particles within the absorbent core. The wrapping layer provides better encapsulation of the SAP, preventing loss at the side edges of the core. Alternatively, such C-shaped wraps may also be formed by either the top or bottom cover layer.

[0015] The absorbent core may also include a double high-fluff layer structure comprising a first high-fluff intermediate layer and a second high-fluff intermediate layer. This structure can provide additional benefits, such as in SAP fixation, and a greater amount of SAP particles can be distributed between the two layers. These and other optional features of the invention will be described in the following description. Attached Figure Description

[0016] Figure 1 A top view of an exemplary absorbent core is shown, in which the top and middle layers are partially removed;

[0017] Figure 2 A schematic exploded cross-sectional view of the absorber core is shown;

[0018] Figure 3 A schematic exploded cross-sectional view of an alternative absorber core is shown;

[0019] Figure 4 A schematic cross-sectional view of an alternative absorber core is shown;

[0020] Figure 5As shown Figure 2 A schematic cross-sectional view of the absorber core and the core-encapsulating layer in the image;

[0021] Figure 6 A schematic cross-sectional view of an alternative absorber core including two highly fluffy intermediate layers is shown;

[0022] Figure 7 It shows including Figure 5 A schematic cross-sectional view of the absorbent core of the absorbent product;

[0023] Figure 8 This is a schematic diagram of the method for preparing the absorber core of the present invention;

[0024] Figure 9 This is a partial cross-sectional side view of a suitable permeability measurement system used for urine permeability measurement testing;

[0025] Figure 10 This is a cross-sectional side view of the piston / cylinder assembly used for urine permeability measurement testing;

[0026] Figure 11 It is applicable Figure 10 A top view of the piston head of the piston / cylinder assembly shown;

[0027] Figure 12 yes Figure 10 A cross-sectional side view of the piston / cylinder assembly placed on a sintering disk for the swollen phase. Detailed Implementation

[0028] introduction

[0029] As used herein, the terms “comprising” or “including” are open-ended terms; each specifies the presence of a subsequent feature, such as a component, but does not exclude the presence of other features, such as elements, steps, or components, known in the art or disclosed herein. These terms based on the verb “comprising” should be interpreted to cover the narrower term “substantially constitutes…”, which excludes any unmentioned elements, steps, or components that significantly affect the manner in which said feature performs its function; and the broader term “consisting of…”, which excludes any unspecified elements, steps, or components. Any preferred or exemplary embodiments described below do not limit the scope of the claims unless expressly stated otherwise. Words such as “usually,” “often,” “preferably,” “advantageously,” “specifically,” etc., also define the feature, and they are not intended to limit the scope of the claims unless expressly stated otherwise.

[0030] As used herein, the terms “nonwoven fabric,” “nonwoven layer,” or “nonwoven fiber web” are used interchangeably to refer to engineered fiber components that are primarily planar and have been given a design-level structural integrity through physical and / or chemical means, but do not include weaving, knitting, or papermaking (as defined in ISO 9092:2019). Oriented or randomly oriented fibers are bonded together by friction and / or cohesive and / or adhesive forces. These fibers may be derived from natural or synthetic sources and may be short fibers, continuous filaments, or in-situ formed fibers. Commercially available fibers have diameters ranging from less than about 0.001 mm to greater than about 0.2 mm and come in several different forms, such as short fibers (known as chemically woven short fibers or chopped fibers), continuous monofilaments (filaments or monofilaments), untwisted continuous filament bundles (tows), and twisted continuous filament bundles (yarns). Nonwoven fiber webs can be formed by a variety of methods, such as meltblown, spunbond, solution spinning, electrospinning, carding, and air-jet spinning. The basis weight of nonwoven fiber webs is usually expressed in grams per square meter (g / m²). 2 (or gsm) indicates.

[0031] General description of the absorption core

[0032] As used herein, the term "absorbent core" refers to a component of an absorbent article comprising absorbent material capable of absorbing and retaining bodily fluids, particularly urine. Absorbent cores according to the invention are typically manufactured in a continuous flow that can be stored and transported, for example, as rolls of absorbent core material, and then individualized upon integration into absorbent articles such as diapers. The absorbent core has the majority of the absorbent capacity of a component of the absorbent article and comprises all or at least most of a superabsorbent polymer (referred to herein as "SAP") particles. The terms "absorbent core" and "core" are used interchangeably herein. Some absorbent articles may include two or more different absorbent cores, but typically only one absorbent core is found in absorbent articles such as diapers.

[0033] The absorbent core of the present invention is substantially planar. “Substantially planar” means that the absorbent core can be laid flat on a flat surface and extends primarily along the x and y directions. The absorbent core can also typically be thin and conformable, such that it can be laid out on curved surfaces, such as a tumbler, during the manufacturing process, or stored and handled as a continuous stock roll of material comprising multiple cores before being converted into an absorbent article.

[0034] An exemplary individualized absorber core is shown in a flat state. Figure 1 The height of the absorbing core in the z-direction is relatively small compared to its other dimensions in the lateral x-direction and longitudinal y-direction. Unless otherwise specified, the dimensions and areas disclosed herein apply to the core in this planar configuration.

[0035] For ease of discussion, the absorbent cores, articles, and methods of the present invention will be discussed with reference to the accompanying drawings and the figures cited in those drawings; however, unless specifically indicated otherwise, these are not intended to limit the scope of the claims.

[0036] High-volume middle layer 43

[0037] The absorbent core of the present invention includes a highly fluffy intermediate layer 43, such as Figures 1 to 2 First, as shown. The term "high-loft" refers to a low-density, loose fabric compared to a flat, papery fabric. High-loft fiber webs are characterized by a relatively high porosity. This means that there is a relatively high amount of void space within which superabsorbent polymer particles can be distributed.

[0038] The high-loose layer (without superabsorbent particles) of the present invention can achieve a density of less than 0.20 g / cm³ at a pressure of 4.14 kPa (0.6 psi). 3 Especially at 0.05g / cm 3 Up to 0.15 g / cm 3 Density within the range.

[0039] The high-loose layer (without superabsorbent particles) of the present invention can achieve a density of less than 0.20 g / cm³ at a pressure of 2.07 kPa (0.3 psi). 3 Especially at 0.02 g / cm 3 Up to 0.15 g / cm 3 Density within the range.

[0040] The high-loose layer (without superabsorbent particles) of the present invention can achieve a density of less than 0.15 g / cm³ at a pressure of 0.83 kPa (0.12 psi). 3 Especially at 0.01 g / cm 3 Up to 0.15 g / cm 3 Density within the range.

[0041] The density can be calculated by dividing the basis weight of the high-loft layer by the thickness measured at the corresponding pressure shown (see the method details in the "Test Procedures" section below).

[0042] The interlayer is preferably a nonwoven fabric, but other types of high-loft materials are not excluded. The interlayer may contain or be composed of synthetic fibers, optionally blended with natural fibers such as cellulose fibers, cotton fibers, or viscose fibers. The interlayer may be substantially free of free cellulose fibers that are not bonded to other fibers of the nonwoven fabric. The amount of such free cellulose fibers in the absorbent core may be less than 10%, less than 5%, less than 1% of the total absorbent core weight, or completely free of such free cellulose fibers. The high-loft material may contain at least 10%, 30%, 50%, 70%, 90%, and up to 100% synthetic fibers by weight of the high-loft layer.

[0043] The fibers forming the intermediate layer can be made partly or entirely of relatively elastic synthetic fibers, particularly polypropylene (PP), polyamide (PA, such as nylon), or polyethylene terephthalate (PET) fibers. The diameter of the fibers can, for example, range from 0.01 mm to 0.50 mm.

[0044] The thickness, basis weight, and density of the interlayer are typically uniform in both the transverse (x) and longitudinal (y) directions. The fiber orientation within the interlayer can be non-uniform, such as having a dominant fiber orientation in one direction (x or y), as in carded nonwovens. Furthermore, the fiber orientation in the thickness direction (z) of the interlayer can differ from the dominant orientation in one direction (x or y) or in both directions (x and y).

[0045] As measured at a pressure of 4.14 kPa (0.6 psi) (according to the test method further described below), the high-loft interlayer may in particular have a thickness of at least 0.30 mm, especially in the range of 0.30 mm to 2.00 mm or from 0.50 mm to 1.5 mm.

[0046] Measured at a pressure of 0.83 kPa (0.12 psi) (according to the test method described further below), the high-loft layer can in particular have a thickness ranging from 0.30 mm to 2.50 mm, or from 0.5 mm to 2.0 mm, or from 0.7 mm to 1.3 mm.

[0047] The basis weight of a high-loft intermediate layer can be, for example, in the range of 15 gsm to 500 gsm, particularly 20 gsm to 200 gsm, and more particularly 30 gsm to 100 gsm.

[0048] Unless otherwise specified, the values ​​for the intermediate layers mentioned herein are for high-loft materials only, i.e., before SAP particles are deposited between fibers or before an adhesive is applied thereon. When the absorbent core contains two or more high-loft intermediate layers, these intermediate layers may be the same or different.

[0049] While the invention is not limited to specific types of nonwovens or fibers, a specific example of a suitable nonwoven layer is a bonded carded fiber web (“BCW”). A “bonded carded fiber web” refers to a nonwoven fabric made of short fibers fed through a combing or carding unit that longitudinally separates and typically aligns the short fibers to form a fiber nonwoven web with a generally longitudinal orientation. This fiber web can then be stretched through a heated drum, thereby creating bonding across the entire fabric without applying specific pressure (a ventilated bonding process). Such ventilated bonded carded fiber web (TABCW) materials provide a low-density, loosely ventilated bonded carded fiber web. Examples of suitable TABCWs are disclosed, for example, in WO2000 / 71067 (KIM DOO-HONG et al.). Carded fiber webs can also be bonded by other methods, such as the mechanical entanglement of fibers (e.g., needle punching).

[0050] In carded nonwoven fabrics, the fibers in the web are primarily aligned longitudinally and exhibit a more uniform fiber arrangement than in other nonwoven fabrics, resulting in greater stability and internal bond strength, especially in the longitudinal direction. The chosen bonding technique affects the integrity of the fabric. Air-ventilated bonded carded fiber webs offer excellent softness, bulk density, and compressibility, as well as rapid penetration and good rewetting. A wide variety of synthetic, natural, and regenerated fibers in denier can be used. Soft PE / PP bicomponent short fibers are particularly useful. Carded nonwoven materials may, for example, contain short fibers ranging from about 3 denier to about 10 denier. Carded nonwovens are also available directly from all common suppliers of nonwoven fiber webs used in absorbent articles, such as Fitesa Ltd or Fiberweb Technical Nonwovens.

[0051] High-loft layers can also be spunbond nonwovens. Spunbond is a general term describing the direct fabrication of nonwoven fiber webs from thermoplastic polymers. Spunbond includes two processes and combinations of both: spunbond (also known as spunbond) nonwovens and meltblown nonwovens. In the spunbond process, polymer particles melt, and the molten polymer is extruded through a spinneret. Continuous filaments are cooled and deposited onto a conveyor to form a uniform fiber web. Some residual heat can cause the filaments to adhere to each other, but this cannot be considered the primary method of bonding. The spunbond process has the advantage of resulting in stronger nonwovens, but the flexibility of the raw material is more limited. Co-extrusion of a second component is used in several spunbond processes, typically to provide additional properties or bonding capabilities. In meltblown fiber web formation, a low-viscosity polymer is extruded into a high-speed gas stream as it leaves the spinneret. This disperses the melt, solidifies it, and breaks it down into a fiber web.

[0052] The periphery of the intermediate layer 43 typically defines a front edge 280, a rear edge 282, and two longitudinally extending side edges 284, 286 of the absorbent core 28. The front and rear edges are typically shorter than the side edges. The front edge of the intermediate layer corresponds to an edge intended to be positioned toward the front edge of the absorbent article, in which the core is or will be integrated.

[0053] The superabsorbent material can be uniformly distributed on the surface of the core. Alternatively, the superabsorbent material can be irregularly shaped, with a higher amount of SAP (superabsorbent polymer) towards the front half of the core relative to the rear half. This is because more fluid typically flows towards the front of the article, where the core will be contained within it. In addition to irregular SAP distributions in the longitudinal direction (y), SAP can also be irregularly shaped in the transverse direction (x). However, SAP is typically uniformly distributed in both the transverse (x) and longitudinal (y) directions, which simplifies production: in this case, either of the two shorter sides can be considered the front edge, while the opposite side will be the rear edge. The absorbent core may comprise one, two, or more highly fluffy intermediate layers. See below. Figure 6 Further discussion includes the absorption core with two highly fluffy intermediate layers.

[0054] Intermediate layers (or multiple intermediate layers) serve as the substrate for SAP particles 60, 62, which are at least partially distributed within the pores of the intermediate layers. The SAP particles can be substantially uniformly blended across the entire thickness of the high-loft layer. However, the SAP particles can be unevenly distributed in the vertical direction. SAP particles are typically deposited on one side of the nonwoven fabric and are drawn into the high-loft nonwoven fabric, for example, by gravity or negative pressure on the opposite side of the nonwoven fabric. In this way, some particles remain close to the surface of the high-loft intermediate layer, while other, generally smaller particles can penetrate deeper into the pores of the high-loft nonwoven fabric. SAP particles that are not trapped within the pores of the high-loft layer but remain on the surface can be further secured by adhesive layers 71 or 72. The adhesive can be applied to the top and bottom capping layers before bonding, while still adhering to the high-loft intermediate layer. Typically, SAP particles are applied sequentially from each side of the high-loft layer as a first layer 60 and a second layer 62 of SAP, as shown below. Figure 8 As further illustrated, when viewed in the z-direction, this SAP particle deposition process can result in a z-shaped distribution pattern of SAP within the intermediate layer, comprising two or more density peaks separated by at least one buffer zone.

[0055] Top cover layer 41 and bottom cover layer 42

[0056] A high-loft interlayer 43 is sandwiched between a top cover layer 41 and a bottom cover layer 42. The top cover layer 41 is located on the wearer-facing side of the core, closest to the absorbent article. Therefore, the top cover layer is liquid-permeable, allowing fluid to easily pass through it to the interlayer during use. The bottom cover layer is positioned on the opposite side of the interlayer. The bottom cover layer can be liquid-permeable or liquid-impermeable. The top and bottom cover layers provide coverage on both sides of the interlayer to prevent SAP particles from detaching from the high-loft material during core and article preparation and / or during use of the absorbent article.

[0057] The top and bottom capping layers can be made of relatively thin and inexpensive materials, such as those commonly used in the production of conventional cores. The top and bottom capping layers can be, for example, thin paper (breathable felt or wet-laid web) with a basis weight range of, for example, 5 gsm to 50 gsm, particularly 10 gsm to 30 gsm. The top and bottom capping layers can also be formed from low-basis-weight nonwoven fiber webs with a basis weight between 5 gsm and 30 gsm, such as carded nonwovens, spunbond nonwovens (“S”), or meltblown nonwovens (“M”), and laminates of any of these. For example, spun melt polypropylene nonwovens are suitable, particularly nonwovens with a laminated web structure of SMS, SMMS, or SSMMS and a basis weight range of about 5 gsm to 20 gsm. Such materials are disclosed, for example, in US7,744,576, US2011 / 0,268,932A1, US2011 / 0319848A1, and US2011 / 0,250,413A1. Nonwoven materials generally have inherent hydrophobicity and can therefore be made hydrophilic, for example, by treating the top cover with a surfactant or other methods known in the art. The top and bottom covers can be made of the same or different materials, and optionally the top or bottom covers can be treated differently to make the top cover more hydrophilic than the bottom cover.

[0058] The top cover layer 41 may be wider than the bottom cover layer 42, allowing the excess material to be folded around the longitudinal side edges 284, 286 of the core to form a C-shaped wrap seal over the bottom cover layer 42, such as... Figure 3 As shown. Alternatively, the bottom cover layer 42 may be wider than the top cover layer 41, allowing the excess material to be folded around the longitudinal side edges 284, 286 of the core to form a C-shaped wrap seal over the top cover layer 41, as shown. Figure 4 As shown.

[0059] In addition to the top and bottom cover layers, the absorbent core may also include a wrapping layer 3 that surrounds the high-loft intermediate layer and the two cover layers, such as forming a C-shaped wrapping through the longitudinally extending side edges 284, 286 around the core. Figure 5 As shown. A “C-shaped wrap” refers to a layer that at least covers the top or bottom side of the core, extending along its side edges to form folds, which are then typically folded and attached to the opposite side of the core by adhesive. The wrapping layer 3 can therefore have a cross-section resembling the letter C (when rotated 90°). The C-shaped wrap structure can further facilitate the inclusion of SAP particles during the preparation or wearing of absorbent articles. The wrapping layer can be made, for example, from a low-basis-weight nonwoven layer, such as a basis weight of 5 to 40 gsm, particularly 8 to 25 gsm, especially SMS nonwovens, but other materials are certainly possible. The wrapping layer 3 in… Figure 5 The C-shaped wrapping layer 3 extends from the bottom side of the core and has flaps folded over the top side of the core. An inverted configuration is also possible, in which the C-shaped wrapping layer 3 extends from the top side and the flaps fold over the bottom side. The folded flaps may terminate and attach near the longitudinally extending side edge of the core, or may be longer than represented, so that they overlap and attach to another. It is also conceivable that the C-shaped wrapping structure may be formed by one of a top cover layer or a bottom cover layer that extends laterally along the longitudinally extending side edge of the core and forms flaps as described for wrapping layer 3. The presence of wrapping layers is optional, but is particularly preferred if the top and bottom cover layers are not sealed along their longitudinal sides.

[0060] The top cover layer 41 and / or the bottom cover layer 42 are preferably attached to the intermediate layer 43. Adhesive layer 71 may be applied, for example, between the top cover layer and the intermediate layer 43. Any type of conventional adhesive and adhesive application method can be used. Typically, hot melt adhesive can be sprayed onto substantially the entire surface of both layers before bringing them into close contact to allow them to attach. Adhesive can also be applied to one of the two layers (specifically the top or bottom cover layer in this case) by contact application, typically by applying a series of parallel lines of adhesive in a longitudinal (y-direction) groove. Adhesive layer 72 may similarly be applied between the bottom cover layer 42 and the intermediate layer 43. These adhesive layers also have the advantage that they can fix the SAP particles in a dry state, which have not penetrated into the intermediate layer during core preparation.

[0061] Superabsorbent polymer particles 60, 62, 64

[0062] SAP is a water-insoluble but water-swellable crosslinked polymer capable of absorbing large amounts of fluid. SAP is in particulate form so that it is flowable in a dry state. Typical particulate SAP is a polyacrylate polymer; however, other polymer materials can also be used. For example, starch-based particulate absorbent polymers, as well as polyacrylamide copolymers, ethylene maleic anhydride copolymers, crosslinked carboxymethyl cellulose, polyvinyl alcohol copolymers, and starch-grafted copolymers of crosslinked polyethylene oxide and polyacrylonitrile can also be used.

[0063] SAP can be an internally and / or surface-crosslinked polyacrylate and polyacrylic acid polymer. The superabsorbent polymer of the present invention can be selected from internally and surface-crosslinked polyacrylate and polyacrylic acid polymers. The superabsorbent polymer can be internally crosslinked, i.e., polymerized in the presence of a compound having two or more polymerizable groups, which can be free-radical copolymerized into the polymer network. Exemplary superabsorbent polymer particles of the prior art are described, for example, in WO2006 / 083584, WO2007 / 047598, WO2007 / 046052, WO2009 / 155265, and WO2009 / 155264. Preferably, the SAP particles comprise a crosslinked polymer of polyacrylic acid or its salts or polyacrylates or derivatives thereof.

[0064] The absorbent core of this invention comprises at least two different types of SAP. The first SAP particle is referred to herein as "SAP1," and the second SAP particle as "SAP2," both collectively referred to as SAP. SAP1 and SAP2 are both in granular form and are deposited on the top and bottom surfaces of a high-loft interlayer, respectively. The SAP particles are typically deposited sequentially on each side of the high-loft layer, wherein the high-loft side is laminated and flipped between depositions. During the deposition steps, the SAP particles can at least partially penetrate into the pores of the high-loft layer, such that they are at least partially distributed within the high-loft interlayer nonwoven fabric. Thus, on one hand, the particles are fixed within the pores of the high-loft layer and secured by a paper or nonwoven layer laminated onto each of the top and bottom surfaces of the high-loft interlayer.

[0065] The term “superabsorbent polymer” (abbreviated herein as “SAP” in both singular and plural forms) generally refers to an absorbent material that can absorb at least 10 times its weight of a 0.9% saline solution (referred to herein as capacity) as measured using a centrifugation retention capacity (CRC) test (EDANA method NWSP 241.0.R2 (19)). The SAP used in this invention is preferably highly absorbent, wherein SAP1 has a higher capacity than SAP2.

[0066] The capacity of SAP1 can be at least 30 g / g, preferably in the range of 32 g / g to 50 g / g, and the capacity of SAP2 can be at least 20 g / g, preferably in the range of 25 g / g to 45 g / g. The capacity of SAP1 can be at least 2 g / g higher than the capacity of SAP2, preferably at least 4 g / g.

[0067] The UPM testing method typically measures the flow resistance of the pre-swollen layer of superabsorbent polymer particles, i.e., the flow resistance at equilibrium. Therefore, such superabsorbent polymer particles with high UPM values ​​exhibit high permeability when a significant volume of the absorbent article has been wetted by the liquid effluent. These embodiments demonstrate good absorption characteristics not only during the initial flow but also during subsequent flows.

[0068] UPM permeability can be expressed as a UPM value, where 1 UPM unit is 1 × 10 -7 (cm 3 (s) / g. According to the present invention, the permeability of SAP2 is greater than 5 UPM units, and more preferably higher than that of SAP1. The permeability at equilibrium is measured using the UPM method further described below. The UPM value is measured according to the UPM test method described herein. This method is closely related to some SFC test methods already used in the prior art.

[0069] SAP2's penetration is preferably greater than 6 × 10⁻⁶. -7 cm 3 .s / g or at least 7.5×10 -7 cm 3 .s / g or at least 10×10 - 7 cm 3 .s / g or at least 15×10 -7 cm 3 .s / g, preferably at 30×10 -7 cm 3 .s / g to 70×10 -7 cm 3 Within the range of .s / g, SAP2's permeability can be at least 5 × 10⁻⁶ higher than SAP1's. -7 cm 3 .s / g, preferably with a permeability at least 10 × 10 ppm higher than SAP1. -7 cm 3 .s / g.

[0070] Superabsorbent materials with the desired properties can be sourced from commercial suppliers with a wide range of available SAP properties. Typically, capacity and permeability are traded off, as a SAP with high capacity may have relatively low permeability, and vice versa.

[0071] SAP particles can be relatively small in their dry state (their longest dimension is less than 1 mm) and can be generally spherical in shape, but granules, fibers, flakes, spheres, powders, plates, and other shapes and forms are also known to those skilled in the art. Typically, SAP can be in the form of spherical particles. Therefore, absorbent materials can consist of or be substantially composed of SAP distributed within a high-loft nonwoven fabric.

[0072] Some SAP particles in SAP particles can aggregate, as taught in EP3,391,961A1 (Kamphus, P&G). Aggregated superabsorbent polymer particles can be obtained by various methods. Aggregated particles can be obtained, for example, by aggregating precursor particles with an interparticle crosslinking agent that reacts with the polymeric material of the precursor particles to form crosslinks between the precursor particles, as disclosed, for example, in US5,300,565, US5,180,622 (both granted to Berg), US5,149,334, US5,102,597 (both granted to Roe), and US5,492,962 (Lahrman). Other methods for obtaining aggregated SAP particles are described, for example, in EP3056521B1 (Kim et al.), EP1512712B1 (Koji et al.), US10414876B2 (Jang et al.), US7429009B2 (Nagasawa et al.), EP220224911 (Higashimoto et al.), and EP2011803B1 (Handa et al.).

[0073] Aggregated superabsorbent polymer particles can also be obtained by a method comprising the steps of: providing superabsorbent polymer particles and mixing the superabsorbent polymer particles with a solution containing water and a multivalent salt having a valence of 3 or higher. EP2,944,376A1 further discloses this method. The superabsorbent polymer particles of the core of the present invention may particularly comprise at least 5% or at least 10% or at least 20% or at least 30% or at least 40% or at least 50% aggregated superabsorbent polymer particles by weight.

[0074] The surface of SAP particles may be coated. The surface of SAP may be surface cross-linked. SAP particles may also contain surface and / or edge-modified clay lamellae. Preferably, the clay lamellae are montmorillonite, lithium montmorillonite, synthetic lithium saponite, or mixtures thereof. Preferably, the clay lamellae are synthetic lithium saponite. SAP may contain 0.1% to 5% by weight of clay lamellae with modified surfaces and / or edges compared to the weight of the precursor superabsorbent polymer particles.

[0075] SAPs can also be characterized by the time (so-called T20) taken to reach an absorption capacity of 20 g / g being less than 220 s, as measured by the SAP K(t) test method described below. Either SAP1 and / or SAP2 can have a T20 in the range of 100 s to 220 s. The T20 value of SAP1 or SAP2 or both SAPs can be less than 200 s or less than 180 s or less than 160 s. The time T20 can also be at least 100 s, 104 s, 120 s or 140 s, and any combination of these upper and lower limits, to form, for example, a range from 100 s to 200 s.

[0076] SAPs with the required T20 can be synthesized using, for example, the teaching content of WO2015 / 041,784A1, which discloses SAPs with a T20 of 104s to 211s. SAPs with the required T20 can also be obtained directly from conventional SAP vendors. For example, the following embodiment of the invention uses an SAP purchased via Amazon under the product name SCHAUCH HVDE 235 "Der Alleskoenner", with a measured SAP T20 of 165s.

[0077] Unless otherwise specified, the values ​​used to define SAP (e.g., CRC capacity, UPM permeability, AAP, T20, etc.) mentioned herein refer to the properties of SAP as considered as raw material at the time of supply. These properties should be measured as much as possible before manufacturing the absorbent core; otherwise, it may be difficult to separate the SAP from the finished absorbent core because some of the larger particles may partially adhere to the top or bottom substrate layer, and smaller particles may have further migrated within the pores of the high-bulk layer.

[0078] The total amount of SAP present in the absorbent core can also vary depending on the intended user of the product. Newborn diapers require less SAP than infant or adult incontinence diapers. For a typical baby diaper, the total amount of all SAP in the core can be, for example, about 2g to 50g, particularly 5g to 40g or 10g to 20g. The absorbent core typically contains 3g to 10g of SAP1 and / or 3g to 10g of SAP2. The basis weight of all SAP within the absorbent core can be, for example, at least 50g / m³. 2 100g / m 2 200g / m 2 300g / m 2 400g / m 2 500g / m 2 Or larger, or 200g / m 2 Up to 400g / m 2 The average basis weight of SAP1 can be at least 50 g / m³. 2Preferably 100g / m 2 Up to 300g / m 2 The average basis weight of SAP2 can be at least 50 g / m³. 2 Preferably 100g / m 2 Up to 300g / m 2 The average basis weight is calculated by dividing the weight of the SAP under consideration by the surface area of ​​the high-loft interlayer.

[0079] The absorbent core typically contains at least 60% by weight of superabsorbent polymer particles (all added SAP) based on the total weight of the core, preferably at least 70% by weight.

[0080] Preparation method

[0081] An exemplary continuous method for preparing an absorber core is shown in Figure 8 The methods and equipment discussed above are generally similar to those in CN101797201 or WO2020 / 025401 (BASF, Ge et al.). Figure 3 The method and equipment disclosed in the figure are shown. The arrows in the figure indicate the rotation direction of the dewinding and winding cylinders and the direction of material movement during the production process. Other methods and modifications are, of course, also possible.

[0082] like Figure 8 As shown, the equipment for preparing the absorbent core may include a bottom cover layer fiber web unwinding machine 6, a bottom cover layer glue spray nozzle 7, a high-loft intermediate layer fiber web unwinding machine 8, a first SAP particle distributor 9 and optional vacuum suction box 10, first pair of rollers 11 and 12, a second SAP particle distributor 13 and optional vacuum suction box 14, a top cover layer fiber web unwinding machine 15, a top cover layer nozzle 16, second pair of rollers 17 and 18, trimming blades 19 and 20, and a product roll winding roller 21.

[0083] Both the first SAP pellet distributor 9 and the second SAP pellet distributor 13 can be equipped with a variable frequency speed control device. Figure 8 (not shown in the image) The variable frequency speed control device is adjusted to maintain a vibration frequency that matches the linear speed of the product winding roller 21, and to ensure that most of the deposited SAP is evenly distributed on the high-loft fiber web 43.

[0084] During production, a roll of bottom cover material 42 (e.g., a roll of paper or nonwoven fabric) is mounted on a bottom cover fiber web unwinding machine 6. A roll of high-loft nonwoven fabric 43 is mounted on an intermediate layer fiber web unwinding machine 8. The initial density and thickness of the high-loft intermediate layer can be conveniently measured on the raw material using the thickness and density measurement methods described further below.

[0085] SAP particles are loaded into a first SAP particle sieve plate 9 and a second SAP particle sieve plate 13. A roll of top cover material 41 (which may be a paper or nonwoven roll) is mounted on a top cover fiber web unwinder 15. In a continuous process of preparing the absorbent core, a bottom cover layer 42 passes through a nozzle 7 and is applied with adhesive 72 on one side, and is then attached to an intermediate layer 43 between first pressure rollers 11 and 12. A high-loft nonwoven intermediate layer 43 passes through a first SAP distributor 9 and a vacuum suction box 10, where SAP particles 62 are deposited into the intermediate layer and at least partially distributed from the first side into the fibers of the intermediate layer.

[0086] After the bottom cover layer 42 and the intermediate layer 43 are pressed together between rollers 11 and 12, these combined layers optionally pass between the second SAP particle sieve plate 13 and the vacuum suction box 14, which cooperate to deposit SAP particles 60 onto the second surface of the intermediate layer and to blend the SAP particles from the second surface into the fibers of the intermediate layer. The top cover layer 41, with adhesive 72 applied via the spray nozzle 16, is then bonded to the intermediate layer to cover the second surface of the intermediate layer between the two pressure rollers 17 and 18. Of course, the top and bottom cover layers can be used interchangeably in the foregoing.

[0087] Pressure rollers 17 and 18 may have substantially flat surfaces, or they may have raised areas where additional pressure and heat should be applied to the core. These raised areas may coincide with groove areas, thereby providing mechanical bonding, ultrasonic bonding, and / or thermal bonding within groove area 26. Pressure rollers 11 to 12, 17 to 18 may be heated. It is also possible that these rollers have raised areas along the longitudinal side edges and / or the rear and front edges (360° circumference) of the core. Better bonding can be achieved in these areas when they are free of SAP, as in groove area 26. Trimming blades 19 and 20 may be provided to trim the longitudinal side edges of the absorbent core continuous strip before the absorbent core material flow is finally wound into an absorbent core material roll by product roll winding roller 21.

[0088] The resulting absorbent core material rolls can be stored or transported to the product manufacturing site, where they are further transformed into absorbent products. Alternatively, the absorbent core material stream can be fed directly into the conversion line without forming rolls; in this case, the absorbent cores are individualized by cutting along their front and rear edges.

[0089] Such as about Figure 5 As shown and discussed, the wrapping layer 3 ( Figure 8 (Not shown) It can also be fed before the core material is rolled up to wrap the top, middle, and bottom cover layers to prevent SAP loss through the side edges of the absorbent core. Alternative wrapping layers of this type can also be attached to the core when the core material fiber web is further transformed.

[0090] Core 28b with double high-loft nonwoven layers 431 and 432

[0091] The absorbent core 28 discussed above comprises a single high-loft nonwoven layer; however, the absorbent core may also include two (or more) high-loft nonwoven layers between the top and bottom overlays. This is, for example, in... Figure 6 As shown, the absorbent core 28b, which includes a first intermediate layer 431 and a second intermediate layer 432, is shown sandwiched between the top cover layer 41 and the bottom cover layer 42.

[0092] Therefore, the absorbent core 28b may include a first intermediate layer 431 and a second intermediate layer 432, each being a high-loft fiber nonwoven layer comprising, for example, three or more layers of superabsorbent polymer particles 60, 62, 64 at least partially distributed within the pores of the high-loft intermediate layer. The two (or more) high-loft intermediate layers may be composed of the same material or different high-loft nonwoven fabrics. For example, the permeability of the upper intermediate layer can be enhanced by using a low-basic-weight high-loft material, and the softness of the bottom cover layer can be enhanced by using a denser high-loft material. Of course, other configurations are also possible. The two or more intermediate layers may have the same dimensions in the x-plane and y-plane of the core, but they may also have different lengths and / or widths. Two intermediate layers of unequal lengths may be advantageous in providing different amounts of SAP along the absorbent core, and can be prepared, for example, by adding cut and slit units to the second layer patch and preparing it before bonding it to the first layer.

[0093] At least one of the two high-loft interlayers comprises two different types of SAP as discussed above, wherein the first SAP (SAP1) has a higher capacity than the second SAP, as measured by the CRC method, and the second SAP (SAP2) has a UPM value greater than 5 UPM units, as measured by the UPM method, and preferably has a higher UPM value than SAP1. For example, for SAP1, the SAP layer may be placed in the top cover layer closest to the absorber core (60), and the SAP2 layer may be one of the underlying layers (e.g., Figure 6 SAP layer 62 or 64 in the middle.

[0094] The absorbent core, comprising two high-loft nonwoven layers, can be prepared by a method adapted from one of the disclosed methods described above, see, for example, WO2016 / 106021A1, which describes two separate high-loft release cylinders to provide a first high-loft interlayer 431 and a second high-loft interlayer 432. Alternatively, a high-loft fiber web with double the width can be used: this wide roll, after being released longitudinally, can be cut in half to provide two strands of high-loft nonwoven material, which are then deposited separately with SAP particles. These two strands of high-loft material 431, 432 can then be combined with a top cap and a bottom cap, respectively, and then SAP particles 60 are deposited onto the top and bottom caps, respectively, using a suitable SAP deposition apparatus.

[0095] Absorbent product 20

[0096] Absorbent cores can be incorporated into any type of personal hygiene product, particularly short diapers and adhesive diapers, as well as inserts in hybrid systems that include washable covers and disposable inserts. Figure 7 A schematic cross-sectional view is shown, illustrating some of the main components of the diaper absorbent article 20. The view shows... Figure 5 The absorbent core (with a wrapping layer 3) is present, but this is not limiting and is for illustrative purposes only. Absorbent articles typically consist of a liquid-permeable top sheet 36 facing the wearer and a liquid-impermeable bottom sheet 38 facing the garment, attached to each other along their circumference. The absorbent core is positioned between these layers and can be attached directly and indirectly to these layers, typically by adhesive or heat / pressure bonding.

[0097] The topsheet 36 is preferably soft, gentle to the touch, and non-irritating to the wearer's skin. Furthermore, at least a portion of the topsheet is liquid-permeable, allowing liquid to easily penetrate its thickness. Suitable topsheets can be made from a variety of materials, such as porous foam, mesh foam, porous plastic film, or woven or nonwoven materials of natural fibers (e.g., wood fibers, cotton fibers, or viscose fibers), synthetic fibers or filaments (e.g., polyester or polypropylene or bicomponent PE / PP fibers or mixtures thereof), or combinations of natural and synthetic fibers. If the topsheet includes fibers, the fibers can be processed by spunbonding, carding, wet web forming, meltblowing, hydroentangling, or other methods known in the art, particularly spunbond PP nonwovens. Typical diaper topsheets have a basis weight of about 10 gsm to about 28 gsm, particularly about 12 gsm to about 18 gsm, but other basis weights are also possible.

[0098] The film 38 is typically impermeable to liquids such as urine. The film may be, for example, a thin plastic film, such as a thermoplastic film with a thickness of less than about 0.10 mm. Exemplary film films include those manufactured by Tredegar Corporation, headquartered in Richmond, VA, and sold under the trade name CPC2 film. Other suitable film materials may include a breathable material that allows vapors to escape from the article while still preventing exudates from penetrating the film. A low-basic-weight nonwoven fabric may be attached to the outer surface of the film to provide a softer feel.

[0099] The absorbent article may also include a liquid management layer 54 (also known as a fluid collection or fluid distribution layer) directly beneath the top sheet 36. This layer functions to rapidly collect fluid from the top sheet away from the wearer-facing side and / or distribute it over a larger area, allowing for more efficient absorption by the absorbent core. This liquid management layer may also be placed between the backsheet and the absorbent core. Another layer 4 may be present between the liquid management layer 54 and the absorbent core 28. This other layer 4 may be another such collection or distribution layer, or it may be a thin paper or low-basic-weight NW layer that provides additional wrapping around the absorbent core 28' to prevent SAP particles from escaping from the core.

[0100] Absorbent articles such as diapers or training pants may also include components that improve the fit of the article around the wearer's legs, particularly barrier leg cuffs 32 and liner cuffs 34. The barrier leg cuff may be formed from a single piece of material (typically a nonwoven fabric) that is partially bonded to the remainder of the article and may partially protrude away from and thus stand upright from the plane defined by the top piece. The barrier leg cuff is typically defined by a proximal edge and a free end edge that engages with the remainder of the article (typically the top and / or bottom piece) and is designed to contact the wearer's skin and form a seal. The upright portion of the cuff typically includes an elastic element, such as one or more elastic strands 35. The barrier leg cuff provides improved inhibition of fluids and other bodily exudates at the junction of the wearer's torso and legs.

[0101] In addition to the blocking leg cuffs, the article may include a liner cuff 34 formed in the same plane as the base structure of the absorbent article, particularly one that may at least partially enclose the top or blocking leg cuff and the bottom piece, and may be positioned laterally outward relative to the upright blocking leg cuff. The liner cuff provides a better seal around the wearer's thighs. Typically, each liner leg cuff will include one or more elastic bands or elastic elements 33 included in the base of the diaper, for example, between the top and bottom pieces in the leg opening area.

[0102] Absorbent articles may also include other typical components found in diapers, training pants, replaceable inserts, or adult incontinence products (not further described). A releasable fastening system may be provided for adhesive diapers to provide lateral tension around the perimeter of the absorbent article, thereby holding the absorbent article to the wearer. This fastening system is not necessary for training pants, as the waist area of ​​these articles is already bonded. Fastening systems typically include fasteners such as tape tabs, hook-and-loop fasteners, interlocking fasteners such as tabs and slots, snaps, buttons, fasteners, and / or androgynous fasteners, although any other known fasteners are generally acceptable. A landing zone is typically located on the front waist area of ​​the article for releasably attached fasteners.

[0103] Absorbent articles may include front and back ear flaps as known in the art. The ear flaps may be integral parts of the basic structure, formed, for example, as side flaps from a top and / or bottom flap. Alternatively, they may be separate elements attached by adhesive bonding and / or heat embossing. The back ear flap is advantageously stretchable to facilitate attachment of the flap to the landing area and to hold the adhesive diaper in proper position around the wearer's waist. The front ear flap may also be elastic or stretchable to provide a more comfortable and conformal fit to the wearer through an initial conformal fit to the absorbent article, and to maintain this fit throughout wear when the absorbent article is loaded with exudate, as the elastic ear flap allows the absorbent article to stretch and contract laterally.

[0104] Typically, adjacent layers are joined together using conventional bonding methods, such as adhesive coatings applied via troughing or spraying onto the entire surface or a portion of the surface of the layer, or thermal bonding, or pressure bonding, or combinations thereof. For clarity and readability, except for adhesive layers 71, 72, in most of the figures, especially... Figure 7 The bonding between components is not shown. Unless otherwise specifically mentioned, adjacent layers of an article should be considered as attached to another layer. For example, the backing sheet and bottom cover of an absorbent core are typically glued together. The adhesive used may be any standard hot melt adhesive as known in the art.

[0105] Package

[0106] Absorbent articles can be packaged in any type of conventional packaging. Absorbent articles can be particularly compressed during packaging to save space. Specifically, a package may include multiple absorbent articles, wherein the package has an in-bag stacking height of less than about 80 mm according to the in-bag stacking height test described in US 8,585,666B2 (Weisman), which is incorporated herein by reference. Alternatively, packages of absorbent articles of this disclosure may have an in-bag stacking height of about 72 mm to about 80 mm or about 74 mm to about 78 mm according to the in-bag stacking height test described in US 8,585,666B2 (Weisman), specifically enumerated within the specified range and all 0.5 mm increments within or formed thereof.

[0107] Examples and Experimental Results

[0108] a)SAP

[0109] The properties of SAPs from different commercial sources were measured and reported in Table 1 below. Values ​​indicated by "na" in the table were not measured. These SAPs were used to prepare absorber cores, as shown in Table 2.

[0110]

[0111] Table 1

[0112] SAP B and SAP C are superabsorbent particles with relatively high CRC, while SAP D, E, and F have relatively high permeability. SAP A has the lowest capacity and medium permeability of 5 units.

[0113] b) Core structure

[0114] Absorbent cores using different SAP combinations are industrially produced on the core manufacturing line in a similar manner. In all cases, the high-loft interlayer has a density of 0.021 g / cm³. 3 The density and thickness of the 45gsm air-bonded combed nonwoven fabric (Haoyue) measured at 1.2kPa are 2.1mm. The top cover is 23gsm PP spunbond nonwoven fabric, and the bottom cover is 32gsm PET spunlace nonwoven fabric.

[0115] Each individual core comprises 6.375 g of corresponding SAP1 (basis weight 170 gsm) deposited on the top side of the high-bulk layer and 5.775 g of corresponding SAP2 (basis weight 154 gsm) deposited on the bottom side of the high-bulk layer. SAP1 and SAP2 are uniformly deposited on the corresponding sides of the high-bulk intermediate layer NW, and adhesive (Bostik) is immediately sprayed on and the corresponding capping layer is laminated onto each side. The amount and properties of SAP used on each side of the core are shown in Table 2 below.

[0116]

[0117] Table 2

[0118] It can be seen that the features of Examples 1 to 4 are that SAP1 has a higher capacity value than SAP2, and SAP2 has a UPM value greater than 5 UPM units. Comparative Example 1 (C.Ex.1) has SAP2 with a permeability value of 5 UPM units, and Comparative Example 2 (C.Ex.2) has SAP1 with a relatively lower capacity and SAP2 with a relatively higher capacity in the underlying layer.

[0119] Different cores were incorporated into the commercial diaper base structure in a similar manner, and the resulting diapers were tested using the bend global sampling method and the touch dryness-to-touch (cGAM-LTD) test. This cGAM-LTD test is an internal method used to measure the time required to collect three consecutive 75 ml saline flows, and the amount of rewetting in the diaper after each flow using absorbent paper at a low rewetting pressure (0.03 psi). Lower cGAM times for different flows are advantageous, as are lower weights for the LTD value. The results of this test are summarized in Table 3.

[0120]

[0121] Table 3

[0122] In summary, Examples 2 and 3 exhibit optimal design for rapid acquisition speed and best reflow performance during the second and third inrushes. Examples 2 and 3 used SAP1 with a high CRC (36.6 g / g) and SAP2 with a high UPM (45 / 50 units). Examples 1 and 4 demonstrate acceptable performance. Example 1 has a similar design structure to Example 2, but SAP2 has a lower UPM (7.5 units), resulting in a relatively slower acquisition speed and higher reflow.

[0123] Comparative Example 1 exhibited the worst performance among the tested chips, using SAP2, which had relatively low CRC and UPM.

[0124] Comparative Example 2 exhibits the fastest sampling rate, likely due to the high UPM permeability value of SAP1 in the three inflows. However, the reflow measured at the third LTD is high, and therefore this core design is generally considered inferior to Examples 1 through 4, and especially Examples 2 through 3, as a good balance between sampling rate and reflow is desired.

[0125] Test Procedure

[0126] Centrifugation retention capacity (CRC)

[0127] CRC is a measure of the ability of superabsorbent polymer particles to absorb excess liquid and swell freely. CRC is measured according to EDANA method NWSP241.0.R2 (19).

[0128] Compressive absorption rate

[0129] AAP was measured according to EDANA standard test NWSP 242.0 R2 (19) at pressures of 0.7 psi and 0.3 psi, respectively, which are expressed as AAP at 0.7 psi and AAP at 0.3 psi.

[0130] Thickness and density measurement methods

[0131] This method is used to measure the thickness (thickness diameter) of the high-bulk interlayer in a standardized manner. The density can then be calculated from the layer thickness and basis weight. Unless otherwise specified, the thickness and density are indicated for high-bulk materials in the absence of SAP particles. This measurement should preferably be performed on the high-bulk material before it is transformed into the absorbent core and thus free of SAP. If the feedstock is unavailable, the high-bulk interlayer can be obtained by carefully removing it from the absorbent core and removing most of the SAP particles, for example, by careful shaking or suction. Cryo-spraying can be used to separate the interlayer from the other layers. Samples should be held at 21°C ± 2°C and 50% ± 10% RH for at least 24 hours to reach equilibrium, especially if they have been previously compressed.

[0132] Equipment: Mitutoyo manual diaphragm gauge with 0.01mm resolution, or equivalent instrument.

[0133] Contact foot: A round, flat foot with a diameter of 16.0 mm (±0.2 mm). A round weight can be applied to the foot (e.g., a weight with a slot to facilitate application around the instrument axis) to obtain the target weight. Select the total weight of the foot and the added weight (including the axis) to provide the desired pressure to the sample, such as 4.14 kPa (0.6 psi). The thickness can be determined at different pressures using different weights applied to the foot. The thickness and density measurements indicate the applied pressure, such as at 4.14 kPa (0.6 psi) or 1.2 kPa.

[0134] Install the gauge with the lower surface of the contact foot in a horizontal plane, such that the lower surface of the contact angle contacts the center of the flat, horizontal upper surface of a substrate approximately 20cm x 25cm. With the contact angle resting on the substrate, the gauge length is set to zero.

[0135] Scale: A calibration metal scale with a millimeter graduation.

[0136] Stopwatch: with an accuracy of 1 second.

[0137] Sample preparation: The intermediate layer is conditioned for at least 24 hours as described above.

[0138] Measurement Procedure: Lay the layer flat with the bottom side facing down, i.e., place the film in the finished product with the sides facing downwards. Carefully mark the measurement point on the top side of the layer, i.e., the center of the sample, taking care not to compress or deform the layer. In cases where it is unlikely that the high-bulk nonwoven layer is not uniform in the transverse or longitudinal directions, these values ​​are measured at the center of the sample, corresponding to the center of the absorbent core to be made from the sample.

[0139] Raise the contact feet of the gauge and place the intermediate layer flat on the base plate of the gauge, with the top side of the core facing upward, so that when it descends, the center of the feet is on the marked measurement point.

[0140] Gently lower the foot onto the sample and release it (ensure the scale is "0" before starting the measurement). Read the thickness value 10 seconds after releasing the foot, accurate to 0.01 mm.

[0141] This procedure is repeated for each measurement point. For a given material, ten samples are measured in this manner, and the average thickness is calculated and recorded with an accuracy of one-tenth of a mm. The basis weight of each sample is calculated by dividing the weight of each sample by its area.

[0142] In g / cm 3 Density is expressed in units of the material's basis weight (in g / cm³). 2 The calculation is done by dividing the thickness (in cm) by the unit of measurement.

[0143] Urine osmolarity measurement (UPM) test method

[0144] Laboratory conditions :

[0145] The test must be conducted in a climate-controlled room under standard conditions of 23℃±2℃ temperature and 45%±10% relative humidity.

[0146] Urine osmotic measurement system

[0147] This method determines the permeability of the swollen hydrogel layer 1318. The equipment used in this method is described below.

[0148] Figure 9 A permeability measurement system 1000 is shown, which is equipped with a constant hydrostatic head reservoir 1014, an open pipe 1010 for air intake, a stopper 1012 for refilling, a laboratory rack 1016, a transfer pipe 1018 with a flexible tube 1045 having a Tygon nozzle 1044, a rotary valve 1020, a cover plate 1047 and a support ring 1040, a receiving container 1024, a balance 1026 and a piston / cylinder assembly 1028.

[0149] Figure 10 The diagram shows a piston / cylinder assembly 1028 comprising a metal weight 1112, a piston shaft 1114, a piston head 1118, a cap 1116, and a cylinder 1120. The cylinder 1120 is made of transparent polycarbonate (such as Lexan). ® It is made with an inner diameter p of 6.00 cm and an area of ​​28.27 cm². 2 The inner cylindrical wall 1150 is smooth. The bottom 1148 of the cylinder 1120 is covered with a stainless steel mesh (ISO 9044 material 1.4401, mesh size 0.038 mm, wire diameter 0.025 mm) (not shown), which is biaxially stretched to a taut state before being attached to the bottom 1148 of the cylinder 1120. The piston shaft 1114 is made of transparent polycarbonate (e.g., Lexan). ® The piston shaft 1114 is made of a material with an overall length q of approximately 127 mm. The middle portion 1126 of the piston shaft 1114 has a diameter r of 22.15 (±0.02) mm. The upper portion 1128 of the piston shaft 1114 has a diameter s of 15.8 mm, thus forming a shoulder 1124. The lower portion 1146 of the piston shaft 1114 has a diameter t of approximately 5 / 8 inch (15.9 mm) and is threaded to securely screw into the center hole 1218 of the piston head 1118 (see [link to relevant documentation]). Figure 10 The piston head 1118 is perforated and is made of transparent polycarbonate (e.g., Lexan). ®The piston head 1118 is made of stainless steel and is also sieved using stretched stainless steel mesh (ISO 9044 material 1.4401, mesh size 0.038 mm, wire diameter 0.025 mm) (not shown). The weight 1112 is made of stainless steel, has a central hole 1130, slides onto the upper portion 1128 of the piston shaft 1114, and rests on the shoulder 1124. The combined weight of the piston head 1118, piston shaft 1114, and weight 1112 is 596 g (±6 g), which corresponds to 0.30 psi on the inner surface area of ​​the cylinder 1120. The combined weight can be adjusted by drilling a blind hole downwards along the central axis 1132 of the piston shaft 1114 to remove material and / or by providing a cavity to add weight. The cylindrical cap 1116 has a first cap opening 1134 at its center for vertical alignment with the piston shaft 1114, and a second cap opening 1136 near the edge 1138 for introducing fluid from the constant static head reservoir 1014 into the cylinder 1120.

[0150] A first linear indicator mark (not shown) is radially drawn along the upper surface 1152 of the weight 1112, transverse to the central axis 1132 of the piston shaft 1114. A corresponding second linear indicator mark (not shown) is radially drawn along the top surface 1160 of the piston shaft 1114, transverse to the central axis 1132 of the piston shaft 1114. A corresponding third linear indicator mark (not shown) is drawn along the middle portion 1126 of the piston shaft 1114, parallel to the central axis 1132 of the piston shaft 1114. A corresponding fourth linear indicator mark (not shown) is radially drawn along the upper surface 1140 of the cylindrical cap 1116, transverse to the central axis 1132 of the piston shaft 1114. Furthermore, a corresponding fifth linear indicator mark (not shown) is drawn along the lip 1154 of the cylindrical cap 1116, parallel to the central axis 1132 of the piston shaft 1114. A corresponding sixth linear indicator mark (not shown) is drawn along the outer cylinder wall 1142, the sixth linear indicator mark being parallel to the central axis 1132 of the piston shaft 1114. The first, second, third, fourth, fifth, and sixth linear indicator marks are aligned so that the weight 1112, piston shaft 1114, cylinder cap 1116, and cylinder 1120 are repositioned with the same orientation relative to each other during each measurement.

[0151] The specifications of cylinder 1120 are as follows: :

[0152] The outer diameter u of cylinder 1120 is 70.35 mm (±0.05 mm).

[0153] The inner diameter p of cylinder 1120 is 60.0 mm (±0.05 mm).

[0154] The height ν of cylinder 1120 is 60.5mm. The cylinder height must be no less than 55.0mm!

[0155] Cylindrical cap 1116 specifications details are as follows :

[0156] The outer diameter w of the cylindrical cap 1116 is 76.05 mm (±0.05 mm).

[0157] The inner diameter of the cylindrical cap 1116 is 70.5 mm (±0.05 mm).

[0158] The thickness y of the cylindrical cap 1116, including the lip edge 1154, is 12.7 mm.

[0159] The thickness z of the roller cap 1116 without lip 1154 is 6.35mm.

[0160] The diameter a of the first cap opening 1134 is 22.25 mm (±0.02 mm).

[0161] The diameter b of the second cap opening 1136 is 12.7 mm (±0.1 mm).

[0162] The distance between the centers of the first and second cap openings 1134 and 1136: 23.5 mm

[0163] The specifications of weight 1112 are as follows: :

[0164] Outer diameter c: 50.0mm

[0165] The diameter d of the center boring hole 1130 is 16.0 mm.

[0166] Height e: 39.0mm

[0167] Piston head 1118 specifications details are as follows :

[0168] Diameter f: 59.7mm (±0.05mm)

[0169] Height g: 16.5mm. The piston head height must be no less than 15.0mm.

[0170] The outer holes 1214 (a total of 14) have a diameter h of 9.30 (±0.25) mm. The outer holes 1214 are equidistant from each other, with the center distance from the center of the center hole 1218 being 23.9 mm.

[0171] The inner holes 1216 (7 in total) have a diameter i of 9.30 (±0.25) mm. The inner holes 1216 are equidistant from each other, and their center is 13.4 mm away from the center of the center hole 1218.

[0172] The center hole 1218 has a diameter of approximately 5 / 8 inch (15.9 mm) and is threaded to receive the lower part 1146 of the piston shaft 1114.

[0173] Before use, check the stainless steel screens (not shown) of the piston head 1118 and cylinder 1120 for blockages, holes, or excessive stretching, and replace them if necessary. Urine permeability measuring devices with damaged screens may output incorrect UPM results and should never be used before the screens are replaced.

[0174] Mark a 5.00cm mark 1156 on the cylinder 1120 at a height k of 5.00cm (±0.05cm) above the screen (not shown) attached to the bottom 1148 of the cylinder 1120. This mark indicates the fluid level to be maintained during the analysis. Maintaining a correct and constant fluid level (hydrostatic pressure) is critical for measurement accuracy.

[0175] A constant static pressure head reservoir 1014 is used to transfer the salt solution 1032 to the cylinder 1120 and maintain the level of the salt solution 1032 at a height k of 5.00 cm above a screen (not shown) attached to the bottom 1148 of the cylinder 1120. The bottom 1034 of the air inlet pipe 1010 is positioned so that the level of the salt solution 1032 in the cylinder 1120 is maintained at the desired height k of 5.00 cm during measurement, i.e., when the cylinder is positioned on the cover plate 1047 and the support ring 1040 (with a circular inner opening of not less than 64 mm in diameter) above the receiving container 1024, the bottom 1034 of the air inlet pipe 1010 is located in approximately the same plane 1038 as the 5.00 cm mark 1156 on the cylinder 1120.

[0176] The cover plate 1047 and support ring 1040 are components used in the apparatus described herein for the method "K(t) test method (time effective permeability and absorption kinetics measurement test method)," and are referred to as "ZeitabhängigerDurchlässigkeitsprüfstand" or "Time Dependent Permeability Tester," equipment number 03-080578, and are commercially available at BRAUN GmbH, Frankfurter Str. 145, 61476 Kronberg, Germany. Detailed technical drawings are also available upon request.

[0177] Alignment of the inlet pipe 1010 with the appropriate height of the 5.00 cm mark 1156 on the cylinder 1120 is critical for the analysis. A suitable reservoir 1014 comprises a wide-mouth bottle 1030 containing: a horizontally oriented L-shaped transfer tube 1018 for fluid transfer connecting a flexible tube 1045 (e.g., a Tygon tube, capable of connecting a nozzle and the reservoir outlet) and a Tygon tube nozzle 1044 (with an inner diameter of at least 6.0 mm and a length of approximately 5.0 cm); a vertically oriented end-opening tube 1010 for allowing air to be at a fixed height within the constant static head reservoir 1014; and a stopper 1012 for refilling the constant static head reservoir 1014. The tube 1010 has an inner diameter of approximately 12 mm, but not less than 10.5 mm. A transfer tube 1018, positioned near the bottom 1042 of the constant hydrostatic head reservoir 1014, houses a rotary valve 1020 for starting / stopping the transfer of the brine solution 1032. The outlet 1044 of the transfer flexible tube 1045 is sized (e.g., 10 mm outer diameter) and inserted through a second cap opening 1136 on the cylindrical cap 1116, its end positioned below the surface of the brine solution 1032 in the cylinder 1120 (after the brine solution 1032 has reached a height of 5.00 cm in the cylinder 1120). An O-ring gasket 1049 holds the inlet tube 1010 in place. The constant hydrostatic head reservoir 1014 can be positioned at a suitable height relative to the cylinder 1120 on the laboratory rack 1016. The component dimensions of the constant hydrostatic head reservoir 1014 are customized to quickly fill the cylinder 1120 to the desired height (i.e., hydrostatic head) and maintain that height throughout the measurement. The constant static head reservoir 1014 must be able to transfer the salt solution 1032 at a flow rate of at least 2.6 g / s for at least 10 minutes.

[0178] The piston / cylinder assembly 1028 is positioned on a support ring 1040 in the cover plate 1047 or on a suitable alternative rigid support. The salt solution 1032 passing through the piston / cylinder assembly 1028, which includes a swollen hydrogel layer 1318, is collected in a receiving container 1024 disposed below (but not in contact with) the piston / cylinder assembly 1028.

[0179] Place the receiving container 1024 on a balance 1026 accurate to at least 0.001 g. Connect the digital output of the balance 1026 to a data acquisition system 1048 for computer processing.

[0180] Preparation of reagents (not shown)

[0181] Jayco Synthetic Urine (JSU) 1312 (see also...) Figure 12A 0.118 M sodium chloride (NaCl) solution is used as the swelling phase (see UPM procedure below), and a 0.118 M sodium chloride (NaCl) solution 1032 is used as the mobile phase (see UPM procedure below). The following preparations are based on a standard 1 L volume. If the preparation differs from a 1 L volume, all quantities are therefore weighed proportionally.

[0182] JSU: Fill a 1L volumetric flask to 80% capacity with distilled water and place a magnetic stir bar inside. Using an analytical balance, weigh the following dried components (accurate to ±0.01g) separately with weighing paper or a beaker, and add them quantitatively to the volumetric flask in the same order listed below. Stir the solution on a suitable stirring plate until all solids dissolve. Remove the stir bar and dilute the solution to a 1L volume with distilled water. Replace the stir bar and stir the solution again for a few minutes.

[0183] Salt dosage for preparing 1 liter of Jayco synthetic urine:

[0184] Potassium chloride (KCl) 2.00g

[0185] Sodium sulfate (Na2SO4) 2.00g

[0186] Ammonium dihydrogen phosphate (NH4H2PO4) 0.85g

[0187] Diammonium hydrogen phosphate ((NH4)2HPO4) 0.15g

[0188] Calcium chloride (CaCl2) 0.19g — [or hydrated calcium chloride (CaCl2•2H2O) 0.25g]

[0189] Magnesium chloride (MgCl2) 0.23g — [or hydrated magnesium chloride (MgCl2•6H2O) 0.50g]

[0190] For faster preparation, in a 1L volumetric flask, mix and dissolve potassium chloride, sodium sulfate, ammonium dihydrogen phosphate, ammonium phosphate (dibasic form), and magnesium chloride (or hydrated magnesium chloride) in 80% distilled water. Dissolve calcium chloride (or hydrated calcium chloride) separately in about 50ml of distilled water (e.g., in a glass beaker), and after all other salts have completely dissolved, transfer the calcium chloride solution to the 1L volumetric flask. Then, add distilled water to 1L (1000ml ± 0.4ml) and stir the solution for several more minutes. Jayco synthetic urine can be stored for 10 days in a clean plastic container. If the solution becomes cloudy, it should not be used.

[0191] 0.118M Sodium Chloride (NaCl) Solution: Use 0.118M sodium chloride as the salt solution 1032. Weigh 6.90 (±0.01 g) of sodium chloride using weighing paper or a beaker and quantitatively transfer it to a 1 L volumetric flask (1000 ml ± 0.4 ml); then dilute the volumetric flask to volume with distilled water. Add a stir bar and stir the solution on a stirring pan until all solids dissolve.

[0192] The conductivity of the prepared Jayco solution must be in the range of approximately 7.48–7.72 mS / cm, and the conductivity of the prepared 0.118 M sodium chloride (NaCl) solution must be in the range of approximately 12.34 mS / cm to 12.66 mS / cm (e.g., measured by a COND 70 instrument (#50010522) without a cell, equipped with CellVPT51-01 C=0.1 obtained from an XS instrument, or by an LF 320 / Set (LF 320 / group), #300243 equipped with a TetraCon 325 obtained from WTW, or by a COND 330i, #02420059 equipped with a TetraCon 325 obtained from WTW). The surface tension of each solution must be in the range of 71-75 mN / m (e.g., measured by a K100 tensiometer, obtained from Kruess, with Pt sheet).

[0193] Test preparation

[0194] Using a solid reference cylindrical weight (not shown) (50 mm diameter; 128 mm height), set the caliper gauge (not shown) (measuring range 25 mm, accurate to 0.01 mm, piston pressure maximum 50 g; e.g., a Mitutoyo digital height gauge) to zero. This operation is conveniently performed on a smooth and level worktable (not shown) of at least approximately 11.5 cm × 15 cm. Position the piston / cylinder assembly 1028, which does not contain superabsorbent polymer particles, below the caliper gauge (not shown), and record the reading L1, accurate to 0.01 mm.

[0195] Fill the constant hydrostatic head reservoir 1014 with salt solution 1032. Position the bottom 1034 of the inlet pipe 1010 so that the top (not shown) of the liquid meniscus (not shown) in the cylinder 1120 is kept at the 5.00 cm mark 1156 during measurement. Proper height alignment of the inlet pipe 1010 at the 5.00 cm mark 1156 on the cylinder 1120 is critical for analysis.

[0196] The receiving container 1024 is placed on the balance 1026, and the digital output of the balance 1026 is connected to the data acquisition system 1048 for computer processing. A cover plate 1047 with a support ring 1040 is positioned above the receiving container 1024.

[0197] UPM program

[0198] 1.5 g (±0.05 g) of superabsorbent polymer particles were weighed onto suitable weighing paper or weighing aids using an analytical balance. The moisture content of the superabsorbent polymer particles was measured according to Edana Moisture Content Test Method NWSP 230.0.R2(15) or by a moisture analyzer (HX204, from Mettler Toledo, drying temperature 130°C, starting superabsorbent weight 3.0 g (±0.5 g), stop standard 1 mg / 140 s). If the moisture content of the superabsorbent polymer particles was greater than 3% by weight, the superabsorbent polymer particles were dried to a moisture content of <3% by weight, for example, by drying in an oven at 105°C for 3 hours or, for example, at 120°C for 2 hours.

[0199] An empty cylinder 1120 is placed on a horizontal worktable 1046 (not shown), and superabsorbent polymer particles are quantitatively transferred into the cylinder 1120. The superabsorbent polymer particles are uniformly dispersed on a screen (not shown) attached to the bottom 1148 of the cylinder 1120 while the cylinder 1120 is rotated, for example via a (manual or electric) turntable (e.g., Petriturn-E or Petriturn-M, derived from Schuett). Uniform distribution of the particles on the screen (not shown) attached to the bottom 1148 of the cylinder 1120 is important for obtaining the highest accuracy results. After the superabsorbent polymer particles have been uniformly distributed on the screen (not shown) attached to the bottom 1148 of the cylinder 1120, the particles must not adhere to the inner cylinder wall 1150. The piston shaft 1114 is inserted through the first cap opening 1134, wherein the lip 1154 of the cap 1116 faces the piston head 1118. The piston head 1118 is carefully inserted into the cylinder 1120 to a depth of several centimeters. The cap 1116 is then placed on the upper edge 1144 of the cylinder 1120, while carefully keeping the piston head 1118 away from the superabsorbent polymer particles. The weight 1112 is placed on the upper part 1128 of the piston shaft 1114 so that it rests on the shoulder 1124, aligning the first and second linear indicator marks. The cap 1116 and piston shaft 1126 are then carefully rotated to align the third, fourth, fifth, and sixth linear indicator marks, and then with the first and second linear indicator marks. The piston head 1118 is then gently lowered (through the piston shaft 1114) to rest on the dry superabsorbent polymer particles. The proper positioning of the cap 1116 prevents the weight from sticking to the hydrogel layer 1318 and ensures uniform distribution.

[0200] Swelling phase :

[0201] Place a sintering dish 1310 with a diameter of at least 8 cm (e.g., 8-9 cm) and a thickness of at least 5.0 mm (e.g., 5-7 mm), and with “coarse” or “extra-coarse” porosity (e.g., Chemglass Inc. # CG 201-51, coarse pores; or, for example, Robu 1680, porosity 0) 1310 in a wide-bottomed culture dish 1314, and add JSU 1312 by pouring it into the center of the sintering dish 1310 until the JSU 1312 reaches the top surface 1316 of the sintering dish 1310. The height of the JSU must not exceed the height of the sintering dish 1310. It is important to avoid any air or air bubbles being trapped in or at the bottom of the sintering dish 1310.

[0202] The entire piston / cylinder assembly 1028 is lifted and placed on the sintering tray 1310 within the culture dish 1314. JSU 1312 from the culture dish 1314 passes through the sintering tray 1310 and is absorbed by the superabsorbent polymer particles (not shown) to form a hydrogel layer 1318. The JSU 1312 available in the culture dish 1314 should be sufficient for all the swollen phases. If necessary, more JSU 1312 may be added to the culture dish 1314 during hydration to maintain the JSU 1312 level at the top surface 1316 of the sintering tray 1310. After a period of 60 minutes, the piston / cylinder assembly 1028 is removed from the sintering tray 1310, taking care to ensure that the hydrogel layer 1318 does not lose JSU 1312 or draw in air during this step. The piston / cylinder assembly 1028 is placed under a caliper (not shown) and the reading L2 is recorded to an accuracy of 0.01 mm. If the readings change over time, only the initial values ​​are recorded. The thickness L0 of the hydrogel layer 1318 is determined from L2-L1, accurate to 0.1 mm.

[0203] Transfer the piston / cylinder assembly 1028 to the support ring 1040 in the cover plate 1047. Position the constant static head reservoir 1014 such that the transfer tube nozzle 1044 is placed through the second cap opening 1136. Begin measurements in the following order:

[0204] a) Open the rotary valve 1020 of the constant hydrostatic head reservoir 1014 to allow the brine solution 1032 to reach the 5.00 cm mark 1156 on the cylinder 1120. This brine solution 1032 level should be achieved within 10 seconds of opening the rotary valve 1020.

[0205] b) Once a 5.00 cm salt solution of 1032 is obtained, initiate the data collection procedure.

[0206] Using a computer 1048 attached to a balance 1026, the mass (in grams, to an accuracy of 0.001 g) of the salt solution 1032 passing through the hydrogel layer 1318 is recorded at 20-second intervals over a period of 10 minutes. At the end of the 10 minutes, the rotary valve 1020 on the constant hydrostatic head reservoir 1014 is closed.

[0207] Data collected from 60 seconds into the experiment was used in the UPM calculation. Data collected before 60 seconds was not included in the calculation.

[0208] For each 20-second interval after the initial 60 seconds of the experiment (time t) (i-1) To t i ), corresponding traffic Fs (t) (in g / s) and the corresponding midpoint of time t (1 / 2)t (In seconds) Calculate according to the following formula:

[0209] and (II)

[0210] Each time interval (t) (i-1) To t i The flow rate Fs (t) Relative to each time interval (t) (i-1) To t i The midpoint of time t) (1 / 2) Plot the graph. The intercept is calculated as Fs(t=0).

[0211] Intercept calculation :

[0212] The intercept is calculated using the best-fit regression line, for example as follows: The formula for the regression line intercept 'a' is:

[0213] (III)

[0214] The slope b is calculated as follows:

[0215] (IV)

[0216] And where x AVG and y AVG These are the sample means, i.e., the average value of known x and the average value of known y, respectively.

[0217] Calculation of urine osmolarity measurement Q :

[0218] The intercept Fs (t=0) is used to calculate Q according to the following formula:

[0219] (V)

[0220] Where the flow rate Fs (t=0) is given in g / s, L0 is the initial thickness of the hydrogel layer 1318 in cm, and ρ is the density of the salt solution 1032 in g / cm³. 3 Units (e.g., 1.003 g / cm³ at room temperature) 3 A (derived from the above formula) is in cm 2 The area of ​​the hydrogel layer 1318 is calculated (e.g., 28.27 cm²). 2 ), ΔP is in dynes / cm 2 The hydrostatic pressure of the meter (e.g., 4920 dynes / cm) 2 ), and urine osmolarity measurement Q in cm 3 The unit is sec / g. The average of three measurements should be recorded.

[0221]

[0222] SAP K(t) Test Method

[0223] This method determines the time-dependent effective permeability (SAP K(t)) and absorption kinetics of a gel layer formed by superabsorbent polymer particles that form a hydrogel, or an absorbent structure containing such particles under confining pressure. The aim of this method is to assess the ability of a gel layer formed by superabsorbent polymer particles that form a hydrogel, or an absorbent structure containing them, to collect and distribute bodily fluids when the polymer is present in a high concentration in the absorbent article and exposed to mechanical pressure, which typically occurs during the use of the absorbent article. Darcy's law and steady-state flow methods are used to calculate the effective permeability (see below). (See also, for example, "Absorbency," edited by P.K. Chatterjee, Elsevier, 1982, pp. 42–43, and "Chemical Engineering," Vol. II, 3rd edition, J.M. Coulson and J.F. Richardson, Pergamon Press, 1978, pp. 122–127).

[0224] Compared to previously disclosed methods, the sample was not pre-swollen, so the hydrogel was not formed by pre-swelling superabsorbent polymer particles in synthetic urine to form the hydrogel, but rather the measurement began with the dry structure.

[0225] The equipment used in this method is called "Zeitabhängiger Durchlässigkeitsprüfstand" or "TimeDependent Permeability Tester," with equipment number 03-080578, and is commercially available from BRAUN GmbH, Frankfurter Str. 145, 61476 Kronberg, Germany, as described below. Operating instructions, wiring diagrams, and detailed technical drawings are also available upon request. The equipment and principles are further described in detail in WO2015 / 041784 (P&G).

[0226] The SAP K(t) test method is specifically designed to measure the time required to reach an absorbance of 20 g / g, known as T20, starting from 0 s (t0) and expressed in seconds. Using this test method, the time required to reach a specific absorbance can be determined by linear interpolation. The time to first reach an absorbance of 20 g / g is called T20. The average T20 is reported from three replicates with the required accuracy known to the technician.

[0227] Miscellaneous

[0228] It should be understood that the dimensions and values ​​disclosed herein are not intended to be strictly limited to the precise numerical values ​​cited. Rather, unless otherwise specified, each such dimension is intended to represent the stated value and a range around which it is functionally equivalent. For example, a dimension disclosed as “40 mm” is intended to represent “approximately 40 mm”.

Claims

1. An absorbent core (28) for an absorbent article (20), the absorbent core extending in a transverse direction (x) and a longitudinal direction (y) and having a thickness in a perpendicular direction (z) perpendicular to the transverse and longitudinal directions, the absorbent core comprising: - a liquid permeable top cover layer (41); - a bottom cover layer (42); - a high loft intermediate layer (43) located between the top and bottom cover layers, the high loft intermediate layer having a top surface oriented towards the top cover layer and a bottom surface oriented towards the bottom cover layer; - a first superabsorbent polymer "SAP1" (60) in particulate form deposited on the top surface of the high loft intermediate layer, wherein the SAP1 particles are at least partially distributed within a high loft intermediate nonwoven; - a second superabsorbent polymer (62) "SAP2" in particulate form deposited on the bottom surface of the high loft intermediate layer, wherein the SAP2 particles are at least partially distributed within the high loft intermediate layer; - wherein each of SAP1 and SAP2 has a respective capacity and permeability as measured by the CRC method and UPM method described herein, respectively, and - wherein SAP1 has a higher capacity than SAP2, and wherein the permeability of SAP2 is greater than 5xl0 -7 cm 3 s / g.

2. The absorbent core according to claim 1, wherein SAP2 has a higher permeability than SAP1.

3. The absorbent core according to claim 1 or 2, wherein: - the capacity of SAP1 is at least 30 g / g, preferably in the range of 32 g / g to 50 g / g; - the capacity of SAP2 is at least 20 g / g, preferably in the range of 25 g / g to 45 g / g; and - preferably wherein the capacity of SAP1 is at least 2 g / g, more preferably at least 4 g / g higher than the capacity of SAP2.

4. The absorbent core according to any of the preceding claims, wherein: - the permeability of the SAP2 is at least 10 x 10 -7 cm 3 .s / g, preferably at least 15 x 10 -7 cm 3 .s / g, more preferably in the range of 30 x 10 -7 cm 3 .s / g to 70 x 10 -7 cm 3 .s / g; and - the permeability of SAP2 is at least 5 x 10 -7 cm 3 .s / g higher than the permeability of SAP1, preferably wherein the permeability of SAP2 is at least 10 x 10 -7 cm 3 .s / g higher than the permeability of SAP1.

5. The absorbent core according to any of the preceding claims, wherein the average basis weight of the SAP1 is at least 50 g / m2 2 , preferably 100 g / m 2 to 300 g / m 2 .

6. The absorbent core according to any of the preceding claims, wherein the average basis weight of SAP2 is at least 50 g / m 2 , preferably 100 g / m 2 to 300 g / m 2 .

7. The absorbent core according to any of the preceding claims, wherein the absorbent core comprises 3 g to 10 g of SAP1, and / or wherein the absorbent core comprises 3 g to 10 g of SAP2.

8. The absorbent core according to any of the preceding claims, wherein the top and / or bottom cover layers are each attached to the high loft intermediate layer by a glue layer (71, 72), optionally wherein the glue layer also fixes at least a portion of the SAP particles that are not distributed within the high loft intermediate layer in the dry state.

9. The absorbent core (28') according to any of the preceding claims, further comprising a wrap layer (3), in particular a nonwoven wrap layer, at least partially wrapping the top cover layer, the bottom cover layer and the intermediate layer.

10. The absorbent core according to any of the preceding claims, wherein the absorbent core comprises at least 60 wt% of SAP, preferably at least 70 wt% of SAP, by total weight of the core.

11. An absorbent core according to any of the preceding claims, comprising a first high loft intermediate layer (431) and a second high loft intermediate layer (432) between the top cover layer and the bottom cover layer, wherein at least one of the first and second intermediate layers is an intermediate layer having SAP1 and SAP2 partially distributed therein.

12. An absorbent article (20) comprising a topsheet (36), a backsheet (38) and an absorbent core (28, 28’) according to any of the preceding claims, wherein the top cover layer of the absorbent core is oriented towards the topsheet of the article.

13. A package comprising a plurality of absorbent articles according to claim 12.

14. A method for making an absorbent core (28) according to any of claims 1 to 11, the method comprising the following steps in any order: - providing a high loft intermediate layer (43), a liquid permeable top cover layer (41) and a bottom cover layer (42); - depositing a first layer of superabsorbent particles “SAP1” (60) on a first side of the high loft intermediate layer; - attaching the first side of the intermediate layer with the liquid permeable top cover layer (41), in particular using a first adhesive (71); - depositing a second layer of superabsorbent particles “SAP2” (62) on a second side of the high loft intermediate layer; - attaching the second side of the intermediate layer with the bottom cover layer (43), in particular using a second adhesive (72); wherein the steps of depositing SAP1 and SAP2 can be performed in any order.

15. A method for preparing an absorbent core according to the preceding claims, wherein the initial density of the highly fluffy interlayer is 0.05 g / cm³ at 4.14 kPa (0.6 psi), as measured using the thickness and density measurement methods described herein. 3 Up to 0.15 g / cm 3 Within the range, and / or at 4.14 kPa (0.6 psi), the initial thickness of the intermediate layer is greater than 0.30 mm.

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