Absorbent core and absorbent article including same

Abstract

The present invention relates to an absorbent core for use in an absorbent article and an absorbent article comprising the same, the absorbent core comprising a liquid permeable top cover layer; a bottom cover layer; and an absorbent layer disposed between the top cover layer and the bottom cover layer, the absorbent layer comprising superabsorbent polymer particles; and wherein the top cover layer comprises pulp and has an MD tensile strength of at least about 12 N, where the top cover layer has a first MD wicking length at 3 minutes, and the bottom cover layer has a second MD wicking length at 3 minutes, as measured according to the wicking length test, where the first MD wicking length is at least about 70 mm, and the bottom cover layer has a second MD wicking length at 3 minutes, as measured according to the wicking length test. And is at least about 3 times the second MD wicking length.

Description

Technical Field

[0001] This invention relates to absorbent cores and their use in personal hygiene absorbent products. Background Technology

[0002] 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.

[0003] Absorbent cores should be able to absorb and retain waste 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.

[0004] Recently, absorbent cores made of non-fluffed cellulose fibers (also known as "non-breathable felt" cores) have been proposed. SAP particles can be, for example, encapsulated within discrete pockets. It has also been proposed to attach SAP particles with a microfiber adhesive network to a nonwoven substrate using an adhesive (see, for example, WO2008 / 155699A1, Hundorf et al.). WO 2021 / 132295A discloses an absorbent sheet comprising a first fiber sheet, a second fiber sheet, and an absorbent polymer disposed between these fiber sheets, wherein the Klemm absorbent height of the first fiber sheet is higher than that of the second fiber sheet.

[0005] Recently, airless felt cores comprising high-loft fiber-centered nonwoven sheets have been disclosed, wherein SAP is at least partially distributed within the central high-loft nonwoven fabric (see, for example, WO2016 / 106,021A1, Bianchi et al.). SAP particles are applied to one or both sides of the high-loft nonwoven fabric, wherein the SAP particles deposited on the surface of the central nonwoven sheet are at least partially distributed and fixed within the pores of the central nonwoven sheet. The nonwoven fabric is further adhesively attached to each of the high-loft central nonwoven sheets to further fix the particles within the high-loft central nonwoven sheet. At least a top cover layer oriented towards the top sheet on the absorbent article should be fluid-permeable. Additional wrapping layers can typically be used to further stabilize these layers and form the absorbent core. 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).

[0006] There is a constant need to improve the performance of absorbent cores, particularly in terms of absorption rate, absorption capacity, low rewetting, and / or wearing comfort, while keeping the total manufacturing cost as low as possible. Summary of the Invention

[0007] This invention relates to an absorbent core for use in absorbent articles, the absorbent core extending in a transverse and longitudinal direction, the absorbent core comprising a liquid-permeable top cover layer; a bottom cover layer; and an absorbent layer disposed between the top cover layer and the bottom cover layer, the absorbent layer comprising superabsorbent polymer particles, wherein the top cover layer comprises pulp and has a minimum tensile strength of about 12 N, wherein the top cover layer has a first wicking length at 3 minutes and the bottom cover layer has a second wicking length at 3 minutes, as measured by a wicking length test, wherein the first wicking length is at least about 70 mm and is at least about 3 times the second wicking length.

[0008] The present invention also relates to an absorbent core for use in an absorbent article, the absorbent core extending in a transverse and longitudinal direction, the absorbent core comprising a liquid-permeable top cover layer; a bottom cover layer; and an absorbent layer comprising superabsorbent polymer particles, wherein the top cover layer comprises a first absorbent fiber and a second absorbent fiber, the second absorbent fiber being different from the first absorbent fiber, and wherein the total amount of the first absorbent fiber and the second absorbent fiber is at least about 70% by weight of the top cover layer.

[0009] This invention relates to an absorbent article comprising a top sheet, a bottom sheet, and an absorbent core, disclosed herein, disposed between the top sheet and the bottom sheet. The article is shown in the accompanying drawings as an adhesive diaper. For ease of discussion, the absorbent article and the collection-dispensing system will be discussed with reference to the figures cited in these drawings. However, unless explicitly stated otherwise, the drawings and detailed descriptions should not be considered as limiting the scope of the claims. Specifically, the invention can also be used in a wide variety of absorbent article forms, such as trouser diapers, which are pre-formed and worn like underwear or feminine hygiene pads. Attached Figure Description

[0010] Figure 1 A top view of an exemplary absorbent core is shown, in which the top nonwoven sheet and the center nonwoven sheet are partially removed.

[0011] Figure 2 A schematic cross-sectional view of the absorber core is shown.

[0012] Figure 3 A schematic cross-sectional view of an alternative absorber core is shown.

[0013] Figure 4 A schematic cross-sectional view of an alternative absorber core is shown.

[0014] Figure 5 A schematic cross-sectional view of an alternative absorber core is shown.

[0015] Figure 6 As shown Figure 3 A schematic cross-sectional view of the absorber core and the core-encapsulating layer.

[0016] Figure 7 A schematic cross-sectional view of an alternative absorbent core comprising two central nonwoven sheets is shown.

[0017] Figure 8 This is a schematic diagram of a method for preparing wet-laid nonwoven fabrics.

[0018] Figure 9 It shows including Figure 6 A schematic cross-sectional view of an absorbent product with an absorbent core.

[0019] Figure 10 This is a schematic diagram of the method for preparing the absorber core of the present invention.

[0020] Figure 11A and Figure 11B The wicking area test will be shown as an example.

[0021] Figure 12 An example of equipment used in improving fluid acquisition testing is shown.

[0022] Figure 13A A side view of a bent component used in an improved fluid acquisition test.

[0023] Figure 13B for Figure 13A End view of the curved component.

[0024] Figure 13C for Figure 13A Bottom view of the curved component.

[0025] Figure 13D for Figure 13A Bottom perspective view of the curved component.

[0026] Figure 13E for Figure 13A Top perspective view of the curved component.

[0027] Figure 14A An example of a top plate assembly used in an improved fluid acquisition test is shown.

[0028] Figure 14B An example of equipment used in improving fluid acquisition testing is shown. Detailed Implementation

[0029] Definitions of Terms

[0030] As used herein, the term "absorbent article" refers to a disposable product that is worn close to or adjacent to the wearer's body to absorb and contain bodily fluids such as urine, feces, and menstrual flow, such as adhesive diapers, diapers (pants) with a closed waist opening, feminine hygiene products, etc. Typical absorbent articles include a top sheet, a back sheet, an absorbent core, a collection layer, and other components. The liquid-permeable top sheet forms at least a portion of the article on the wearer-facing side, and the back sheet forms at least a portion of the article on the garment side and typically forms the entire garment side. The article may be provided with fastening elements, such as tape (adhesive diapers), or may be pre-formed with a waist opening and a pair of leg openings, as in underwear (pants-style diapers). Absorbent articles are intended for infants, young children, women, or incontinent adults. Typical characteristics of absorbent articles are discussed further below.

[0031] As used herein, the term "cellulose fiber" is intended to include natural cellulose fibers, such as pulp and cotton; and regenerated cellulose fibers, such as rayon (including viscose, lyocell, MODAL (products of Lenzing AG, Lenzing, Austria) and cuprammonium rayon), unless otherwise stated.

[0032] As used herein, the terms “joining” or “bonding” or “attachment” cover a configuration in which an element is directly secured to another element by attaching it directly to the other element (e.g., by gluing), and a configuration in which an element is indirectly secured to another element by attaching it to a central member (which in turn is attached to the other element).

[0033] The terms “comprising,” “including,” and “having” are open-ended terms, each specifying the presence of a feature structure, such as a component, but not excluding the presence of other feature structures, 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 the feature structure performs its function; and the broader term “consisting of…”, which excludes any unspecified elements, steps, or components. Any preferred or exemplary examples described below do not limit the scope of the claims unless expressly stated otherwise. The words “usually,” “often,” “advantageously,” etc., also define the features but are not intended to limit the scope of the claims unless expressly stated otherwise.

[0034] The term "longitudinal" or "MD" refers to the direction parallel to the direction of travel of the fiber web during manufacturing. Longitudinal direction is typically the longitudinal direction of a component in an absorbent article. "Transverse" or "CD" is a direction substantially perpendicular to the MD and located within a plane generally defined by the fiber web.

[0035] 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 designed level of 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.

[0036] Absorbent Core

[0037] As used herein, the term "absorbent core" refers to a component of an absorbent article that includes absorbent material capable of absorbing and retaining bodily fluids such as urine and menstrual blood.

[0038] The term "absorbent material" refers to materials with some absorption or liquid retention properties, such as SAP, cellulose fibers, and synthetic fibers. Generally, the adhesives used to prepare absorbent cores do not possess absorption properties and are not considered absorbent materials. For the purpose of assessing the percentage of SAP in the absorbent core, the core coating is not considered an absorbent material.

[0039] The absorbent core according to the invention can be manufactured in a continuous flow, which can be stored and transported, for example, as rolls of absorbent core material, and then individualized when integrated into absorbent articles such as diapers and sanitary napkins. The absorbent core has the majority of the absorbent capacity of the components of the absorbent article and comprises all or at least most of the SAP particles. The terms "absorbent core" and "core" are used interchangeably herein.

[0040] The absorbent core of the present invention can be 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.

[0041] An exemplary individualized absorber core is shown in a flat state. Figure 1 In the middle. Although Figure 1 The absorbent core 28 is a rectangular shape with a front edge 280, a rear edge 282 and two longitudinally extending side edges 284, 286, but the absorbent core of the present invention can be in various shapes to meet various needs.

[0042] 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.

[0043] See Figure 2 and Figure 3 The absorbent core of the present invention includes a liquid-permeable top cover layer 41, a bottom cover layer 42, and an absorbent layer 43 disposed between the top cover layer 41 and the bottom cover layer 42, the absorbent layer including SAP 60. See also Figure 2 SAP is deposited on at least one of the inner surface of the top capping layer 41 and the inner surface of the bottom capping layer 42.

[0044] See Figure 3The absorbent layer may further include a central nonwoven sheet 44 having a top surface oriented toward the top cover layer 41 and a bottom surface oriented toward the bottom cover layer 42, wherein SAP is deposited on at least one of the top surface and the bottom surface of the central nonwoven sheet 44.

[0045] In a first embodiment of the invention, the absorbent core includes a top cover layer having a first MD wicking length at 3 minutes as measured by a wicking length test, and a bottom cover layer having a second MD wicking length at 3 minutes as measured by a wicking length test, wherein the first MD wicking length is at least 3 times, at least 4 times, or at least 5 times the second MD wicking length. When the MD wicking length of the top cover layer is significantly higher than that of the bottom cover layer, the absorbent core of the invention can rapidly and efficiently draw fluid from the top sheet and drive the top sheet drying, and better utilize the SAP in the absorbent core.

[0046] In a second embodiment of the invention, the top cover layer includes a first absorbent fiber and a second absorbent fiber different from the first absorbent fiber, and the total amount of the first absorbent fiber and the second absorbent fiber is at least about 70%, or at least about 80%, or at least about 90% by weight of the top cover layer.

[0047] 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.

[0048] Absorbent Layer

[0049] See Figure 2 and Figure 3 The absorbent core of the present invention includes an absorbent layer 43, which includes superabsorbent polymer particles 60, 62, and 64. The absorbent layer 43 is disposed between a top cover layer 41 and a bottom cover layer 42.

[0050] See Figures 3 to 7 The absorbent layer may further include a central nonwoven sheet 44 having a top surface oriented toward the top cover layer 41 and a bottom surface oriented toward the bottom cover layer 42, wherein superabsorbent polymer particles 60, 62, 64 are deposited on at least one of the top surface and the bottom surface of the central nonwoven sheet 44.

[0051] Superabsorbent polymer particles can be uniformly distributed within the core. Alternatively, the superabsorbent polymer particles 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 included. In addition to irregular SAP distribution 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.

[0052] The absorbent layer may be substantially free of free cellulose fibers, which are not bound to other fibers in the nonwoven fabric. "Substantially free of free cellulose fibers" means that the amount of free cellulose fibers may be less than 10% by weight of the absorbent layer, or less than 5% by weight of the absorbent layer, or less than 1% by weight of the absorbent layer, or may be completely free of such free cellulose fibers.

[0053] Top Cover and Bottom Cover

[0054] The top cover 41 is located on the side of the absorbent core closest to the absorbent article, facing the wearer, and may be liquid-permeable. The bottom cover is positioned on the opposite side of the central nonwoven sheet. The bottom cover may be liquid-permeable or liquid-impermeable. The top and bottom covers provide coverage on both sides of the central nonwoven sheet to prevent SAP particles from detaching from the central nonwoven sheet during the core and article preparation process and / or during use of the absorbent article.

[0055] In a first embodiment of the present invention, the length of the first MD wick is at least about 70 mm, or at least about 80 mm, or at least about 90 mm, or at least about 100 mm.

[0056] The top cover has a first MD wicking length at 3 minutes as measured by a wicking length test, and the bottom cover has a second MD wicking length at 3 minutes as measured by a wicking length test, and the first MD wicking length may be at least about 3 times, or at least about 5 times, or at least about 7 times, or at least 10 times the second MD wicking length.

[0057] With a high first MD wick length and a significantly higher MD wick length in the top cover layer than in the bottom cover layer, the absorber core of the present invention can quickly and effectively draw fluid from the top sheet and drive the top sheet to dry, and better utilize the SAP in the absorber core.

[0058] Nonwoven materials are typically inherently hydrophobic, and optionally, the top or bottom cover layers may be treated differently to make the top cover layer more hydrophilic than the bottom cover layer.

[0059] 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 28 to form a C-shaped wrap seal over the bottom cover layer 42, such as... Figure 4 As illustrated. 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 28 to form a C-shaped wrap seal over the top cover layer 41, as shown. Figure 5 exemplified.

[0060] In addition to the top and bottom overlays, the absorbent core may also include a wrapping layer 3 that surrounds the central nonwoven sheet and the two overlays, such as forming a C-shaped wrapping through longitudinally extending side edges 284, 286 around the core. Figure 6 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, of a low-basis-weight nonwoven layer, such as a basis weight of 5 gsm to 40 gsm, particularly 8 gsm to 25 gsm, especially SMS nonwovens, but other materials are of course also possible. As an example, the wrapping layer 3 can extend from the bottom side of the core 28 and have folds folded over the top side of the core, such as... Figure 6 As shown. 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 edges of the core, or may be longer than represented, so that they overlap and attach to one another. The presence of the wrapping layers is optional, but is particularly preferred if the top and bottom cover layers are not sealed along their longitudinal sides.

[0061] The top cover layer 41 and / or the bottom cover layer 42 are preferably at least partially attached to the absorbent layer 43 or the central nonwoven sheet 44.

[0062] Adhesive layer 71 can be applied, for example, between the top cover layer 41 and the absorbent 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 adhere. Adhesive can also be applied to one of the 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 can similarly be applied between the bottom cover layer 42 and the absorbent 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 central nonwoven sheet during core preparation.

[0063] Top Cover

[0064] Therefore, the top cover is liquid-permeable, allowing fluid to easily pass through the top cover and reach the absorbent layer during use.

[0065] The top cover layer includes absorbent fibers.

[0066] In a first embodiment of the invention, the top cover layer comprises absorbent fibers containing pulp. The top cover layer may comprise pulp ranging from about 30% to 70%, or about 40% to 60%, or about 30% to 60% by weight of the top cover layer.

[0067] When the amount of pulp is less than 30% by weight of the top cover, the top cover may not provide sufficient wicking capacity required by the present invention, and this may also increase production costs, given that the pulp needs to be made of more expensive absorbent fibers. When the amount of pulp is greater than 70% by weight of the top cover, the MD tensile strength of the top cover is low and it does not have sufficient mechanical strength.

[0068] The top cover layer may include absorbent fibers comprising at least about 70%, at least about 80%, at least about 80%, or at least about 90% pulp by weight of the top cover layer. The top cover layer may also include 100% absorbent fibers.

[0069] In a second embodiment of the invention, the top cover layer includes a first absorbent fiber and a second absorbent fiber different from the first absorbent fiber. The total amount of the first absorbent fiber and the second absorbent fiber is at least about 70%, at least about 80%, at least about 80%, or at least about 90% by weight of the top cover layer. The top cover layer may include 100% absorbent fiber.

[0070] When the absorbent core of the present invention is a component in an absorbent article, the absorbent fibers provide absorption of liquid intrusions from the top sheet. Any suitable absorbent fiber can be used. Some examples of absorbent fibers are cellulose fibers, including cotton, pulp, synthetic fibers, or regenerated cellulose, or combinations thereof.

[0071] The absorbent fibers suitable for the top cover layer can have any suitable shape. Some examples include trefoil, "H", "Y", "X", "T", circular or flat strips. Furthermore, the absorbent fibers can be solid, hollow, or multi-hollow.

[0072] When a top cover sheet comprising absorbent fibers (especially pulp fibers) absorbs liquid, it tends to lose some of its structural integrity, resulting in weakened mechanical strength of both the top cover sheet and the final absorbent core. This reduces the elasticity of the absorbent article including the absorbent core and leads to increased aggregation and leakage risk during use.

[0073] To address the potential problems associated with the loss of structural integrity and mechanical strength illustrated above, the top cover layer disclosed herein may include a first absorbent fiber and a second absorbent fiber different from the first absorbent fiber. The first absorbent fiber may contribute more to high weakening capacity, and the second absorbent fiber may contribute more to the mechanical strength of the top cover layer. The first absorbent fiber may be pulp fiber. The second absorbent fiber may be viscose fiber. When the top cover layer includes pulp, the amount of pulp may be in the range of about 30% to 70%, or about 40% to 60%, or about 30% to 60% by weight of the top cover layer.

[0074] In some examples, the top cover layer comprises at least about 30% pulp fiber and at least about 40% viscose fiber by weight of the top cover layer.

[0075] The top cover may also include synthetic fibers. Optional synthetic fibers forming the top cover can be made wholly or partially of relatively elastic synthetic fibers, particularly polypropylene (PP), polyamide (PA, such as nylon), or polyethylene terephthalate (PET) fibers. Synthetic fibers can impart better MD tensile strength to the top cover.

[0076] The top cover may have a first MD wicking length of at least about 70 mm, at least about 80 mm, at least about 90 mm, or even at least 100 mm at 3 minutes, as measured according to the wicking length test disclosed herein.

[0077] The top cover layer may have a thickness of at least approximately 100 mm. 2 At least approximately 150mm 2 At least approximately 170mm 2 Or at least approximately 190mm2 The first wicking area, as measured according to the wicking area test disclosed herein.

[0078] The top cover layer may be, for example, a nonwoven fabric with a basis weight between 5 gsm and 60 gsm, or between 10 gsm and 50 gsm, or between 20 gsm and 50 gsm.

[0079] The top cover layer may include a wet-laid nonwoven fabric. The top cover layer may be composed of a wet-laid nonwoven fabric. The principle of wet-laid fabrication is similar to papermaking. See also Figure 8 The diluted slurry of water and fibers in container 810 is deposited on a moving wire mesh screen, where water is drained and fibers form a fiber web (820). The fiber web can be further dehydrated (830) and dried (850) by pressing between rollers. Impregnation with a binder is typically included in later stages of the process (840).

[0080] The top cover layer may have a tensile strength of at least 12 N, or at least about 14 N, or at least about 15 N, as measured according to the tensile strength test disclosed herein. Materials with an tensile strength of less than 12 N, such as facial tissues, are not suitable for the top cover layer of the present invention because they do not have sufficient mechanical strength to withstand the core manufacturing process and the absorbent article manufacturing process. The top cover layer may have an tensile strength / basis weight of at least about 1.5 N / gsm, or at least 1.8 N / gsm, or at least 2 N / gsm.

[0081] The top cover can be made hydrophilic, for example, by treating it with a surfactant or other methods known in the art.

[0082] Bottom Cover

[0083] The bottom cap can be made of relatively thin and inexpensive materials, such as those commonly used in the production of conventional cores. The bottom cap can be, for example, formed of a nonwoven fiber web with a basis weight between 5 gsm and 50 gsm, such as carded nonwovens, spunbond nonwovens (“S”), or meltblown nonwovens (“M”), and laminates of any of these. For example, spun melt-blown polypropylene nonwovens are suitable, particularly those with a laminated web structure of SMS, SMMS, or SSMMS and a basis weight range of approximately 5 gsm to 20 gsm.

[0084] The bottom cover layer may have a second MD wicking length of not more than about 30 mm, or not more than about 20 mm, or not more than about 10 mm at 3 minutes, as measured according to the wicking length test disclosed herein.

[0085] Central Nonwoven Sheet

[0086] The absorbent core of the present invention may include a central nonwoven sheet 44, such as Figures 3 to 7 As illustrated, a central nonwoven sheet 44 is sandwiched between a top cover layer 41 and a bottom cover layer 42. The central nonwoven sheet 44 may include a high-loft nonwoven fabric.

[0087] The term "high-loft" refers to a low-density, loose fabric compared to a flat, paper-like fabric. High-loft fiber webs are characterized by a relatively high porosity. This means that a relatively high amount of void space exists within which superabsorbent polymer particles can be distributed. High-loft nonwovens without SAP particles can have densities below 0.20 g / cm³ at 4.14 kPa (0.6 psi), specifically in the range of 0.05 g / cm³ to 0.15 g / cm³, or below 0.20 g / cm³ at 2.07 kPa (0.3 psi), specifically in the range of 0.02 g / cm³ to 0.15 g / cm³, or below 0.15 g / cm³ at 0.83 kPa (0.12 psi), specifically in the range of 0.01 g / cm³ to 0.15 g / cm³.

[0088] Density can be calculated by dividing the basis weight of the high-loft nonwoven fabric by its thickness measured under the corresponding pressure, based on the thickness and density tests disclosed herein.

[0089] The central nonwoven sheet preferably comprises a high-loft nonwoven fabric, but other types of high-loft materials are not excluded. The central nonwoven sheet may comprise or consist of synthetic fibers, optionally blended with natural fibers such as cellulose fibers, cotton fibers, or viscose fibers. The central nonwoven sheet may be substantially free of free cellulose fibers that are not bonded to the other fibers of the nonwoven fabric. The amount of such free cellulose fibers in the absorbent core may be less than 10% by weight of the total absorbent core, or less than 5% by weight of the total absorbent core, or less than 1% by weight of the total absorbent core, or may be completely free of such free cellulose fibers. The high-loft material may comprise at least 10%, 30%, 50%, 70%, 90%, and up to 100% synthetic fibers by weight of the central nonwoven sheet.

[0090] The fibers forming the central nonwoven sheet 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.

[0091] The thickness, basis weight, and density of a central nonwoven sheet are typically uniform in both the transverse (x) and longitudinal (y) directions. However, the fiber orientation in a central nonwoven sheet can be nonuniform, 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 a central nonwoven sheet can differ from its dominant orientation in one or both directions (x and y).

[0092] The central nonwoven sheet can, 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, as measured under a pressure of 4.14 kPa (0.6 psi) according to the test methods further described below. The central nonwoven sheet can, in particular, have a thickness in the range of 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, as measured under a pressure of 0.83 kPa (0.12 psi) according to the test methods further described below.

[0093] The basis weight of the central nonwoven sheet can be, for example, in the range of 15 gsm to 500 gsm, particularly 20 gsm to 200 gsm, and even more particularly 30 gsm to 100 gsm.

[0094] Unless otherwise specified, the values ​​for the central nonwoven sheet referred to herein are for high-loft materials considered individually, i.e., before SAP particles are deposited between the fibers or before an adhesive is applied thereto. When the absorbent core comprises two or more central nonwoven sheets, these central nonwoven sheets may be the same or different.

[0095] While the invention is not limited to specific types of nonwovens or fibers, a specific example of a suitable nonwoven as a central nonwoven sheet is a bonded carded fiber web (“BCW”). A “bonded carded fiber web” refers to a nonwoven 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 generally longitudinally oriented. 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).

[0096] In carded nonwovens, the fibers in the fiber web are primarily aligned longitudinally and exhibit a more uniform fiber arrangement than in other nonwovens, resulting in higher stability and internal bond strength, especially in the longitudinal direction. The chosen bonding technique affects the integrity of the fabric. 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, comprise short fibers ranging from about 3 denier to about 10 denier.

[0097] Nonwoven sheets can also include 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.

[0098] When the central nonwoven sheet 44 is rectangular, the front and rear edges are typically shorter than the side edges. The front edge of the central nonwoven sheet corresponds to the edge intended to be positioned towards the front edge of the absorbent article, where the core may be integrated.

[0099] The absorbent core may include one, two, or more high-loft central nonwoven sheets. See below for reference. Figure 7 Further discussion includes the absorbent core of a nonwoven sheet with two high-loft centers.

[0100] A central nonwoven sheet (or multiple central nonwoven sheets) serves as the substrate for SAP particles 60, 62, 64, which are at least partially distributed within the pores of the central nonwoven sheet. The SAP particles can be substantially uniformly blended across the entire thickness of the central nonwoven sheet. However, the SAP particles can be unevenly distributed in the vertical direction. The SAP particles are typically deposited on one side of the nonwoven fabric and are drawn into the nonwoven fabric, for example, by gravity or negative pressure on the opposite side. In this way, some particles remain close to the surface of the central nonwoven sheet, while other, generally smaller particles can penetrate deeper into the pores of the nonwoven sheet. SAP particles that are not trapped within the pores of the central nonwoven sheet but remain at the surface can be further secured by an optional adhesive layer 71 or 72. The adhesive can be applied to the top and bottom overlays prior to bonding, while still adhering to the central nonwoven sheet. Typically, SAP particles are sequentially applied to the central nonwoven sheet from each side as a first SAP layer including SAP 60 and a second SAP layer including SAP 62, as shown below. Figure 10 Further illustration. When viewed in the z-direction, this SAP particle deposition process can result in a z-shaped distribution pattern of SAP within the central nonwoven sheet, comprising two or more density peaks separated by at least one buffer zone.

[0101] Superabsorbent Polymer Particles

[0102] The term “superabsorbent polymer” (abbreviated as “SAP” in both singular and plural forms herein) 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 by centrifugation retention capacity (CRC) test (EDANA method NWSP 241.0.R2 (19)).

[0103] 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 starch-grafted copolymers of polyacrylamide, ethylene maleic anhydride, crosslinked carboxymethyl cellulose, polyvinyl alcohol, crosslinked polyethylene oxide, and polyacrylonitrile can also be used.

[0104] SAP can be an internally and / or surface-crosslinked polyacrylate and polyacrylic acid polymer. The superabsorbent polymer used in the absorbent core 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 copolymerized into the polymer network in a free radical manner. 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.

[0105] When the absorbent core of the present invention comprises an optional central nonwoven sheet, it includes a first SAP layer comprising a first SAP (“SAP1”) and a second SAP layer comprising a second SAP (“SAP2”). See also Figures 3 to 6 The first SAP layer, including SAP1 (SAP 60 in this document), is located near the top overlay 41, and the second SAP layer, including SAP2 (SAP 62 in this document), is located near the bottom overlay 42.

[0106] SAP1, which constitutes the first SAP layer, and SAP2, which constitutes the second SAP layer, can be the same type of SAP. Alternatively, SAP1, which constitutes the first SAP layer, and SAP2, which constitutes the second SAP layer, can be different types of SAP.

[0107] When the absorbent core of the present invention comprises an optional central nonwoven sheet, SAP particles are typically deposited sequentially on each side of the central nonwoven sheet, wherein the central nonwoven sheet sides are laminated and flipped between depositions. During the deposition steps, the SAP particles may at least partially penetrate into the pores of the central nonwoven sheet, such that they are at least partially distributed within the central nonwoven sheet. Thus, on one hand, the particles are fixed within the pores of the central nonwoven sheet and secured by a top or bottom cover layer laminated onto each of the top and bottom surfaces of the central nonwoven sheet.

[0108] The total amount of SAP present in the absorbent core can vary depending on the intended user of the product. For a typical baby diaper, the total amount of all SAP in the core can be, for example, from about 2g to 50g, particularly 5g to 40g or 10g to 20g.

[0109] The absorbent core typically includes 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.

[0110] The absorbent core 28 discussed above comprises a single, optional central nonwoven sheet; however, the absorbent core may also comprise two (or more) central nonwoven sheets between the top and bottom overlays. This is, for example, in... Figure 7 As illustrated, the absorbent core 28b, which includes a first central nonwoven sheet 441 and a second central nonwoven sheet 442, is shown sandwiched between the top cover layer 41 and the bottom cover layer 42.

[0111] Therefore, the absorbent core 28b may include a first central nonwoven sheet 441 and a second central nonwoven sheet 442, each comprising, for example, layers of superabsorbent polymer particles 60, 62, 64 at least partially distributed within the pores of the central nonwoven sheet. The two (or more) central nonwoven sheets may be composed of the same material or different nonwoven fabrics. For example, the permeability of the upper central nonwoven sheet can be enhanced by using a low-basic-weight nonwoven fabric, and the softness of the bottom overlay can be enhanced by utilizing a denser nonwoven material. Of course, other configurations are also possible. The two or more central nonwoven sheets may have the same dimensions in the X and Y planes of the core, but they may also have different lengths and / or widths. Two central nonwoven sheets of unequal lengths may be advantageous in providing different amounts of SAP along the absorbent core.

[0112] At least one of the two central nonwoven sheets includes two different types of SAPs as discussed above, with the first SAP 60 having a higher capacity than the second SAP. See, for example... Figure 7 The first SAP can be placed in the SAP layer of the top cover layer closest to the absorber core, and the second SAP 62 and / or 64 can be placed in one of the lower layers.

[0113] Components of the absorbent articles described herein may be at least partially composed of a bio-based content, as described in U.S. Patent Application No. 2007 / 0219521A1. For example, superabsorbent polymer components may be bio-based rather than derived from bio-based acrylic acid. Bio-based acrylic acid and methods for producing it are described in U.S. Patent Application Publication No. 2007 / 0219521 and U.S. Patent Nos. 8,703,450, 9,630,901, and 9,822,197. Other components, such as nonwoven and membrane components, may comprise bio-based polyolefin materials. Bio-based polyolefins are further discussed in U.S. Patent Application Publications Nos. 2011 / 0139657, 2011 / 0139658, 2011 / 0152812, and 2016 / 0206774 and U.S. Patent No. 9,169,366. Example bio-based polyolefins used in this disclosure include those that may be named SHA7260. ™ SHE150 ™ Or SGM9450F ™The obtained polymers (all available from Braskem SA).

[0114] Absorbent article components may include, for example, bio-based content values ​​of about 10% to about 100%, about 25% to about 100%, about 40% to about 100%, about 50% to about 100%, about 75% to about 100%, or about 90% to about 100%, as measured using ASTM D6866-10 Method B.

[0115] Channel

[0116] The absorber core 28 may include at least one longitudinally extending region that is substantially free of SAP particles. These one or more regions that are substantially free of SAP particles are referred to herein as “grooves”.

[0117] The term "substantially SAP-free" means that the basis weight of the SAP material in each of these zones is at least less than 25%, specifically less than 20%, and specifically less than 10%, based on the average basis weight of SAP in the central nonwoven sheet as a whole. A groove can specifically refer to a region of the central nonwoven sheet where SAP particles are absent. In this regard, the minimum amount of contaminants that may occur during preparation, such as unintentional SAP particle contaminants, are not considered part of the absorbent material.

[0118] The term "longitudinal extension" means that the groove extends further in the longitudinal direction (y) than in the transverse direction (x). The groove can be oriented parallel to the longitudinal direction. However, it is not excluded that the groove can be curved, especially concave towards the longitudinal axis, or it can be straight and inclined at an angle relative to the longitudinal direction.

[0119] Method for Absorbent Core Preparation

[0120] An exemplary continuous method for preparing an absorber core is shown in Figure 10 The methods and equipment discussed above are generally similar to CN101797201A or WO2020 / 025401 (BASF, Ge et al.). Figure 3 The methods and equipment disclosed herein. Figure 10 The arrows in the diagram indicate the rotation direction of the unwinding and winding cylinders, as well as the direction of material movement during the production process. Other methods and modifications are, of course, also possible.

[0121] like Figure 10As illustrated, 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 center nonwoven sheet fiber web unwinding machine 8, a first SAP granule dispenser 9 and optional vacuum suction box 10, first rollers 11 and 12, a second SAP granule dispenser 13 and optional vacuum suction box 14, a top cover layer fiber web unwinding machine 15, a top cover layer nozzle 16, second rollers 17 and 18, trimming blades 19 and 20, and a product roll winding roller 21.

[0122] 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.

[0123] 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 44 is mounted on a center nonwoven sheet fiber web unwinding machine 8. The initial density and thickness of the high-loft sheet can be conveniently measured on the raw material using the thickness and density tests described further below.

[0124] 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. During the continuous process of preparing the absorbent core, a bottom cover layer 42 is passed through a nozzle 7 and glue 72 is applied to one side, and then attached to a central nonwoven sheet 44 between first pressure rollers 11 and 12. The high-loft nonwoven central nonwoven sheet 44 passes through a first SAP distributor 9 and a vacuum suction box 10, where SAP particles 62 are deposited into the central nonwoven sheet and distributed at least partially from the first side into the fibers of the central nonwoven sheet.

[0125] After the bottom cover layer 42 and the central nonwoven sheet 44 are pressed together between rollers 11 and 12, these combined layers can 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 central nonwoven sheet and to blend the SAP particles from the second surface into the fibers of the central nonwoven sheet. The top cover layer 41, with adhesive 72 applied via the spray nozzle 16, is then bonded to the central nonwoven sheet to cover the second surface of the central nonwoven sheet between the two pressure rollers 17 and 18. Of course, the top and bottom cover layers can be used interchangeably in the foregoing.

[0126] 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 in the core, thereby providing mechanical bonding, ultrasonic bonding, and / or thermal bonding within the groove areas. 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.

[0127] 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 individually cut along their front and rear edges.

[0128] Such as about Figure 6 As shown and discussed, the wrapping layer 3 ( Figure 10 (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. When the core material fiber web is further transformed, alternative wrapping layers of this type can also be attached to the core.

[0129] The absorbent core, including the dual-center nonwoven sheet, can be prepared by a method adapted from one of the disclosed methods above, see, for example, WO2016 / 106021A1, which describes two separate center nonwoven sheet release cylinders to provide a first center nonwoven sheet 441 and a second center nonwoven sheet 442. Alternatively, a center nonwoven fiber web with double the width can be used: this wide roll can be cut in half after longitudinal release, providing two strands of high-loft nonwoven material, which are then deposited separately with SAP particles. These two strands of center nonwoven sheet material 441, 442 can then be bonded to a top cap and a bottom cap, respectively, and SAP particles are then deposited onto the top and bottom caps, respectively, using suitable SAP deposition devices.

[0130] Absorbent Article 20

[0131] 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 9 A schematic cross-sectional view is illustrated in the diagram, showing some of the main components of the diaper absorbent article 20. Figure 9In, it is shown Figure 6 The absorbent core (with a wrapping layer 3) is present, but this is not limiting and is merely illustrative. 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.

[0132] 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.

[0133] 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. Suitable film materials may include breathable materials that allow vapors to escape from the absorbent article while still preventing effluent from passing through the film. A low-basis-weight nonwoven fabric with coverage may be attached to the outer surface of the film to provide a softer feel.

[0134] 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 sheet of paper or a low-basic-weight NW layer that provides additional wrapping around the absorbent core 28' to prevent SAP particles from escaping from the core.

[0135] 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.

[0136] 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 structure of the diaper, for example, between the top and bottom pieces in the leg opening area.

[0137] 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.

[0138] 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.

[0139] 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 9 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.

[0140] Measurement

[0141] 1. Basis Weight Test

[0142] The basis weight of the material was measured according to WSP 604.0 (08). All measurements were performed in a laboratory maintained at 23°C ± 2°C and 50% ± 2% relative humidity, and the samples were conditioned in this environment for at least 2 hours prior to testing. To obtain nonwoven samples, samples with an area of ​​100 cm² were used. 2 (For example, cut a rectangular nonwoven sample from a 100mm × 100mm article and measure its basis weight according to the measurement principle used in the standard method described above.) Test at least five parallel samples and report the average of at least five parallel samples, accurate to 1 gsm (g / m³). 2 ), which serves as the basis weight of the sample.

[0143] 2. Thickness and Density Test

[0144] This test is used to measure the thickness (thickness diameter) of the nonwoven fabric 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-loft materials in the absence of SAP particles. This measurement should preferably be performed on the high-loft material before it is transformed into an absorbent core and thus free of SAP. If the starting material is unavailable, a high-loft central nonwoven sheet 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 central nonwoven sheet 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.

[0145] Equipment: Mitutoyo manual diaphragm gauge with 0.01mm resolution, or equivalent instrument.

[0146] 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.

[0147] 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.

[0148] Scale: A calibration metal scale with a millimeter graduation.

[0149] Stopwatch: with an accuracy of 1 second.

[0150] Sample preparation: The central nonwoven sheet should be conditioned for at least 24 hours as indicated above.

[0151] 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 that will be made from the sample.

[0152] Raise the contact foot of the gauge and place the center nonwoven sheet flat on the base plate of the gauge with the top side of the core facing upward, so that when it is lowered, the center of the foot is on the marked measurement point.

[0153] 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.

[0154] 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.

[0155] Density in g / cm³ is determined by measuring the basis weight of the material (in g / cm³). 2 The calculation is done by dividing the thickness (in cm) by the unit of measurement.

[0156] 3. Tensile Strength Test

[0157] The MD tensile strength of the specimens was measured under the following conditions according to NWSP 110.4-09.

[0158] - Test speed: 100mm / min

[0159] - Sample width: 50mm

[0160] - Sample length: sufficiently longer than the gauge length

[0161] - Gauge length: 100mm

[0162] 4. Wicking Length Test

[0163] The wicking length in the longitudinal direction of nonwoven fabrics is measured according to ISO 9073-6:2000 “Textiles – Test methods for nonwovens – Part 6: Absorption 6. Liquid wicking rate” (EN29073 Part 6).

[0164] When the nonwoven fabric to be tested is available in raw material form, cut a 30mm × 250mm sample from the raw material. When the nonwoven fabric is an absorbent core or part of the finished product, use a razor blade to remove the nonwoven fabric from the core or finished product to separate the nonwoven fabric from other parts of the finished product, providing a 30mm × 250mm nonwoven fabric sample cut from the raw material. If necessary, a cryogenic sprayer (such as Cyto-Freeze, Control Company, Houston TX) can be used to remove the nonwoven fabric sample from other parts of the finished product.

[0165] Test four parallel samples for each sample and record the average (arithmetic mean) of the four parallel samples as the MD wick length.

[0166] 5. Wicking Area Test

[0167] This method measures the XY distribution area by freely dripping 0.1 ml of test liquid onto a test material such as a nonwoven fabric. The test liquid, namely 0.9% NaCl with a dye color, is prepared by dissolving 45 g of NaCl in 2500 ml of deionized water and staining the resulting solution with a colorant.

[0168] When the nonwoven fabric to be tested is available in raw material form, cut a 100mm x 100mm sample from the raw material. When the nonwoven fabric is an absorbent core or part of the finished product, use a razor blade to remove the nonwoven fabric from the core or finished product to separate the nonwoven fabric from other parts of the finished product, providing a 100mm x 100mm nonwoven fabric sample cut from the raw material. If necessary, a cryogenic sprayer (such as Cyto-Freeze, Control Company, Houston TX) can be used to remove the nonwoven fabric sample from other parts of the finished product.

[0169] Procedure

[0170] 1. Cut a sample with a size of 100mm × 100mm from the raw material or absorbent core.

[0171] 2. Place the cylindrical support with a circular cavity (6cm-8cm in diameter) on the worktable.

[0172] 3. See also Figure 11A Place the sample flat on the support so that the center of the sample is at the center of the circular cavity of the support.

[0173] 4. Drop 10 μL of test liquid into the center of the sample. Start the stopwatch at this point.

[0174] 5.1 minutes later, remove the sample from the holder and place it on the worktable.

[0175] 6. Draw the outline of the wicking area (colored area) on the sample, see [reference]. Figure 11B .

[0176] 7. Measure the wicking area at an appropriate magnification using an ImageJ or VHX digital microscope or equivalent software program to capture the entire wicking area.

[0177] 8. Repeat steps 1-7 for the four additional parallel samples. Report the average stenotic area of ​​the five samples as the stenotic area of ​​the sample.

[0178] 6. Modified Fluid Acquisition Test

[0179] The modified fluid collection (“MFA”) test was designed to measure the rate at which a 0.9% saline solution was absorbed into an absorbent article compressed at 2.07 kPa. A known volume was introduced four times, with each subsequent dose initiated five (5) minutes after the previous dose had been absorbed. The time required to absorb each dose was recorded. The test fluid was a 0.9% w / v saline solution, prepared by weighing 9.0 g ± 0.05 g of NaCl into a weighing boat, transferring it to a 1 L volumetric flask, and diluting it by volume with deionized water.

[0180] MFA equipment shown Figures 12 to 14B The MFA device includes a capsule assembly 3001 and a top plate assembly 3200 including a deposition assembly 3100. A controller 3005 is used to 1) monitor the impedance across electrode 3106 and record time intervals of a 0.9% brine solution in cylinder 3102; 2) interact with a liquid pump 3004 to start / stop dispensing; and 3) measure the time interval between dispensings. The controller 3005 is capable of recording time events accurate to ±0.01 seconds. An indoor air source 3014 is connected to a pressure regulator 3006, which delivers air at an appropriate flow rate / pressure to maintain 2.07 kPa in the capsule assembly 3001. Liquid pump 3004 (Ismatec MCP-Z gear pump or equivalent purchased from Cole Palmer (Vernon Hills, IL)) is capable of delivering a flow rate of 10 mL to 80 mL at a rate of 3 mL / s to 15 mL / s, and is attached to steel pipe 3104 of deposition assembly 3100 via polyethylene conduit 3015.

[0181] The capsule assembly 3001 is made of 12.7mm thick resin glass with overall dimensions of 80cm long x 30cm wide x 10cm high. A pressure gauge 3007 for measuring the pressure inside the assembly and a pressure gauge 3006 for regulating the introduction of air into the assembly are installed through two holes on the right side. The capsule 3013 is assembled as follows: a 50mm x 100mm siloxane diaphragm (0.02" thickness, Shore A hardness rating 20, purchased from McMaster-Carr (Cleveland, OH) with part number 86435K85) is placed over the top of the box, leaving sufficient slack so that the diaphragm touches the bottom of the box at its center point. A flanged aluminum frame 3003 is fitted onto the top of the diaphragm and secured in place using a mechanical clamp 3010.

[0182] When properly positioned, the assembly should not crack or leak under a pressure of 3.45 kPa. The sample is anchored using the front 3008 sample support (5 cm x 30 cm x 1 mm) and the rear 3009 sample support. The absorbent article is attached to the top surface of the sample support using adhesive tape or mechanical "hook" fasteners. These supports can be adjusted along the length of the aluminum frame 3003 via a simple pin-hole system to accommodate absorbent articles of different sizes and to correctly align their cutting points.

[0183] The top plate assembly 3200 is made of a 12.7mm resin glass sheet measuring 80cm by 30cm, which is reinforced with an aluminum frame 3109 to enhance rigidity. The plate has a 170mm wide by 201mm long cutout laterally centered on the plate, 170mm from the front of the plate 3201 for mounting the deposition assembly. Furthermore, the top plate has thirty-six (36) through-holes, such as... Figure 14A The diagram shows 3.2 mm diameter holes. These holes are designed to prevent air from being trapped under the top plate when the bladder inflates. The top plate assembly 3200 is connected to the bladder assembly 3001 via two hinges 3012. During use, the top assembly is closed onto the bladder assembly and locked in place using mechanical clamps 301l.

[0184] The deposition assembly 3100 is adapted into the top plate 3200 and includes 1) a liquid inlet cylinder 3102; 2) a curved surface 3101 at the loading point of the absorbent article; and 3) an electrode 3106 for detecting the fluid in the cylinder 3102. Detailed dimensions of the curved component are provided in... Figures 13A to 13E middle. Figure 13A This is a side view of the curved component. Figure 13B This is an end view of the bent component. Figure 13C This is a bottom view of the curved component. Figure 13D This is a bottom perspective view of the curved component. Figure 13E This is a top perspective view of the curved component. The curved component can be milled or 3D printed. The top portion of the inlet cylinder is a 50.8mm outer diameter resin glass cylinder 3102 with a 38.1mm LD. It is fitted into the curved component to give the inlet cylinder a total height of 100mm. The embedded electrode extends from a connector on the upper surface of the curved component and terminates flush with the inner wall of the inlet cylinder, 2mm from the bottom of the cylinder. The two electrodes are positioned 180 degrees apart. A nylon mesh 3107 is cut and attached flush with the bottom of the cylinder so that the sample cannot swell into the cylinder. In the adjacent area of ​​the two electrodes, a 5mm semicircle is cut in the mesh. Figure 14AThe deposition assembly is inserted into the top plate such that the curved surface is flush with the bottom of the top plate assembly 3200. The top of the inlet cylinder 3102 has a loosely fitted nylon cap 3103. The cap has a steel tube 3104 with an outer diameter of 6.35 mm inserted through its center. When the cap is in place, the bottom of the tube terminates 20 mm above the screen 3107. The cap also has vents 3105 to ensure that negative pressure does not impede the absorption rate.

[0185] First, prepare the absorbent article by removing any inner or outer leg hoops, waist caps, elastic lugs, or side plates, taking care not to interfere with the top plate residing above the core area of ​​the article. Place the absorbent article flat on a laboratory workbench and identify the intersection of the longitudinal centerline and the loading point, which is sized as defined in Table 1.

[0186] Table 1. Conditions for Modified Fluid Acquisition Test :

[0187]

[0188] *Use the boy's loading point for unisex diapers.

[0189] The front end of the absorbent article is attached to the top surface of the front sample plate 3008, with the top plate facing upwards, using adhesive tape or mechanical "hook" fasteners. This placement ensures that only the base structure, not the absorbent core, is stacked. The sample plate 3008 is attached to the aluminum frame 3003 such that, when the top plate assembly is closed, the size-dependent loading point of the absorbent article (as defined in Table 1) is longitudinally and laterally centered within the cylinder 3102. The rear end of the absorbent article is secured to the rear sample plate 3009 using adhesive tape or mechanical "hook" fasteners, again ensuring that only the base structure, not the absorbent core, is stacked. The rear sample plate 3009 is then attached to the aluminum frame 3003 such that the article is taut but not stretched. The top plate assembly is closed and secured, and the capsule is pressurized to 2.07 kPa ± 0.07 kPa. The pressure is maintained at this level throughout the complete loading sequence of the test.

[0190] Prepare pump 3004 for immediate use and then calibrate it to deliver the size-dependent volumes and flow rates selected from Table 1. Volume and flow rates must be within ±2% of the target values. Place top cap 3103 into cylinder 3102. Start controller 3005, which then delivers the first dose of 0.9% saline solution. After the volume has been absorbed, the controller waits 5.0 minutes before adding the next dose. Repeat this cycle for a total of four doses. If fluid leaks out or surrounds the article (i.e., is not absorbed into the article), the test is stopped. Additionally, the test is stopped if any collection time exceeds 1200 seconds. Collection time is defined as the difference between the start time (i.e., when the 0.9% saline solution is first introduced into the cylinder and the conductive fluid connects the circuit between the electrodes) and the stop time (i.e., when the liquid has completely drained from the cylinder and the circuit between the electrodes is disconnected). The collection time for each dose is recorded by the controller to an accuracy of 0.01 seconds. After obtaining the last dose, apply pressure and maintain pressure for 10 minutes. Open pressure relief valve 3016 to depressurize the capsule, and then remove the sample from the collection system.

[0191] For each absorbable product to be evaluated, a total of eight (8) parallel samples were run in a similar manner. The “collection time” (seconds) for each dose was calculated and reported as the arithmetic mean of the parallel samples, accurate to 0.01 seconds.

[0192] 7. Rewet Test

[0193] The backflow test is performed immediately after the MFA test. The backflow test involves measuring the mass of fluid extruded from the absorbent article under pressure after loading according to the MFA procedure. Filter paper is used as the backflow substrate. Suitable filter paper is Whatman filter paper with a diameter of 125 mm. ™ (Cytiva catalog number 1001-125) or equivalent. Upon receipt, the filter paper was stored for 2 hours at approximately 23°C ± 2°C and approximately 50% ± 2% relative humidity prior to testing. The apparatus used for this test consisted of a resin glass disc with a diameter of 70.0 mm and a stainless steel restraining weight placed on it. The combined mass of the disc and the restraining weight was 812.5 g, which corresponds to a pressure of 2.07 kPa. The filter paper was stacked together as a stack of three (3) for use during the reabsorption test. The mass of the dried filter paper stack was measured and recorded to an accuracy of 0.001 g.

[0194] Within 30 seconds of the MF test, remove the absorbent article from the collection device and place it flat on the worktable with the top plate facing upwards. Then, center the pre-weighed stack of filter paper at the loading point (as determined previously in the MF test), place the resin glass dish on the stack, and gently place the limiting weight on the dish. Wait 15.0 seconds ± 0.5 seconds and remove the weight and dish. Immediately measure and record the mass of the wetted filter paper, accurate to 0.001 g. Calculate and record the filter paper value as the difference between the wet and dry weight of the stack, accurate to 0.001 g.

[0195] For each absorbent product to be evaluated, a total of eight (8) parallel samples were run in a similar manner. The “collagen reabsorption” (mg) for each dose was calculated and reported as the arithmetic mean of the parallel samples, accurate to 0.001 g.

[0196] Examples

[0197] Example 1 : Nonwoven

[0198] The MD wicking length and XY wicking area were tested on various nonwovens according to the test methods disclosed herein, and are shown in Table 2 below.

[0199] Table 2

[0200]

[0201] - Nonwoven fabric 1, as well as nonwoven fabrics 2 and 3, are produced by different manufacturers.

[0202] Table 2 - Continued

[0203]

[0204] * Polyethylene / polyethylene terephthalate sheath / core bicomponent fiber

[0205] Nonwoven fabrics 1-3 comprise at least 30% pulp by weight of the nonwoven fabric and have high MD core length and high MD tensile strength. Nonwoven fabrics 1-3 have MD tensile strengths well above 12 N and MD tensile strength / basis weight well above 1.5 N / gsm.

[0206] Example 2: Absorbent Core

[0207] The absorbent core for various top and bottom overlays, common center nonwoven sheets, and commercially available SAPs is manufactured according to Table 3 below. In all cases, the center nonwoven sheet has a density of 0.018 g / cm³. 3The density and 40 gsm air-bonded combed nonwoven fabric with a thickness of 2.1 mm measured at 2.07 kPa.

[0208] Table 3

[0209]

[0210] Example 3: Absorbent Article

[0211] Baby diapers 1-4, which are exemplary absorbent articles having the absorbent core of Embodiment 2 described above, are manufactured using a common top sheet, a distribution layer, and a bottom sheet. Baby diapers 5-8, which are exemplary absorbent articles having the absorbent core of Embodiment 2 described above, are manufactured using a common top sheet, a distribution layer, and a bottom sheet.

[0212] The collection time and backflow of each diaper in diapers 1-8 were measured according to the collection rate test and backflow test disclosed in this article, and the results are indicated in Table 4 below.

[0213] Table 4

[0214]

[0215] Compared to diapers 2-4 and 6-8, diapers 1 and 5, which have absorbent cores according to the invention, exhibit significantly faster collection speeds and significantly lower rewetting.

[0216] The dimensions and values ​​disclosed herein should not be construed as strictly limited to the precise numerical values ​​cited. Rather, unless otherwise specified, each such dimension is intended to represent the stated value and the range surrounding its functional equivalent. For example, a dimension disclosed as “40 mm” is intended to represent “approximately 40 mm”.

[0217] Unless expressly excluded or otherwise limited, every reference cited herein, including any cross-references or related patents or patent applications, and any patent application or patent claiming priority to or benefiting from it, is incorporated herein by reference in its entirety. Reference to any reference is not an endorsement of it as prior art to any disclosed or protected art herein, nor is it an endorsement of any such invention, either on its own or in combination with any one or more references. Furthermore, where any meaning or definition of a term in this invention conflicts with any meaning or definition of the same term in referenced documents, the meaning or definition given to that term in this invention shall prevail.

[0218] Although specific embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, it is intended that all such changes and modifications falling within the scope of the invention be covered by the appended claims.

Claims

1. An absorbent core for use in an absorbent article, the absorbent core extending in a transverse direction and a longitudinal direction and having a thickness in a vertical direction perpendicular to the transverse direction and the longitudinal direction, the absorbent core comprising: A liquid-permeable top cover; Bottom cover layer; and An absorption layer, disposed between the top cover layer and the bottom cover layer, comprising superabsorbent polymer particles. The top cover layer comprises pulp and has a tensile strength of at least about 12 N. The top cover layer has a first MD wicking length at 3 minutes, and the bottom cover layer has a second MD wicking length at 3 minutes, as measured by a wicking length test. The first MD wick length is at least about 70 mm and is at least about 3 times the length of the second MD wick.

2. An absorbent core for use in an absorbent article, the absorbent core extending in a transverse direction and a longitudinal direction and having a thickness in a vertical direction perpendicular to the transverse direction and the longitudinal direction, the absorbent core comprising: A liquid-permeable top cover; Bottom cover layer; and The absorption layer comprises superabsorbent polymer particles. The top cover layer includes a first absorbent fiber and a second absorbent fiber, wherein the second absorbent fiber is different from the first absorbent fiber, and The total amount of the first absorbent fiber and the second absorbent fiber is at least about 70% based on the weight of the top cover layer.

3. The absorbent core according to claim 1 or 2, wherein the first MD core length is at least about 100 mm.

4. The absorbent core according to claim 1 or 2, wherein the absorbent layer further comprises a central nonwoven sheet having a top surface oriented toward the top cover layer and a bottom surface oriented toward the bottom cover layer, wherein at least a portion of the superabsorbent polymer particles are deposited on at least one of the top surface and the bottom surface of the central nonwoven sheet.

5. The absorbent core according to claim 4, wherein the central nonwoven sheet comprises a high-loft carded nonwoven fabric.

6. The absorbent core according to any one of the preceding claims, wherein the absorbent layer is substantially free of free cellulose fibers.

7. The absorbent core according to any one of the preceding claims, wherein the top cover layer comprises at least about 80% absorbent fibers by weight of the top cover layer.

8. The absorbent core according to any one of the preceding claims, wherein the top cover layer comprises pulp and viscose fiber.

9. The absorbent core according to any one of the preceding claims, wherein the top cover layer comprises at least about 30% pulp by weight of the top cover layer.

10. The absorbent core of claim 2, wherein the top cover layer has a tensile strength of at least about 12 N.

11. The absorbent core according to any one of the preceding claims, wherein the top cover layer is substantially composed of absorbent fibers.

12. The absorbent article according to any one of claims 1 to 10, wherein the top cover layer further comprises synthetic fibers.

13. The absorbent core according to any one of the preceding claims, wherein the top cover layer comprises a wet-laid nonwoven fabric.

14. The absorbent core according to any one of the preceding claims, wherein the top cover layer has a first wicking area, wherein the first wicking area is at least 100 mm². 2 .

15. The absorbent core according to any one of the preceding claims, wherein the bottom cover layer comprises synthetic fibers.

16. The absorbent core according to any one of the preceding claims, wherein the bottom cover layer comprises a spunbond nonwoven fabric.

17. The absorbent core according to any one of the preceding claims, wherein the absorbent core further comprises at least one longitudinally extending groove that is substantially free of superabsorbent polymer particles.

18. An absorbent article comprising a top sheet, a bottom sheet, and an absorbent core disposed between the top sheet and the bottom sheet, wherein the absorbent core is an absorbent core according to any one of claims 1 to 17.

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