Method of forming a multilayer nonwoven material having topographical protrusions via differential contraction

Abstract

A method and system for producing a nonwoven material are disclosed. A foam-formed nonwoven web includes a first layer and a second layer. The first layer shrinks relative to the second layer such that the first layer forms a plurality of protrusions on an outer surface of the first layer facing away from the second layer.

Description

Background Technology

[0001] There are many different types of nonwoven materials designed to have different functions. In many embodiments, nonwoven materials are designed to have liquid handling properties. These nonwoven materials can be used in absorbent articles or in the production of wiping products, tissue products, etc. Absorbent articles, also known as personal care products such as diapers, diaper pants, training pants, adult incontinence products, and feminine hygiene products, can include a variety of substrates. For example, diapers can include absorbent structures, nonwoven materials, and membranes. Similarly, facial tissues, wipes, and wipes can also include a variety of substrates.

[0002] In some applications, multilayer nonwoven materials include a collection layer for receiving fluids. Generally, the collection layer preferably has high porosity and compressibility. However, conventional methods for forming nonwoven materials provide limited porosity and compressibility in the collection layer. Improved methods for forming nonwoven materials with a collection layer possessing high porosity and compressibility would be useful. Summary of the Invention

[0003] Generally speaking, this disclosure relates to a nonwoven material and a method for manufacturing the nonwoven material. In multilayer nonwoven webs formed from foam, such as double-layer nonwoven webs,

[0004] Adjacent layers may be at least partially structurally interconnected (e.g., fiber entanglement between adjacent layers, gradient interfaces between layers, interlayer adhesion, etc.), and

[0005] The nonwoven web can be heated such that one layer shrinks less than at least one of the other layers, which can cause one layer to deform and create multiple protrusions. For example, the first layer of the nonwoven web can be at least partially (e.g., completely) cured and / or dried while the first layer is under tension. The first layer may correspond to the collection layer of the nonwoven web. Curing the first layer can define the structural relationship between the different first and second layers of the nonwoven web. For example, at least partially curing the first layer can define the interlayer adhesion between the first and second layers. After the top layer has been at least partially cured, the second layer can be cured and / or dried while the second layer is under tension. The tension in the first and / or second layers can be controlled during curing such that the shrinkage of the second layer deforms the first layer, thereby forming morphological protrusions on the outer surface of the first layer. As will be described in more detail below, exemplary aspects of this disclosure offer a number of different advantages and benefits. For example, the collection layer of the nonwoven material can advantageously have high porosity and compressibility due to the morphological protrusions.

[0006] In terms of examples, various mechanisms can be used to form morphological protrusions via differential shrinkage between the first and second layers. For example, the second forming layer may include fibers capable of hydrogen bonding. The shrinkage of the second layer may be at least partially due to capillary condensation and hydrogen bonding during drying. As another example, the second forming layer may include superabsorbent particles that partially swell during treatment at the wet end of a foam forming process. The shrinkage of the second layer during drying may be at least partially due to the shrinkage of the superabsorbent particles as water is removed. As yet another example, the second layer may include fibers or other materials, such as PLA staple fibers, that shrink upon heating. The shrinkage of the second layer during heating may be at least partially due to the shrinkage of the heat-shrinkable material. Various combinations of fibers capable of forming hydrogen bonds, superabsorbents, and / or heat-shrinkable fibers or other materials can also be utilized. Thus, for example, the shrinkage of the second layer may be due to a combination of these mechanisms.

[0007] In one example embodiment, a method for forming a nonwoven material includes: forming a nonwoven web having multiple layers by foam molding; at least partially curing a first layer of the multiple layers while the nonwoven web is under tension; after at least partially curing the first layer, curing a second layer of the multiple layers while the nonwoven web is under tension; and relaxing the nonwoven web such that the second layer shrinks and the first layer deforms to create a plurality of protrusions on the outer surface of the first layer opposite to the second layer.

[0008] In another example embodiment, the nonwoven material comprises a foam-formed nonwoven web having a first layer and a second layer. The first layer contracts relative to the second layer, such that the first layer forms a plurality of protrusions on its outer surface opposite to the second layer.

[0009] In another example embodiment, a method for forming a nonwoven material includes: forming a nonwoven web having multiple layers by foam molding; heating a first layer of the multiple layers of the nonwoven web under tension, wherein the water content in the first layer decreases during the heating of the first layer; after heating the first layer and while the nonwoven web is under tension, heating a second layer of the multiple layers of the nonwoven web, wherein the water content in the second layer decreases during the heating of the second layer; and after heating the second layer, relaxing the nonwoven web such that the first layer deforms to have multiple protrusions on the outer surface of the first layer opposite to the second layer.

[0010] In another example embodiment, a method for forming a nonwoven material includes: forming a nonwoven web having multiple layers by foam molding, wherein a first layer and a second layer of the multiple layers are at least partially interconnected; and heating the nonwoven web such that the shrinkage of the second layer is less than that of the first layer, wherein the first layer deforms to create a plurality of protrusions at an outer surface of the first layer opposite to the second layer.

[0011] Other features and aspects of this disclosure are discussed in more detail below. Attached Figure Description

[0012] The disclosure, which is comprehensive and enables the implementation of this disclosure, is set forth in more detail in the remainder of the specification and with reference to the accompanying drawings, in which:

[0013] Figure 1 This is a schematic diagram of a system for producing nonwoven materials according to an example embodiment of the present disclosure;

[0014] Figure 2 yes Figure 1 A schematic diagram of the component feeding system of the example system;

[0015] Figure 3 A method for forming nonwoven materials according to an example implementation of this topic is illustrated.

[0016] Figure 4 Another example implementation of this topic illustrates a method for forming nonwoven materials.

[0017] Figure 5 This is a side front view of a nonwoven material according to an example implementation of this topic, wherein the nonwoven material is under tension.

[0018] Figure 6 yes Figure 5 Example side front view of a nonwoven material, where the nonwoven material is in a relaxed state.

[0019] Figure 7 This is a perspective view of a nonwoven material based on an example implementation of this topic.

[0020] Figure 8 yes Figure 7 Example of a partial side front view of a nonwoven material.

[0021] Figure 9 This is a perspective view of a nonwoven material based on an example implementation of this topic.

[0022] The repeated use of reference numerals in this specification and drawings is intended to indicate the same or similar features or elements of this disclosure. Detailed Implementation

[0023] Those skilled in the art will understand that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of this disclosure.

[0024] Each example is given illustratively and is not intended to be limiting. For example, a feature illustrated or described as part of one embodiment or drawing may be used in another embodiment or drawing to produce yet another embodiment. It is intended that this disclosure include such modifications and variations.

[0025] When describing elements of this disclosure or its preferred embodiments, the articles “a,” “an,” “the,” and “the” are intended to indicate the presence of one or more of that element. The words “comprising,” “including,” and “having” are intended to be inclusive, meaning that additional elements beyond those listed may be present. As used herein, the terms “first,” “second,” “third,” etc., do not specify a particular order but are used as a means of distinguishing different events when referring to the various features of this disclosure. Many modifications and variations may be made to this disclosure without departing from its spirit and scope. Therefore, the exemplary embodiments described herein should not be construed as limiting the scope of the invention.

[0026] As used herein, the term "foam-formed product" means a product formed from a suspension of a mixture comprising solids, liquids and dispersed bubbles.

[0027] As used herein, the term "foam forming process" refers to a process used to manufacture products involving suspensions of mixtures comprising solids, liquids, and dispersed bubbles.

[0028] As used herein, the term "foaming fluid" means any one or more known fluids that are compatible with other components in the foam forming process. Suitable foaming fluids include, but are not limited to, water.

[0029] As used in this article, the term "foam half-life" refers to the time elapsed until half of the initial foaming foam material has reverted to liquid water.

[0030] As used herein, the term "layer" refers to a structure that provides material or a region of substrate in the height direction of a substrate composed of similar components and structures.

[0031] As used in this article, the term "nonwoven web" refers to a web having a structure of individual fibers or threads arranged in layers but not in an identifiable manner (as in a knitted web).

[0032] As used herein, unless otherwise expressly indicated, when used in relation to the composition of materials, the terms “percentage,” “%,” “weight percentage” or “weight %” each refer to the amount of a component as a percentage of the total amount by weight, unless otherwise expressly indicated.

[0033] The term "personal care absorbent articles" as used herein refers to articles intended or adapted to be placed close to or near the wearer's body (i.e., adjacent to the body) to absorb and contain various liquid, solid, and semi-solid excretions from the body. Examples include, but are not limited to, diapers, diaper pants, training pants, youth pants, swim trunks, feminine hygiene products (including but not limited to menstrual pads or pants), incontinence products, medical clothing, surgical pads, and bandages, etc.

[0034] As used herein, the term “superabsorbent material” refers to a water-swellable, water-insoluble organic or inorganic material, including superabsorbent polymers and compositions thereof that, under most favorable conditions, are capable of absorbing at least about 10 times, at least about 15 times, or at least about 25 times their weight in an aqueous solution containing 0.9% by weight of sodium chloride.

[0035] As used herein, the term "longitudinal" refers to the direction of travel of the shaped surface on which fibers are deposited during the formation of the nonwoven web.

[0036] As used herein, the term "lateral" refers to a direction perpendicular to both the longitudinal and vertical directions (e.g., perpendicular to both the longitudinal and lateral directions).

[0037] As used herein, the term "pulp" refers to fibers derived from natural sources such as woody and non-woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, Spanish grass, milkweed, straw, jute, hemp, and bagasse. Pulp fibers can include hardwood fibers, softwood fibers, and mixtures thereof. As used herein, the term "average fiber length" refers to the average length of fibers, fiber bundles, and / or fibrous materials determined by measurement using microscopy. A sample of at least 20 randomly selected fibers is separated from a liquid suspension of the fibers. The fibers are placed on a microscope slide prepared to suspend the fibers in water. A staining dye is added to the suspended fibers to stain the cellulose-containing fibers so that they can be distinguished or separated from synthetic fibers. The slide is placed under a Fisher Stereomaster II microscope—S19642 / S19643 series. Twenty fibers in the sample were measured using a 0-20 mil scale at 20X linear magnification, and the average length, minimum and maximum length, and deviation or coefficient of variation were calculated. In some cases, the average fiber length was calculated as a weighted average length of the fibers (e.g., fibers, fiber bundles, fibrous materials), determined using a Kajaani Fiber Analyzer model FS-200, for example, from Kajaani Oy Electronics, Kajaani, Finland. The sample was treated with an impregnation solution according to standard testing procedures to ensure the absence of fiber bundles or debris. Each sample was decomposed in hot water and diluted to a suspension of approximately 0.001%. When testing using standard Kajaani fiber analysis testing procedures, approximately 50 ml to 100 ml of test sample was drawn from each diluted suspension. The weighted average fiber length can be an arithmetic mean, a length-weighted mean, or a weight-weighted mean, and can be expressed by the following equation:

[0038]

[0039] in

[0040] k = maximum fiber length

[0041] x i =Fiber length

[0042] n i =Number of fibers of length xi

[0043] n = the total number of fibers measured.

[0044] A characteristic of the average fiber length data measured by the Kajaani fiber analyzer is that it does not distinguish between different types of fibers. Therefore, the average length represents the average length based on all different types (if any) of the fibers in the sample.

[0045] As used herein, the term "short fiber" refers to discontinuous fibers made from synthetic polymers or regenerated cellulose such as polypropylene, polyester, post-consumer recycled (PCR) fibers, nylon, viscose, rayon, etc., and those that are non-hydrophilic can be treated to become hydrophilic. Short fibers can be cut fibers, etc. Short fibers can have cross-sections that are round, bicomponent, multicomponent, molded, hollow, etc.

[0046] Generally, this disclosure relates to methods and systems for producing nonwoven materials, and to nonwoven materials themselves. Furthermore, this disclosure relates to methods and systems for producing nonwoven materials via foam molding. The nonwoven material can be a multilayer material, such as a bilayer nonwoven material. According to an example aspect of this disclosure, the nonwoven material can be formed on the outer surface of one layer of the nonwoven material to have a three-dimensional morphology. Three-dimensional morphology can provide numerous advantages and benefits. The nonwoven materials of this disclosure can be used in a variety of different end-use applications. Three-dimensional morphology can provide significantly improved functionality tailored to specific applications.

[0047] In one example, the three-dimensional topography can form bumps that advantageously increase the void volume of the collection layer in absorbent articles, wiping products, etc., and increase compressibility. The three-dimensional topography can also form fluid control channels for rapid suction and distribution of fluid, which can provide advantages when incorporated into absorbent articles, wiping products, etc.

[0048] In addition to the above, three-dimensional morphology can significantly improve the breathability of materials. Nonwoven materials manufactured according to exemplary aspects of this disclosure, when included in absorbent articles, can create an optimal microclimate by allowing better air exchange at the interface between the three-dimensional morphology and the wearer's skin. When incorporated into diapers, adult incontinence products, etc., the three-dimensional morphology can be configured to collect and remove bodily waste and other fluids to protect the skin and provide clothing that promotes better health. Because the contact area between the three-dimensional morphology and the wearer's skin is reduced, the three-dimensional morphology can also help to keep the skin drier.

[0049] Nonwoven materials manufactured according to this disclosure can also provide enhanced comfort. For example, a three-dimensional shape can provide the user with a "padded" feel. The three-dimensional shape can also be configured for visual appeal or as a signal to highlight some other benefits of the product to the user.

[0050] Nonwoven materials manufactured according to exemplary aspects of this disclosure can be formed from fibers and optionally other solid materials via a foam forming process. Nonwoven materials can be multilayer materials, such as bilayer materials.

[0051] refer to Figure 1 For illustrative purposes only, one embodiment of a method for forming a nonwoven material or substrate according to an exemplary aspect of this disclosure is shown. Figure 1 The illustrated processes and systems can be examples of foam molding processes. For example... Figure 1 As shown, apparatus 10 is configured to form substrate 12. Furthermore, apparatus 10 may be configured as part of a foam forming process to manufacture substrate 12 as a foam-formed product. Apparatus 10 may include a first tank 14 configured to maintain a first fluid supply 16. In some example embodiments, the first fluid supply 16 may be foam. The first fluid supply 16 may include fluid supplied by a supply device of fluid 18. In some example embodiments, the first fluid supply 16 may include multiple fibers supplied by a supply of fiber 20; however, in other example embodiments, the first fluid supply 16 may contain no or substantially no multiple fibers. The first fluid supply 16 may also include a surfactant supplied by a surfactant supply 22. In some example embodiments, the first tank 14 may include a mixer 24, which will be discussed in more detail below. The mixer 24 is operable to mix (e.g., agitate) the first fluid supply 16 to mix the fluid, fibers (if present), and surfactant with air or some other gas to form foam. Mixer 24 can also mix foam with fibers (if present) to produce a foam suspension of fibers, wherein the foam holds and separates the fibers to promote fiber distribution within the foam (e.g., as an artificial byproduct of the mixing process in the first tank 14). Uniform fiber distribution can promote desired substrate properties, including, for example, visual appearance of strength and quality.

[0052] In some example embodiments, device 10 may further include a second tank 26 configured to maintain a second fluid supply 28. In some example embodiments, the second fluid supply 28 may be foam. The second fluid supply 28 may include fluid supplied by a supply device of fluid 30 and surfactant supplied by surfactant supply 32. In some example embodiments, the second fluid supply 28 may include multiple fibers in addition to or as an alternative to the fibers present in the first fluid supply 16. In some example embodiments, the second tank 26 may include a mixer 34. The mixer 34 may be operable to mix the second fluid supply 28 to mix the fluid and surfactant with air or some other gas to form foam.

[0053] For either or both of the first tank 14 and the second tank 26, the first fluid supply 16 or the second fluid supply 28 may be operated to form foam. In some example embodiments, the foaming fluid and other components may be acted upon to form a porous foam with an air content greater than about fifty percent (50%) by volume and ideally greater than about sixty percent (60%) by volume. In some example aspects, highly expanded foam is formed with an air content between about sixty percent (60%) and about ninety-five percent (95%) by volume, and in other example aspects, the air content between about sixty percent (65%) and about eighty-five percent (85%) by volume. In some example embodiments, the foam may be acted upon to introduce foam such that the expansion ratio (the volume of air in the expanded stable foam to the other components) is greater than 1:1, and in some embodiments, the air-to-other-component ratio may be between about 1.1:1 and about 20:1, or between about 1.2:1 and about 15:1, or between about 1.5:1 and about 10:1, or even between about 2:1 and about 5:1.

[0054] Foam can be generated by one or more mechanisms and methods known in the art. Examples of suitable methods include, but are not limited to, vigorous mechanical agitation by mixers 24, 34, injection of compressed air, etc. Mixing components by using a high-shear, high-speed mixer is particularly suitable for forming the desired highly porous foam. Various high-shear mixers are known in the art and are considered applicable to exemplary aspects of this disclosure. High-shear mixers typically use a tank to hold the foam precursor and / or one or more conduits through which the foam precursor is guided. High-shear mixers may use a series of screens and / or rotors to process the precursor and result in vigorous mixing of the components and air. In a particular example embodiment, a first tank 14 and / or a second tank 26 are provided, having one or more rotors or impellers and an associated stator. The rotors or impellers rotate at high speed to induce flow and shear. For example, air may be introduced into the tank at various locations or simply drawn in by the action of mixers 24, 34. While specific mixer designs may influence the speeds required to achieve the desired mixing and shearing, in some example embodiments, suitable rotor speeds may be greater than about 500 rpm, and for example, between about 1,000 rpm and about 6,000 rpm, or between about 2,000 rpm and about 4,000 rpm. In some example embodiments, mixers 24, 34 may be operated with the foam until the eddies in the foam disappear or a sufficient volume increase is achieved, relative to a rotor-based high-shear mixer.

[0055] Additionally, it should be noted that for the first tank 14 and / or the second tank 26, the foaming process can be completed in a single foam-generating step or in consecutive foam-generating steps. For example, in one exemplary embodiment, all components of the first fluid supply 16 in the first tank 14 (e.g., the supply of fluid 18, fiber 20, and surfactant 22) can be mixed together to form a slurry from which foam is formed. Alternatively, one or more individual components can be added to the foaming fluid to form an initial mixture (e.g., a dispersion or foam), and then the remaining components can be added to the initially foamed slurry, after which all components come into play to form the final foam. In this regard, fluid 18 and surfactant 22 can begin mixing and functioning to form the initial foam before any solids are added. If desired, fibers can then be added to the water / surfactant foam, and these fibers subsequently function further to form the final foam. As another example alternative, fluid 18 and fiber 20 (such as high-density cellulose pulp) can be vigorously mixed at a high consistency to form an initial dispersion, after which foaming surfactants, additional water, and other components (such as synthetic fibers) are added to form a second mixture, which is then mixed and acts to form foam.

[0056] The foam density forming the first fluid supply 16 in the first tank 14 and / or the foam forming the second fluid supply 28 in the second tank 26 can vary depending on the specific application and various factors, such as the fiber raw material used. In some example embodiments, the foam density can be greater than about 100 g / L, such as greater than about 250 g / L, such as greater than about 300 g / L. The foam density can typically be less than about 800 g / L, such as less than about 500 g / L, such as less than about 400 g / L, such as less than about 350 g / L. In some example implementations, lower density foams may be used, typically less than about 350 g / L, such as less than about 340 g / L, such as less than about 330 g / L.

[0057] In some example embodiments, device 10 may further include a first pump 36 and a second pump 38. The first pump 36 may be in fluid communication with a first fluid supply 16 and may be configured to pump the first fluid supply 16 to transfer the first fluid supply 16. The second pump 38 may be in fluid communication with a second fluid supply 28 and may be configured to pump the second fluid supply 28 to transfer the second fluid supply 28. In some example embodiments, the first pump 36 and / or the second pump 38 may be a screw pump or a centrifugal pump; however, it is contemplated that other suitable types of pumps may be used. Additionally, as discussed further below, in some example embodiments, the device may be provided with a single pump that can pump a single fluid supply to both the first fluid supply 16 and the second fluid supply 28.

[0058] like Figure 1 and Figure 2 As depicted, the device 10 may optionally include a component feeding system 40. For example, the component feeding system 40 may be configured to feed particulate material (such as superabsorbent particles) into the fiber formulation. However, when the matrix is ​​formed solely from fibers, the component feeding system 40 may not be necessary, including the use of a second fluid supply 28. When present, the component feeding system 40 may include a component supply area 42 for receiving the supply of component 44, such as... Figure 2 A partial cross-section of the illustrated component supply region 42 is shown. The component feeding system 40 may also include an outlet conduit 46. The cross-sectional shape of the outlet conduit 46 may be circular or may be constructed in a rectangular form to form a slot. The component feeding system 40 may also include a hopper 48. The hopper 48 may be connected to the component supply region 42 and may be configured to refill the component supply region 42 with the supply of component 44.

[0059] In some example embodiments, the component feeding system 40 may include a solid volumetric pump. Examples of solid volumetric pumps that may be used herein include systems utilizing screws / augers, belts, vibratory trays, rotary tables, or other known systems for handling and discharging the supply of component 44. Other types of feeders may be used in the component feeding system 40, such as batching feeders, such as those manufactured by Christy Machine & Conveyor, Fremont, Ohio. In some example embodiments, the component feeding system 40 may also be configured as a conveying system.

[0060] The component feeding system 40 may also include a fluid control system 50. The fluid control system 50 may be configured to control gas entrainment into a fluid supply in which the supply of component 44 is placed. In some example embodiments, the fluid control system 50 may include a housing 52. The housing 52 may form a pressurized, sealed volume around the component feeding system 40. In other example embodiments, the fluid control system 50 may be formed as an integral part of the component feeding system 40 itself, making a separate housing 52 around the component feeding system 40 potentially unnecessary. Figure 1 and Figure 2 As shown, in some example embodiments, the fluid control system 50 may also include a vent 54.

[0061] The supply of component 44 can be in the form of particles and / or fibers. In one example embodiment described herein, the supply of component 44 can be in the form of superabsorbent material (SAM) in particulate form. In some example embodiments, SAM can be in the form of fibers. Of course, other types of components can also be considered for use in the apparatus 10 and method described herein, as further described below. The component feed system 40 described herein can be particularly advantageous for the supply of component 44 best suited for maintenance in a dry environment, with minimal exposure to the fluids or foams used in the apparatus 10 and method described herein.

[0062] In some example embodiments, the device 10 and method described herein may include a first mixing connector 56 and a second mixing connector 58. In a preferred example embodiment, the first mixing connector 56 may be an injector. The first mixing connector 56 may be in fluid communication with the outlet conduit 46 of the component feed system 40 and with the second fluid supply 28. The first mixing connector 56 may be configured as a coaxial injector. The first mixing connector 56 may mix the supply of component 44 from the component feed system 40 with the second fluid supply 28.

[0063] Refer again Figure 1In some example embodiments, device 10 may include a second mixing joint 58. The second mixing joint 58 may be configured to mix a second fluid supply 28 (including components supplied from component 44) with a first fluid supply 16. The second fluid supply 28 may be transferred to the second mixing joint 58 as it exits the outlet 64 of the first mixing joint 56. The first fluid supply 16 may be delivered to the second mixing joint 58 by a first pump 36. The second mixing joint 58 may mix the first fluid supply 16 and any components of the first fluid supply 16 (e.g., fluid 18, fiber 20, surfactant 22) with the second fluid supply 28 and any components of the second fluid supply 28 (e.g., fluid 30, surfactant 32) and components supplied from component 44 to provide a resulting slurry 76. The resulting slurry 76 may be transferred from the second mixing joint 58 through the outlet 78 of the second mixing joint 58 to a headbox 80.

[0064] A headbox 80 may be provided to transfer the resulting slurry 76 to form the substrate 12. The headbox 80 may have a longitudinal direction 81 and a transverse direction 83. The longitudinal direction 81 may be the direction in which the resulting slurry 76 is transferred through the headbox 80. The wet slurry 76 may be deposited from the headbox 80 onto a shaped surface 94 manufactured according to an exemplary aspect of this disclosure.

[0065] exist Figure 1 In the illustrated example embodiment, the forming surface 94 is shown in a horizontal position. In alternative example embodiments, the forming surface 94 may be positioned or oriented at an angle relative to the headbox 80 such that the slurry 76 moves upward once deposited onto the forming surface 94. For example, the forming surface 94 may be positioned relative to the horizontal plane at an angle greater than about five degrees (5°), such as greater than about ten degrees (10°), such as greater than about fifteen degrees (15°), and generally less than about fifty degrees (50°), such as less than about forty degrees (40°), such as less than about thirty degrees (30°), such as less than about twenty degrees (20°). The headbox 80 may be designed to produce a single-layer substrate or may be used to produce a multi-layer substrate. The substrate 12 may be made according to exemplary aspects of this disclosure, for example, having two (2) layers, three (3) layers, four (4) layers, five (5) layers, etc. Each layer may have a different fiber formulation if desired.

[0066] Once the slurry 76 is deposited onto the forming surface 94, fluid can be removed from the suspension to form a nonwoven substrate. In this regard, the forming surface 94 can be a porous plate and can be at least partially made of woven tape or screen. The system may also include a dewatering system 96 configured to remove liquid from the slurry 76 through the forming surface 94. For example, the dewatering system 96 can provide a vacuum to the slurry 76 to extract fluid from the slurry, thereby forming a consolidated substrate 12.

[0067] like Figure 1 As shown, the process may also include a drying system 98. The drying system 98 may be configured to dry the newly formed nonwoven substrate 12. Generally, any suitable dryer can be incorporated into the drying system 98. For example, the drying system 98 may be a ventilated dryer, one or more heated rollers, an oven, etc. The process may also include a winding system 99, which may be configured to wind the substrate 12 into a roll after drying.

[0068] As described above, the nonwoven substrate manufactured according to the exemplary aspects of this disclosure can be formed using a foam forming process. The foam forming process offers various advantages. For example, it allows for easier handling of longer fibers, requires less water to form the web, and may require less energy to dry the web.

[0069] When forming a nonwoven substrate according to a foam forming process, the wet slurry 76 can be a fiber foam suspension, alone or in combination with other solid materials. In some example embodiments, the foaming fluid may comprise about 85% (85%) to about 99% to 99% (99.99%) of the foam (by weight). In some example embodiments, the foaming fluid used to produce the foam may comprise at least about 85% (85%) of the foam (by weight). In some example embodiments, the foaming fluid may comprise about 90% (90%) to about 99% to 99% (99.9%) of the foam (by weight). In some other example embodiments, the foaming fluid may comprise about 93% (93%) to 99.5% (99.5%) of the foam (by weight), or even about 95% (95%) to about 99% (99%). In a preferred example embodiment, the foaming fluid may be water; however, other processes are conceivable that other foaming fluids may be utilized.

[0070] The foam forming process described herein can utilize one or more foaming agents (such as surfactants) to form foam. The fibers and surfactants, together with the foaming liquid and any additional components, can form a stable dispersion that can maintain a substantially high porosity for a longer period than a drying process. In this regard, surfactants can be selected to provide foams with a foam half-life of at least two minutes (2 minutes), more preferably at least five minutes (5 minutes), and most preferably at least ten minutes (10 minutes). The foam half-life can be a function of surfactant type, surfactant concentration, foam component / solids level, and mixing capacity / air content in the foam. The foaming surfactant used in the foam can be selected from one or more foaming surfactants known in the art that can provide the desired level of foam stability. In this regard, the foaming surfactant can be selected from anionic, cationic, nonionic, and amphoteric surfactants, provided that the foaming surfactant, alone or in combination with other components, provides the necessary foam stability or foam half-life. It should be understood that more than one surfactant can be used, including surfactants of different types (provided the surfactants are compatible) and more than one surfactant of the same type. For example, due to the compatibility between surfactants, combinations of cationic and nonionic surfactants or combinations of anionic and nonionic surfactants can be used in some example embodiments. However, in some example embodiments, combinations of cationic and anionic surfactants may not be satisfactory due to incompatibility between the surfactants.

[0071] Anionic surfactants considered applicable to the exemplary aspects of this disclosure include, but are not limited to, anionic sulfate surfactants, alkyl ether sulfonates, alkyl aryl sulfonates, or mixtures or combinations thereof. Examples of alkyl aryl sulfonates include, but are not limited to, alkylbenzene sulfonic acids and their salts, dialkylbenzene disulfonic acids and their salts, dialkylbenzene sulfonic acids and their salts, alkylphenol sulfonic acids / condensed alkylphenol sulfonic acids and their salts, or mixtures or combinations thereof. Examples of other anionic surfactants considered applicable to exemplary aspects of this disclosure include alkali metal sulforicinate; sulfonated glycerol esters of fatty acids such as sulfonated monoglycerides of coconut oil; salts of sulfonated monovalent alcohol esters such as sodium oleylisethianate; metal soaps of fatty acids; amides of aminosulfonic acids, such as sodium salts of oleylmethyl taurine; sulfonated products of fatty acid nitriles, such as palmitonitrile sulfonate; alkali metal alkyl sulfates, such as sodium lauryl sulfate, ammonium lauryl sulfate, or triethanolamine lauryl sulfate; ether sulfates having an alkyl group having eight (8) or more carbon atoms, such as sodium lauryl ether sulfate, ammonium lauryl ether sulfate, sodium alkyl aryl ether sulfate, and ammonium alkyl aryl ether sulfate; sulfates of polyoxyethylene alkyl ethers; and sodium, potassium, and amine salts of alkyl naphthalene sulfonic acids. Certain phosphate surfactants, including phosphate esters such as sodium lauryl phosphate ester, or those available under the trade name TRITON from Dow Chemical Company, are also considered suitable. A particularly desirable anionic surfactant is sodium dodecyl sulfate (SDS).

[0072] Cationic surfactants are also considered suitable for use in conjunction with exemplary aspects of this disclosure in some exemplary embodiments for manufacturing substrates. In some exemplary embodiments, such as those including superabsorbent materials, the use of cationic surfactants may be less preferred due to potential interactions between the cationic surfactant and the superabsorbent material (which may be anionic). Foaming cationic surfactants include, but are not limited to, monocarbonyl ammonium salts, dicarbonyl ammonium salts, tricarbonyl ammonium salts, monocarbonyl phosphonium salts, dicarbonyl phosphonium salts, tricarbonyl phosphonium salts, carbonyl carboxyl salts, quaternary ammonium salts, imidazolines, ethoxylated amines, quaternary phospholipids, etc. Further examples of cationic surfactants include various fatty acid amines and amides and their derivatives, as well as salts of fatty acid amines and amides. Examples of aliphatic fatty acid amines include dodecylamine acetate, octadecylamine acetate, and acetates of amines of tallow fatty acids; homologues of aromatic amines containing fatty acids, such as dodecylaniline; fatty amides derived from aliphatic diamines, such as undecylimidazoline; fatty amides derived from aliphatic diamines, such as undecylimidazoline; fatty amides derived from disubstituted amines, such as oleylaminodiethylamine; derivatives of ethylenediamine; quaternary ammonium compounds and their salts, such as trimethylammonium tallow chloride, dioctadecyldimethylammonium chloride, didodecyldimethylammonium chloride, dihexylammonium chloride, alkyltrimethylammonium hydroxide, dioctadecyldimethylammonium hydroxide, trimethylammonium tallow chloride, trimethylammonium hydroxide, methylpolyoxyethylene cocoyl ammonium chloride, and dipalmitylhydroxyethylmethylammonium sulfate; amide derivatives of amino alcohols, such as β-hydroxyethylstearamide; and amine salts of long-chain fatty acids. Further examples of cationic surfactants that are considered applicable to the exemplary aspects of this disclosure include benzalkonium chloride, benzyl chloride, cetrimonium bromide, distearate dimethyl ammonium chloride, tetramethyl ammonium hydroxide, etc.

[0073] Nonionic surfactants considered applicable to the exemplary aspects of this disclosure include, but are not limited to, condensates of ethylene oxide with long-chain fatty alcohols or fatty acids, condensates of ethylene oxide with amines or amides, condensates of ethylene oxide and propylene oxide, fatty acid alkanolamides, and fatty amine oxides. Various additional examples of nonionic surfactants include alkyl polysaccharides, stearyl alcohol, sorbitan monostearate, octyl glucoside, octaethylene glycol monododecyl ether, lauryl glucoside, cetyl alcohol, cocoamide MEA, glyceryl monolaurate, polyoxyethylene alkyl ethers (such as polyethylene glycol long-chain (12-14C) alkyl ethers), polyoxyethylene sorbitan ethers, polyoxyethylene alkoxylated esters, polyoxyethylene alkylphenol ethers, ethylene glycol-propylene glycol copolymers, polyvinyl alcohol, alkyl polysaccharides, polyethylene glycol sorbitan monooleate, octylphenol ethylene oxide, etc.

[0074] Foaming surfactants can be used in varying amounts as needed to achieve desired foam stability and air content in the foam. In some example embodiments, the foaming surfactant may comprise about five parts per thousand (0.005%) to about five percent (5%) of the foam (by weight). In some example embodiments, the foaming surfactant may comprise about five percent (0.05%) to about three percent (3%) of the foam (by weight), or even about five percent (0.05%) to about two percent (2%).

[0075] The fibers and / or other solid materials used to form the nonwoven substrate according to exemplary aspects of this disclosure may vary depending on the specific application and desired results. For example, the nonwoven substrate may be formed from pulp fibers, other natural fibers such as cotton fibers, regenerated cellulose fibers, synthetic polymer fibers, binder fibers, superabsorbent particles, and mixtures thereof. For example, when producing tissue products, the nonwoven substrate may contain more than about ninety percent (90%) of pulp fibers by weight. When producing wiping products, the nonwoven substrate may be made from pulp fibers alone or in combination with polymeric synthetic fibers such as polyester fibers. When producing nonwoven substrates for use in absorbent articles, the nonwoven substrate may include superabsorbent particles in combination with at least one type of fiber. At least one type of fiber may include pulp fibers, pulp fibers in combination with polymeric synthetic fibers, pulp fibers in combination with binder fibers, pulp fibers in combination with synthetic polymer fibers and binder fibers, pulp fibers in combination with regenerated cellulose fibers, or any other suitable mixture.

[0076] A wide variety of cellulose fibers are considered applicable herein. In some exemplary embodiments, the fibers used may be conventional papermaking fibers, such as wood pulp fibers formed through various pulping processes, such as kraft pulp, sulfite pulp, bleached chemithermomechanical pulp (BCTMP), chemithermomechanical pulp (CTMP), pressure / pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemimechanical pulp (TMCP), etc. By way of example only, fibers and methods for preparing wood pulp fibers are disclosed in US4793898, US4594130, US3585104, US5595628, US5522967, etc., issued to Laamanen et al., Chang et al., Kleinhart, Gordon et al., and Shet. Furthermore, the fibers may be any wood pulp with a high average fiber length, wood pulp with a low average fiber length, or mixtures thereof. Examples of suitable high average length pulp fibers include softwood fibers, such as, but not limited to, northern softwood, southern softwood, mahogany, red cedar, hemlock, pine (e.g., southern pine), spruce (e.g., black spruce), etc. Examples of suitable low average length pulp fibers include hardwood fibers, such as, but not limited to, eucalyptus, maple, birch, poplar, etc.

[0077] Furthermore, if desired, secondary fibers derived from recycled materials, such as pulp from sources like newsprint, recycled paperboard, and office waste paper, can be used. In a particularly preferred example embodiment, refined fibers are utilized in the tissue paper web, thereby reducing the total amount of virgin and / or high-average-fiber-length wood fibers (such as cork fibers).

[0078] Regardless of the source of the wood pulp fibers, the wood pulp fibers may preferably have an average fiber length greater than about two-tenths of a millimeter (0.2 mm) and less than about three millimeters (3 mm), such as from about thirty-five percent of a millimeter (0.35 mm) to about two and a half millimeters (2.5 mm), or between about half a millimeter (0.5 mm) and about two millimeters (2 mm), or even between about seven-tenths of a millimeter (0.7 mm) and about one and a half millimeters (1.5 mm).

[0079] Additionally, other cellulose fibers that can be used in the exemplary aspects of this disclosure include non-wood fibers. As used herein, the term "non-wood fiber" generally refers to cellulose fibers derived from the stems of non-woody monocotyledonous or dicotyledonous plants. Non-limiting examples of dicotyledonous plants that can be used to produce non-wood fibers include kenaf, jute, flax, ramie, and hemp. Non-limiting examples of monocotyledonous plants that can be used to produce non-wood fibers include cereal straw (wheat, rye, barley, oats, etc.), stalks (corn, cotton, sorghum, Heitzperrhoa, etc.), vines (bamboo, sisal, bagasse, etc.), and grasses (Miscanthus sinensis, Spanish grass, lemon, saba, switchgrass, etc.). In some other cases, non-wood fibers may be derived from aquatic plants such as water hyacinth, microalgae such as spirulina, and macroalgae such as red or brown algae.

[0080] Additionally, other cellulose fibers used to manufacture the substrates described herein may include synthetic cellulose fiber types formed by spinning, including rayon in all its types, and other fibers derived from viscose fibers or chemically modified cellulose, such as, for example, those available under the trade names LYOCELL and TENCEL.

[0081] In some example embodiments, non-wood and synthetic cellulose fibers may have a fiber length greater than about two-tenths of a millimeter (0.2 mm), including, for example, having an average fiber size between about half a millimeter (0.5 mm) and about thirty millimeters (30 mm), or between about seventy-five percent of a millimeter (0.75 mm) and about eight millimeters (8 mm), or even between about one millimeter (1 mm) and about five millimeters (5 mm).

[0082] Additional fibers that may be used in the exemplary aspects of this disclosure include synthetic polymer fibers. By way of non-limiting example, such fibers may include polyolefins, polyesters (PET), polyamides, polylactic acid, or other fiber-forming polymers. Polyolefin fibers such as polyethylene (PE) and polypropylene (PP) are particularly suitable for the exemplary aspects of this disclosure.

[0083] The synthetic polymer fibers may have a fiber length greater than about two-tenths of a millimeter (0.2 mm), including, for example, having an average fiber size between about half a millimeter (0.5 mm) and about fifty millimeters (50 mm), or between about seventy-five millimeters (0.75) and about ten millimeters (10 mm), or between about one millimeter (1 mm) and about eight millimeters (8 mm). In one example embodiment, the synthetic polymer fibers may be short fibers with a fiber length greater than about two millimeters (2 mm), such as greater than about three millimeters (3 mm), such as greater than about four millimeters (4 mm), and generally less than about eight millimeters (8 mm), such as less than about seven millimeters (7 mm), such as less than about six millimeters (6 mm), such as less than about five millimeters (5 mm), such as less than about four millimeters (4 mm). The size of the polymer fibers may be less than about five (5) deniers, such as less than about three (3) deniers, such as less than about two (2) deniers, and greater than about half (0.5) deniers, such as greater than about one (1) denier.

[0084] In one example embodiment, the fiber formulation may include an adhesive material that reinforces the substrate once activated. For example, the fiber formulation may include adhesive fibers that bond to adjacent fibers upon heating, such as during substrate drying.

[0085] The adhesive materials that can be used in the exemplary aspects of this disclosure may include, but are not limited to, thermoplastic adhesive fibers, such as PET / PE two-component adhesive fibers, and water-compatible adhesives, such as latex. In some exemplary embodiments, the adhesive materials used herein may be in powder form, such as thermoplastic PE powder. Importantly, the adhesive may include an adhesive that is insoluble in water on a dry substrate. In some exemplary embodiments, the latex used in the exemplary aspects of this disclosure may be cationic or anionic to facilitate application and adhesion to cellulose fibers that may be used herein. For example, latexes considered suitable include, but are not limited to, anionic styrene-butadiene copolymers, polyvinyl acetate homopolymers, vinyl acetate-ethylene copolymers, vinyl acetate-acrylic acid copolymers, ethylene-vinyl chloride copolymers, ethylene-vinyl chloride-vinyl acetate terpolymers, acrylic polyvinyl chloride polymers, acrylic polymers, nitrile polymers, and other suitable anionic latex polymers known in the art. Examples of such latexes are described in US4785030, granted to Hager; US6462159, granted to Hamada; US6752905, granted to Chuang et al., etc. Examples of suitable thermoplastic binder fibers include, but are not limited to, single-component and multi-component fibers of at least one thermoplastic polymer such as polyethylene with a relatively low melting point. In some example embodiments, short polyethylene / polypropylene sheath / core fibers may be used. The binder fibers may have lengths consistent with those described above regarding synthetic polymer fibers.

[0086] The binder in liquid form (such as a latex emulsion) may comprise from about 0% (0%) to about 10% (10%) of the substrate weight. When used, binder fibers may be added proportionally to the other components to achieve the desired fiber ratio and structure. For example, in some exemplary embodiments, the binder fibers may comprise from about 0% (0%) to about 50% (50%) of the total fiber weight, more preferably, in some exemplary embodiments, from about 5% (5%) to about 40% (40%) of the total fiber weight.

[0087] An additional additive that may be added during the formation of the substrate 12 as described herein may be a superabsorbent material (SAM). SAMs are typically provided in particulate form and, in some examples, may comprise polymers of unsaturated carboxylic acids or derivatives thereof. These polymers are typically made insoluble in water but water-swellable by crosslinking them with a difunctional or polyfunctional internal crosslinking agent. These internally crosslinked polymers are at least partially neutralized and typically contain side-attached anionic carboxyl groups on the polymer backbone, which enable the polymer to absorb aqueous fluids, such as bodily fluids. Typically, the SAM particles are post-treated to crosslink the side-attached anionic carboxyl groups on the particle surface. SAMs are manufactured using known polymerization techniques, ideally via gel polymerization in an aqueous solution. The product of this polymerization process is an aqueous polymer gel, i.e., a SAM hydrogel whose size is reduced to small particles by mechanical force, and then dried using drying procedures and equipment known in the art. After the drying process, the resulting SAM particles are pulverized to the desired particle size. Examples of superabsorbent materials include, but are not limited to, those described in US7396584, Dodge et al., US7935860, Azad et al., US2005 / 5245393, Bergam et al., WO2008 / 027488, Chang et al. Additionally, to aid processing, SAM can be treated to make the material temporarily nonabsorbent during foam formation and the formation of highly expanded foam. For example, in one aspect, SAM can be treated with a water-soluble protective coating having a selected dissolution rate so that the SAM is substantially not exposed to the aqueous carrier until the highly expanded foam has formed and the drying operation begins. Alternatively, to prevent or limit premature expansion during processing, SAM can be introduced into the process at a low temperature.

[0088] Superabsorbent materials can typically be incorporated into a nonwoven substrate in amounts from about one percent (1%) to about ninety-five percent (95%) by weight, including all increments of one percent (1%) by weight therein. For example, superabsorbent materials can be present in the substrate in amounts greater than about ten percent (10%) by weight, such as greater than about twenty percent (20%) by weight, such as greater than about thirty percent (30%) by weight, such as greater than about forty percent (40%) by weight, such as less than about fifty percent (50%) by weight, and typically in amounts less than about sixty-five percent (65%) by weight, such as less than about fifty-five percent (55%) by weight, such as less than about forty-five percent (45%) by weight.

[0089] Other additives that can be incorporated into nonwoven substrates include wet strength additives, permanent wet strength additives, temporary wet strength additives, and dry strength additives.

[0090] Other additional components that may be added to the substrate may, as needed, include one or more pigments, opacifiers, antimicrobial agents, pH adjusters, skin-beneficial agents, odor absorbers, fragrances, thermally expandable microspheres, foam particles (such as pulverized foam particles), etc., to impart or improve one or more physical or aesthetic properties. In some example embodiments, the substrate may include skin-beneficial agents such as antioxidants, astringents, conditioning agents, emollients, deodorants, topical analgesics, film-forming agents, humectants, water-soluble growth promoters, pH adjusters, surface modifiers, skin care agents, etc. When used, miscellaneous components are expected to comprise less than about two percent (2%) (by weight) of the substrate.

[0091] Figure 3 A method 200 for forming a nonwoven material according to an exemplary embodiment of this subject matter is illustrated. Method 200 can be carried out in apparatus 10 as part of a foam forming process for a nonwoven material (such as substrate 12). Therefore, method 200 is described in more detail below in the context of apparatus 10. However, it should be understood that in alternative exemplary embodiments, method 200 can be performed or implemented in any suitable foam forming system. Using method 200, a three-dimensional morphology of the nonwoven material (such as substrate 12) can be formed, for example, on the outer surface of one layer of the substrate 12.

[0092] At 210, the substrate 12 may be formed with multiple layers. For example, at 210, the headbox 80 may deposit various slurries 76 onto the forming surface 94 to form a substrate 12 having multiple layers (such as two (2), three (3), four (4), five (5) or more layers). At 210, the foam forming substrate 12 may include the deposition of a first foam and a second foam onto the forming surface 94 using the headbox 80.

[0093] In some example embodiments, each layer in substrate 12 may have a different fiber composition. For example, such as Figure 5 and Figure 6As shown, substrate 12 may include a first layer 410 and a second layer 420. The first layer 410 may be configured as a collection layer, and the second layer 420 may be configured as an absorbent layer. Thus, the first layer 410 may be configured to collect and remove bodily waste and other fluids, for example, toward or to the second layer 420, which is configured to collect waste and other fluids therein. In some example embodiments, the first layer 410 and the second layer 420 may have different fiber compositions. For example, the second layer 420 may include, for example, a highly absorbent material in an amount from about one percent (1%) to about ninety-five percent (95%) by weight. Conversely, the first layer 410 may be substantially free of superabsorbent material. As another example, the second layer 420 may be substantially free of PET fibers, while the first layer 410 includes PET fibers. Therefore, for example, the first foam may include water and a plurality of first binder fibers, such as PET / PE fibers (e.g., a PET core and a PE sheath), and the second foam may include water and a plurality of second binder fibers, such as PET / PE fibers (e.g., fibers with a different fiber diameter and / or length than the PET / PE fibers of the first binder fibers). The difference in fiber composition between the first layer 410 and the second layer 420 may facilitate differential shrinkage between the first layer 410 and the second layer 420, as discussed in more detail below.

[0094] In some example implementations, the basis weight 410 of the first layer may be selected to help form a three-dimensional topography on the first layer 410. For example, the basis weight of the first layer 410 may typically be greater than about 40 gsm, such as greater than about 50 gsm, such as greater than about 60 gsm, such as greater than about 70 gsm, such as greater than about 80 gsm, such as greater than about 90 gsm, such as greater than about 100 gsm. The basis weight of the first layer 410 may typically be less than about 200 gsm, such as less than about 150 gsm, such as less than about 100 gsm.

[0095] like Figure 5 and Figure 6As shown, the first layer 410 and the second layer 420 may also have different dimensional characteristics. For example, each of the first layer 410 and the second layer 420 may have a corresponding thickness, for example, perpendicular to both the longitudinal direction 81 and the transverse direction 83. Furthermore, the first layer 410 may have a thickness T1, and the second layer 420 may have a thickness T2. The thickness T2 of the second layer 420 may be different from the thickness T1 of the first layer 410. For example, in some example embodiments, the thickness T2 of the second layer 420 may be greater than the thickness T1 of the first layer 410. For example, the thickness T2 of the second layer 420 may be not less than one and a half times (1.5X) the thickness T1 of the first layer 410, such as not less than two times (2X), such as not less than three times (3X), such as not less than five times (5X), such as not less than ten times (10X). Thus, for example, the thickness T2 of the second layer 420 may be significantly greater than the thickness T1 of the first layer 410. Such relative dimensional differences between the first layer 410 and the second layer 420 can facilitate different shrinkages between the first layer 410 and the second layer 420, as discussed in more detail below.

[0096] At 220, the curable substrate 12 is such that the second layer 420 shrinks less than the first layer 410. This differential shrinkage can deform the first layer 410 to create a plurality of protrusions 412 on, for example, the outer surface 414 of the first layer 410 facing away from the second layer 420. For example, at 220, the drying system 98 may be configured to at least partially dry the substrate 12. In some example embodiments, the first layer 410 may be exposed to or placed in contact with a heating roller, oven, etc., such that the first layer 410 cures or dries faster than the second layer 420 during 220. Thus, for example, the first layer 410 may face the heating element within the oven, contact the surface of the heating roller, or be exposed to a stream of heated air through the drying system, such that at 220 the first layer 410 shrinks to a greater extent than the second layer 420. The relative dimensional difference between the first layer 410 and the second layer 420 may also facilitate differential shrinkage between the first layer 410 and the second layer 420. Furthermore, when the second layer 420 is thicker than the first layer 410, the first layer 410 may cure or dry faster than the second layer 420 in the drying system 98 at point 220. The difference in fiber composition between the first layer 410 and the second layer 420 may also contribute to differential shrinkage between them. Additionally, when the second layer 420 includes superabsorbent material and the first layer 410 is substantially free of superabsorbent material, the first layer 410 may cure or dry faster than the second layer 420 in the drying system 98 at point 220. Therefore, at point 220, the relative dimensional difference between the first layer 410 and the second layer 420 and / or the difference in fiber composition between them may contribute to differential shrinkage between them.

[0097] It should be understood that, in addition to at least partial curing of the first layer, the choice of materials between the first and second layers can also result in differential shrinkage between the two layers. For example, incorporating PET fibers into the second layer 420 can cause the second layer 420 to shrink significantly more during drying and curing than the first layer 410 (e.g., without PLA fibers), such that reducing tension in the nonwoven material can cause small local buckling of the first layer 410, thereby forming elastic protrusions on the first layer 410. As another example, the second layer 420 may include fibers capable of hydrogen bonding. In such example embodiments, the differential shrinkage between the first layer 410 and the second layer 420 may be at least partially due to capillary condensation and hydrogen bonding during drying. In another example embodiment, the second layer 420 may include superabsorbent particles that partially swell during processing at the wet end of the foam forming process. In such example embodiments, the differential shrinkage between the first layer 410 and the second layer 420 may be at least partially due to the shrinkage of the superabsorbent particles during water removal. In another example embodiment, the second layer 420 may comprise fibers or other materials that shrink upon heating, such as short PLA fibers. In such example embodiments, the differential shrinkage between the first layer 410 and the second layer 420 during heating may be at least in part due to the shrinkage of the heat-shrinkable material. Any suitable combination of the above-described mechanisms may also be used to provide differential shrinkage between the first layer 410 and the second layer 420.

[0098] As a specific example, heat-shrinkable bicomponent fibers (such as PLA / co-PLA fibers commercially available from Trevira under the trade name T-450) are capable of shrinking at least 30% of their original length upon heating. When used as a binder fiber in the second layer 420, both the first layer 410 and the second layer 420 can be dried and cured simultaneously at a temperature below the shrinkage temperature of the T-450 bicomponent fibers. Once formed, the multilayer nonwoven material can be exposed to a temperature close to or slightly above the curing temperature of the T-450 bicomponent fibers to trigger the shrinkage of the second layer 420, thereby creating a protrusion 412 on the outer surface 414 of the first layer 410. Other shrinkable materials that can be triggered by temperature or other mechanisms can also be used to form the protrusion 412.

[0099] During differential shrinkage between the first layer 410 and the second layer 420, small segments of the first layer 410 may locally buckle to form protrusions 412. The three-dimensional morphology provided by the protrusions 412 can advantageously increase the void volume of the first layer 410 and increase its compressibility. Therefore, due to the protrusions 412 formed on the first layer 410 during method 200 by differential shrinkage between the first layer 410 and the second layer 420, the first layer 410 can be configured as a collection layer in absorbent articles, wiping products, etc. Figure 7 and Figure 8An example three-dimensional morphology provided by protrusion 412 is illustrated. As shown, protrusion 412 can be a circular dome formed, for example, by the first layer 410 under relatively low tension. Figure 9 Another example of a three-dimensional morphology provided by protrusion 412 is illustrated. As shown, protrusion 412 can be, for example, a circular corrugation formed under relatively high tension. The corrugation can extend longitudinally 81 on the first layer 410.

[0100] Each of the protrusions 412 may have a height, for example, perpendicular to the longitudinal direction 81 and the transverse direction 83. The height of the protrusion 412 may typically be greater than about half a millimeter (0.5 mm), such as greater than about one millimeter (1 mm), such as greater than about one and a half millimeters (1.5 mm), such as greater than about two millimeters (2 mm), such as greater than about five millimeters (5 mm). The height of the protrusion 412 may typically be less than about fifteen millimeters (15 mm), such as less than about ten millimeters (10 mm), such as less than about seven millimeters (7 mm), such as less than about five millimeters (5 mm), such as less than about three millimeters (3 mm). It should be understood that the above heights may correspond to the average height of the protrusions 412 on the outer surface 414, and the individual heights of the protrusions 412 may vary (e.g., be less than or greater than the above values).

[0101] Figure 4 A method 300 for forming a nonwoven material according to an exemplary embodiment of this subject matter is illustrated. Method 300 can be carried out in apparatus 10 as part of a foam forming process for a nonwoven material (such as substrate 12). Therefore, method 300 is described in more detail below in the context of apparatus 10. However, it should be understood that in alternative exemplary embodiments, method 300 can be performed or implemented in any suitable foam forming system. Using method 300, a three-dimensional morphology of the nonwoven material (such as substrate 12) can be formed, for example, on the outer surface of one layer of the substrate 12.

[0102] At 310, the substrate 12 may be formed with multiple layers. For example, at 310, the headbox 80 may deposit various slurries 76 onto the forming surface 94 to form a substrate 12 having multiple layers (such as two (2), three (3), four (4), five (5) or more layers). At 310, the foam forming substrate 12 may include the deposition of a first foam and a second foam onto the forming surface 94 using the headbox 80.

[0103] In some example embodiments, each layer in the substrate 12 may have a different fiber composition. For example, as described above and as... Figure 5 and Figure 6As shown, substrate 12 may include a first layer 410 and a second layer 420. The first layer 410 may be configured as a collection layer, and the second layer 420 may be configured as an absorbent layer. Thus, the first layer 410 may be configured to collect and remove bodily waste and other fluids, for example, toward or to the second layer 420, which is configured to collect waste and other fluids therein. In some example embodiments, the first layer 410 and the second layer 420 may have different fiber compositions. For example, the second layer 420 may include, for example, a superabsorbent material in an amount from about one percent (1%) to about seventy percent (70%) by weight. Conversely, the first layer 410 may be substantially free of superabsorbent material. As another example, the second layer 420 may include PET fibers, and the first layer 410 may be substantially free of PET fibers. In some example embodiments, for example, the first foam may include water and multiple first binder fibers, such as PE fibers, and the second foam may include water and multiple second binder fibers, such as PET fibers. The difference in fiber composition between the first layer 410 and the second layer 420 can facilitate differential shrinkage between the first layer 410 and the second layer 420, as discussed in more detail below.

[0104] In some example implementations, the basis weight 410 of the first layer may be selected to help form a three-dimensional topography on the first layer 410. For example, the basis weight of the first layer 410 may typically be greater than about 40 gsm, such as greater than about 50 gsm, such as greater than about 60 gsm, such as greater than about 70 gsm, such as greater than about 80 gsm, such as greater than about 90 gsm, such as greater than about 100 gsm. The basis weight of the first layer 410 may typically be less than about 200 gsm, such as less than about 150 gsm, such as less than about 100 gsm.

[0105] like Figure 5 and Figure 6As shown, the first layer 410 and the second layer 420 may also have different dimensional characteristics. For example, each of the first layer 410 and the second layer 420 may have a corresponding thickness, for example, perpendicular to both the longitudinal direction 81 and the transverse direction 83. Furthermore, the first layer 410 may have a thickness T1, and the second layer 420 may have a thickness T2. The thickness T2 of the second layer 420 may be different from the thickness T1 of the first layer 410. For example, in some example embodiments, the thickness T2 of the second layer 420 may be greater than the thickness T1 of the first layer 410. For example, the thickness T2 of the second layer 420 may be not less than one and a half times (1.5X) the thickness T1 of the first layer 410, such as not less than two times (2X), such as not less than three times (3X), such as not less than five times (5X), such as not less than ten times (10X). Thus, for example, the thickness T2 of the second layer 420 may be significantly greater than the thickness T1 of the first layer 410. Such relative dimensional differences between the first layer 410 and the second layer 420 can facilitate different shrinkages between the first layer 410 and the second layer 420, as discussed in more detail below.

[0106] At 320, the first layer 410 may be at least partially cured while the substrate 12 is under tension. For example, at 320, the drying system 98 may be configured to at least partially dry the first layer 410. Therefore, at 320, the water content of the first layer 410 may be reduced during its curing. In some example embodiments, the first layer 410 may be exposed to or placed in contact with a heating roller, oven, etc., such that the first layer 410 cures or dries faster than the second layer 420. Thus, for example, the first layer 410 may face the heating element within the oven, contact the surface of the heating roller, or be exposed to a heated airflow through the drying system, such that the curing or drying rate of the first layer 410 is greater than that of the second layer 420. The relative dimensional difference between the first layer 410 and the second layer 420 may also facilitate faster curing or drying of the first layer 410 than the second layer 420. Furthermore, when the second layer 420 is thicker than the first layer 410, the first layer 410 can cure or dry faster than the second layer 420 in the drying system 98. Differences in the fiber composition between the first layer 410 and the second layer 420 can also facilitate faster curing or drying of the first layer 410 compared to the second layer 420. Additionally, when the second layer 420 includes superabsorbent material and the first layer 410 is substantially free of superabsorbent material, the first layer 410 can cure or dry faster than the second layer 420 in the drying system 98. Therefore, at 320, the relative dimensional difference between the first layer 410 and the second layer 420 and / or the difference in the fiber composition between the first layer 410 and the second layer 420 can facilitate the curing of the first layer 410, for example, while the second layer 420 remains substantially uncured and / or undried. Therefore, at 320, after curing the first layer 410, the water content in the second layer 420 can be greater than the water content in the first layer 410.

[0107] In some example embodiments, at 320, a portion of the first layer 410 can be cured when the substrate 12 is under tension. Therefore, for example, the curing or drying rate of the first layer 410 at a first portion of the first layer 410 may differ from the curing or drying rate of the first layer 410 at a second portion of the first layer 410. Furthermore, at 320, the curing or drying pattern of the first layer 410 can be shaped or selected to control differential shrinkage between the first layer 410 and the second layer 420, thus controlling the three-dimensional morphology provided by the protrusions 412.

[0108] At 330, after the first layer 410 has been at least partially cured at 320, the second layer 420 may be cured while the substrate 12 is under tension. For example, at 330, the drying system 98 may be configured to dry the second layer 420. In some example embodiments, the second layer 420 may be exposed to or placed in contact with a heating roller, oven, etc., such that the second layer 420 is cured or dried. Thus, for example, the second layer 420 may face the heating element within the oven, contact the surface of the heating roller, or be exposed to a flow of heated air through the drying system.

[0109] As can be seen from the above, the first layer 410 is at least partially cured at 320, and then the second layer 420 is subsequently cured at 330. By first at least partially curing the first layer 410, the relationship between the first layer 410 and the second layer 420 can be fixed at least in a region of the substrate 12. Furthermore, at least partially curing the first layer 410 can define the interlayer adhesion between the first layer 410 and the second layer 420 before the subsequent curing of the second layer 420.

[0110] At 340, the substrate 12 can be relaxed. During the relaxation of the substrate 12 at 340, the second layer 420 can shrink, and the first layer 410 can deform to create a plurality of protrusions 412 on, for example, the outer surface 414 of the first layer 410 opposite to the second layer 420. Figure 5 In the diagram, substrate 12 is shown under tension. As described above, substrate 12 may be under tension during the curing of the first layer 410 and the second layer 420 at points 310 and 320. Conversely, Figure 6 The diagram shows a substrate 12 in a relaxed state, wherein a protrusion 412 is formed at the first layer 410 due to differential shrinkage between the first layer 410 and the second layer 420 when the substrate is relaxed at 340. The substrate 12 may be relaxed at least partially at 340 during the curing of the second layer 420 at 330. Alternatively, the relaxation of the substrate 12 at 340 may be performed after the second layer 420 has been at least partially cured at 330.

[0111] During the relaxation of the substrate 12 and the curing of the second layer 420, small segments of the first layer 410 may locally buckle to form protrusions 412. The three-dimensional morphology provided by the protrusions 412 advantageously increases the void volume of the first layer 410 and increases its compressibility. Therefore, due to the protrusions 412 formed on the first layer 410 during method 300 by differential shrinkage between the first layer 410 and the second layer 420, the first layer 410 can be configured as a collection layer in absorbent articles, wiping products, etc. Figure 7 and Figure 8An example three-dimensional morphology provided by protrusion 412 is illustrated. As shown, protrusion 412 can be a circular dome formed, for example, by the first layer 410 under relatively low tension. Figure 9 Another example of a three-dimensional morphology provided by protrusion 412 is illustrated. As shown, protrusion 412 can be, for example, a circular corrugation formed under relatively high tension. The corrugation can extend longitudinally 81 on the first layer 410.

[0112] Each of the protrusions 412 may have a height, for example, perpendicular to the longitudinal direction 81 and the transverse direction 83. The height of the protrusion 412 may typically be greater than about half a millimeter (0.5 mm), such as greater than about one millimeter (1 mm), such as greater than about one and a half millimeters (1.5 mm), such as greater than about two millimeters (2 mm), such as greater than about five millimeters (5 mm). The height of the protrusion 412 may typically be less than about fifteen millimeters (15 mm), such as less than about ten millimeters (10 mm), such as less than about seven millimeters (7 mm), such as less than about five millimeters (5 mm), such as less than about three millimeters (3 mm). It should be understood that the above heights may correspond to the average height of the protrusions 412 on the outer surface 414, and the individual heights of the protrusions 412 may vary (e.g., be less than or greater than the above values).

[0113] As can be seen from the above, this subject matter can advantageously provide an elastic layer with high porosity on nonwoven materials. Such layers are particularly suitable for use as a collection layer in diapers or wipes. Generally, exemplary aspects of this subject matter use a combination of material selection and paired drying or curing processes to control interlayer adhesion and shrinkage between two layers of nonwoven materials to produce a three-dimensional morphology in one of the layers. Thus, for example, during the forming of the nonwoven material under tension, the top layer of a multilayer (e.g., double-layer) nonwoven material can be fully cured or cured at the target portion, such that the relationship between the top layer and the underlying second layer is fixed in at least some areas. The second layer can then be cured and dried while controlling the tension in the second layer, thereby controlling the shrinkage of the nonwoven material due to the drying of the second layer. When the second layer dries, the second layer will shrink, and the reduction of tension in the nonwoven material can cause small local buckling of the first layer to form elastic protrusions on the first layer. Due to the dome shape of the protrusions, the protrusions advantageously increase the porosity volume of the first layer and also increase elasticity. Controlling the bonding points in interlayer bonding can also adjust and / or optimize the three-dimensional morphology (such as local buckling) to obtain the stiffness and fluid handling characteristics of the nonwoven material. Thus, for example, the shape and / or distribution of elastic protrusions can be controlled by the bonding points in the interlayer bonding between the first and second layers of the nonwoven material. In some example aspects, the overall structural stiffness of the nonwoven material can be advantageously controlled due to the formation of the three-dimensional morphology without adding additional raw materials that would increase the overall stiffness.

[0114] This disclosure can be better understood by referring to the following embodiments.

[0115] Example

[0116] The following examples are produced based on the content of this disclosure.

[0117] In Example 1, a double-layer nonwoven substrate was formed on the forming surface. The top layer of the nonwoven substrate consisted of approximately 35% by weight of two-component binder fibers and 65% by weight of PET staple fibers, with a basis weight of approximately 40 gsm. The bottom layer consisted of approximately 30% by weight of two-component binder fibers, 40% by weight of cross-linked pulp fibers (which are substantially non-hydrogen-bonding), and approximately 30% by weight of PET fibers. For the second layer of fibers, the basis weight was approximately 75 gsm. The second layer also included superabsorbent particles with a basis weight of approximately 400 gsm. The nonwoven substrate was dried in two passes over a total length of 14 feet at a running speed of 6 feet per minute and a residence time of 120 seconds. The temperature for the first pass was 270°F, and the temperature for the second pass was 220°F. The estimated shrinkage of the nonwoven substrate was 5%.

[0118] In Example 2, a double-layer nonwoven substrate was formed on the forming surface. The top layer of the nonwoven substrate consisted of approximately 20% by weight of two-component binder fibers and 80% by weight of PET staple fibers, with a basis weight of approximately 40 gsm. The bottom layer of the nonwoven substrate consisted of approximately 40% by weight of two-component binder fibers, 10% by weight of PET fibers, and 50% by weight of NBSK wood pulp (capable of forming hydrogen bonds). The second layer of fibers had a basis weight of approximately 20 gsm. The second layer also included superabsorbent particles with a basis weight of approximately 345 gsm. The nonwoven substrate was dried in a single pass at a total length of 7 feet, a running speed of 3 feet per minute, a residence time of 120 seconds, and a temperature of 294˚F. The estimated shrinkage of the nonwoven substrate was 29%.

[0119] In Example 3, a double-layer nonwoven substrate was formed on the forming surface. The top layer of the nonwoven substrate consisted of approximately 20% by weight of two-component binder fibers and 80% by weight of PET staple fibers, with a basis weight of approximately 60 gsm. The bottom layer of the nonwoven substrate consisted of approximately 40% by weight of two-component binder fibers, 10% by weight of PET fibers, and 50% by weight of NBSK wood pulp (capable of forming hydrogen bonds). The second layer of fibers had a basis weight of approximately 20 gsm. The second layer also included superabsorbent particles with a basis weight of approximately 400 gsm. The nonwoven substrate was dried in a single pass at a total length of 7 feet, a running speed of 3 feet per minute, a residence time of 120 seconds, and a temperature of 294˚F. The estimated shrinkage of the nonwoven substrate was 31%.

[0120] In the third example of the nonwoven material, a longitudinally oriented three-dimensional morphology is formed on the top layer of the nonwoven material. It is observed that the longitudinally oriented three-dimensional morphology depends on sufficient shrinkage of the second layer (mainly in the transverse direction due to the large longitudinal tension) and also on sufficient basis weight in the first layer.

[0121] All relevant portions of the documents referenced in the specific implementation are incorporated herein by reference; any reference to any document should not be construed as an admission that it is prior art concerning the invention. In the event of any conflict between the meaning or definition of any term in this written document and any meaning or definition of a term in the documents incorporated by reference, the meaning or definition assigned to the term in this written document shall prevail.

[0122] These and other modifications and variations of the invention can be practiced by those skilled in the art without departing from the spirit and scope of the invention as more specifically described in the appended claims. Furthermore, it should be understood that aspects of the various embodiments may be interchanged, in whole or in part. Moreover, those skilled in the art will appreciate that the above description is merely illustrative and is not intended to limit the invention further described in the appended claims.

[0123] Example Implementation Plan

[0124] First Example Implementation: A method for forming a nonwoven material, comprising: forming a nonwoven web having multiple layers by foam molding; at least partially curing a first layer of the multiple layers while the nonwoven web is under tension; after at least partially curing the first layer, curing a second layer of the multiple layers while the nonwoven web is under tension; and relaxing the nonwoven web such that the second layer shrinks and the first layer deforms to create a plurality of protrusions on the outer surface of the first layer opposite to the second layer.

[0125] Second example implementation: The method of the first example implementation, wherein forming the nonwoven web by foam molding includes depositing a first foam and a second foam onto a molding surface, the first foam comprising water and a plurality of first binder fibers, and the second foam comprising water and a plurality of second binder fibers.

[0126] Third example implementation: The method as described in the first example implementation or the second example implementation, wherein the first layer comprises a plurality of first binder fibers, and the second layer comprises a plurality of second binder fibers and a plurality of superabsorbent particles.

[0127] Fourth example implementation: The method as described in any one of the first to third example implementations, wherein after the curing of the first layer, the water content in the second layer is greater than the water content in the first layer.

[0128] Fifth example implementation: The method of any one of the first to fourth example implementations, wherein the first layer comprises a plurality of first adhesive fibers, the second layer comprises a plurality of second adhesive fibers, and the second adhesive fibers are different from the first adhesive fibers.

[0129] Sixth Example Implementation: The method described in the fifth example implementation, wherein the second adhesive fiber comprises PET fiber.

[0130] Seventh Example Implementation: The method as described in any one of the first to sixth example implementations, wherein the protrusion comprises a plurality of circular corrugations.

[0131] Eighth Example Implementation: The method as described in any one of the first to seventh example implementations, wherein the void volume of the first layer increases as the nonwoven web relaxes.

[0132] Ninth Example Implementation: The method as described in any one of the first to eighth example implementations, wherein during the curing of the first layer, the first layer adheres at least partially to the second layer.

[0133] Tenth Example Implementation: The method as described in any one of the first to ninth example implementations, wherein the thickness of the second layer is greater than the thickness of the first layer.

[0134] Eleventh Example Implementation: The method as described in any one of the first to tenth example implementations, wherein: curing the first layer at least partially comprises heating the first layer, wherein the water content in the first layer decreases during the heating of the first layer; and curing the second layer comprises heating the second layer, wherein the water content in the second layer decreases during the heating of the second layer.

[0135] Twelfth Example Implementation: The method as described in any one of the first to tenth example implementations, wherein the nonwoven web is a double-layer nonwoven web, and the plurality of layers comprises only the first layer and the second layer.

[0136] Thirteenth Example Implementation: The method as described in any one of the first to tenth example implementations, wherein curing the first layer at least partially comprises curing a first portion of the first layer at a rate different from that of a second portion of the first layer.

[0137] Fourteenth Example Implementation: A nonwoven article comprising a nonwoven material manufactured according to any one of the first to eleventh example implementations.

[0138] Fifteenth Example Implementation: A nonwoven material comprising: a foam-formed nonwoven web having a first layer and a second layer, wherein the first layer contracts relative to the second layer such that the first layer forms a plurality of protrusions on its outer surface opposite to the second layer.

[0139] Sixteenth Example Implementation: The nonwoven material as described in the fifteenth example implementation, wherein the first layer comprises a plurality of first binder fibers, and the second layer comprises a plurality of second binder fibers and a plurality of superabsorbent particles.

[0140] Seventeenth Example Implementation: A nonwoven material as described in the fifteenth or sixteenth example implementation, wherein the first layer comprises a plurality of first adhesive fibers, the second layer comprises a plurality of second adhesive fibers, and the second adhesive fibers are different from the first adhesive fibers.

[0141] Eighteenth Example Implementation: A nonwoven material as described in any one of the fifteenth to seventeenth example implementations, wherein the second binder fiber comprises PET fiber.

[0142] Nineteenth Example Implementation: A nonwoven material as described in any one of the fifteenth to seventeenth example implementations, wherein the protrusion comprises a plurality of circular corrugations.

[0143] Twentieth Example Implementation: A nonwoven material as described in any one of the fifteenth to nineteenth example implementations, wherein the thickness of the second layer is greater than the thickness of the first layer.

[0144] Example 21: An absorbent article comprising a nonwoven material as described in any one of Example 15 to Example 20, wherein the outer surface of the first layer faces the wearer when the absorbent article is worn by the wearer of the absorbent article.

[0145] Example Implementation 22: A method for forming a nonwoven material, comprising: forming a nonwoven web having multiple layers by foam molding; heating a first layer of the multiple layers of the nonwoven web under tension, wherein the water content in the first layer decreases during the heating of the first layer; after heating the first layer and while the nonwoven web is under tension, heating a second layer of the multiple layers of the nonwoven web, wherein the water content in the second layer decreases during the heating of the second layer; and relaxing the nonwoven web while heating the second layer, causing the first layer to deform and have multiple protrusions on the outer surface of the first layer opposite to the second layer.

[0146] Example Implementation 23: A method for forming a nonwoven material, comprising: forming a nonwoven web having multiple layers by foam molding, wherein a first layer and a second layer of the multiple layers are at least partially interconnected; and heating the nonwoven web such that the shrinkage of the second layer is less than that of the first layer, wherein the first layer is deformed to produce a plurality of protrusions at an outer surface of the first layer opposite to the second layer.

[0147] Example 24: The method described in Example 23, wherein forming the nonwoven web by foam molding includes depositing a first foam and a second foam onto a molding surface, the first foam comprising water and a plurality of first binder fibers, and the second foam comprising water and a plurality of second binder fibers.

[0148] Example 25: The method described in Example 23 or Example 24, wherein the first layer comprises a plurality of first binder fibers and the second layer comprises a plurality of second binder fibers and a plurality of superabsorbent particles.

[0149] Example 26: The method of any one of Example 23 to Example 25, wherein the first layer comprises a plurality of first adhesive fibers, the second layer comprises a plurality of second adhesive fibers, and the second adhesive fibers are different from the first adhesive fibers.

[0150] Example 27: The method described in Example 26, wherein the second adhesive fiber comprises PET fiber.

[0151] Example 28: The method as described in any one of Example 23 to Example 27, wherein the protrusion comprises a plurality of circular corrugations.

[0152] Example 29: The method as described in any one of Example 23 to Example 28, wherein the void volume of the first layer increases as the nonwoven web relaxes.

[0153] Thirtieth Example Implementation: The method of any one of the twenty-third to twenty-ninth example implementations, wherein the thickness of the second layer is greater than the thickness of the first layer.

[0154] Example 31: The method as described in any one of Example 23 to Example 30, wherein the nonwoven web is a double-layer nonwoven web, and the plurality of layers comprises only the first layer and the second layer.

[0155] Example 32: A nonwoven article comprising a nonwoven material manufactured according to any one of Example 23 to Example 31.

Claims

1. A method for forming a nonwoven material, comprising: A nonwoven web with multiple layers is formed through foam molding; The first layer of the plurality of layers is at least partially cured when the nonwoven web is under tension; The curing or drying rate of the first layer at the first part of the first layer is different from the curing or drying rate of the first layer at the second part of the first layer. After the first layer is at least partially cured, the second layer of the plurality of layers is cured while the nonwoven web is under tension; as well as The nonwoven web is relaxed, causing the second layer to shrink and the first layer to deform to create a plurality of protrusions at the outer surface of the first layer away from the second layer. The first layer comprises multiple first adhesive fibers, and the second layer comprises multiple second adhesive fibers and multiple superabsorbent particles; The thickness of the second layer is greater than the thickness of the first layer.

2. The method of claim 1, wherein forming the nonwoven web by foam molding comprises depositing a first foam and a second foam onto a molding surface, the first foam comprising water and a plurality of first binder fibers, and the second foam comprising water and a plurality of second binder fibers.

3. The method of claim 1, wherein after the curing of the first layer, the water content in the second layer is greater than the water content in the first layer.

4. The method of claim 1, wherein the first layer comprises a plurality of first adhesive fibers, the second layer comprises a plurality of second adhesive fibers, and the second adhesive fibers are different from the first adhesive fibers.

5. The method of claim 4, wherein the second adhesive fiber comprises PET fiber.

6. The method of claim 1, wherein the protrusion comprises a plurality of circular corrugations.

7. The method of claim 1, wherein the void volume of the first layer increases as the nonwoven web relaxes.

8. The method of claim 1, wherein during the curing of the first layer, the first layer adheres at least partially to the second layer.

9. The method of claim 1, wherein: At least partially curing the first layer includes heating the first layer, wherein the water content in the first layer decreases during the heating of the first layer; and Curing the second layer includes heating the second layer, during which the water content in the second layer decreases.

10. The method of claim 1, wherein the nonwoven web is a double-layer nonwoven web, and the plurality of layers comprises only the first layer and the second layer.

11. A nonwoven article comprising a nonwoven material manufactured according to the method of claim 1.

12. A nonwoven material prepared by the method of any one of claims 1 to 10, said nonwoven material comprising: A foam-formed nonwoven web, the foam-formed nonwoven web having a first layer and a second layer. The first layer contracts relative to the second layer, causing the first layer to form multiple protrusions at the outer surface of the first layer opposite to the second layer. The first layer comprises multiple first adhesive fibers, and the second layer comprises multiple second adhesive fibers and multiple superabsorbent particles; The thickness of the second layer is greater than the thickness of the first layer.

13. The nonwoven material of claim 12, wherein the first layer comprises a plurality of first binder fibers, the second layer comprises a plurality of second binder fibers, and the second binder fibers are different from the first binder fibers.

14. The nonwoven material of claim 13, wherein the second binder fiber comprises PET fiber.

15. The nonwoven material of claim 12, wherein the protrusion comprises a plurality of circular corrugations.

16. An absorbent article comprising the nonwoven material of claim 12, wherein when the absorbent article is worn by a wearer of the absorbent article, the outer surface of the first layer faces the wearer.

17. A method for forming a nonwoven material, comprising: A nonwoven web with multiple layers is formed through foam molding; The first layer of the plurality of layers in the nonwoven web is heated while the nonwoven web is under tension, and the water content in the first layer decreases during the heating of the first layer; The curing or drying rate of the first layer at the first part of the first layer is different from the curing or drying rate of the first layer at the second part of the first layer. After heating the first layer and while the nonwoven web is under tension, a second layer of the plurality of layers in the nonwoven web is heated, and the water content in the second layer decreases during the heating of the second layer; as well as When the second layer is heated, the nonwoven web is relaxed, causing the first layer to deform and have multiple protrusions on the outer surface of the first layer away from the second layer. The first layer comprises multiple first adhesive fibers, and the second layer comprises multiple second adhesive fibers and multiple superabsorbent particles; The thickness of the second layer is greater than the thickness of the first layer.

18. A method for forming a nonwoven material, comprising: A nonwoven web having multiple layers is formed by foam molding, wherein the first and second layers of the multiple layers are at least partially interconnected; as well as The nonwoven web is heated so that the shrinkage of the second layer is less than that of the first layer, and the first layer is deformed to create multiple protrusions on the outer surface of the first layer away from the second layer; The first layer comprises multiple first adhesive fibers, and the second layer comprises multiple second adhesive fibers and multiple superabsorbent particles; The thickness of the second layer is greater than the thickness of the first layer; The curing or drying rate of the first layer at the first part of the first layer is different from the curing or drying rate of the first layer at the second part of the first layer.

19. The method of claim 18, wherein forming the nonwoven web by foam molding comprises depositing a first foam and a second foam onto a molding surface, the first foam comprising water and a plurality of first binder fibers, and the second foam comprising water and a plurality of second binder fibers.

20. The method of claim 18, wherein the first layer comprises a plurality of first adhesive fibers, the second layer comprises a plurality of second adhesive fibers, and the second adhesive fibers are different from the first adhesive fibers.

21. The method of claim 20, wherein the second binder fiber comprises PET fiber.

22. The method of claim 18, wherein the protrusion comprises a plurality of circular corrugations.

23. The method of claim 18, wherein the void volume of the first layer increases as the nonwoven web relaxes.

24. The method of claim 18, wherein the nonwoven web is a double-layer nonwoven web, and the plurality of layers comprises only the first layer and the second layer.

25. A nonwoven article comprising a nonwoven material manufactured according to the method of claim 18.

26. The method of claim 18, wherein the second layer comprises fibers capable of hydrogen bonding, and the shrinkage of the second layer is at least in part due to capillary condensation and hydrogen bonding during drying.

27. The method of claim 26, wherein the fibers capable of forming hydrogen bonds comprise wood pulp.

28. The method of claim 18, wherein the second layer comprises a superabsorbent material that partially swells after the nonwoven web is formed by foam molding, and the shrinkage of the second layer is at least in part due to the shrinkage of the superabsorbent material during the heating of the nonwoven web.

29. The method of claim 18, wherein the second layer comprises a heat-shrinkable material, and the shrinkage of the second layer is at least in part due to the shrinkage of the heat-shrinkable material during the heating of the nonwoven web.

30. The method of claim 29, wherein the heat-shrinkable material comprises PLA short fibers.

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