Nonwoven fabric containing filament layers

Abstract

A nonwoven fabric comprising a plurality of filament layers: - a first layer (A) forming the outer surface of the nonwoven fabric and comprising continuous multicomponent filaments consisting of components, said components comprising: - forming at least 20% of the filament surface, - glued within the first layer (A), - a first layer (A) which is a component having a melting point at least 5°C lower than the melting points of the other components of the filaments of the first layer (A); a second layer (B) comprising continuous multicomponent filaments consisting of components, said components comprising: - forming at least 20% of the filament surface, - glued in the second layer (B), - a second layer (B) which is a component having a melting point at least 5°C lower than the melting points of the other components of the filaments of the second layer (B); Including, - The bulk density of the fabric is 60 kg / m 3 is less than A nonwoven fabric characterized by:

Description

[Technical Field]

[0001] The present invention relates to nonwoven fabrics comprising a hierarchy of filaments. [Background technology]

[0002] Nonwoven fabrics used in different sectors must meet different requirements depending on the intended field of use: for example, in sectors such as disposable hygiene products, disposable cleaning products and medical applications, softness, high loft and good recovery are important properties.

[0003] Carded materials have been and are currently used for many of these applications. However, producing nonwoven products from carded fibers is complex, and the fiber-to-fiber adhesion in such nonwovens can result in significantly lower pile length and softness, or insufficient fiber-to-fiber adhesion, resulting in poor quality nonwovens, i.e., insufficient abrasion resistance.

[0004] Air-through bonded spunlay technology is a viable solution to meet the industry's requirements, and this technology overcomes some of the drawbacks of carded materials, primarily due to their long fiber length. Various approaches are known in the industry.

[0005] For example, the desired bulk and softness can be achieved as disclosed in patent application WO2018059610, which describes the use of crimped filaments with a so-called crimped cross-section (e.g., eccentric core / sheath), or as disclosed, for example, in PF Non Woven's patent application WO2020103964, which describes the use of filaments with a non-crimped cross-section (e.g., concentric core-sheath).

[0006] Nonwoven fabrics with good abrasion resistance as measured by the Martindale abrasion test are described, for example, in WO2020112705.

[0007] WO2020107421 discloses a method for air-through bonding of nonwoven fabrics to produce soft-loft fabrics. A continuous fiber fabric is guided between a porous rotating member and a porous belt, and heated air is passed through the fabric first from one side and then from the other. However, the description of the method is very vague and no data on the resulting product is provided.

[0008] Nonwoven fabrics that meet both requirements—softness and loft (e.g., compressibility, drapeability, flexibility, non-stiffness, and comfortable feel)—and three-dimensional stability (e.g., abrasion resistance and pilling resistance)—are considered ideal fabrics in the industry. It is clear that softness and three-dimensional stability are not simple values ​​that can be easily measured, quantified, and compared, but are instead complex characteristics that encompass a variety of fabric properties, and indeed, a variety of fabrics, all under one term. Numerous patents and applications claim fabrics with softness, loft (high thickness at low basis weight), and several types of durability. Those skilled in the art can easily recognize that many of these patents or applications understand the terms "softness" and "durability" very differently. For example, the aforementioned application WO2020103964 understands softness as "soft loft" and defines the softness of a fabric based on a specific coefficient. Conversely, the aforementioned WO2020112705 also defines softness based on a compression rebound test. Even if both fabrics are defined as soft, their behavior and end-user feel may be significantly different, making it difficult to compare them.

[0009] The object of the present invention is to provide a nonwoven fabric that is soft and bulky yet does not easily pill during use.

[0010] The object of the present invention is achieved by a nonwoven fabric, said nonwoven fabric comprising a plurality of filament strata as defined in claim 1: - a first layer (A) forming a first outer surface of the nonwoven fabric and comprising continuous multicomponent filaments consisting of components, - extending along the longitudinal direction of said filament, - forming at least 20% of the surface of said filaments, - forming interfilament bonds within said first layer (A), - a first layer (A) that is a component having a melting point that is at least 5°C lower than the melting points of the other components of the filaments of the first layer (A); a second layer (B) comprising continuous multicomponent filaments consisting of components, said components comprising: - extending along the longitudinal direction of said filament, - forming at least 20% of the surface of said filaments, - forming interfilament bonds within said second layer (B), - a second layer (B) which is a component having a melting point at least 5°C lower than the melting points of the other components of the filaments of said second layer (B); Including, - Bulk density of the fibre is 60 kg / m 3 is less than It is characterized by:

[0011] Further embodiments of the invention are defined in the dependent claims.

[0012] definition The term "filament" is defined herein as essentially an endless filament, while the term "staple fiber" refers to a fiber that has been cut to a defined length. The terms "fiber" and "filament" are used interchangeably herein. In the case of cut fibers, only the term "staple fiber" is used.

[0013] The term "interfilament bonding" refers to all possible interactions between individual filaments or individual parts of a filament, i.e., adhesive, partially adhesive, or non-adhesive contact, crossing, interconnection, parallel contact, etc. Interfilament bonding can form an adhesion between filaments, but it can also cause two independent filaments to contact each other without any restriction on the relative movement of the filaments.

[0014] The term "interfilament bond" or "bond point" typically refers to a bond connecting two filaments where they cross, contact, or are adjacent to one another. A bond point / consolidation bond can connect more than two filaments or two locations on the same filament. Therefore, the term "bond point" as used herein refers to the connection of two or more fibers / filaments at a contact point due to the interconnection of lower-melting-point components. At the bond point, the higher-melting-point components formed in the filament are generally less impacted than the lower-melting-point components formed in the filament, i.e., the sheath melts slightly, while the core remains essentially unchanged. Conversely, the term "bonding impression" refers to the surface where the bumps of the calender roller act. The bonding impression has an area defined by the size of the bumps on the bonding roller and is typically thinner than the adjacent areas. During the bonding process, the area of ​​the bonding impression is typically subjected to high mechanical pressure, which, together with the temperature, may affect the shape of all filament components within the area of ​​the bonding impression.

[0015] The term "monocomponent filament" or "monocomponent fiber" refers to a filament formed from a single polymer or a single polymer blend, and is therefore distinct from a bicomponent or multicomponent filament.

[0016] The term "multicomponent fiber" or "multicomponent filament" refers to a fiber or filament incorporating two or more individual subcomponents in its cross section, each of which is composed of a different polymer compound or a different blend of polymer compounds. Therefore, the term "multicomponent fiber / filament" is a broader term that includes, but is not limited to, "bicomponent fiber / filament." The various components of a multicomponent filament are typically arranged in clearly defined regions along the cross section of the filament and extend continuously along the length of the filament. The cross section of a multicomponent filament may be divided into several subsections, each of which may be of any shape or arrangement, including, for example, a coaxial arrangement of the subcomponents, a core / sheath arrangement, a radial arrangement, or a so-called "lands-in-the-sea" arrangement.

[0017] The terms "bicomponent" and "bicomponent" used to describe filaments are used interchangeably herein.

[0018] The design of multicomponent filaments has a decisive impact on the crimpability of these filaments. A good way to recognize the design of multicomponent filaments is to review and evaluate cross-sections that visualize the location of the different components of the filament. Often, the different components are formed from different polymer formulations that are selected and characterized, for example, by different melting points and / or different shrinkage properties after spinning, quenching, drawing, and final fiber consolidation. Typically, a rotationally symmetrical location of the filament components in the cross-section (e.g., concentric core / sheath) results in non-crimped filaments, while an asymmetrical location of the filament components (e.g., side-by-side or eccentric core / sheath) results in differential crimp potential for achieving either self-crimping and / or heat-activated crimped filaments. To simplify the terminology in this application, the terms "crimpable cross-section" and "non-crimpable cross-section" are used instead of the terms "filaments with a cross-section that supports crimping" and "filaments with a cross-section that does not support crimping." As used herein, the term "crimpable cross-section" refers to a multicomponent fiber in which components with different shrinkage characteristics are arranged in the cross-section, such that these filaments either self-crimp during filament drawing and consolidation, or crimp upon heating above the activation temperature and subsequent slow cooling, causing the fibers to follow the shrinkage force vector. Thus, when the fiber is unwound, a so-called helical crimp is formed; however, when the fibers are in a fibrous layer, an ideal helix cannot be formed due to the interfiber adhesion. For multicomponent fibers, the center of mass of each individual component in the fiber cross-section can be determined (taking into account the area / location of each component in the cross-section). Without being bound by theory, a fiber is considered "non-crimpable" if the centers of mass of all areas of each component are located at approximately the same point, as described for a rotationally symmetric concentric core / sheath configuration. For example, for a round bicomponent fiber with a symmetric or central core / sheath cross-sectional structure, the center of mass is located at the center of the cross-section (see Figure 1).

[0019] The measurement "filament diameter" is expressed in μm. The terms "grams of filament per 9000 m" (also called denier or den) or "grams of filament per 10000 m" (also called dTex) are used to express the degree of fineness or coarseness of the filament, as they correlate to the filament diameter (assuming a circular filament cross section) multiplied by the density of the material or materials used.

[0020] "Machine direction" (MD) - In relation to the manufacture of nonwoven fibrous materials and the actual nonwoven fibrous materials themselves, the term "machine direction" (MD) refers to the direction that corresponds essentially to the direction of forward movement of the nonwoven fibrous material on the manufacturing line that produces that material.

[0021] "Cross Direction" (CD) - In relation to the manufacture of nonwoven fibrous materials and the actual nonwoven fibrous material itself, the term "cross direction" (CD) refers to a direction that lies essentially in the plane of the nonwoven fibrous material, but is transverse to the direction of forward movement of the nonwoven fibrous material on the manufacturing line on which it is produced.

[0022] "z-direction" - in the context of the manufacture of nonwoven fibrous materials, is the direction perpendicular to the planar machine direction x cross-machine direction (MD x CD). The z-direction of elongation represents the thickness of the nonwoven material.

[0023] "Nonwoven material" or "nonwoven fabric" means a belt-like or fibrous formation made from directionally or randomly oriented filaments which are first formed during the formation of a filament layer, then consolidated together by friction or the induced cohesive or adhesive forces, and finally by the formation of interbonds. This consolidation may be achieved thermally (e.g., by airing, calendaring, ultrasonic effects, etc.), chemically (e.g., by the use of adhesives), mechanically (e.g., by hydroentangling, etc.), or by a combination of these methods. The term does not refer to fabrics formed by weaving or knitting, or to fabrics which use yarns or fibers to form bonded seams. The fibers may be of natural or synthetic origin and may be staple yarns, continuous fibers, or fibers produced directly at the processing site. Commercially available fibers range in diameter from less than about 0.001 mm to more than about 0.2 mm and come in a variety of forms: short fibers (known as staple or cut fibers), continuous individual fibers (filament or monofilament fibers), untwisted bundles of filaments (combed fibers), and twisted bundles of filaments (yarns). Nonwoven fabrics can be produced using many processes, including techniques such as meltblowing with staple fibers, spunbonding, spunmelt, solvent-based spinning, electrospinning, carding, film fibrillation, fibrillation, air-laying, dry-laying, wet-laying, and various combinations of these processes known in the art. The basis weight of a nonwoven fabric is typically measured in grams per square meter (g / m 2 )

[0024] The "spunbond" or "spunlaid" process is a nonwoven fabric manufacturing process in which a layer of nonwoven filaments having randomly oriented filaments is formed by converting a polymer directly into filaments and then depositing the filaments thus formed. This nonwoven layer of filaments is then consolidated into an envelope of the nonwoven fabric by forming bonds between the filaments. The consolidation process can be accomplished using various methods, such as through-airing or calendaring.

[0025] The term "batt" refers to material in filament form as seen before bonding, a process that can be carried out in various ways, e.g., air-through bonding, calendering, etc. A "batt" consists of individual filaments whose interconnections are usually not yet fixed, even if the filaments have been pre-bonded / pre-consolidated in a certain way. Here, this pre-consolidation may occur during or immediately after the filament laying in the spunlaying process. However, in this pre-consolidation, many filaments are still able to move freely and rearrange themselves. The above-mentioned "batt" may also consist of several layers formed by the accumulation of filaments from several spinning beams in the spunlaying process.

[0026] As used herein, the term "layer" refers to a partial component or element of a fabric. A "layer" may be in the form of multiple filaments produced on a single spin beam or on two or more successively arranged spin beams that form essentially the same filaments. For example, two successively arranged spin beams intended for spunbonding processes can be combined to produce a single layer by being set up essentially the same and processing polymers of essentially the same composition. Conversely, if two spunbond-type spin beams, one producing, for example, monocomponent filaments and the other producing, for example, bicomponent filaments, two distinct layers are formed. The composition of a layer can be determined based on knowledge of the individual settings and components that determine the resin (polymer) composition used to form the layer, or by analysis of the nonwoven itself, for example, using an electron microscope, or by analysis of the composition used to produce the filaments contained in the layer by DSC or NMR techniques. Adjacent layers of filaments do not necessarily need to be strictly separated; intermingling of layers at their boundaries may occur as a result of filaments from a later layer falling into gaps between the filaments of a previously deposited layer. In nonwoven fabrics, layers may form a typical structure independent of the hierarchical structure (e.g., spunbond + meltblown + spunbond (SMS)). A layer can contain one, two, or more hierarchical layers.

[0027] As used herein, the term "stratum" (plural "strata") refers to a region of filaments extending generally along the MD and CD planes of a nonwoven fabric, having a particular thickness in the z-direction of the fabric, and having a generally uniform filament density (i.e., mass of filaments per volume). The filament density of a stratum within a nonwoven fabric cannot be precisely measured but may be assessed visually in a cross-section of the nonwoven fabric. A stratum may also be characterized by a generally uniform density of interfilament bonds and / or a generally uniform content of strong and weak interfilament bonds (although there may be a slight gradient in density values ​​from the outer surface of the outer stratum to the intermediate region). It is understood that filament stratums within a nonwoven fabric are never perfectly uniform; because the filaments in a nonwoven fabric are randomly positioned and oriented, filaments from one stratum may interpenetrate into another stratum; and, further, certain regions of a stratum may locally expand or elongate from the plane of the majority of the stratum, and some filaments from that stratum may interpenetrate into adjacent stratums or extend beyond the surface of the nonwoven fabric. The hierarchical structure can be observed by analysis of the nonwoven itself, for example by using an electron microscope (especially from a cross-sectional view), for example by tomography or micro-CT measurements.

[0028] The term "compressibility" as used herein refers to the distance in millimeters that a nonwoven fabric will compress under the influence of the load defined in the measurement of "resilience."

[0029] The term "recovery" as used herein refers to the ability of a fabric to recover its original shape after compression, which is primarily related to the ability to recover bulkiness based on the ratio of the fabric thickness after the release of the applied load to the initial thickness of the fabric.

[0030] As used herein, the term "drawdown ratio" or "draw ratio" refers to the value calculated by dividing the capillary cross-sectional area by the filament cross-sectional area. To calculate the filament cross-sectional area, the fiber fineness, measured based on the apparent diameter, is used. Other non-circular cross-sections cannot be calculated using this method, and therefore require analysis of SEM images showing the actual cross-section.

[0031] Preferred embodiments of the present invention are further described in more detail below with reference to the accompanying schematic drawings, photographs and three-dimensional models. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is an example of a crimped cross section. [Figure 2] 1 is a scanning electron microscope (SEM) micrograph showing a cross section of one embodiment of the present invention. [Figure 3] 1 is a schematic diagram showing a cross section of one embodiment of the present invention. [Figure 4] FIG. 10 is a schematic diagram showing a cross section of another embodiment of the present invention. [Figure 5A] FIG. 10 is a schematic plan view showing a non-adhesive type inter-filament bond. [Figure 5B] FIG. 5B is a schematic cross-sectional view showing the interfilament bond of FIG. 5A. [Figure 6A] FIG. 10 is a schematic plan view showing a weakly bonded inter-filament bond portion. [Figure 6B] FIG. 6B is a schematic cross-sectional view showing the interfilament bond of FIG. 6A. [Figure 7A] FIG. 10 is a schematic plan view showing a fully bonded inter-filament bond portion. [Figure 7B] FIG. 7B is a schematic cross-sectional view showing the interfilament bond of FIG. 7A. [Figure 8A] FIG. 1 is a schematic plan view showing a tree-stem type interfilament bond. [Figure 8B] FIG. 8B is a schematic cross-sectional view showing the interfilament bond of FIG. 8A. [Figure 9] 1 is a photograph showing a cross section of one embodiment of the present invention when fixed to a resin. [Figure 10] 1 is a SEM micrograph showing a cross section of one embodiment of the present invention. [Figure 11] 1 is a schematic diagram showing a cross section of a fabric with a very low interfilament interconnection density level and a relatively large void volume. [Figure 12] FIG. 1 is a schematic diagram showing a cross section of a fabric with a uniformly low interfilament interconnection density. [Figure 13] Schematic diagram showing a cross section of a fabric with a uniformly high level of interfilament interconnection density and a relatively small void volume. [Figure 14] Schematic diagram showing the cross section of a fabric with very high interfilament interconnection density levels and low void volume. [Figure 15] 1 is an SEM micrograph showing a nonwoven fabric according to the present invention after delamination, showing evidence of bond failure. [Figure 16] 1 is an SEM micrograph showing a nonwoven fabric according to the present invention after delamination, showing evidence of bond failure. [Figure 17] 1 is an SEM micrograph showing a nonwoven fabric according to the present invention after delamination, showing evidence of bond failure. [Figure 18] 1 is an SEM micrograph showing a nonwoven fabric according to the present invention after delamination, showing evidence of bond failure. [Figure 20A] 1 is an SEM micrograph showing a cross section of one embodiment of the present invention comprising non-crimped filaments. [Figure 20B] 1 is an SEM micrograph showing a cross section of one embodiment of the present invention comprising non-crimped filaments; [Figure 21] FIG. 10 is a schematic diagram showing a cross section of yet another embodiment of the present invention. [Figure 22] 1 is a SEM micrograph showing a cross section of one embodiment of the present invention. [Figure 23] 1 is a schematic diagram showing a process line for producing the nonwoven fabric of the present invention. [Figure 24] 1 is a SEM micrograph showing a cross section of Example 1. [Figure 25]1 is a SEM micrograph showing a cross section of Example 2. [Figure 26] 1 is a photograph showing a cross section of Example 2 fixed in resin. [Figure 27] 1 is a three-dimensional model showing X-ray tomography in Example 1. [Figure 28] This is a digital cutaway of the three-dimensional model in Figure 27. [Figure 29] 1 is an SEM micrograph showing a cross section of Example 3. [Figure 30] 1 is an SEM micrograph showing a cross section of Example 4. [Figure 31] 1 is an SEM micrograph showing a cross section of Example 5. [Figure 32] 1 is an SEM micrograph showing a cross section of Example 6. [Figure 33] 1 is an SEM micrograph showing a cross section of Example 7. [Figure 34] 1 is an SEM micrograph showing a cross section of Example 8. [Figure 35] 1 is an SEM micrograph showing a cross section of Example 9. [Figure 36] none [Figure 37] 1 is an SEM micrograph showing a cross section of Example 11. [Figure 38] FIG. 1 is a perspective view of the Martindale Average Abrasion Rating Testing Apparatus. [Figure 39] This is the rating index for evaluating fuzzing in the Martindale Average Abrasion Rating Test. [Figure 40] FIG. 1 is a schematic diagram showing a delamination test. [Figure 41] FIG. 1 is a schematic diagram showing a delamination test. [Figure 42A] 1 is a photograph showing a holder for a sample for SEM microscopy. [Figure 42B] 1 is a photograph showing a holder for a sample for SEM microscopy. [Figure 43A] 1 is a photograph showing a holder for performing three-dimensional tomography. [Figure 43B] 1 is a photograph showing a holder for performing three-dimensional tomography. [Figure 43C] 1 is a photograph showing a holder for performing three-dimensional tomography. [Figure 44] 1 is a three-dimensional model of a micro-CT analysis of a sample according to the present invention. [Figure 45] 1 is a three-dimensional model of a micro-CT analysis of a sample according to the present invention. [Figure 46] 1 is a three-dimensional model of a micro-CT analysis of a sample according to the present invention.

[0033] Detailed Description Spunbond and / or spunmelt nonwovens are well known in the industry. Endless filaments produced using a spinning beam are laid on a production belt to form a batt, which is then pre-consolidated and bonded to form the fabric. The bonding step can be performed using several known options, such as: - mechanical entanglement, carried out for example by needles or water jets; - chemical bonding, which is carried out using adhesives or other additives added for bonding purposes; - Thermal bonding is achieved by exposing the batt to heat, which causes at least a portion of the polymer composition to melt and consolidate, forming a bond. Heat may be provided by, for example, a pair of calender rolls, radiant heat, or a hot fluid passing through a vat.

[0034] Each of the listed methods has certain advantages and disadvantages and provides a typical appearance and properties to each fabric, which can be controlled by configuring the process within given limits. The examples listed above are for illustrative purposes only, and one skilled in the art will recognize that other bonding methods or various combinations thereof can be used to achieve the desired properties of the fabric.

[0035] Fabrics consolidated by thermal fluid flow are known in the industry, as are carding techniques utilizing staple fibers to produce soft, thermally bonded fabrics. The primary advantage of thermal fluid bonding is that the bond is distributed throughout the fabric, allowing each individual fiber intersection to form a bond. Each bond is small and occurs between two or more fibers that are in contact with each other. Staple fiber technology takes advantage of the ability to blend multiple fibers into a homogeneous fiber blend and precisely control the amount of fiber containing a low-melting polymer (the adhesive polymer). For example, if a very soft, lofty fabric is desired, only small amounts of the fiber containing the adhesive polymer may be present in the fiber premix, and vice versa.

[0036] In contrast, spunmelt nonwoven fabrics are typically made from a single type of filament, and the amount of adhesive polymer can only be controlled by the adhesive polymer content in each fiber (polymer ratio in the bicomponent filament). Spunmelt production lines are equipped with multiple spinning beams, and layered fabrics with different adhesive polymers can be produced by combining the beams in various ratios. Multiple layers with different adhesive polymer ratios provide different properties, and fabrics can take advantage of the synergistic effects of strongly and moderately adhesive layers. The adhesive polymer ratios in the filament composition are exemplary herein; more technical features can be combined, for example, as described in Reifenhauser's unpublished application EP19189238.9 from 2018. This application describes a fabric consisting of at least two layers, one providing high abrasion resistance and the other providing softness and bulk.

[0037] Although the above-mentioned solutions provide fabrics with a desirable combination of properties, they also hide one disadvantage for fabric manufacturers from a process point of view: the best abrasion resistance and softness (in the sense of flexibility or drapeability) can only be achieved when the first layer forms a thin skin on the second layer. This means that the basis weight of the first layer is low and therefore, in a two-beam production line, the first beam cannot be used to optimize its throughput.

[0038] The solution of the present invention provides a spunmelt material in which the "skin" of the "soft and voluminous" portion can be formed by setting up a high temperature fluid flow bonding process, and the thickness of the "skin" can be controlled depending on the desired final properties of the fabric.

[0039] The fabric according to the present invention can be produced from a batt comprising multicomponent filaments containing a low-melting adhesive polymer on at least a portion of its surface. The batt on the moving belt is subjected to a heat treatment. Heat can be transferred to the batt by a hot fluid, e.g., hot air. In general, heat can be transferred to the batt at different stages of the manufacturing process, e.g., immediately after laying the filaments on the belt to pre-consolidate the structure, during the heat activation process, during the bonding process, etc.

[0040] As the hot fluid penetrates the surface of the filament batt and flows around the filaments, some of the heat it carries is transferred to the cooler filaments. As some of the heat is transferred to the filaments on the surface of the batt, the temperature of the hot fluid decreases somewhat, as does the temperature difference between the filaments and the hot fluid. Those skilled in the art will recognize that as the surface filaments acquire this heat, their temperature increases while the temperature difference between the hot fluid and the filaments decreases. With sufficient time and heat, it is possible to heat all of the filaments in a fabric to a uniform temperature, resulting in homogeneous fiber-to-fiber bonding throughout the thickness of the fabric. Thus, the fabric is said to be uniformly, completely, or fully bonded.

[0041] Surprisingly, it has been found that fabrics with non-uniform bond point density throughout their thickness can offer significant advantages. Fabrics according to the present invention—when viewed in cross section—include regions of strong interfilament bonding (where more filaments are in contact with one another, e.g., allowing for more interfilament bonding and / or stronger bonds) and regions of weak interfilament bonding; bonding is defined here as all possible interactions between individual filaments, i.e., bonded, partially bonded, or non-bonded contact, crossing, interconnection, parallel contact, etc. (defined in more detail below). This distinction between these regions correlates with the filament density (number of filaments in a given region) for a single filament type (based on fiber surface characteristics). Regions of higher bonding typically form on the outer surface of the filament batt, where hot fluids enter the fabric. While high and low filament density regions (layers) are generally well visible, there is typically no strict boundary between them. Fabrics according to the present invention include at least two distinct filament layers through their thickness. Hierarchies are generally defined as three-dimensional regions with a generally uniform level of interfilament adhesion and / or filament density oriented in the planar MD-CD direction. The formation of such hierarchy is influenced by various factors, and hierarchy can be recognized in several ways.

[0042] For example, layers with a higher level of interfilament bonding will also have a higher filament or fiber density. The filaments are closer to each other than those in layers formed from the same batt but with lower fiber bonding. Fiber density levels can be estimated, for example, by looking at SEM microscopy cross sections, as shown in Figure 2, or can be analyzed and calculated, for example, from tomography or micro-CT measurements. In this case, 2D digital cross-sections can be created and used to accurately determine filament density.

[0043] For example (see Figure 3), a fabric according to the present invention may comprise at least two different filament layers (A, B) having different filament densities across its thickness. Preferably, the ratio of the filament density of layer A to the filament density of layer B is at least 1.5; more preferably at least 2.0; more preferably at least 2.5; more preferably at least 3, and even more preferably at least 5.

[0044] For example, a fabric according to the present invention may comprise at least two different filament layers, where a first layer (A) having a higher filament density forms one surface of the nonwoven fabric, and a second layer (B) having a lower filament density forms the middle region or second surface of the nonwoven fabric.

[0045] For example (see FIG. 4), a fabric according to the present invention may comprise at least three different layers. In this case, there is a first layer (A) forming a first outer surface of the fabric, a second layer (B), and a third layer (C) forming a second outer surface of the fabric. Here, the second layer (B) is located between the first layer (A) and the third layer (C). The second layer (B), which forms the intermediate region, has a lower filament density than the first layer (A) and the third layer (C). It should be noted that the outer layers (A, C) may have the same characteristics, but do not necessarily have the same filament density, as long as it is higher than the (inner) second layer (B). Preferably, the ratio of the filament density of the first layer (A) to the filament density of the second layer (B) is at least 1.5; more preferably at least 2.0; more preferably at least 2.5; more preferably at least 3, and even more preferably at least 5. Also preferably, the ratio of the filament density of the third layer (C) to the filament density of the second layer (B) is at least 1.5; more preferably at least 2.0; more preferably at least 2.5; more preferably at least 3, and even more preferably at least 5.

[0046] For example, interfilament bond density can be measured directly or estimated using, for example, optical or SEM microscopy. Both methods can only be used to analyze the surface of a fabric sample. A complete sample analysis is known in the industry as a method for determining fiber shape statistics for nonwoven fabrics, where 3D micro-CT images are converted into a fabric model. This method uses a machine learning approach to identify individual fibers in the sample, followed by a shape analysis of these fibers, resulting in statistics suitable for characterizing the material. The results include fiber orientation and density distribution. This analysis workflow was developed by Math2Market and is part of GeoDict The Digital Material Laboratory.

[0047] For example, a fabric according to the invention may comprise at least two different filament layers (A, B) through its thickness, having different interfilament bond densities. Preferably, the ratio of the interfilament bond density of the first layer (A) to the interfilament bond density of the second layer (B) is at least 2; more preferably at least 3; more preferably at least 4; more preferably at least 5; and even more preferably at least 7.

[0048] For example, a fabric according to the present invention may comprise at least three distinct layers: a first layer (A) forming a first outer surface of the nonwoven fabric; a second layer (B); and a third layer (C) forming a second outer surface of the fabric, with the second layer (B) disposed between the first layer (A) and the third layer (C). The interfilament bond density of the first layer (A) and the third layer (C) is higher than the interfilament bond density of layer (B), which forms the intermediate region of the fabric. Note that both outer layers (A, C) may have the same properties, but need not be the same, as long as the interfilament bond density is higher than that of the (inner) second layer (B), which has the lowest interfilament bond density. Preferably, the ratio of the interfilament bond density of layer (A) (or the third layer (C)) to the interfilament bond density of layer (B) is at least 2; more preferably at least 3.0; more preferably at least 4; more preferably at least 5; and even more preferably at least 7.

[0049] Interfilament Bonding The interfilament bond density correlates with the density of bonds in the fabric, in other words, the length of the portion of the filaments between the bond points. It should be noted here that not all interfilament bonds form bonds, and if they do, different types of bonds will appear depending on the composition of the filaments and the ambient conditions. Without being bound by theory, the inventors believe that four typical cases can be mentioned: 1) No Bonding - When two filaments come into contact, no bonding occurs (see Figures 5A and 5B). For example, in the case of parallel fiber types where the polymer is only partially bonded to the filament surface, the filaments may face each other in areas where the bonding polymer is not available. Thus, the filaments may come into contact with each other but are not connected or bonded. Also, for example, if a fabric is bonded and then the filament crimp is restarted using a technique that does not heat the fabric to the melting point of the bonding polymer, the filaments may intertwine, forming more interfilament contact points, but no new / additional interfilament bonds will be formed. 2) Weak or tangential adhesion - Two filaments may contact each other "tangentially" and the adhesive polymer may form a "neck" between them (see Figures 6A and 6B). This can occur, for example, when there is only slight contact between the fibers, e.g., when there is a small amount of adhesive polymer available. 3) Full adhesion - two filaments touch each other and the adhesive polymer covers the filaments with a bonding sheath (see Figures 7A and 7B). This can occur, for example, when the fibers are slightly pressed together or, for example, when there is a large amount of adhesive polymer available to form a coating. 4) "Tree Trunk" - Two filaments contact each other longitudinally and the adhesive polymer forms a neck or bond coat on both fibers along a certain length, e.g., a length greater than the sum of the diameters of the two bonded filaments (see Figures 8A and 8B).

[0050] It should be noted that it is possible for more than two fibers to form a bond and for different bond types to be combined, e.g. a tree trunk with a weak bond / tangential bond can be bonded to a third fiber etc. It should also be noted that the classification presented above is a typical example for illustrative purposes, and in reality different types of bonds can be found in fabrics, especially transient bonds between weak and perfect bonds, and tree trunks can form very short to very long bonds.

[0051] For example, a story with a higher number of interfilament bonds may have a higher density of bonds 3 (fully bonded) and 4 (stem) than a story with a lower number of interfilament bonds.

[0052] For example, a fabric according to the present invention may comprise at least two different filament layers (A, B) along its thickness having different levels of full bond and tree-stem bond density. Preferably, the ratio of full bond density to tree-stem bond density in the first layer (A) and the second layer (B) is at least 1.5; more preferably at least 2.0; more preferably at least 3.0; more preferably at least 4.0, and even more preferably at least 5.

[0053] For example, a fabric according to the present invention may comprise at least three distinct layers: a first layer (A) forming a first outer surface of the nonwoven; a second layer (B); and a third layer (C) forming a second outer surface of the fabric, wherein the second layer (B) is disposed between the first layer (A) and the third layer (C). The combined density of the full bond and the tree-stem bond in the first layer (A) and the combined density of the full bond and the tree-stem bond in the third layer (C) are higher than the combined density of the full bond and the tree-stem bond in the second layer (B). Note that the outer layers (A, C) may have the same properties, but need not be the same, as long as they have a higher combined density of the full bond and the tree-stem bond than the (inner) second layer (B). Preferably, the ratio of the total density of the full bond and the tree-stem bond of the first layer (A) (or the third layer (C)) to the second layer (B) is at least 1.5; more preferably at least 2.0; more preferably at least 3.0; more preferably at least 4.0, and even more preferably at least 5.0.

[0054] All four bond types may be present in a single fabric sample. Bond strength increases from the first option (no bond), through weak / tangential bonds, to full bonds, and to wood-stem bonds. The number and proportion of different bond types in a fabric can affect the final fabric properties. For example, a higher number of strong bonds can promote the resistance and tensile strength of the fabric, but can also result in a stiffer fabric. In particular, a higher number of wood-stem bonds with a large void volume can create undesirable inner stiff areas that can be negatively characterized as, for example, rough or uncomfortable to wear.

[0055] For example, multiple void volumes can be seen in nonwoven fabrics when viewed in cross section. Large void volumes, called "voids," can be seen in the cross section of nonwoven fabrics and are three-dimensional. Regions with a high level of interfilament bonding typically have small void volumes between the filaments, and the total void volume for the entire region is generally small. Conversely, regions with low levels of interfilament bonding have large void volumes, and the total void volume for a given region is also large. Large voids, called voids, can also be observed in the cross section of fabrics. In cross sections along the long axis (MD) of a nonwoven fabric, the length of the void is significantly greater than the height of the void.

[0056] For example, a nonwoven fabric according to the present invention may include a layer B containing cavities, where the ratio of length to height of the cavities, L:H, is at least 3:1, preferably 5:1, and most preferably 10:1. See, e.g., Figures 9 and 10.

[0057] While the nonwoven fabric itself can be analyzed using different types of microscopes or other visualization techniques to account for differences in its fiber structure, from the end user's perspective, the fabric properties are a key advantage. Without being bound by theory, and assuming that if a nonwoven fabric is made from a uniform filament batt of the same filaments, the level of interfilament bonding is proportional to the bond density, it becomes possible to predict final properties based on the interfilament bond density level.

[0058] For example, a single-ply batt subjected to a spunbond air-through bonding process is pre-consolidated on a belt, where a hot fluid flows onto the fabric from above, and then the batt is transferred to an air-through bonding unit and bonded onto a belt or drum, where the hot fluid flows onto the batt from the same side as the pre-consolidation air. Depending on the correct technology and process conditions, a variety of structures with different properties can be formed.

[0059] If insufficient heat is applied to the batt filaments, the adhesive polymer will not soften or melt sufficiently, and the resulting bond will generally be weak. The resulting fabric will typically have a very low interfilament bond density level and a relatively large void volume. Such fabrics are sometimes referred to as "underbonded." It is usually easy to break or remove parts from the filaments, and the resistance (both to surface and delamination / collapse) is very low. The fabric may also be described as unstable. On the other hand, such fabrics are considered very soft in terms of compressibility, flexibility, drapeability, etc. See Figure 11.

[0060] When heat (preferably at the lower end of the preferred heat range) is introduced into the batt filaments, particularly when the heat has had enough time to be distributed as uniformly as possible throughout the batt and introduced into the filaments, or when the batt is permeable to heat flow so that, for example, it passes through at the same temperature gradient at all locations (a person skilled in the art can easily determine suitable process settings), the adhesive polymer (at the lower end of the preferred adhesive temperature range) will soften or melt sufficiently to form interfilament bonds. The resulting fabric typically exhibits a uniformly low interfilament bond density level, with a still relatively large void volume. Such fabrics are sometimes referred to as "low bond." The fabrics are typically high in loft (high pile) and soft in terms of compressibility, flexibility, drapeability, etc., while maintaining a certain (low) level of surface and peel resistance. See Figure 12.

[0061] Layered structures may also form when heat is introduced into the batt filaments and distributed unevenly, with more accepted by the fibers in the outer regions (viewed from the direction of heat input) and less by the fibers in the interior of the fabric.

[0062] The hierarchical structure requires a high interfilament bond density level on the outer surface and a low interfilament bond density level in the interior of the fabric (see Figure 3).

[0063] Heat can be introduced into the filament batt from one side or both sides simultaneously (e.g., one side and a hot air stream from a hot surface, such as a belt, table, drum, etc.; a hot air stream from the other side), or from both sides in separate steps (one side, then the other). Under these circumstances, a first layer (A) with a high interfilament bond density level may be formed on the first outer surface, a third layer (C) with a high interfilament bond density level may be formed on the second outer surface, and a second layer (B) with the lowest interfilament bond density level may constitute the intermediate region. See Figure 4.

[0064] Without being bound by theory, the inventors believe that a number of process elements and parameters working together can lead to the formation of layered structures. For example, slight compressive forces under heat (e.g., tension on a fabric on the cylindrical surface of a drum or roll) may promote the formation of outer layers with higher interfilament bond density levels. For example, heat flowing into the filaments may soften or partially soften non-adhesive polymers in the polymer composition, and partial softening of the filaments closest to the heat source may aid in the formation of outer layers. For example, filaments with a crimpable cross-section or containing a shrinkable polymer may attempt to transition from a semi-stable state to a more stable state under heat. Even if the process is not strong enough to form crimps, the force of the internal filaments can promote layer formation. Patent application WO2020103964 describes the theory of internal shrinkage force and fiber / filament resistance threshold, explaining the formation of bulky structures with non-crimpable cross-sections. Without being bound by theory, the inventors believe that similar principles may be used in an oven to explain the forces that move some of the filaments in the z-direction to form hierarchical structures. For example, cooling immediately after removal from the oven may help to form, or at least freeze, the hierarchical structures that are formed.

[0065] Fabrics made in accordance with the present invention that combine layers with high and low interfilament bond density levels in their construction offer an excellent combination of properties, where good resistance (both the surface resistance of the layers with high interfilament bond density levels and the high resistance to delamination that occurs at the bond strength of the weakest layer B with low interfilament bond density levels) is combined with good loft and softness (in terms of compressibility, flexibility, drapeability, etc.) promoted by the high loft layers with low interfilament bond density levels.

[0066] Without being bound by theory, the inventors believe that the balance between softness / bulk and resistance / tensile strength properties can also take advantage of the synergistic effects achieved by blurring the boundaries between adjacent layers. For example, a particular filament may extend partially into the first or third layer (A, C) with a high interfilament bond density level, while extending partially into the second layer (B) with a lower interfilament bond density level. For example, a hierarchical structure formed within one layer of a filament batt will have increased internal complexity compared to a similar structure formed from a different fiber layer. When heat (preferably at a mid- to high-level of the preferred heat range) is introduced into the batt filaments, particularly when there is sufficient time for the heat to infuse the filaments as uniformly as possible at all locations in the fabric, or when the batt is permeable to heat flow, e.g., passing through the same thermal gradient at all locations (a person skilled in the art can easily determine suitable process settings), the adhesive polymer will soften or melt sufficiently (at the upper end of the preferred bonding temperature range) to form interfilament bonds. The resulting fabrics typically exhibit a uniform, high interfilament bond density level and a relatively small void volume. Such fabrics are sometimes referred to as "fully bonded." They typically have low bulk, high stiffness, and maintain a high level of surface resistance, especially delamination resistance. See Figure 13.

[0067] If too much heat flows into the batt filaments, the adhesive polymer melts completely, primarily forming full bonds and tree-stem bonds. It can also affect other polymers from the filament composition, potentially causing it to bend more easily and potentially causing the filament batt to disintegrate into the filament composition itself. The resulting fabric typically has a very high interfilament bond density level and a small void volume. Such fabrics are sometimes referred to as "over-bonded." The fabric is typically stiff and durable, but may also lack bulk and a soft feel. See Figure 14.

[0068] It should be noted that the above hypothesis that fabric thickness decreases with increasing heat absorption is based on the assumption that the filaments do not undergo significant changes during bonding that induce internal forces that alter the filament shape (e.g., crimp activation, controlled shrinkage, etc.). Under these circumstances, the fabric's heat absorption versus thickness curve may be different, i.e., there may be single or multiple peaks at optimal crimp / shrinkage values, and the thickness may decrease for weakly bonded and over-bonded fabrics. The bonding principle is generally the same, allowing for the formation of hierarchical structures with all the advantages.

[0069] It is well known in the art that a specific combination of polymers with different shrinkage levels arranged in a so-called crimpable cross-section results in a so-called crimp. This crimp can be either an immediate self-crimp or a latent crimp, where the fiber must be activated (e.g., by heat activation) to develop the crimp. The crimpable cross-section of a fiber results in a regular crimp that forms a so-called helical crimp. Very simply, a fiber with a crimpable cross-section tends to bend toward the component with the higher shrinkage rate, resulting in a nearly uniform helical crimp. In other words, the crimpable cross-section causes the internal force vectors of the first and second components to shift toward each other in a regular manner. Without being bound by theory, the inventors believe that the regularity of this shift is the primary reason for the regular crimp of a free single fiber. In contrast, in accordance with the present invention, and without being bound by theory, the inventors believe that in fibers with non-crimping cross sections, the shift between the internal contraction force vectors of the first and second components is not regular, and thus the fiber forms irregular bows or waves in any direction. Very simply, one could say that the fiber has no uniform tendency to bend toward any particular part of its cross section or periphery, resulting in an irregular final shape. After activation, the fiber cross section remains largely uncrimped.

[0070] For example, a fabric according to the invention may comprise multicomponent filaments having an adhesive polymer on at least a portion of their surface. The adhesive polymer may be selected from the group of polyolefins (i.e., polypropylene or polyethylene), low-melting polymers, including low-melting polyester grades (i.e., aliphatic, such as polylactic acid, or aromatic, such as polyethylene terephthalate), copolymers, or blends of suitable polymers. It is within the scope of the invention for the adhesive polymer to consist of or essentially consist of a plastic from the polyester group, such as polyester copolymer (coPET) or polylactic acid copolymer (COPLA).

[0071] For example, a fabric according to the invention may comprise multicomponent filaments comprising a first polymer having a melting point higher than that of the adhesive polymer, preferably with a melting point difference of at least 5°C. The first polymer may be selected from the group of polyolefins (i.e., polypropylene or polyethylene), polyesters (i.e., aliphatic, such as polylactic acid, or aromatic, such as polyethylene terephthalate), copolymers, or blends of suitable polymers. It is within the scope of the present invention for the first polymer to consist of or essentially consist of a plastic from the polyester group, such as polyester copolymer (coPET) or polylactic acid copolymer (COPLA).

[0072] Preferred combinations of components for bicomponent filaments according to the present invention include polypropylene (PP) / polyethylene (PE), polyethylene terephthalate (PET) / PE, PET / PP, PET / copolyethylene terephthalate (CoPET), polylactic acid (PLA) / copolylactic acid (COPLA), PLA / PE, and PLA / PP.

[0073] For example, fabrics according to the present invention may comprise multicomponent filaments, preferably bicomponent filaments.

[0074] Fabrics according to the present invention are formed from a lofty batt, preferably also from a batt containing crimped filaments or filaments with a latent crimp that can self-crimp under appropriate activation.

[0075] For example, fabrics according to the present invention may comprise multicomponent filaments having a crimpable cross-section, preferably bicomponent filaments having a crimpable cross-section, more preferably filaments having an eccentric core / sheath (eC / S) or sheath / sheath (S / S) cross-section. For example, some preferred combinations of eC / S cross-sections include: PP / PE, PET / PE, PLA / PE, PET / PP, PLA / PP, PP / coPP, PET / coPET, PLA / coPLA, where the specified polymers form at least 75% of the filament components.

[0076] For example, a fabric according to the present invention may comprise multicomponent filaments with a non-crimping cross-section comprising a shrinkable polymer, preferably bicomponent filaments with a core / sheath (C / S) cross-section comprising a polyester in its composition, preferably in the core. For example, some preferred combinations of C / S cross-sections include: PET / PE, PET / PP, PET / coPET, PLA / PE, PLA / PP, PLA / coPLA, where the specified polymer forms at least 75% of the filament components.

[0077] Without being bound by theory, the inventors believe that in certain cases, hierarchical structures can form, but if the amount of adhesive polymer available at the surface of the filament is low, the bond formed will be too weak to hold it in place and achieve the desired structure. On the other hand, if the filament contains too much adhesive polymer that melts during the bonding process, the remaining solid portion of the filament that does not melt will be too weak to hold the structure in place and achieve the desired structure again when subjected to heat flow.

[0078] For example, a fabric according to the invention may comprise at least 15% by weight of adhesive polymer, preferably at least 18% by weight of adhesive polymer.

[0079] For example, a fabric according to the invention may comprise up to 75% by weight of adhesive polymer, preferably up to 80% by weight of adhesive polymer.

[0080] Various amounts of different polymer combinations can be used. For example, a fabric according to the invention having PP / PE filaments may contain at least 25% by weight of adhesive polymer, preferably at least 30% by weight of adhesive polymer, more preferably at least 35% by weight of adhesive polymer. For example, a fabric according to the invention having PP / PE filaments may contain up to 75% by weight of adhesive polymer, preferably up to 70% by weight of adhesive polymer, more preferably up to 65% by weight of adhesive polymer.

[0081] Also, note that the adhesive polymer must be present on the surface of the filament. In the case of a core-sheath or eccentric core-sheath, the adhesive polymer must be part of, or preferably form, the sheath.

[0082] For example, a fabric according to the present invention may comprise an adhesive polymer that forms at least 20% of the filament surface area, preferably at least 35% of the filament surface area, and more preferably at least 50% of the filament surface area. The hierarchical structure according to the present invention provides a balance between fabric durability and softness / bulk properties.

[0083] For example, fabric durability is always a requirement. Fabrics need to be durable enough to survive the conversion process into a final product without damage and to withstand the use of the final product. Two very important aspects of durability are the surface stability of the fabric (resistance to fibers unraveling from the surface) and the delamination stability of the fabric (resistance to the top of the fabric tearing from the bottom). These two types of durability are often evaluated, along with other durability such as abrasion resistance, using a Martindale test method with a set number of rounds, followed by a human rating of the results on a scale of 1 to 5. While this test is well suited to establishing a threshold for a binary pass / fail rating for a particular product, its rough scale and lack of additional information to compare passing samples with the best results make it less than the best option for making the detailed distinctions necessary to illustrate the benefits of this invention.

[0084] In other words, the tensile strength of a fabric in the z-direction is lower for layers with a lower level of interfilament bonding. The tensile strength of a fabric in the z-direction can be measured, for example, by a delamination strength test. The fabric will tear at its weakest layer. If the delamination strength is too low, the fabric will be insufficiently stable, and under the loads of conversion or normal operation, the fabric will tend to delaminate and tear apart, or to delaminate only in specific areas where the delaminated areas remain partially connected, resulting in the formation of undesirable pilling. Similarly, even if the fabric surface is very abrasion resistant, the presence of delamination can compromise the results by causing pilling or the so-called spider web effect during the Martindale abrasion test.

[0085] Without being bound by theory, the inventors believe that for fabrics with hierarchical structures, the key resistance metric is peel strength. Fully bonded fabrics with no or low levels of hierarchical structure have good surface stability and high delamination strength. Fully formed hierarchical structures are characterized by good surface stability and moderate delamination strength. Fabrics with weak or non-existent hierarchical structure and poor adhesion are prone to surface collapse and characterized by low delamination / collapse strength.

[0086] For example, a fabric according to the invention may comprise at least two different layers, in which case the delamination strength is 0.5N or greater, preferably greater than 0.6N, preferably greater than 0.7N, preferably greater than 0.8N.

[0087] For example, a fabric according to the present invention may comprise at least two different layers, in which case the delamination strength is 2.0N or less.

[0088] Delamination force is the force required to separate the outer portion / layer of a nonwoven fabric along the weakest area within the nonwoven fabric. When a fabric has a layered structure, delamination is believed to occur at the layer with the lowest interlayer bond density level. Note that, in a typical nonwoven fabric composition, the adhesive polymer has a lower tensile strength than other polymers, meaning that the weakest point is usually the adhesive bond, not the filament itself. This property is also often influenced by the fiber cross-section. For example, polyethylene as an adhesive polymer has a lower tensile strength than polypropylene or polyester. For example, the sheath is typically a relatively thin coating on the inner core, so the bond between core / sheath filaments using polyethylene as the sheath is relatively weak. As a result, it is generally easier to break the bond between filaments than to break the filaments themselves. See Figures 15-19.

[0089] For example, loft is an important characteristic. As mentioned above, the filament batt should be sufficiently lofty to allow adequate flow of hot fluids during bonding, e.g., during an air-through bonding process. Bulk is very important to human perception; a loftier fabric is often perceived as softer, so the final fabric should also be lofty. Loft is provided by the layered structure; for example, layer B is typically very lofty, increasing the loft of the overall structure. On the other hand, a higher level of interfilament bonding density in one or more layers reduces the loft of the overall structure, and in extremely lofty structures, the outer layer or layers may not form at all.

[0090] For example, the bulk density of the fabric according to the present invention is 60 kg / m 3 Less than 58 kg / m 3 Less than 56 kg / m 3 Less than 54 kg / m 3 It may be less than.

[0091] For example, the bulk density of the fabric according to the present invention is 15 kg / m 3 More than 20 kg / m 3More than 25 kg / m 3 More than 30 kg / m 3 It may be super.

[0092] Bulk / bulkness represents the number of kilograms per cubic meter, so the smaller the value, the bulkier the material; at the same time, dm is used to represent the volume of 1 kilogram of fabric in liters. 3 A "thickness to basis weight ratio" of / kg or l / kg can be used, the higher this value the higher the bulk / bulkiness.

[0093] For example, the thickness to basis weight ratio of a fabric according to the present invention may be at least 16.5 l / kg, preferably at least 17.0 l / kg, preferably at least 18.0 l / kg, more preferably at least 18.5 l / kg.

[0094] For example, the bulk density of the fabric according to the invention may be up to 66 l / kg, preferably up to 50 l / kg, preferably up to 40 l / kg, more preferably up to 33 l / kg.

[0095] For example, fabrics according to the present invention may have a basis weight of at least 5 grams per square meter (gsm), preferably at least 10 gsm, and more preferably at least 15 gsm.

[0096] For example, the basis weight of fabrics according to the present invention may be 200 gsm or less, preferably 150 gsm or less, and more preferably 100 gsm or less.

[0097] For example, the recovery rate of a fabric according to the present invention may be at least 0.5 (which corresponds to a recovery rate of 50% of the original thickness), preferably at least 0.6, more preferably at least 0.7, more preferably at least 0.8, and most preferably at least 0.9.

[0098] For example, the resilience of a fabric according to the present invention may be at least 5%, preferably at least 10%, more preferably at least 13%, more preferably at least 15%, more preferably at least 18%.

[0099] The above description of hierarchical structures, particularly those depicted, assumes that all filaments within the batt are uniformly laid out in all three dimensions. Such uniformity is desirable for most nonwoven applications. Nonuniformities are typically directly visible to the human eye. A fabric will appear denser / thicker in some areas and less dense / thinner / weaker in others. In extreme cases, a fabric may appear to be composed of islands of high density spaced apart and connected by a sparse weave of filaments. However, even fabrics that a human observer perceives as uniform may contain small, nonuniform regions of high or low density throughout the entire three-dimensional structure of the fabric.

[0100] Fibers with crimps, usually resulting from self-crimping, activated crimping, or fully controlled shrinkage, tend to form structures characterized by high-density and low-density regions: they form micro-aglomerates in certain areas, while other areas remain relatively hollow. When examining the cross-section of a fabric at the microscale, high-density regions can partially obscure layers with fewer interfilament bonds, and vice versa. See Figures 20A and 20B.

[0101] The purpose of this invention is to describe hierarchical structures and their advantages over layered approaches. As mentioned above, hierarchical structures can be formed in one layer of nonwoven fabric, in other words, hierarchical structures can be formed independently from the fabric layers.

[0102] A hierarchical structure can be advantageously combined with layering, for example, a fabric according to the invention consisting of two or more filament layers, in which at least one outer layer of filaments can be constructed into at least one outer layer having a high interfilament bond density level and at least one other layer having a low interfilament bond density level.

[0103] As detailed above, a single layer can comprise one, two, or more layers. In general, a layer can form part of, or be equal to, a layer, or even comprise more layers. Within the scope of the present invention, layered fabrics are contemplated, which comprise at least one layer from which at least two layers are formed.

[0104] For example, a fabric according to the present invention comprises at least one layer of endless filaments formed into at least two strata.

[0105] For example, layers with different filament thicknesses and amounts of adhesive polymer can be combined to achieve a fabric with one surface that has very good abrasion resistance (provided by layers with finer fibers and higher amounts of adhesive polymer) and overall bulk (provided by layers with coarser fibers and lower amounts of adhesive polymer), as described, for example, in the example of Reifenhauser's patent application, European Patent Application No. 19189238.9 (unpublished).

[0106] For example, combining multiple layers with different amounts of bonded polymer on the filament surface, such as combining S / S filaments with C / S or eC / S filaments, can produce a fabric that has improved soft loft properties provided by the layer of filaments with a lower amount of bonded polymer, and very good abrasion resistance on the surface of the filaments with a higher amount of bonded polymer.

[0107] Those skilled in the art may recognize various layer combinations that take advantage of the hierarchical structure formed in part or in its entirety. The hierarchical structure filament layer can also be advantageously combined with one or more short fiber layers, films, etc.

[0108] Layering can also be achieved by exposing the batt to various heat flow sources to achieve specific layered structures. For example, a lofty fabric formed from two layers produced using two spinning beams, pre-consolidated with hot air, and then bonded in a hot air oven can produce a structure with five visible layers, alternating between layers with high and low interfilament bonding density levels. See Figures 21 and 22.

[0109] Without being bound by theory, the inventors believe that an inner layer having a particular interfilament bond density level, located between two layers with lower interfilament bond density levels, may in certain instances be supported by pre-consolidation of the batt, for example by providing a hot fluid source (such as a hot air knife) behind one, some, or each of the manufacturing beams and / or a second or any additional hot fluid source (depending on manufacturing needs) with a vacuum located below the belt to promote the formation of nuclei with high interfilament bond density, thereby increasing the probability of the formation of an inner layer structure with a high interfilament bond density level in the fabric.

[0110] Similar structures can also be produced by combining specific layers, for example, a two-layer fabric in which both layers are made from crimpable fibers with different levels of internal filament crimp strength (e.g., different filament cross-sections, different component ratios, different process settings resulting in different potential crimp levels, etc.), allowing the filaments to move independently in both layers, resulting in a hierarchy of high interfilament bond density levels at the surface of the layers, i.e., both fabric surfaces, and in the interface region between the layers.

[0111] The fabric according to the present invention can be produced from a batt containing multicomponent filaments containing a low-melting adhesive polymer on at least a portion of its surface. The batt on a moving belt is subjected to a heat treatment. Heat can be transferred to the batt by a hot fluid, e.g., hot air. In general, heat can be transferred into the batt at different stages during the manufacturing process, e.g., immediately after laying the filaments on the belt and pre-consolidating the structure, during the heat activation process, during the bonding process, etc.

[0112] The hot fluid enters the surface of the filament batt and flows around the filaments, transferring some of the heat it carries to the cooler filaments. Because some heat is transferred to the filaments at the surface of the batt, the temperature of the hot fluid drops slightly, reducing the temperature difference between the filaments and the hot fluid. Those skilled in the art will recognize that as the surface filaments gain heat, their temperature increases, reducing the temperature difference between the hot fluid and the filaments. With enough time and heat, all of the filaments in the fabric can be heated to a uniform temperature, resulting in homogeneous fiber-to-fiber bonding throughout the entire thickness of the fabric. A fabric can be said to be uniformly, completely, or well bonded.

[0113] Note that the bond formation between filaments also depends on the local fluid resistance pressure intensity; i.e., filaments may be in contact with each other or cross each other, and may form no or only weak bonds, while filaments in stronger contact will be more strongly bonded due to the molten low-melting polymer. Due to the pressure generated as hot air flows through the fabric due to the dynamic fluid resistance of the fabric along the predominantly vertical path of the hot fluid through the fabric, the subsequent fluid's ability to transfer temperature and energy decreases, gradually decreasing from the initial impact point on the exposed fabric surface to the opposite side of the fabric. Here, as the fluid exits the fabric, the temperature and fluid flow velocity decrease, resulting in differences in bond density across the cross-section of the fabric, which manifest in the formation of layers within the fabric.

[0114] Products according to the present invention are claimed to have non-uniform interfilament bond density bonding throughout their thickness. The process setup and machinery used to create such products from filament nonwoven batts must be capable of providing the required hot air at a constant flow rate and temperature in both the CD as well as the MD, which also means that the flow rate and temperature are constant over time. This requirement applies to all hot air delivery devices, such as hot air knives, hot air fields, drum-type thermal bonding ovens, flat belt ovens, or a combination of drum and flat belt bonding.

[0115] A preferred embodiment of the present invention is a multicomponent or preferably bicomponent filament produced by spinning on a spinning machine or by using a spinneret, and then preferably passed through a cooler. Inside the cooler, the filament is typically cooled by a fluid flow, primarily cold air. It is within the scope of the present invention that the spun filament is then also passed through a drawing mechanism, where it is processed by drawing. The drawn (stretched) filament is then accumulated on a moving belt, where it forms a batt of filaments. In one advantageous configuration, by adjusting certain parameters that determine the draw ratio, it is possible to create filaments in the form of a batt with a controlled degree of potential shrinkage. In another advantageous combination, by setting a crimpable filament cross-section and adjusting certain parameters that determine the draw ratio and cooling, it is possible to subsequently create filaments in the form of a batt that are self-crimping or have a desired level of potential crimp.

[0116] According to a preferred embodiment of the machine and process configuration of the present invention, a built-in sprinkler device is used as the magazine mechanism, which controls the accumulation of the filaments and is located between the drawing mechanism and the filament accumulation position. It is within the scope of the present invention to use at least one sprinkler device, the opposing side walls of which diverge from each other in the direction of the filaments passing through. A highly recommended embodiment of the configuration of the present invention is characterized in that the drive units of the cooling mechanism and the drawing mechanism are designed as a closed system. Inside this closed system, no additional air source is provided to supplement the supply of an external cooling medium or cold air to the cooling mechanism. Such a closed system has proven to be particularly suitable for the production of nonwoven fabrics.

[0117] In the case of the manufacture of nonwoven fabrics according to the invention using shrinkage, it has been found that the technical solution according to the invention, which overcomes the problems associated with filament shrinkage, can be functionally reliable and effectively implemented using the aforementioned units, in particular, apart from the particularly preferred configuration, also using a sprinkler device located between the drawing mechanism and the filament accumulation location. As already mentioned, the shrinkage of nonwoven batts produced by the spunbond process can be very clearly adapted or adjusted by the parameters of the draw ratio, the cooling air / polymer ratio and the filament speed.

[0118] In an example utilizing self-crimping filaments to produce a nonwoven fabric according to the present invention, these filaments are released from the aerodynamic stretching forces as they leave the diffuser located at the end of the draw chamber and are subsequently laid down in a vacuum-supported fabric-forming area, where the filaments crimp as soon as the vacuum is at its lowest force at the end of the suction area—in the MD—and such crimped filaments can increase the thickness of the resulting fabric.

[0119] To consolidate the filament orientation and three-dimensional structure and give the fabric batt thickness / bulk, a subsequent process is performed in which hot air is passed through the batt in one direction. The parameters of hot fluid / hot air temperature, penetration rate, and volume are mainly set as follows: - total throughput of spunmelt beams; - Fiber size and polymer combination - Line speed - Butt thickness - Fabric basis weight g / m 2 It depends on the parameter settings of the final adhesive fabric to maintain the desired thickness.

[0120] Since the above process steps can be utilized multiple times by adding additional spunmelt beams of similar or different polymer combinations, fiber dimensions, and basis weights, it is preferred to also utilize a hot fluid-assisted consolidation step on a common conveyor belt to obtain preliminary product properties prior to the final bonding step.

[0121] From the definitions given above, it is clear that spunbond manufacturing consists of the direct conversion of polymers into filaments, which are then randomly spread at a collection location to create a nonwoven batt containing these filaments. The spunbond process determines the properties of both the individual filaments and the final nonwoven fabric. The final nonwoven fabric cannot necessarily be used to determine the various properties and states of the individual filaments, such as rheological properties, polymer structural properties, activated crimp, autogenous crimp level, and shrinkage, that occur during the individual manufacturing steps of the nonwoven fabric. The potential crimp or shrinkage of a nonwoven fabric generally determines its ability to create a high-bulk nonwoven fabric. This ability is achieved by utilizing the crimp or shrinkage of individual filaments to increase the thickness of the filament batt, yet the crimp or shrinkage occurs without disrupting the fabric structure and / or significantly changing the length and width of the filament batt. It is within the scope of the present invention that the crimp / shrinkage of the filaments can be determined by using different raw materials in the composition of the filaments, and / or by setting different material processing conditions during the production of filaments for nonwoven fabrics, and / or by utilizing different filament cross-sectional shapes / configurations, and / or by adjusting the mass ratio between the various input materials, and / or by setting different filament orientations.

[0122] The preferred embodiment of the present invention does not distinguish between filaments having a cross section that accommodates crimping and filaments having a cross section that does not accommodate crimping. Both types can be used advantageously for certain applications. Similarly, layers of crimped and non-crimped filaments can be used to create suitable combinations. It will be apparent to those skilled in the art that there are technical advantages to using filaments having a cross section that does not accommodate crimping, as opposed to crimped filaments, in achieving a bulky, soft, and flexible material.

[0123] The process according to the invention may include one or more different bonding steps, see Figure 23. For example, one batt of filaments can be laid on a moving belt and bonded from one or both sides in a bonding unit located immediately behind the filament laydown from the spinning beam.

[0124] For various reasons, it can be advantageous to increase the distance between the filament spinning beam and the bonding unit. Quite often, multiple spinning beams are used to form a layered structure or for process reasons where the filament batt needs to pass through a gap between a moving belt and a bonding unit. Under these circumstances, which are common in spunmelt production lines, the batt needs to be pre-consolidated prior to bonding to increase its stability so that it can withstand the manufacturing process. Also, for example, heat activation of the latent crimp before bonding may be required. Pre-consolidation and / or activation can be performed using rolls (e.g., compression rolls), hot air (e.g., hot air knife (HAK) or hot air field (HAF) units), thermal radiation (e.g., infrared pre-consolidation), etc. For further illustration, an example including three different bonding steps is chosen to illustrate the process. It should be noted that the layered structure of the present invention can also be formed by different manufacturing processes using a combination of pre-consolidation / activation and a bonding unit.

[0125] For example, one embodiment of the present invention includes thermally pre-consolidating the filament batt, i.e., pre-consolidating the filament batt and possibly including thermally formed bonds. An advantageous embodiment of the present invention also includes thermally activating the resulting nonwoven fabric in order to control the shrinkage and / or crimping of the filaments in at least one layer. Consolidation, and possibly thermal activation, is preferably achieved by at least one of contact with a hot medium flow (e.g., by hot air or infrared radiation) and / or by contact with a hot surface. Examples of such hot surfaces include primarily parts of rollers. Thermal activation is preferably carried out under conditions in which the action occurs uniformly over the entire surface of the fiber layer.

[0126] Thermal activation can be carried out in a chamber supplied with hot air or by passing the layer of filaments through an oven. Thermal activation and consolidation can also be carried out by infrared, ultraviolet, transmitted microwave and / or laser irradiation. Within the scope of this described procedure carried out "on-line", it is necessary to emphasize the fact that thermal consolidation may be carried out immediately after the completion of the preceding steps of the manufacturing procedure, or both steps of the thermal activation and consolidation procedures, which may also be carried out "off-line", i.e. separately from the preceding steps of the manufacturing procedure. Thermal activation can therefore essentially be carried out "off-line", i.e. at a different time and place.

[0127] Advantageously, in the solution according to the invention, a hot medium flow passes through the fabric, so that heat is transferred over the entire volume of the nonwoven.

[0128] The necessary pre-consolidation of the filament fiber batt depends to a large extent on the conditions of the manufacturing process. An important prerequisite is also to correctly set the level of cohesion between the filaments within the filament batt, and thus to be able to control the level of cohesion between the filaments based on the requirements of the subsequent steps in the manufacturing process. If the manufacturing process is performed on-line and activation is performed on the belt itself, the desired cohesion is relatively low, since it is only necessary to prevent collapse or thinning, which would occur due to highly undesirable movements during the activation process. In certain cases, for example, when the filaments cohere very well among themselves, when in contact with each other or with the substrate, and this cohesion is made possible, for example, by the cross-sectional shape / arrangement, the rate of entanglement, or the material composition, the cohesion properties of the filament batt can be sufficiently good even without thermal pre-consolidation. In other cases, for example, if the manufacturing process is divided into two stages, or if the filament batt is pre-consolidated before being fully activated and transported, for example, in the form of a roll, a significantly higher cohesion and, consequently, a significantly higher level of pre-consolidation is also required. A person qualified in the art and familiar with the manufacturing process conditions will be able to readily identify the level of pre-consolidation required in a particular instance.

[0129] For example, to control shrinkage, the activation temperature should be in the range between the glass transition temperature and the softening point (Vicat softening temperature according to International Organization for Standardization (ISO) DIN 306) of component A or components. A person qualified in the art will be able to identify the optimum activation temperature for a given component composition.

[0130] Within a convection cooler, the filaments are typically cooled by a flowing fluid, primarily cold air. As noted above, the potential shrinkage or crimp of the filaments must be uniformly distributed throughout the entire length, width, and thickness of the batt that exhibits the shrinkage. While the filament-related properties can be altered by adapting the draw ratio, cooling air / polymer ratio, and filament speed, according to the present invention, these parameters remain approximately the same for each individual filament.

[0131] The nonwoven fabrics produced are preferably spin-beam 1 It is within the scope of the present invention that the layers are made by the spunbond method. At the same time, multiple layers may be stacked one on top of the other, and then these layers are joined together by at least one forming belt. 2 Mechanism for final consolidation above 3 It is clear that the transfer to

[0132] Spinneret 5 Filament spinning in 4 The filament arrangement may be optimized by staggering the filaments to achieve a situation in which each individual filament has a very similar weight and is supplied with cold air at a very similar temperature. Spinnerets have a variable number of capillaries, which also vary in diameter (d) and length (l). The length (l) is generally calculated as a multiple of the capillary diameter, and in this application area, the length (l) is selected so that l / d is in the range of 2 to 10. The number of capillaries should be selected based on the desired final diameter of the filament and the desired or planned total polymer processing rate, as well as the desired spinning speed of the filament. The number of capillaries may vary from 800 to 7,000 per meter, which will result in filaments with diameters in the range of 8 to 45 μm. The capillary diameter and filament speed are selected to achieve the correct level of potential shrinkage of the final filament. The filament speed should be in the range of 1000-10,000 m / min, and for filaments with a cross-section that does not accommodate crimp and does not exhibit shrinkage, it should be in the range of 3000-5500 m / min. The capillary diameter should be selected in the range of 200-1000 μm, which will result in a favorable process draw ratio in the range of 200-1300 for circular capillaries, while for these circular capillaries, a draw ratio in the range of 300-800 is most advantageous to achieve the desired level of productivity on the production line. Non-circular capillaries generally have higher draw ratio values, which depend largely on the capillary shape and the relative ratio of surface to volume.

[0133] The volume and temperature of the cold air are set in such a way that the draw ratio and cooling conditions are correct. For the present invention, a ratio of cold air volume to spun polymer in the range of 20:1 to 45:1 has proven useful. The volume and temperature of the cold air are controlled in the cooler (6). This temperature can be set in the range of 10°C to 90°C, preferably in the range of 15°C to 80°C, in such a way that said cooling conditions are used in specific cases to control the course of shrinkage. The cooling conditions determine how quickly the filaments cool from their melting point to their glass transition point during the spinning process. For example, setting a higher cold air temperature will result in a slower cooling of the filaments. In fact, for the purposes of the present invention, achieving the required and usable cold air temperature range is facilitated by dividing the cooler into two zones whose temperature ranges can be controlled separately. The first zone is located near the spinneret. 6a In the second zone (6b), the temperature can be set in the range of 10°C to 90°C, preferably in the range of 15°C to 80°C, and most preferably in the range of 15°C to 70°C. In the second zone (6b), located immediately adjacent to the first zone, the temperature can be set in the range of 10°C to 80°C, preferably in the range of 15°C to 70°C, and most preferably in the range of 15°C to 45°C.

[0134] The filament is then drawn into the drawing zone. 7 Here, the filaments are drawn by the drawing force generated by the cold air velocity effect. The cold air volume and the adjustable geometry of the drawing zone allow a specific air velocity to be achieved, which is transferred to the filament velocity. This filament velocity then determines the filament diameter together with the amount of polymer processing. The potential shrinkage / contraction is adjusted by the filament velocity, the draw ratio, and the cooling air / polymer ratio.

[0135] In the next step, the filament is 8 Send to: Diffuser 8 The opposing walls of the woven fabric diverge from each other in the direction of filament movement, and the position of these walls can be adjusted in such a way that it is possible to obtain a nonwoven fabric of uniform composition in which the individual accumulated filaments are oriented in all directions in the MD / CD plane.

[0136] At the same time, it is clear that the accumulated filament batt is subject to air influences, with the effect of directing these filaments to the diffuser. The air flow can be adapted in such a way as to form various configurations, from apparently zigzag filament accumulations to circular loops and even elliptical structures oriented in the CD direction. The filaments are accumulated on a forming belt and are subjected to at least one mechanism for pre-consolidation. 9 The cold air flows through the accumulated filament batt, flows through the forming belt, and is then conveyed away from the processing area. The volume of the suction air can be adjusted in a way that facilitates the accumulation of the filaments, as well as ensures effective contact between the filament batt and the forming belt. The pre-compaction mechanism is located near the diffuser. The formation of the filament batt is controlled by the air sucked in throughout the path between the diffuser and the pre-compaction mechanism. Pre-compaction of the filament batt is performed with hot air.

[0137] The amount of energy transferred to the filament batt is controlled by process parameters that only soften or premelt the filaments to a certain extent, thereby ensuring good cohesion between the individual filaments. After the required cohesion between the filaments has been achieved, the fiber batt can be transported on a forming belt without additional auxiliary mechanisms and without the risk or impact of destruction / damage due to the effects of forces occurring during this transport. This preconsolidation procedure is also sufficient to move the filament batt to different accumulation areas on a production line consisting of several spinning beams. The energy transferred to the filaments may not be sufficient to activate the contraction of these filaments.

[0138] The method according to the invention involves determining a balance between the pre-compaction parameters: pre-compaction temperature, pre-compaction air speed, and pre-compaction time, which is understood to be the time during which the filament batt is modified by the pre-compaction air.

[0139] It is recommended that the pre-consolidation time of the filament batt is in the range of 1-10000 ms, preferably in the range of 2-1000 ms, and most preferably in the range of 4-200 ms.

[0140] The velocity of the pre-compacting air used in this pre-compacting unit is set in the range of 0.1 to 10 m / s, preferably in the range of 0.8 to 4 m / s. It is recommended that the compaction temperature during pre-compacting be in the range of 80°C to 200°C, preferably in the range of 100°C to 180°C. In one embodiment of the configuration, the pre-compacting temperature is in the range of 90°C to 150°C, mainly in the range of 110°C to 140°C.

[0141] In an advantageous configuration in the region of the production line following the diffusion device, the filament batt is transferred to at least one activation unit. 10 The filaments are activated by hot air. At the same time, it is understood that the actual crimping or shrinking of the shrinkable component of the filaments is a function of temperature, as well as the duration of the temperature influence. Furthermore, it is clear that the rate of the crimping / shrinking process also depends on the temperature. The result that can be achieved by this control of the process is a coherent and uniform structure of the nonwoven fabric with a reduced density of the filament structure, which in turn leads to an increase in the thickness of this nonwoven fabric.

[0142] According to one aspect of the present invention, the execution of the steps of the pre-compaction and activation method, the time of pre-compaction and / or activation during the steps, the wind speed required for pre-compaction and / or activation, and the temperature of pre-compaction and activation are controlled by a combined method in a combined mechanism for pre-compaction and activation.

[0143] One advantageous method according to the present invention involves determining a balance between the activation parameters: activation temperature, activation air velocity, and activation time, which is understood to be the time during which the filament batt is modified by the activation air. It is clear that these parameters may be varied within certain ranges depending on the potential shrinkage level of the filaments, as well as in order to set an ideal combination of activation time, activation temperature, and activation air velocity.

[0144] It is recommended that the activation time of the filament butt be in the range of 20-5000 ms, preferably in the range of 30-3000 ms, and most preferably in the range of 50-1000 ms.

[0145] The velocity of the activation air used in this activation unit is set in the range of 0.1 to 2.5 m / s, preferably in the range of 0.3 to 1.5 m / s. The activation temperature during thermal activation is recommended to be in the range of 80 to 200°C, preferably in the range of 100 to 160°C. In one form of configuration, this activation temperature is in the range of 90 to 140°C, mainly in the range of 110 to 130°C.

[0146] An embodiment according to the present invention may include one or more gaps between multiple manufacturing units or processing units. When discharging the preliminary fabric or batt from the conveyor belt along the MD fabric path, it is advantageous to perform this discharging with a minimum possible preliminary speed difference between the conveyor belt and the downstream first friction point in order to maintain the overall geometry, especially the original thickness, as well as the original tactile properties, e.g., the soft surface of the fabric or batt, unchanged.

[0147] The characteristics of the final product may also depend on the tension that needs to be applied to eject the pre-consolidated batt from the conveyor belt and from each active moving surface in the machine direction, also known as the friction point.

[0148] In particular, the tension at the discharge of the bat from the conveyor belt can be important.

[0149] Controlled tension is usually described as a force per linear fabric dimension and its cross-machine stretch, but in terms of the process for defining and controlling parameter settings, it is accepted to "interpret" tension in terms of the velocity difference between two downstream adjacent friction points.

[0150] Since it mainly depends on the fabric weight, line speed and surface friction between fabric and supporting surface, setting the speed difference is a straightforward way to adjust the active drive surface speed.

[0151] For example, in the process according to the present invention, the speed difference between the conveyor belt and the suction drum of the air-through bonding unit may be less than 1.0%, more preferably less than 0.5%, and even more preferably less than 0.3%. A speed difference of less than 1.0% means that the speed of the second device may be in the range of +1.0% to -1.0%.

[0152] One embodiment according to the present invention includes a conveyor belt (2), and this embodiment is carried out under conditions where the fabric strength in the machine direction (MD) of the nonwoven fabric batt is 0.5-5 N / 5 cm, preferably 0.7-3.5 N / 5 cm, more preferably 0.8-3.5 N / 5 cm before transferring the nonwoven fabric batt from the pre-consolidation step to the consolidation unit (3).

[0153] One embodiment according to the present invention includes a conveyor belt (2) which is operated under conditions where the fabric strength in the machine direction (MD) of the nonwoven fabric batt is greater than 6 N / 5 cm, preferably greater than 8 N / 5 cm, and more preferably greater than 10 N / 5 cm before transferring the nonwoven fabric batt from the pre-consolidation step to the consolidation unit (3).

[0154] One embodiment according to the present invention includes intermediate cooling between the pre-consolidation and final consolidation steps. For example, the nonwoven batt between these steps can be exposed to a cooling medium, preferably air at a temperature of 70°C or less, preferably 60°C or less, and most preferably 55°C or less. For example, intermediate cooling may be performed by exposing the pre-consolidated batt to ambient air. Without being bound by theory, the inventors believe that intermediate cooling, particularly where at least one surface of the nonwoven is heated during pre-consolidation, exposed to a low temperature, and then heated during the consolidation step, is advantageous for the formation of a denser outer layer.

[0155] An advantageous configuration according to the present invention includes a final consolidation step, which consists of modifying the filament batt with hot air in a consolidation mechanism (3). In this consolidation mechanism, the filament batt is consolidated into a fabric with interfilament bonds. This consolidation can be achieved by a number of different devices, such as a bell-shaped drum consolidation mechanism, a flat belt consolidation mechanism, or a multi-drum consolidation mechanism. Thermoplastic polymers and their blends are characterized by the phenomenon that, upon exposure to heat, they exhibit a gradually increasing plastic softening (viscosity reduction) above their glass transition point (where all amorphous portions begin to soften) and below their melting point (where all crystalline portions melt). The melting point typically falls within a very narrow temperature range (up to 2.0°C) and is defined by the homopolymer or copolymer used. In the case of polymer blends, the narrow temperature range is determined when the polymer blend becomes tacky and capable of forming interfilament bonds.

[0156] An advantageous configuration according to the invention includes a final consolidation step carried out using at least three different consolidation sections. Essentially, the air flow is approximately perpendicular to the fabric, maintaining a uniform flow with low temperature and volume fluctuations.

[0157] The first consolidation section preheats the fabric to a temperature close to but below the melting point of the adhesive polymer. Preferably, the temperature is set to 5-20°C lower than the melting point of the adhesive polymer. More preferably, the temperature is set to 5-15°C lower than the melting point of the adhesive polymer, advantageously, the temperature is set to 5-10°C lower than the melting point of the adhesive polymer. Advantageously, the first consolidation section alternates the direction of heat flow from the first and second outer surfaces of the fabric.

[0158] In the second consolidation section, the melting point range of the low-melting polymer composition is set to be narrow to enable the formation of fusion. Meanwhile, the temperature set taking into consideration the basis weight, fiber dimensions, and cross-sectional ratio between the constituent polymers of the fabric is in a range of up to 5.0°C lower and up to 3.0°C higher than the melting point of the adhesive polymer. For example, if the melting point is 130°C, the set temperature is preferably in the range of 125°C (130-5) to 133°C (130+3). Preferably, the temperature is set in the range of 5°C lower to the same temperature as the melting point of the adhesive polymer. More preferably, the temperature is set in the range of 4°C to 1°C lower than the melting point of the adhesive polymer. Advantageously, in the second consolidation section, heat flow alternately flows from the direction of the first and second outer surfaces of the fabric.

[0159] The third consolidation section is a cooling section, in which the air is cooled significantly, preferably to a temperature of 10-40°C, more preferably 20-30°C. Ambient air can also be used. The cooling section serves to solidify the filaments, or at least the filaments on the surface of the fabric, and to fix the formed layered structure of the fabric. Advantageously, no excessive tension is applied immediately before or during the cooling process. Advantageously, a further cooling step can be carried out after the consolidation unit. This further cooling can be carried out by means of an additional air flow, a cooling roll, etc. Advantageously, the further cooling is carried out when the temperature of the fabric leaving the third consolidation section has not yet reached ambient temperature. Advantageously, the fabric reaches ambient temperature, preferably a temperature of 40-10°C, more preferably a temperature of 20-30°C. The described process produces bulky, soft, and low-fuzz nonwoven fabrics at high throughputs and high production rates, for reasons of economic advantage.

[0160] For example, in one embodiment according to the present invention, a four-drum, high-temperature air-through consolidation device can be used. This device allows for a process that not only provides short residence times at high speeds, but also fully exposes the fabric to the desired hot air flow and volume along the maximum fabric path to achieve the low viscosity melt flow necessary to form a fusion bond within a defined, narrow parameter range. The machine direction drums provide a contact angle of at least 100°, preferably at least 130°, more preferably at least 150°, and advantageously at least 160°.

[0161] The exact parameter setting ranges for the selected equipment depend on the selected adhesive polymer, filament size, filament cross section, and the mass ratio between the polymer component formulations.

[0162] The four-drum apparatus also allows for alternating, nearly perpendicular, strong hot air flows to be applied to the substrate in a short time. The first pair of drums is positioned to preheat the fabric structure to a temperature just below the softening and melting point of the low-melting polymer composition. The second pair of drums is positioned so that the melting point range of the low-melting polymer composition allows for the formation of fused bonds. To maintain the structure of the fabric and keep the fused bonds intact, the final drum has hot and cold sections along its circumference in the machine direction. It is advantageous to solidify the fabric structure, or at least the surface of the fabric structure, before the fabric is released from the consolidation device. A separate, additional cooling roll with a high flow rate of cold air through the fabric is positioned as close as possible to the last roll of the air-through adhesive consolidation device. This air-through adhesive consolidation device completes the solidification of the fabric with immediate cooling.

[0163] The consolidated nonwoven fabric is wound onto a spool (11) in the final stage. If the surface properties of the nonwoven fabric need to be modified, for example to improve its fluid permeability or its ability to drain fluids, a spray mechanism or dip roll is placed either between the moving belt and the final consolidation mechanism or between the final consolidation mechanism and the spool.

[0164] One form of configuration of the present invention consists in combining activation and consolidation steps, in which the activation time and / or consolidation time, the air speed required for activation and / or consolidation, and the activation and / or consolidation temperature are controlled within the consolidation mechanism.

[0165] Consolidation parameters: Determining the balance between consolidation temperature, consolidation air velocity and consolidation time is an important factor. Consolidation time is understood to mean the time during which the filament batt is reformed by the consolidation air. It is clear that these parameters may be varied within the specified ranges in relation to the potential consolidation level of the filament batt, as well as with the aim of obtaining an ideal combination of consolidation time, consolidation temperature and consolidation air velocity.

[0166] It is recommended that the consolidation time of the filament batt is in the range of 200 to 20,000 ms, preferably in the range of 200 to 15,000 ms, and most preferably in the range of 200 to 10,000 ms.

[0167] The velocity of the compacting air used in this compaction unit is set in the range of 0.2 to 4.0 m / s, preferably in the range of 0.4 to 1.8 m / s. The compaction temperature during hot compaction is recommended to be in the range of 100 to 250°C, preferably in the range of 120 to 220°C. In one form of construction, the compaction temperature is in the range of 90 to 140°C, mainly in the range of 110 to 130°C.

[0168] Example Further details and specific features of the present invention are set forth below with reference to the following examples. The examples illustrate the practice of the invention, but are not intended to be considered limiting. Additional embodiments and modifications will be apparent to those skilled in the art that are within the scope of the invention as claimed. Accordingly, the scope of the invention is intended to be defined by the appended claims.

[0169] The examples were produced using an R5 spunmelt production line manufactured by Reifenhauser Reicofil GmbH & Co. KG. This production line was equipped with two spunbond beams (A, D), each adapted to produce bicomponent filaments. In Example 1, only one of the spunbond beams was used, while in Examples 2-13, both beams were used. Filaments from the first beam were laid onto a moving belt to form the first layer, and filaments from the second beam were laid on top to form the second layer of the batt. Behind each beam, the batt was pre-consolidated with hot air. Thus, behind the first beam, one layer was pre-consolidated, and behind the second beam, both layers were pre-consolidated together. The resulting two-layer batt was transferred to an air-through bonding unit equipped with four drums. The batt was air-through bonded from the first side by the first drum, then from the second side by the second drum, then again from the first side by the third drum, and again from the second side by the fourth drum. The first two drums constitute the first consolidation section, while the third and part of the fourth drum constitute the second consolidation section. Cooling of the nonwoven fabric began on the fourth drum (third consolidation section), where most of the contact surface was used for the final stage of air-through bonding with hot air (second consolidation section), and the final section—corresponding to the 30° contact surface of the drum—was used as the first stage of fabric cooling, i.e., the air-through cooling stage (i.e., the last surface in contact with the nonwoven fabric was used for initial cooling of the fabric just before it exited the air-through bonding unit). The resulting nonwoven fabric was further cooled by air immediately after exiting the air-through bonding unit. Specific characteristics of the manufacturing examples are defined below, and the obtained characteristics of the manufacturing examples are specified in the table below.

[0170] Example 1 - Invention The first beam produced a filament batt in which each filament had a core / sheath structure (non-crimped cross section), the core forming 70% by weight of the filament and comprising polyethylene terephthalate (type 5520, manufactured by Invista), and the sheath forming 30% by weight of the filament and comprising polyethylene (Aspun 6834, manufactured by Dow Chemicals).

[0171] The second beam was turned off.

[0172] The throughput of the first beam was 220 kg / h per meter of the width of the first beam.

[0173] The air-through bonding unit was set to 121°C for the first and second drums, 127°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the remaining part of the drum's 30° contact surface) was set to a temperature of 24°C using ambient air.

[0174] The resulting nonwoven fabric is 75 gsm, and its layered structure is clearly visible in its cross section (as shown in the figure). Dense layers A and C form the outer surface of the fabric, while the hollow, very bulky layer B in the middle provides bulk to the fabric. Note that the layers may or may not be uniformly spaced. For example, in this specification, layer A is much thicker than layer C. See Figure 24.

[0175] TIFF0007818001000001.tif182136

[0176] Example 2 - Invention The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 40% by weight of the filament and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, white colorant TiO2, and erucamide), and the sheath formed 60% by weight of the filament and contained polyethylene (Aspun 6850, Dow Chemicals).

[0177] The second beam produced a second layer of filaments with a parallel configuration, where each parallel section constituted 50% by weight of the filaments. One parallel section contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, TiO2 white colorant, and erucamide), and the second parallel section contained polyethylene (Dow Chemicals Aspun 6850).

[0178] The throughput of the first beam was 160 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0179] The air-through bonding unit was set to 125°C for the first and second drums, 129°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, and a cooling unit was located after the compaction unit in the MD.

[0180] The resulting nonwoven fabric was 25 gsm and had a clearly visible hierarchical structure.

[0181] The hierarchical structure was determined in three different ways: 1) Cross-sections were observed under an SEM microscope. It is easy to recognize the outer layers A and C, and the inner layer B. However, since the SEM microscope looks "inside" the fabric, it can be very complicated to determine the inter-filament bonds and adhesions, and to measure the voids (Figure 25). 2) The nonwoven fabric was fixed in resin and a cross section was prepared. Looking at the cross section alone, the filaments (which are randomly oriented at this microscale) are visible as black dots. It is clear that the filaments (dots) are quite densely packed in layers A and C, while a cavity has formed in the inner layer B (Figure 26). 3) The nonwoven fabric was analyzed by X-ray tomography to improve the spatial resolution of the fabric / filaments on the X-ray images. The samples were metallized in the same way as with SEM microscopy. A 3D model of the fabric was created on a computer (Figure 27) and then digitally cut into 2D fabric cross sections (Figure 28). The metallized filaments are shown as white dots (the size of the white areas may be affected by the amount of metal on the filament surface). The white areas may also represent areas where the filaments are close to each other (high density areas). Here, layers A and C, as well as the inner layer B, are very visible.

[0182] All three methods showed that a hierarchical structure was clearly formed in the samples. Furthermore, the different appearances in different parts of the fabric samples indicated that the inner layer B could be formed near one fabric surface, in the center, or near another fabric surface. It is clear (especially in the SEM images) that the inner layer is not necessarily formed at the layer / layer boundary. Furthermore, the fabric properties shown in the table indicate a good combination of durability and softness for the samples.

[0183] Examples 3-5 - Inventive Step Examples 3, 4, and 5 are almost the same as Example 2. Examples 3, 4, and 5 differ in basis weight and filament thickness (due to different settings before filament laying). The settings for the bonding process were also the same as Example 2. The hierarchical structure was clearly visible (cross-section of fabric shown in the figure). The fabric properties are shown in the table.

[0184] TIFF0007818001000002.tif209141

[0185] Example 6 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 40% by weight of the filament and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, white colorant TiO2, and erucamide), and the sheath formed 60% by weight of the filament and contained polyethylene (Aspun 6850, Dow Chemicals).

[0186] The second beam produced a second layer of filaments with a parallel structure, where each parallel section constituted 50% by weight of the filaments. One parallel section contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, and white colorant TiO2), and the second parallel section contained polyethylene (Dow Chemicals Aspun 6850).

[0187] The throughput of the first beam was 120 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0188] The air-through bonding unit was set to 124°C for the first and second drums, 128°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, with a cooling unit located after the compaction unit in the MD.

[0189] The resulting nonwoven fabric was 25 gsm and had a clearly visible hierarchical structure.

[0190] Example 7 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 40% by weight of the filament and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, white colorant TiO2, and erucamide), and the sheath formed 60% by weight of the filament and contained polyethylene (Aspun 6850, Dow Chemicals).

[0191] The second beam produced a second layer of filaments with a parallel configuration, where the first parallel section comprised 75 wt.% of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, TiO2 white colorant, and erucamide), and the second parallel section comprised 25 wt.% of the filaments and contained polyethylene (Dow Chemicals Aspun 6834).

[0192] The throughput of the first beam was 220 kg / hour per meter of the width of the first beam, and the throughput of the second beam was 240 kg / hour per meter of the width of the second beam.

[0193] The air-through bonding unit was set to 117°C for the first and second drums, 123°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, with a cooling unit located after the compaction unit in the MD.

[0194] The resulting nonwoven fabric was 55 gsm and had a clearly visible hierarchical structure.

[0195] Example 8 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 40% by weight of the filament and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, white colorant TiO2, and erucamide), and the sheath formed 60% by weight of the filament and contained polyethylene (Aspun 6850, Dow Chemicals).

[0196] The second beam produced a second layer of filaments with a parallel structure, where the first parallel section comprised 50 wt.% of the filaments, and the second parallel section comprised 50 wt.% of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, TiO2 white colorant, and erucamide).

[0197] The throughput of the first beam was 120 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0198] The air-through bonding unit was set to 125°C for the first and second drums, 129°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, and a cooling unit was located after the compaction unit in the MD.

[0199] The resulting nonwoven fabric was 25 gsm and had a clearly visible hierarchical structure.

[0200] Example 9 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 50% by weight of the filament and comprised a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, white colorant TiO2, and erucamide), and the sheath formed 50% by weight of the filament and comprised polyethylene (Aspun 6850, Dow Chemicals).

[0201] The second beam produced a second layer of filaments with a parallel structure, where the first parallel section comprised 50 wt.% of the filaments, and the second parallel section comprised 50 wt.% of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, TiO2 white colorant, and erucamide).

[0202] The throughput of the first beam was 160 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0203] The air-through bonding unit was set to 124°C for the first and second drums, 129°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, with a cooling unit located after the compaction unit in the MD.

[0204] The resulting nonwoven fabric had a thickness of 22 gsm and showed a clearly visible hierarchical structure.

[0205] Example 10 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 50% by weight of the filament and comprised a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, white colorant TiO2, and erucamide), and the sheath formed 50% by weight of the filament and comprised polyethylene (Aspun 6850, Dow Chemicals).

[0206] The second beam produced a second layer of filaments with a parallel structure, where the first parallel section comprised 50 wt.% of the filaments, and the second parallel section comprised 50 wt.% of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, TiO2 white colorant, and erucamide).

[0207] The throughput of the first beam was 200 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0208] The air-through bonding unit was set to 124°C for the first and second drums, 131°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, and a cooling unit was located next to the compaction unit in the MD.

[0209] The resulting nonwoven fabric was 65 gsm and had a clearly visible hierarchical structure.

[0210] TIFF0007818001000003.tif244151

[0211] It should be noted that Examples 9 and 10 have low tensile and adhesive strengths and may be considered poor adhesion for many applications, but even in these cases a durable hierarchical structure is formed on the outer fabric surface.

[0212] It should be noted that while the above multi-layer examples use a combination of eC / S and S / S filaments, this combination is not critical to the invention, even though it may provide advantages. Example 11 below illustrates a two-layer fabric in which both layers are formed from filaments having an eC / S cross-section.

[0213] Example 11 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 60% by weight of the filament and comprised a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, white colorant TiO2, and erucamide), and the sheath formed 40% by weight of the filament and comprised polyethylene (Aspun 6850, Dow Chemicals).

[0214] The second beam produced a second layer of filaments with an eccentric core / sheath structure, in which the core formed 50 wt% of the filament and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG475FB type, TiO2 white colorant, and erucamide), and the sheath formed 50 wt% of the filament and contained polyethylene (Aspun 6834, Dow Chemicals).

[0215] The throughput of the first beam was 120 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0216] The air-through bonding unit was set to 124°C for the first and second drums, 129°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, with a cooling unit located after the compaction unit in the MD.

[0217] The resulting nonwoven fabric was 25 gsm and had a clearly visible hierarchical structure.

[0218] TIFF0007818001000004.tif163124

[0219] Example 12 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 50% by weight of the filament and comprised a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, white colorant TiO2, and erucamide), and the sheath formed 50% by weight of the filament and comprised polyethylene (Aspun 6834, Dow Chemicals).

[0220] The second beam produced a second layer of filaments with a parallel structure, where the first parallel section comprised 50% by weight of the filaments, and the second parallel section comprised 50% by weight of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, TiO2 white colorant, and erucamide).

[0221] The throughput of the first beam was 160 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0222] The air-through bonding unit was set to 120°C for the first and second drums, 128°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 24°C using ambient air, with a cooling zone located after the consolidation unit in the MD.

[0223] The resulting nonwoven fabric was 35 gsm and had a clearly visible hierarchical structure.

[0224] Example 13 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 40% by weight of the filament and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, white colorant TiO2, and erucamide), and the sheath formed 60% by weight of the filament and contained polyethylene (Aspun 6850, Dow Chemicals).

[0225] The second beam produced a second layer of filaments with a parallel structure, where the first parallel section comprised 50% by weight of the filaments, and the second parallel section comprised 50% by weight of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, TiO2 white colorant, and erucamide).

[0226] The throughput of the first beam was 120 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0227] The air-through bonding unit was set to 123°C for the first and second drums, 128°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 19°C using ambient air, with a cooling zone located after the consolidation unit in the MD.

[0228] The resulting nonwoven fabric was 25 gsm and had a clearly visible hierarchical structure.

[0229] Example 14 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 50% by weight of the filament and comprised a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, white colorant TiO2, and erucamide), and the sheath formed 50% by weight of the filament and comprised polyethylene (Aspun 6850, Dow Chemicals).

[0230] The second beam produced a second layer of filaments with a parallel structure, where the first parallel section comprised 50% by weight of the filaments, and the second parallel section comprised 50% by weight of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, TiO2 white colorant, and erucamide).

[0231] The throughput of the first beam was 140 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0232] The air-through bonding unit was set to 124°C for the first and second drums, 129°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 21°C using ambient air, with a cooling zone located after the consolidation unit in the MD.

[0233] The resulting nonwoven fabric was 20 gsm and had a clearly visible hierarchical structure.

[0234] Example 15 - Inventive Step The first beam produced a first layer of filaments with an eccentric core / sheath structure, in which the core formed 50% by weight of the filament and comprised a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, white colorant TiO2, and erucamide), and the sheath formed 50% by weight of the filament and comprised polyethylene (Aspun 6850, Dow Chemicals).

[0235] The second beam produced a second layer of filaments with a parallel structure, where the first parallel section comprised 50% by weight of the filaments, and the second parallel section comprised 50% by weight of the filaments and contained a polypropylene blend (Exxonmobile 3155 type, Borealis HG712FB type, TiO2 white colorant, and erucamide).

[0236] The throughput of the first beam was 140 kg / h per meter of the width of the first beam, and the throughput of the second beam was 240 kg / h per meter of the width of the second beam.

[0237] The air-through bonding unit was set to 124°C for the first and second drums, 129°C for the third drum and most of the fourth drum, and the remainder of the fourth drum (corresponding to the 30° contact surface of the drum) was set to a temperature of 18°C ​​using ambient air, with a cooling zone located after the consolidation unit in the MD.

[0238] The resulting nonwoven fabric was 18 gsm and had a clearly visible hierarchical structure.

[0239] TIFF0007818001000005.tif202151

[0240] I. Test Method The "basis weight" of nonwoven fabric is measured using a test method in accordance with European Standard (EN ISO) 9073-1:1989 (corresponding to the Worldwide Strategic Partners (WSP) 130.1 method). 10 layers of nonwoven fabric are used for the measurement. The sample size is 10 x 10 cm. 2 is.

[0241] The "tensile strength" and "elongation rate" of nonwoven fabrics are measured using a test method that complies with the WSP110.4.R4 (12) standard.

[0242] The "thickness" or "measured height" of nonwoven fabrics is measured by the test measurement method according to the European standard EN ISO 9073-2:1995 (corresponding to the method of WSP 120.6) and corrected in the following manner: 1. The material is to be measured using samples taken from production without being subjected to high deformation forces or pressure for more than one day (e.g. pressure from rollers in the production equipment), but must otherwise be left free on any surface for at least 24 hours. 2. The total weight of the upper arm of the measuring machine is 130g including the additional ballast.

[0243] The "bulk", "bulk height" or "bulk density" of nonwoven fabric is kg / m 3 It is expressed in g / m 2It is calculated by dividing the "basis weight" in units by the "thickness" in mm.

[0244] The "thickness to basis weight ratio" of nonwoven fabric is dm 3 / kg or l (liter) / kg, and the "thickness" in mm x 1000 is g / m 2 Calculate by dividing by the unit of "basis weight".

[0245] The "stiffness" of nonwoven fabrics is expressed as a "handle-o-meter" (HOM) measurement and is determined in accordance with International Standard WSP90.3. Unless otherwise stated, the sample dimensions are 100 x 100 mm. HOM is measured separately in the MD and CD directions. The arithmetic mean of these two values ​​is taken unless MD or CD direction is specified.

[0246] The term "regeneration rate" or "recovery rate" of bulk in this specification refers to the ratio of the thickness of a fabric after the applied load is released to the initial thickness of this fabric. The thickness of the fabric is measured according to the standard EN ISO 9073-2:1995 with a preload force equivalent to a pressure of 0.5 kPa. The procedure for measuring regeneration consists of the following steps: 1. Prepare a fabric sample with dimensions of 10 x 10 cm; 2.Measure the thickness of a piece of fabric; 3. Measure the thickness (Ts) of the five overlapping fabrics with a preload force equivalent to a pressure of 0.5 kPa; 4. In the thickness measuring device, a load (2.5 kPa pressure) is applied to five overlapping fabrics for 5 minutes; 5. Remove from the device and wait for 5 minutes; 6. Measure the thickness (Tr) of five overlapping fabrics with a preload force equivalent to a pressure of 0.5 kPa; 7. Calculate the regeneration rate according to the following formula: Regeneration rate = Tr / Ts (unitless) Ts = thickness of new sample Tr = thickness of the regenerated sample

[0247] The term "compressibility" in this specification refers to the distance in millimeters that a nonwoven fabric is compressed under the influence of the load defined when measuring "softness". Compressibility can also be calculated as the product of rebound (unitless) and thickness (mm). The "resilience" or "rebound" of a nonwoven fabric is measured using a test method according to standard EN ISO 964-1, corrected in the following manner: 1.Measure the thickness of one fabric layer; 2. Prepare several fabric samples so that the total thickness after stacking is at least 4 mm, ideally 5 mm. The stacked fabric group contains at least one fabric; 3. Measure the thickness of these stacked fabric samples; 4. Apply a force of 5N to the stacked fabric samples at a loading rate of 5mm / min; 5. Measure the distance traveled by the clamping element; 6. Calculate the repulsive force according to the following formula: R (unitless) = T1 (mm) / T0 (mm) or, R(%) = T1(mm) / T0(mm) x 100% T1 = Distance travelled by the clamping element under a load of 5 N [mm] = Degree of compression of the laminated fabric T0 = ​​thickness (according to standard EN ISO 9073‐2:1995 with a preload force of 1.06 N) [mm].

[0248] "Martindale Average Abrasion Resistance Grade Test" or "Martindale" Figure 38 is a perspective view of the Martindale Average Abrasion Rating Test apparatus. Figure 39 is a rating index for evaluating fuzz in the Martindale Average Abrasion Rating Test herein, as described in U.S. Published Patent Application No. 20200170853A1 filed by Procter & Gamble.

[0249] The Martindale average abrasion resistance rating of the nonwoven fabric is measured using a Martindale abrasion tester, and the test is carried out in a dry state. - Condition the nonwoven fabric sample at a temperature of 23 ± 2°C and a relative humidity of 50 ± 2% for 24 hours. - Cut ten circular samples, each 162 mm (6.375 in) in diameter, from each nonwoven fabric sample. Cut one circular piece, 140 mm in diameter, from the reference felt. - First, place the cut-out felt, then the cut-out nonwoven fabric, and clamp each sample in its respective position on the Martindale abrasion test bench. Then, clamp the nonwoven fabric sample with the clamp ring to prevent it from wrinkling. - Assemble the polisher holder. The polisher is a 38 mm diameter, 1 / 32 inch thick silicone rubber (part number 86045K21-50A, McMaster-Carr) that is FDA compliant. Place the desired weight on the polisher holder so that a pressure of 9 kPa is applied to the sample. Place the assembled polisher holder on the Model #864 so that the polisher is in contact with the NW sample as instructed in the Operator's Guide. - Martindale abrasion under the following conditions: Mode: Wear test Speed: 47.5 cycles / min Cycles: 16 cycles - After the test is complete, place the abraded nonwoven on a smooth, matte black surface and rate the level of fuzz using the scale shown in the diagram. Evaluate each sample by observing both from above to determine the size and number of defects and from the side to determine the height of the defect protrusions. Assign a number from 1 to 5 that best matches this rating index. The Martindale Average Abrasion Resistance Rating is then calculated as the average rating for all samples and reported to the nearest 10-point rating.

[0250] "Peel strength" or "adhesion" can be determined in the following way (see Figures 40 and 41): 1) Cut out a test piece 120 mm long (MD direction) and at least 30 mm wide. 2) Cut two strips of tape 145 mm long and fold the last 25 mm of each tape strip on one side. Reinforce the sample with a 25.4 mm wide piece of tape and adhere it with a 7 kg hand roller, rolling it once in one direction. Cut the sample along the tape to a width of 25 mm in CD. Release the free end of the tape strip. 3) The tensile strength testing machine shall feature two jaws with clamping surfaces in the same plane parallel to the direction of stress application. The jaws shall be aligned to hold the specimen in that plane throughout the test without slippage or damage to the specimen. All four sides of the jaws shall be padded with thin strips of soft gasket rubber to prevent slippage and damage to the specimen. In accordance with American Society for Testing and Materials (ASTM) D76-99, a Twing-Albert, Instron, Zwick, or equivalent may be used for the constant-rate traverse tensile testing machine. 4) Set the parameters as follows: a) Gauge length: 50 mm b) Crosshead speed: 305 mm / min c) Pre-tension length: 10 mm d) Measurement length: 152 mm e) Sample scanning frequency: 50Hz 5) Place the specimen in the testing machine by clamping the free end of the tape, which is properly positioned in the upper grip (Figure 41). Fold the free end of the tape back and secure it in the lower grip. Align the free end of the specimen symmetrically in the grips to ensure uniform tension distribution. Adjust the load range, if necessary, so that the reading is between 30% and 80% of the full load range. 6) Start the tensile tester. 7) Measure 10 samples and calculate the average value. 8) Report the average peel force to the nearest 0.01 N.

[0251] The "type of fiber cross section" can be determined from the process conditions defined in the fiber forming die. If the process conditions are unknown, the following estimation methods can be used: A fabric sample is taken and photographs are taken of the cross sections of at least 20 fibres. The cross sections are measured in the free part of the fibre, not at the bond points or contact points with other fibres where deformation can be expected. For each cross section, mark the component surface on the image separately for each component. Determine the centre of mass for each component based on determining the centre of gravity or geometric centre of a planar object and record its position using a Cartesian coordinate system with centre [0;0] at the geometric centre of the fibre cross section. Calculate the deflection (D) of the centre of mass of each component for each fibre cross section according to the following formula: D = absolute value of the product (x × y), where x and y are the coordinates of the center of mass. If one of the values ​​x, y is 0 and is not equal to the other value, the sample is excluded from the evaluation.

[0252] The mean and standard deviation are calculated for each component.

[0253] A fiber is considered uncrimped if the ratio of ((mean deflection) + (standard deviation)) to the total fiber cross section is less than 5%.

[0254] A fiber is assumed to be uncrimped if the ratio of ((mean deflection) - (standard deviation)) to the total fiber cross section is less than 10%.

[0255] The "interfilament bond density," "filament density," "void length and height," and "void percentage of nonwoven fabric thickness" can be determined from the cross section of the fabric.

[0256] At least 10 samples are taken in the MD and at least 10 samples in the CD. If a hierarchical structure is observed in at least 50% of the samples, the fabric is judged to have a hierarchical structure.

[0257] The material is to be measured using samples taken from production without being subjected to high deformation forces or pressure for more than one day (e.g. pressure from the rollers of the production equipment), but otherwise must be left lying freely on any surface for at least 24 hours.

[0258] Cross sections can be created and analyzed in several ways: How to create a fabric cross section 1) Simple cross section: Place the fabric on a suitable surface and cut it with a sharp razor blade, making sure the cut is approximately the same thickness as the fabric (e.g. the filaments are not compressed or "cut glued"). 2) Resin cross section: The fabric sample is placed in a container and the liquid resin is poured in and allowed to solidify. The resin should be chosen so that in its liquid state it easily fills the entire void volume of the fabric, and in its solid state it is easily distinguishable from the fabric polymer. A block of solid resin is cut in half to create a cross section of the fabric sample. 3) Digital cross section: The sample is scanned (e.g., by tomography, micro-CT) and a digital cross section is created on a computer.

[0259] Sample cross-section analysis method: 1) SEM microscopy a) If necessary, place the filament sample in a suitable holder (see, for example, Figures 42A and 42B) and analyze. b) Metallize the sample with gold (for example, using an Au / Pd metallizer SC 7640 Sputter Coater). c) Analyze the sample using an electron microscope (e.g., a Tescan backscattered electron (BSE) detector) at 30 kV and appropriate magnification (30x to 1000x). 2) 3D tomography a) If necessary, apply a thin layer of contrast material to the sample. For example, polyolefins are not well visualized when using 3D X-ray tomography (Skyscan). For example, the sample can be metallized with gold (e.g., using the Au / Pd Metallizer SC 7640 Sputter Coater). b) The sample is placed in the analysis chamber and scanned. 3) 3D μCT - see "Method for determining geometric and fiber statistics of nonwoven fabrics."

[0260] The above methods and analyses (except 3D μCT) could be implemented, for example, at the Faculty of Engineering, Tomas Bata University in Zlin (Czech Republic).

[0261] The resulting cross-sectional photographs are then analyzed: 1) "Interfilament bonding density" and "filament density" a) Divide the fabric cross section into regular segments, each with a maximum thickness of 0.05 mm (e.g., divide a 0.45 mm thick fabric into 9 sections of 0.05 mm thickness). b) Each segment is at least 0.5 mm long, and this length is preferably visible in the cross-sectional photograph. c) Set the density. i) Calculate the number of interfilament bonds per segment and express it as the density of interfilament bonds (number of bonds / area of ​​segment); or ii) The area occupied by the filaments in each segment is calculated and expressed as filament density (area occupied by filaments / segment area). d) Adjacent segments with the same or very similar density may be joined together to form layers. e) Name strata A, B, and possibly C, and calculate their average values. f) Calculate the ratio value. 2) "Length and height of the cavity" and "% of cavity in the thickness direction of the nonwoven fabric" a) Adopt the hierarchical structure determined above and further investigate the area of ​​hierarchical B. b) Highlight the void volume region. c) Mark the voids (if the area is larger than three times the average filament thickness within the fabric thickness (z-direction of the fabric) and its length (MD x CD plane of the fabric) is more than five times the average filament thickness, the area is considered a void). d) Calculate the area of ​​all cavities and express it as a percentage of the area of ​​Floor B. e) Measure the height of each cavity in the thickness direction of the fabric, and measure its length in the MD x CD plane direction of the fabric, and calculate the L:H ratio using the maximum value of these.

[0262] "Method for determining shape fiber statistics of nonwoven fabrics" This paper describes a software-based method for analyzing nonwoven material samples and characterizing their geometric properties. The method utilizes a machine learning approach to identify the individual fibers contained in the sample, followed by a geometric analysis of these fibers to obtain statistical values ​​suitable for characterizing the material. Results include fiber orientation and density distributions. This analysis workflow was developed by Math2Market and is part of GeoDict, a digital materials laboratory software.

[0263] Step 1: Acquiring a 3D μCT image of the sample First, a 3D image is obtained by digitizing a nonwoven fabric sample using a μCT scanner. This 3D image consists of a uniform Cartesian grid, with each cell (volume element: voxel) storing the X-ray radiation attenuation value of the sample at the corresponding location. Pore spaces typically exhibit the lowest attenuation (lowest grayscale value), while material phases exhibit high attenuation values. The attenuation value depends on the material and the μCT device configuration.

[0264] Step 2: Segmentation of μCT images to separate material from pore space For further analysis, the grayscale images are subjected to noise filtering using a non-local means approach [1]. The images are then binarized using a global threshold derived by the Otsu algorithm [2]. This binarization classifies each voxel in the image as containing either pore space or fiber material. Voxels with gray values ​​below the threshold are classified as pore space. All other voxels are classified as fiber material. For both noise filtering and thresholding operations, the ImportGeo module of the GeoDict software is used.

[0265] Step 3: Analysis of material density distribution Furthermore, the material density distribution in the Z direction is calculated electronically. At each image section (given depth direction Z), the material density is calculated as the number of voxels of white material divided by the total number of voxels in the section. This analysis is performed using the MatDict module of the GeoDict program.

[0266] Step 4: Using neural networks to identify fiber centerlines A major challenge in identifying individual fibers in μCT images is the lack of spatial separation of fibers at their contact points after binarization, which leads to under-segmentation and the incorrect classification of multiple objects (fibers) as a single fiber.

[0267] To separate fibers, Math2Market developed an approach that identifies the center curves of the fibers. These center lines are displayed in a binary voxel image with the same dimensions as the original image. In this image, voxels within a distance of approximately 1-2 voxels from the center of the fiber are marked.

[0268] For this purpose, we used a semantic segmentation approach using neural networks [3]. The image is analyzed by considering sliding 3D input windows that are moved over the image. For each input window, a small output window is defined at the center of the input window. The neural network analyzes the binary voxel values ​​of the input window and predicts each voxel in the output window. The predicted values ​​determine whether a voxel in the output window is part of a centerline or not. Combining the results of all these output windows results in a binary image in which each voxel is classified as a material contained in the original image. This image transformation is performed by the FiberFind-AI module within the GeoDict program using the Tensorflow software library [4].

[0269] Step 5: Creating training data for the neural network To train a neural network to perform the aforementioned transformation, Math2Market used the GeoDict software program's probabilistic FiberGeo structure generation module to create several artificial 3D images of the nonwoven material. This module describes the analytical shape of the fibers as a series of line segments. At the same time, this module outputs a binary image of the fiber structure, which is compared with the binarization result from step 2.

[0270] By changing the fiber diameter by about 2-3 voxels within the analytical depiction, the centerline image corresponding to the artificial fiber structure can be obtained as well.

[0271] These image pairs (fiber and centerline) are then used to train a neural network that transforms fiber images into centerline images. The network effectively learns to "shrink" the fibers onto the centerline curve.

[0272] Step 6: Tracing the fiber centerline to delineate the fiber After shrinking the fibers into fiber centerlines, we assume that the centerlines are not touching each other. Then, we separate the individual centerlines by analyzing the connected components of the centerline image, assuming that each component corresponds to the centerline of one fiber. We define a connected component as a subset of material voxels, where all voxels have the same color and cannot be expanded by adding voxels of the same color that are touching each other.

[0273] For each centerline, we trace a curve through a set of voxels and depict the shape of the corresponding fiber in the form of a series of connected line segments (polylines). This process is also part of the GeoDict program FiberFind-AI.

[0274] The result is a digital 3D model of the fabric, and examples of fabrics containing hierarchical structures can be seen in Figures 44-46.

[0275] Step 7: Computer analysis of the sample To determine "interfilament bond density," "filament density," "void length and height," and "void percentage relative to nonwoven thickness," the filament segments of each cross section were projected onto a plane and divided into subsegments (each up to 0.05 mm thick) for analysis. Values ​​were compared between segments, and, where possible, several adjacent segments with identical or similar results were joined into the same layer. Layers were designated A, B, and sometimes C, and the values ​​for each layer were averaged from the segment data.

[0276] [1] Buades, Antoni, Bartomeu Coll, and JM.Morel. "A non-local algorithm for image denoising", Computer Vision and Pattern Recognition, 2005, CVPR 2005, IEEE Computer Society Conference, Volume 2, IEEE, 2005. [2] Nobuyuki Otsu, "A method for selecting thresholds from gray-level histograms," IEEE transactions on systems, man, and cybernetics 9.1 (1979): pp.62-66 [3] Noh, Hyeonwoo, Seunghoon Hong, and Bohyung Han, "Learning deconvolution network for semantic segmentation," Proceedings of the IEEE International Conference on Computer Vision, 2015. [4] Martin Abadi, Ashish Agarwal, Paul Barham, Eugene Brevdo, Zhifeng Chen, Craig Citro, Greg S. Corrado, Andy Davis, Jeffrey Dean, Matthew Devin, Sanjay Ghemawat, Ian Goodfellow, Andrew Harp, Geoffrey Irving, Michael Isard, Rafal Jozefowicz, Yangqing Jia, Lukasz Kaiser, Manjunath Kudlur, Josh Levenberg, Dan Mane, Mike Schuster, Rajat Monga, Sherry Moore, Derek Murray, Chris Olah, Jonathan Shlens, Benoit Steiner, Ilya Sutskever, Kunal Talwar, Paul Tucker, Vincent Vanhoucke, Vijay Vasudevan, Fernanda Viegas, Oriol Vinyals, Pete Warden, Martin Wattenberg, Martin Wicke, Yuan Yu, and Xiaoqiang Zheng, TensorFlow: Large-scale machine learning on heterogeneous systems, 2015, Available from tensorflow.org.

[0277] The snowflake of the snowflake The present invention can be used wherever a high loft nonwoven with a good softness / durability balance is required - for example, in hygiene industry manufacturing as various components of absorbent hygiene products (e.g., baby diapers, incontinence products, feminine hygiene products, changing pads, etc.), or in the healthcare sector as, for example, wound sponges and / or protective garments, surgical cover sheets, underlayments, and other barrier material products. Further uses are possible in industrial applications, e.g., as part of protective garments, filtration, thermal insulation, packaging, sound absorption, the footwear industry, automotive, furniture, etc. The present invention can be used advantageously in particular in applications that combine the requirements for increased loft, compressibility, and recovery of fabrics with the requirement for endless fibers.

Claims

1. 1. A nonwoven fabric comprising a plurality of filament strata: a first layer (A) forming a first outer surface of the nonwoven fabric and comprising continuous multicomponent filaments comprising a first component, the first component comprising: - extending along the longitudinal direction of said filament, - forming at least 20% of the area of ​​the surface of said filaments, - forming interfilament bonds within said first layer (A), a first layer (A) that is a component having a melting point that is at least 5° C. lower than the melting points of the other components of the filaments of said first layer (A); a second layer (B) comprising continuous multicomponent filaments comprising a first component, said first component comprising: - extending along the longitudinal direction of said filament, - forming at least 20% of the area of ​​the surface of said filaments, - forming interfilament bonds within said second layer (B), a second layer (B) that is a component having a melting point that is at least 5° C. lower than the melting points of the other components of the filaments of said second layer (B); Including, - the bulk density of said nonwoven fabric is 60 kg / m 3 and the ratio of the inter-filament bond density of the first layer (A) to the inter-filament bond density of the second layer (B) is at least 2.

0. A nonwoven fabric characterized by:

2. The nonwoven fabric includes a third layer (C), which forms the second outer surface of the nonwoven fabric such that the second layer (B) is disposed between the first layer (A), which forms the first outer surface, and the third layer (C), which forms the second outer surface of the nonwoven fabric, and which includes continuous multicomponent filaments comprising a first component, the first component comprising: - extending along the longitudinal direction of said filament, - forming at least 20% of the surface of said filaments, - forming interfilament bonds within said third layer (C), - have a melting point at least 5°C lower than the melting points of the other components of said filaments of said third layer (C); 2. The nonwoven fabric according to claim 1.

3. 3. The nonwoven fabric according to claim 1, wherein the ratio of the filament density of the first layer (A) to the filament density of the second layer (B) is at least 1.

5.

4. 4. The nonwoven fabric according to claim 1, wherein the ratio of the interfilament bond density of the first layer (A) to the interfilament bond density of the second layer (B) is at least 3.

0.

5. 5. The nonwoven fabric of claim 1, wherein the first component of the first layer (A) and / or the first component of the second layer (B) comprises an adhesive polymer selected from the group consisting of polyolefins, aliphatic polyesters, aromatic polyesters, or copolymers thereof.

6. 6. The nonwoven fabric according to claim 1, wherein the fabric layer peel strength is 0.5 N or more.

7. 7. The nonwoven fabric according to claim 1, wherein the fabric layer peel strength is 10.0 N or less.

8. 8. The nonwoven fabric according to any one of claims 1 to 7, characterized in that the nonwoven fabric comprises at least a first layer (i) and a second layer (ii) of filaments.

9. An absorbent sanitary product comprising the nonwoven fabric according to any one of claims 1 to 8.

10. 10. A method for producing the nonwoven fabric of claim 1, comprising the steps of: a) melting: a. at least a first polymeric material forming a first component; b. a second polymeric material forming at least one other component; b) feeding a molten polymeric material into a nozzle of a spinning beam and extruding said molten polymeric material through the nozzle, said step comprising: forming an endless filament from the molten polymer material exiting the nozzle; b. the first polymeric material is oriented longitudinally of the filament and forms at least a portion of the surface of the filament, the first polymeric material having a melting point at least 5° C. lower than the melting point of other components of the filament; c) quenching the formed filaments with a fluid medium at a temperature of 10-90°C and drawing the filaments at a drawdown ratio of 200-1300 to achieve a semi-stable crystalline state of at least the second polymeric material; d) randomly laying the filaments on a forming belt to form a nonwoven filament batt; e) pre-consolidating the nonwoven filament batt with a heat flow for 1 to 10,000 ms; f) preheating the nonwoven filament batt with a heat flow at a temperature 5-20° C. below the melting point of the first polymeric material; and g) consolidating the nonwoven filament batt with a heat flow having a temperature at most 5°C below the melting point of the first polymeric material and at most 3°C ​​above the melting point of the first polymeric material, and cooling the thus consolidated nonwoven filament batt with an air flow having a temperature between 10 and 40°C. Including, The method of claim 1, wherein intermediate cooling is performed between the pre-compacting step (e) and the pre-heating step (f) by exposing the pre-compacted nonwoven filament batt to air.

11. 11. The method for producing a nonwoven fabric according to claim 10, wherein the intermediate cooling is carried out with air at a temperature of 70° C. or less.

12. 12. The method for producing a nonwoven fabric according to claim 10 or 11, wherein during the consolidation of the nonwoven filament batt in step g), the heat flow is applied in alternating directions, entering first from one side of the nonwoven filament batt and then from the other side of the nonwoven filament batt.

13. A method for producing a nonwoven fabric according to any one of claims 10 to 12, characterized in that at least a part of step f) and / or step g) is carried out by aligning the nonwoven filament batt with the drum of an air-through consolidation device.

14. 14. The method of claim 10, wherein at least a portion of step f) and / or step g) is performed by passing the nonwoven filament batt through a flat oven consolidation device.

Images