Non-woven element and method of manufacturing same

Abstract

The invention relates to a nonwoven element (1) for forming at least one hook engagement surface for a hook and loop fastener, comprising at least one nonwoven layer formed from a fiber pile (2) which extends in a longitudinal direction (MD) and a transverse direction (CD) and has a thickness (H) perpendicular thereto. The fiber pile (2) comprises a plurality of plastic fibers (5), wherein the nonwoven layer has a pattern of open areas (3) for the engagement of hook elements (7) of a hook and loop fastener and bonded areas (4) surrounding the open areas (3) and having a smaller thickness (D2). According to the invention, the fiber pile (2) is formed from a homogeneous fiber mixture with a first fiber component and a second fiber component. The first fiber component comprises 20 wt.% to 80 wt.% of the fibers.-% of the fiber mixture and is formed from a multi-component fiber, in particular a bi-component fiber, with a first polymer material and a polyolefinic second polymer material. The melting point of the first polymer material is higher than the melting point of the second polymer material. The fiber mixture further comprises a second fiber component consisting of a monofiber made of a polyolefinic third polymer material.

Description

[0001] The invention relates to a nonwoven element for forming a hook engagement surface for a hook and loop fastener, comprising at least one nonwoven layer formed from a fiber pile, which extends in a longitudinal direction (machine direction) and a transverse direction and has a thickness perpendicular to it - also referred to as bulk.

[0002] Hook-and-loop fasteners are releasable mechanical fastening systems in which a first component, the so-called "hook strip," equipped with hooks or locking elements, can be engaged with a so-called "hook engagement surface." The hook engagement surface typically consists of fiber structures, particularly nonwovens or loop materials, into which the hooks or locking elements of the hook strip can engage. Hook-and-loop fastener systems are therefore also referred to as "hook-and-loop fasteners." The mechanical connection is created by the hook strip coming into contact with the hook engagement surface. The hooks or locking elements then make contact with individual fibers in the hook engagement surface, forming a secure, form-fitting connection.

[0003] A hook-and-loop fastener can typically withstand particularly high forces in the same plane as the surfaces of the hook strip and the hook engagement area (contact plane). This is also known as shear force. To detach it, the hook strip and the hook engagement area are pulled apart perpendicular to the contact plane. Ideally, a hook-and-loop fastener exhibits lower resistance to such peel force. The hook connections between the hook strip and the fibers of the hook engagement area are ideally overcome by elastic deformation of the hooks. In this case, the detachment process is completely reversible. However, it can also happen that individual fibers are damaged and / or pulled out of the hook engagement area when the hook strip is detached. This can significantly impair the subsequent holding power of the hook-and-loop fastener.

[0004] Hook-and-loop fasteners are widely used in the field of personal hygiene products, particularly diapers and incontinence products. A key advantage of hook-and-loop fasteners is their ability to be repeatedly fastened and unfastened. Their holding power remains unaffected by any contamination from care products such as creams, baby oil, or other liquids. However, the cost-effective use of hook-and-loop fasteners in such mass-produced items depends on minimizing material and manufacturing costs. Since structured textiles, such as loop-knit fabrics, are expensive to produce, nonwoven fabrics are increasingly being used to create the hook-and-loop fastener areas.

[0005] Nonwovens are formed from a loose, disordered fiber composite – also known as fiber nap – which is subsequently bonded into a nonwoven fabric through a process of consolidation. Various consolidation methods are known, which can be based on either a physical-mechanical entanglement of the individual fibers and / or a chemical or physico-thermal bonding of the fibers.

[0006] Unlike structured textiles—that is, especially knitted, woven, or twilled fabrics—hook-engagement surfaces made of nonwoven elements have a greater tendency for individual fibers to be pulled out when the hook-and-loop fastener is released. Due to the random arrangement of fibers within a nonwoven fabric, the specific connection points between individual fibers are always subject to statistical variations. To prevent fibers from being pulled out in a conventional nonwoven fabric, a particularly high degree of bonding is required. However, this has the disadvantage that with increasing bonding, the hooks penetrate the hook-engagement surface less effectively, thus hindering the formation of hook connections. Furthermore, excessive bonding impairs the visual appearance, tactile properties, and air permeability / breathability.

[0007] The invention therefore relates to a nonwoven fabric element in which the fiber pile comprises a multitude of plastic fibers and the nonwoven layer (in the longitudinal and transverse directions) has a pattern of open areas for the engagement of hook elements of a hook-and-loop fastener and bonded areas surrounding the open areas, which have a reduced thickness. Although the fiber pile is also bonded to form a nonwoven layer in the open areas, a weaker bond between the individual fibers is sufficient there, since the fibers in the bonded areas are firmly connected to one another. This allows the mechanical requirements of a hook-and-loop fastener to be better met. In particular, at least 75% of the fibers are bonded to one another in the bonded areas. For this purpose, the nonwoven layer is compressed to a reduced thickness in the bonded areas.

[0008] The open areas, on the other hand, have a larger volume ("bulk") and are therefore more "open-pored" to accommodate the hook elements of the hook tape. Due to the statistically distributed orientation of the individual synthetic fibers within the fiber pile, the individual fibers extend into at least one open area and at least one bonded area in the majority of cases.

[0009] Such nonwoven elements are known from the prior art, for example from WO 97 / 024 482 A1. Despite the patterned bonding of the nonwoven, the prior art always exists within a tension between ensuring sufficient adhesive strength of the hook and loop fastener and securing the nonwoven fibers against tearing, on the one hand, and other properties of the nonwoven element. Ideally, it should be breathable and air-permeable, and at least visually create a pleasantly "fluffy" impression, while also providing sufficient surface area for the hooks. In addition, there is the constant effort to reduce material and manufacturing costs and to simplify the production process.

[0010] Furthermore, US 2006 / 019572 A1, US 2012 / 276347 A1 and WO 2017 / 112509 A1 show the use of a fiber mixture with a combination of a multi-component fiber and a mono-fiber.

[0011] Against this background, the invention is based on the objective of providing a nonwoven element improved with respect to at least one of these properties for forming a hook engagement surface for a hook and loop fastener. The invention relates to a nonwoven element according to claim 1 and a manufacturing method according to claim 23.

[0012] Based on the prior art, the invention provides that the fiber mat is formed from a homogeneous fiber mixture comprising a first fiber component and a second fiber component. The first fiber component constitutes 20 wt.% to 80 wt.% of the fiber mixture and is formed from multi-component fibers, in particular bi-component fibers with a first polymer material and a polyolefinic second polymer material. The melting point of the first polymer material is higher than that of the second polymer material. Furthermore, the fiber mixture includes a second fiber component consisting of a monofiber made of a polyolefinic third polymer material. Multi-component fibers, especially bi-component fibers with a high-melting-point and a low-melting-point polymer material, offer advantages in processing and the properties of the final product.On the one hand, the high-melting-point polymer component contributes to good structural integrity of the fiber web both during processing and in the finished product. At the same time, at least one low-melting-point polymer component ensures that the processing temperatures required are not as high as those necessary to at least partially melt the high-melting-point component. In the nonwoven element according to the invention, the thermal consolidation steps preferably rely exclusively on partially or fully melting the low-melting-point polymer components. However, the consistent use of multi-component fibers is cost-intensive, as they require not only an additional starting material but also a more complex manufacturing process.To achieve comparable manufacturing costs with similar product and processing properties, the invention provides for the inclusion of an additional polyolefinic fiber component together with the multi-component fiber in a homogeneous fiber mixture. Surprisingly, the second fiber component also benefits from the supporting properties of the high-melting-point polymer material of the first fiber component. This is sufficient to ensure an adequately airy thickness in the open areas. Contrary to intuition, this can also be achieved by adding a low-melting-point monofiber made of the third polymer material. Simultaneously, the polyolefinic third polymer material contributes to particularly good bond strength in the bonded areas.

[0013] The first polymer material is, in particular, a non-polyolefinic plastic. The flexural stiffness of such a non-polyolefin is generally significantly higher than that of polyolefins. This results in a more voluminous fiber structure. Crimping (curling) by bending the fibers is therefore unnecessary.

[0014] According to one embodiment of the invention, the fiber mixture comprises at least a third fiber component with a chemical and / or physical composition that differs from that of the first and second fiber components. This allows, in particular, further properties of the nonwoven element to be influenced. For example, the third fiber component can be finer (lower fiber titer) than the first and second fiber components. This leads to reduced air permeability. The third fiber component is preferably made of a plastic material, in particular a polyolefinic one.

[0015] Multicomponent fibers, particularly bicomponent fibers of the first fiber component, can be configured as core / sheath fibers or as side-by-side extruded double fibers. Asymmetric multicomponent fiber types are also possible. In core / sheath fibers, the low-melting-point second polymer material is located on the outside.

[0016] In particular, the multi-component fibers are composed of 50 to 75 wt.% of the first polymer material and 25 to 50 wt.% of the second polymer material. Particularly good results can be achieved within the scope of the invention with bi-component fibers and a mixing ratio of 65% to 35%, 60% to 40%, or 50% to 50%.

[0017] According to a preferred embodiment of the invention, the fiber pile is composed of 30% to 50% by weight of the first fiber component. Even a small proportion of the costly multi-component fiber, such as 30%, can be sufficient to produce the desired properties in the fiber pile. The use of the multi-component fiber can thus be reduced to less than half or even less than one-third compared to the pure multi-component fiber.

[0018] The first fiber component, the second fiber component, and possibly a third and further fiber components can each be formed with crimped and / or smooth fibers.

[0019] According to a preferred embodiment of the invention, the fiber mixture consists exclusively of the first fiber component and the second fiber component. No further additives – in particular binders – are required. A multilayer structure is also unnecessary, since the desired structural properties can be achieved with a consistently uniform fiber mixture.

[0020] Preferably, the second and / or third polymer material is selected from the group consisting of polypropylene (PP), polypropylene copolymers, polyethylene (PE), or polyethylene copolymers. PE, PP, and their copolymers are readily available, inexpensive, and easy-to-process polyolefinic plastics. They are characterized by well-controlled melting behavior and exhibit good strength and resistance at room temperature.

[0021] Preferably, a recycled, i.e. reused, raw material can be used as a first, second and / or third polymer material, at least as an admixture.

[0022] In order to specifically modify the material properties - for example, to improve the bond strength to the first polymer material in the multi-component fiber - blends of the aforementioned substances, in particular mixtures of polyethylene and its copolymers or polypropylene and its copolymers, can be used as a second and / or third polymer material.

[0023] In general, up to 5% additives can be incorporated into the first polymer material, the second polymer material, and / or the third polymer material. However, the polymer materials are preferably in a technically pure form.

[0024] According to a particularly preferred embodiment of the invention, both the second and third polymer materials are made of the same material. This improves the bond strength between fibers of the first fiber component and fibers of the second fiber component. Since the polymer materials have similar chemical and physical properties, they are in a similar molten state during thermal processing and bond particularly well to each other in the at least partially molten state.

[0025] In a particularly preferred embodiment, the second and third polymer materials have the same main component. In particular, the formulations of the second and third polymer materials are largely identical with respect to their basic chemical chain structure, except for admixtures not exceeding 10 wt%. The second and third polymer materials may differ with respect to the polymerization process, the degree of branching, the proportion of metallocene polyolefins, and / or the density. However, they are particularly preferably identical.

[0026] Regardless of the specific material chosen, it is particularly preferred that the melting point of the second polymer material and the melting point of the third polymer material differ by no more than 5 K. This allows the second polymer material in the first fiber component and the third polymer material in the second fiber component to be melted to a similar degree at a specific temperature during processing.

[0027] To ensure easy processing – even during fiber formation – the second and third polymer materials are designed to have a melt flow index (MFI) of at least 20 g / 10 min, preferably at least 25 g / 10 min and less than 500 g / 10 min, and particularly less than 100 g / 10 min. This guarantees sufficient fluidity during fiber formation. Simultaneously, the second and third polymer materials can be partially melted during thermal solidification by targeted temperature control, enabling adhesive properties to develop without the fibers or fiber components losing their structure.

[0028] The MFI is determined in particular according to ISO 1133, preferably with a test temperature selected according to the material (190°C in particular for PE, 230°C in particular for PP, 280°C in particular for PET) and test weight (2.16 kg).

[0029] The first polymer material preferably comprises polyethylene terephthalate (PET) as its main component. In particular, the first polymer material is composed entirely of polyethylene terephthalate. This polyester exhibits high mechanical stability and is particularly well-suited for combination with polyolefins in multi-component fibers.

[0030] A polyethylene terephthalate / polypropylene bicomponent fiber combined with a polypropylene monofiber is particularly preferred in the invention. Polypropylene exhibits higher mechanical stability than polyethylene. At the same time, the difference in their melting points is sufficient to allow for controlled melting of the polypropylene components during processing, while maintaining the PET content.

[0031] Another inventive aspect of the present development, independent of the specific material selection, concerns the design of the bonded fiber nap in the open areas. This additional aspect of the invention addresses the problem that hook engagement surfaces made of nonwoven fabric often provide insufficient adhesive strength, particularly against shear stresses. This additional aspect of the invention overcomes this problem through the appropriate selection of the fiber nap properties.

[0032] According to the invention, the fiber nap in the open areas has a fiber density between 1 × 1010 (ten billion) fibers / m³ and 1.5 × 1010 (15 billion) fibers / m³. Preferably, the fiber density is between 11 and 13 billion fibers (1.1 to 1.3 × 1010) per cubic meter. The invention is based on the finding that this parameter is of significant importance for the adhesive properties of hook elements of a hook tape in the nonwoven element according to the invention.

[0033] The fiber density (ρfiber, number of fibers per cubic meter) is obtained by relating the number (Nfiber) of fibers to a reference volume (V) - base area (A) times height (h). ρ Faser = N Faser V = N Faser A ⋅ h

[0034] The number of fibers is calculated from the ratio of the total fiber length (L) to the (average) individual fiber length (Ifiber), where the total fiber length (L) is calculated as the weighted average of the ratios of the basis weight (ρA) of the nonwoven element to the fiber titers (Tti) of the individual fiber components: N Faser = L l Faser = A ⋅ ρ A l Faser ∑ i c i Tt i

[0035] The height (h) of the volume under consideration can be influenced by the roller spacing during the manufacturing process. The resulting bulk height is: h Bulk = ρ A g m 2 ρ Faser 1 m 3 ⋅ l Faser 1 mm ∑ i c i % Tt i g 10.000 m

[0036] Based on the other framework conditions, the fiber density according to the invention can be adjusted as desired.

[0037] Nonwovens and nonwoven products are typically characterized primarily by their basis weight – that is, the mass present per unit area. However, this parameter alone is an unsuitable measure for assessing the quality of a hook engagement surface with regard to its mechanical holding power. Basis weight alone provides no information about how the mass is spatially distributed. Furthermore, this parameter is not related to the length of the individual fibers, which is significant for their integration (via the bonded areas).

[0038] The second inventive aspect is based on the realization that the key parameter for hook engagement is the fiber density of individual nonwoven fibers per unit volume. It has been shown that comparable holding forces can be achieved at the same fiber bulk densities by varying the other parameters. For example, in an existing process, the basis weight, fiber length, and fiber fineness can be predetermined by external boundary conditions. The invention then teaches adjusting the thickness of the open areas (bulk) so that the nonwoven element exhibits a fiber bulk density within the range specified by the invention. The applicant's tests have shown that a particularly good hook engagement force can be achieved within this parameter range, while the other parameters remain variable.

[0039] This works particularly well when the fiber nap has an average fineness (titer) of 1 dtex to 8 dtex, especially 1.3 dtex to 6.7 dtex. Finenesses greater than 2 dtex, especially 2.2 dtex to 6.7 dtex, can be used when good air permeability and breathability are required. A certain degree of air permeability is also necessary if the material is to be held under negative pressure during the manufacturing process. If the nonwoven element is also intended to regulate air and / or water vapor transport, a lower fiber titer between 1.3 dtex and 1.9 dtex must be used.

[0040] Preferably, the nonwoven element has a basis weight between 30 and 60 g / m², particularly between 35 and 45 g / m² (grams per square meter, gsm). Sufficient mechanical stability and adhesive strength can already be provided within this range.

[0041] Preferably, the fiber pile has average fiber lengths between 35 mm and 75 mm, particularly between 38 mm and 72 mm. Due to the fine structure, an average fiber length of preferably between 40 mm and 50 mm is recommended for good workability.

[0042] The fibers of the fiber mixture – in particular the first fiber component and / or the second fiber component – ​​may preferably have a non-circular cross-section – in particular a trilobal cross-section. This allows the desired fiber density to be achieved due to higher stiffness at the same density (dtex) and at a lower basis weight.

[0043] Further inventive aspects of the development concern the pattern formed by the open and bonded areas. These exhibit, in particular, an ellipsoidal shape.

[0044] Starting from one of the preceding claims or the preamble of claim 1, a third inventive aspect provides that the open areas at least partially have a regular pattern consisting of its first shape and a second shape, wherein the first shape has a larger area than the second shape. Both the first shape and the second shape are convex. The convex shape allows a particularly large number of fibers within the area to project into an immediately adjacent bonded area and thus be fixed. This improves the integration of the individual fibers into the nonwoven element. The pulling out of individual fibers when the hook-and-loop fastener is released can therefore be reduced.

[0045] According to one variant, the first and second shapes consist entirely of open areas without any bonded zones within them. According to an alternative variant, a bonding line extending parallel to the edge of the respective shape is arranged within the first shape and / or within the second shape.

[0046] To achieve the greatest possible surface area utilization with many open areas, the first and second forms differ in size. Preferably, the first form is at least twice the size of the second form. Particularly preferably, the size of the first form is approximately five times that of the second form. In a most particularly preferred embodiment, the second form has a surface area of ​​approximately 1 / 10 that of the first form.

[0047] To maintain a uniform appearance, the first and second forms are preferably geometrically similar. This also allows for a shape optimized for fiber adhesion in both cases.

[0048] The first forms are preferably arranged in a grid along a first direction, particularly approximately the longitudinal direction, and in a second direction – preferably perpendicular to it – particularly approximately the transverse direction. In this arrangement, the first forms overlap in both the first and second directions. This allows for continuous hook engagement across the entire length and width of the nonwoven element. Misposition of the hooks relative to the open areas is thus prevented.

[0049] The inclination α between the first direction and the longitudinal direction, or between the second direction and the transverse direction, is preferably no more than 5°. An inclination of no more than 2°, and particularly about 1.2°, is especially preferred.

[0050] The grid dimension - between the centers of adjacent first forms - is preferably between 8 mm and 9 mm, preferably about 8.5 mm in the first direction and preferably between 9 mm and 10 mm, particularly about 9.6 mm, in the second direction.

[0051] The second (smaller) forms are preferably arranged on the same grid between the larger first forms. They thus essentially fill the spaces in the grid of the first forms.

[0052] The first types of shapes are particularly favorably elliptical, with primary axes (largest diameter) and secondary axes (smallest diameter). The second types of shapes are also elliptical, with secondary axes and secondary axes. The primary axes are parallel to each other and perpendicular to the secondary axes of the second types. This allows for particularly good tiling of the nonwoven material with open areas. Simultaneously, the elliptical shape improves fiber adhesion in aligned (carded) nonwoven fibers.

[0053] The first main axes preferably have a size between 6 and 8 mm, in particular approximately 7 mm. The first secondary axes preferably measure 4 to 8 mm, in particular 5 mm. The second main axes preferably measure 2 to 4 mm, in particular 2.7 mm. The second secondary axes preferably measure between 1 and 2 mm, in particular approximately 1.3 mm.

[0054] In a particularly preferred embodiment, the nonwoven element has a single continuous bonded area, between which the first forms and second forms are formed as open areas.

[0055] Advantageously, adjacent first and second forms have a minimum distance of between 0.25 mm and 0.7 mm, particularly approximately 0.4 mm. Such a narrow bonded area between them is sufficient to provide adequate fiber retention. At the same time, the bonded areas—i.e., those not involved in hook engagement—are minimized.

[0056] Another inventive aspect of the development concerns an alternative pattern of the free areas and the bonded areas. This can, in particular, also be combined with the previously described features of the nonwoven element. According to this fourth aspect of the invention, the bonded areas form a line pattern. The line pattern comprises a first group of parallel lines and a second group of parallel lines inclined at an angle β relative to the first group. The lines of the first group and the lines of the second group enclose a plurality of rhomboid cells. Furthermore, the line pattern has at least one elliptical arc—not a full circumferential arc—which is arranged in a cell such that the elliptical arc is tangential to all four lines of the first and second groups enclosing the cell.The line pattern is formed from a multitude of different linear bonded areas. These linear bonded areas have an approximately constant width of less than 1.5 mm and a significantly greater longitudinal extent. Within the pattern according to the fourth aspect of the invention, the open areas form cushion-shaped centers, which are bordered on at least three sides and in a C-shape by the open elliptical arc. Additionally, a diamond-shaped grid is formed by the lines of the first group and the lines of the second group, which encompasses and stabilizes the elliptical arc-shaped line segments. Furthermore, the open areas lying outside the elliptical arcs are subdivided and stabilized by the lines running within them. Due to the tangential connection of the elliptical arc, these areas connect to the diamond pattern in a particularly space-saving and stable manner.

[0057] Preferably, the lines of the first group and / or the lines of the second group are not continuous, so that the lines of the first group and the lines of the second group do not touch. In particular, the bonded area is omitted in the corner areas of the diamond-shaped cells – i.e., at the intersections of the lines of the first group and the lines of the second group – so that an open area is also present there. Thus, a grid of open areas, enclosed by the bonded areas, is also formed within the grid of the diamond-shaped cells. In this case, the bonded line areas also form a continuous pattern across the entire material web of the nonwoven element.

[0058] According to all aspects of the present invention, it is preferably provided that the bonded areas comprise a surface area of ​​between 15% and 30%, and particularly between 20% and 25%, of the area of ​​the nonwoven element. Particularly in conjunction with elliptical pads in the open areas—whether enclosed by an elliptical arc or fully elliptical—it can be mathematically demonstrated that, from a surface area of ​​20% upwards, there is a high probability that a large proportion of the plastic fibers are embedded in the bonded areas and thus secured against being pulled out of the nonwoven element. This achieves the optimal compromise between the largest possible open area and securing all fibers.

[0059] The pattern scaling is preferably chosen such that the fibers randomly arranged in the open areas are highly likely to be held in bonded areas on both sides. It has been shown that separate analysis in the longitudinal (machine direction) and transverse directions is sufficient to predict the pull-out behavior and thus the adhesion properties. It is also sufficient to consider only the largest open areas.

[0060] As an estimate of the probability that a particular fiber oriented longitudinally or transversely is bound only at one end, the ratio of the extent (u) of the open area in this longitudinal or transverse direction at a given location (x) to the fiber length (Ifiber) can be considered. Then the probability (Pbound) of a bound fiber (at a specific location) is given by: P gebunden x = 1 − u x l Faser

[0061] Particularly good fiber adhesion results when – both when considering the longitudinal and transverse directions – the average probability of bonding over the entire open area is... P bound A local binding probability of at least 70%, preferably at least 80%, is achieved. The minimum local binding probability is particularly preferred. min x P gebunden x greater than 70% in both longitudinal and transverse directions, and especially greater than 80%.

[0062] A further independently inventive aspect of the present development lies in the method for producing the nonwoven element. This method allows the production of a previously described nonwoven element according to at least one previously described aspect of the invention. Within the framework of the inventive concept, a fiber nap is first formed and subsequently thermally bonded. A key aspect of the invention is that both air-through bonding (ATB) and thermal calendering are used for bonding. These two bonding methods are typically in exclusive competition with each other and are used alternatively.The inventive concept lies in the fact that – particularly in conjunction with a previously described homogeneous fiber mat consisting of a multi-component fiber and a low-melting-point monofiber – different bonding objectives are pursued and combined: In air-through bonding, a heated airflow is passed through the fiber mat perpendicular to the machine direction and transverse direction. The heated air has a temperature that leads to targeted heating of the fiber mat. According to the invention, the temperature is controlled so that the fibers only melt superficially and are thereby bonded to one another at random points of contact between the individual plastic fibers. The geometric configuration of the fiber mat existing before the air-through bonding process is not changed or only changed to a minor extent.In particular, a loosely stacked fiber pile retains its voluminous and airy structure after fiber formation. Similarly, an ATB (Automatic Fiber Bonding) is effective in the open areas of an already patterned fiber pile. There, the airy structure is consolidated and preserved by the ATB. The second consolidation process – thermal calendering – involves rolling the fiber pile with a structured and heated profile roller. As an alternative to thermal calendering, similar structuring processes, such as ultrasonic bonding, can also be used. Thermal calendering compresses the fiber pile in specific areas, pressing the heated and partially melted fibers together in a confined space. This creates the bonded areas, which anchor the fibers of the fiber pile within the nonwoven element.At the same time, they have low air permeability and limited access for hook elements.

[0063] According to the invention, air-through bonding is performed prior to thermal calendering. In the first bonding step – ATB – the fibers are initially loosely anchored to one another within the pile, so that even under compression during the subsequent calendering, elastic recovery can occur, at least in the open areas. The targeted combination of the two bonding processes allows the nonwoven element to be adapted to the technical requirements. The open areas are made voluminous and held in place by the separate air-through bonding. While they may appear "fluffy" in this state, they have a rather "hard" feel. However, this is irrelevant for the intended application, as the primary concern is the optimal mechanical properties of the hook-and-loop fastener.

[0064] The fiber nap is preferably carded or folded before thermal bonding. This step aligns the fibers of the nap – at least partially – in the direction of the machine. This increases the mechanical stability of the nonwoven element and also improves the likelihood that all fibers will be securely embedded in the bonded areas.

[0065] The aspects of the invention are explained below with reference to drawings that merely illustrate exemplary embodiments. These schematically depict: Fig. 1 a cross-section through a nonwoven element according to the invention, Fig. 2 a top view of a nonwoven element according to the invention with a first pattern, Fig. 3 a top view of a nonwoven element according to the invention with a second pattern and Fig. 4 a schematic representation of a manufacturing process according to the invention.

[0066] The Fig. 1Figure 1 shows a cross-section through a nonwoven element 1 according to the invention. This element has a fiber pile 2 which, in accordance with the first aspect of the invention, is formed from a homogeneous fiber mixture comprising a first fiber component and a second fiber component. In the exemplary embodiment, the first fiber component comprises 50 wt.% of the fiber mixture and is formed from a bi-component fiber with polyethylene terephthalate (PET) as the first polymer material at a weight fraction of 60 wt. (30% of the fiber mixture, corresponding to 3.3 dtex) and polyethylene (PE) as the second polymer material at a weight fraction of 40 wt. (20% of the fiber mixture, corresponding to 2.2 dtex). The melting point of the polyolefinic polyethylene is lower than that of PET. Furthermore, the fiber mixture contains 50 wt.% (corresponding to 1.9 dtex) of a polypropylene (PP) monofiber.

[0067] The nonwoven element forms a web of material extending in a longitudinal direction (machine direction, MD) and a transverse direction (CD). Perpendicular to this web plane, the nonwoven element has a thickness d1,d2 (bulk) measured in a vertical direction H, which varies locally along the web.

[0068] The nonwoven layer has a pattern of open areas 3 with a first thickness d1, which are surrounded by bonded areas 4 with a smaller second thickness d2. In the bonded areas 4, the plastic fibers 5 of the fiber pile 2 are compressed and, in the compressed state, bonded to one another by partial melting of the fibers 5. Within the bonded areas 4, almost all of the fibers 5 extending into them are firmly bonded to one another by at least one bonding point and are thus securely held within the fiber pile 2.

[0069] Within the open areas 3, the fibers 5 are only loosely attached to one another at random intersection points 6. The connection points 6 do not reliably prevent individual fibers 5 from being pulled out. However, they serve to maintain the structure of the open area 3, in particular to form the preset height d 1. This height is selected such that, for a given fiber fineness, basis weight, and average fiber length, a preferred fiber density of 1.2 × 10< fibers / m 3< is achieved in the open areas 3. The open areas 3 serve as the engagement point for hook elements 7 of an associated hook strip 8, which are embedded in a carrier layer 8a. The hook strip 8, together with the nonwoven element 1, forms a hook-and-loop fastener, with the nonwoven element 1 forming a hook engagement surface with the open areas 3.

[0070] In the Fig. 2The top view of a nonwoven element 1 shows a first possible pattern of the open areas 3 and bonded areas 4. The open areas 3 form a regular pattern consisting of a convex first shape 9a and a convex second shape 9b. The first shape 9a has an area ten times larger than the second shape 9b. These shapes are geometrically similar to each other, forming ellipses, and are arranged in a grid along a first direction L1 and a second direction L2. The first shapes 9a overlap in both directions. In the illustrated embodiment, there is an inclination α of 1.2° between the first direction L1 and the longitudinal direction MD, as well as between the second direction L2 and the transverse direction CD. This slight inclination offers advantages in production, particularly when using profile rollers.

[0071] The first shapes 9a each have an elliptical shape with parallel principal axes a1 of approximately 7 mm and minor axes a2 of approximately 5 mm. The second shapes 9b also have an elliptical shape with principal axes b1 of approximately 2.7 mm and minor axes b2 of approximately 1.3 mm. The principal axes a1 and b1 of the ellipses are approximately perpendicular to each other. The grid spacing between the first shapes 9a and the second shapes 9b is (center to center) s2 = 9.6 mm in the second direction L2 and s1 = 8.5 mm in the first direction L1. In this pattern, the bonded areas 4 comprise approximately 20% of the surface area, and the open areas comprise approximately 80%. The first forms 9a alone account for approximately 70% of the total area. The minimum distance d between two adjacent first forms 9a, or between first forms 9a and adjacent second forms 9b, is approximately...0.4 mm.

[0072] The Fig. 1 can be seen as a cut through Fig. 2 along line AA.

[0073] The Fig. 3Figure 1 shows an alternative pattern in accordance with a further inventive aspect of the present application. The bonded areas 4 form a line pattern. The line pattern comprises a first group of parallel lines 10a and a second group of parallel lines 10b inclined at an angle β to the lines of the first group 10a. The lines of the first group 10a and the lines of the second group 10b are interrupted such that breaks are provided at the intersection points 11, which are not bonded but open areas 3. Outside the intersection points 11, the lines of the first group and the second group 10a, 10b are continuous. The lines of the first group 10a and the lines of the second group 10b are each arranged equidistantly such that they enclose rhombus-shaped cells 12, the corners of which are formed by the intersection points 11.The side edges of the diamond-shaped cells 12 are each formed by uninterrupted sections of lines of the first group 10a and lines of the second group 10b.

[0074] Within each of the diamond-shaped cells 12, a partially circumferential elliptical arc 13 of the line pattern is arranged. This arc tangentially touches the line segments surrounding the cell 12. In the illustrated embodiment, the elliptical arc 13 is designed such that a complete quadrant is omitted between the points of contact of two adjacent edge segments. Within the elliptical arc 13, a cushion-shaped section 14 of an open area 3 is formed, which, due to the interruption of lines 10a, 10b at the intersection point 11, also connects seamlessly to open areas 15 outside the elliptical arcs 13 in adjacent cells 12. The width b of the cushion-shaped section 14 is approximately 12 mm in the exemplary embodiment. The height h of the cushion-shaped section 14 at the maximum height of the elliptical arc 13 is approximately 8 mm.

[0075] The Fig. 4Figure 1 schematically illustrates a manufacturing process according to the invention. In a first step I, a fiber mixture, in particular a homogeneous fiber mixture consisting of a multi-component fiber and a low-melting-point monofiber, is produced. The staple fibers 16 laid in this way are first fed to a carding machine 17 and roughly aligned there. The carded fiber web 18 is then subjected to a first thermal bonding II by air-through bonding (ATB). In this process, the carded fiber web 18 is transferred via a suction roller 19 to a large drum 20 into which a continuous hot air stream 21 enters. The temperature of the hot air stream 21 is selected such that the fibers of the fiber web 18 melt superficially and bond to one another at random points of contact 6. The pre-bonded fiber web 23 is removed from the drum 20 via a second roller 22, which is optionally equipped with a cooling function.

[0076] The pre-consolidated fiber web 23 is then fed through the roller gap between two rollers 24, at least one of which is profiled, for thermal calendering III. By appropriately temperature-controlling the rollers 24, the pre-consolidated fiber web 23 is compressed and melted more intensely, at least in certain areas—specifically, in the areas 4 that will later be bonded. This creates the pattern of open areas 3 and bonded areas 4. The geometry of the embossed pattern can be determined by the patterning of the profiled rollers 24. The finished nonwoven element 1 can then be wound onto a roll 25.

Claims

1. A non-woven element (1) for forming at least one hook-engagement surface for a hook-and-loop fastener, the element comprising at least one non-woven layer formed from a fibre web (2) that extends in a machine direction (MD) and a cross direction (CD) and has a thickness (d1, d2) perpendicular thereto, wherein the fibre web (2) comprises a plurality of polymer fibres (5), wherein the non-woven layer (1) has a pattern made up of open regions (3) for engagement of hook elements (7) of a hook-and-loop fastener and bonded regions (4) surrounding the open regions (3) and having a smaller thickness (d2), wherein the fibre web (2) is formed from a homogeneous fibre blend having a first fibre component and a second fibre component, the first fibre component constituting 20 wt% to 80 wt% of the fibre blend and being formed of multicomponent fibres, in particular bicomponent fibres, having a first polymer material and a polyolefinic second polymer material, the melting point of the first polymer material being higher than the melting point of the second polymer material, and wherein the fibre blend has as the second fibre component a monocomponent fibre consisting of a polyolefinic third polymer material, characterized in that the fibre web (2) in the open regions (3) has a fibre volume density between 1.0 × 1010 fibres / m3 and 1.5 × 1010 fibres / m3.

2. The non-woven element (1) according to claim 1, characterized in that the fibre blend comprises 30 wt% to 50 wt% of the first fibre component.

3. The non-woven element (1) according to claim 1 or 2, characterized in that the fibre blend consists solely of the first fibre component and the second fibre component.

4. The non-woven element (1) according to any one of claims 1 to 3, characterized in that the second polymer material and / or the third polymer material is selected from the group consisting of polypropylene (PP), polypropylene copolymers, polyethylene (PE) or polyethylene copolymers.

5. The non-woven element (1) according to claim 4, characterized in that both the second polymer material and the third polymer material are selected from the same group.

6. The non-woven element (1) according to any one of claims 1 to 5, characterized in that the melting point of the second polymer material and the melting point of the third polymer material differ by no more than 5 K.

7. The non-woven element (1) according to any one of claims 1 to 6, characterized in that the second polymer material and the third polymer material have a melt flow index (MFI) between 20 g / 10 min and 500 g / 10 min.

8. The non-woven element (1) according to any one of claims 1 to 7, characterized in that the first polymer material is polyethylene terephthalate (PET).

9. The non-woven element (1) according to any one of claims 1 to 8, characterized in that the fibre web (2) in the open regions (3) has a fibre volume density between 1.1 × 1010 fibres / m3 and 1.3 × 1010 fibres / m3.

10. The non-woven element (1) according to any one of claims 1 to 9, characterized in that the fibres of the first fibre component and / or the fibres of the second fibre component have a non-round, in particular trilobal, cross section.

11. The non-woven element (1) according to any one of claims 1 to 10, characterized in that the fibre web (2) has an average fineness (titre) of 1 dtex to 8 dtex, in particular 1.3 dtex to 6.7 dtex.

12. The non-woven element (1) according to any one of claims 1 to 11, characterized in that the non-woven element (1) has a basis weight between 30 and 60 g / m2, in particular 40 to 50 g / m2.

13. The non-woven element (1) according to any one of claims 1-12, characterized in that the open regions (3) at least in part have a regular pattern of a convex first shape (9a) and a convex second shape (9b), wherein the first shape (9a) has a larger area than the second shape (9b).

14. The non-woven element (1) according to claim 13, characterized in that the first shape (9a) and the second shape (9b) are geometrically similar.

15. The non-woven element (1) according to any one of claims 13 or 14, characterized in that the first shapes (9a) are arranged in a grid along a first direction, in particular the machine direction, and a second direction, in particular the cross direction, and that the first shapes (9a) overlap in both the first and the second direction.

16. The non-woven element (1) according to any one of claims 13 to 15, characterized in that the first shapes (9a) are elliptical with first major axes (a1) and first minor axes (a2) that are in particular arranged parallel to one another and that the second shapes (9b) are elliptical with second major axes (b1) and second minor axes (b2) that are in particular arranged parallel to one another, and that the first major axes (a1) are oriented parallel to one another and each approximately perpendicular to the second major axes (b1).

17. The non-woven element (1) according to any one of claims 13 to 16, characterized in that the bonded region (4) is continuous / contiguous between the first shapes (9a) and the second shapes (9b).

18. The non-woven element (1) according to any one of claims 13 to 17, characterized in that the adjacent first areas and second areas have a minimum spacing between 0.25 mm and 0.7 mm, in particular 0.4 mm.

19. The non-woven element (1) according to any one of claims 1 to 12, characterized in that the bonded regions (4) form a line pattern, the line pattern comprises a first group of parallel lines (10a) and a second group of parallel lines (10b) inclined by an angle (β) relative to the first group, the lines of the first group (10a) and the lines of the second group (10b) enclose a plurality of rhombic cells (12) and the line pattern has at least one non-closed elliptical arc (13) arranged in a cell, in such a manner that the elliptical arc (13) lies tangentially against all four lines of the first group (10a) and the second group (10b) that enclose the cell.

20. The non-woven element (1) according to claim 19, characterized in that the lines of the first group (10a) and / or the lines of the second group (10b) are discontinuous and the lines of the first group (10a) and of the second group (10b) do not touch one another.

21. The non-woven element (1) according to claim 19 or 20, characterized in that in each of the rhombic cells (12) a non-closed elliptical arc (13) is arranged so as to lie tangentially.

22. The non-woven element (1) according to any one of claims 1 to 21, characterized in that the bonded regions (4) account for between 15% and 30%, in particular between 20% and 25%, of the area of the non-woven element (1).

23. A method for producing a non-woven element (1) according to any one of claims 1 to 22, wherein a fibre web (2) is first formed and subsequently thermally consolidated, characterized in that both air-through bonding (ATB; II) and thermal calendaring (III) are employed, and the air-through bonding (II) is performed before the thermal calendaring (III).

24. The method according to claim 23, characterized in that the fibre web (2) is garnetted and / or carded prior to thermal consolidation.

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