Apparatus and method for producing non-isotropic fiber oriented nonwoven fabric

Abstract

The present invention relates to a device and a method for producing a nonwoven fabric with a non-isotropic fiber orientation, i.e., a fiber orientation that is directional, unlike classical random lay-ups where an isotropic fiber orientation prevails.

Description

[0001] The present invention relates to a device and a method for producing a nonwoven fabric with a non-isotropic fiber orientation, i.e., a fiber orientation that is directional, unlike classical random lay-ups where an isotropic fiber orientation prevails.

[0002] Classical wet-forming process technology for the production of nonwovens from staple fibers or from a short-fiber template (e.g., pulp) typically produces a quasi-isotropic, randomly distributed nonwoven structure. This means that it is usually desirable for the resulting wet-formed nonwoven products to exhibit a nearly uniform fiber orientation within the plane of the nonwoven in all directions. If variations in fiber orientation do occur in individual cases, these exhibit very low degrees of anisotropy, are represented globally across the nonwoven structure, and are only oriented in the take-up direction (or an orientation perpendicular to it).

[0003] There are numerous applications for which it is of great interest that a nonwoven web produced using wet nonwoven technology has a fiber orientation that can be modified as locally as possible in a wide range of degrees of freedom.

[0004] Two methods are known from the state of the art that focus on a similar target product and are currently in active use. The core technological aspects and their limitations or delimitations are briefly summarized below: HiPerDiF technology (University of Bristol or company "LINEAT Composites"):

[0005] The technology is used to produce thin nonwoven webs consisting of individual filaments arranged quasi-parallel in a highly fiber-preferred longitudinal direction. The implementation of the patented process has been successfully demonstrated with various technical staple fibers (including glass and carbon fibers). For the past few years, the further economic development and commercialization of the HiPerDiF technology has been pursued through a spin-off startup (LINEAT Composites).

[0006] A disadvantage of the previously described HiPerDiF technology is that nonwoven webs have currently only been demonstrated up to a width of approximately 150 mm, with significantly greater system complexity and hardware limitations becoming apparent with wider webs. The technology presented in this invention disclosure has already been successfully demonstrated for a web width of 600 mm and is relatively easy to scale up considerably further with regard to the nonwoven web width.

[0007] While HiPerDiF also utilizes staple fibers from technical fiber material classes (e.g., carbon, glass fibers), the process requires these fibers to be of high cutting quality (i.e., uniform fiber length, clean cut edge, etc.), as otherwise quality losses result or processing is impossible altogether. This is particularly true when dealing with discontinuous fiber stocks, i.e., fiber length distributions, such as in the case of recycled fiber stocks or natural fibers. Fiber orientation in HiPerDiF is limited to a parallel alignment in the take-up direction and a globally uniform orientation across the entire web. TUFF technology (University of Delaware):

[0008] The technology is used to produce flat web materials with a relatively low basis weight in the form of nonwovens, in which all individual filaments exhibit a high degree of fiber alignment. Successful demonstrations have already been carried out with various technical fibers (including carbon fibers).

[0009] As with HiPerDiF technology, TUFF technology also has a significant limitation regarding the necessarily high initial quality of the fiber feedstock (cutting quality, short fiber length, fiber length distribution), resulting in a corresponding restriction on the processing of recycled or natural fiber feedstocks. Furthermore, productivity, i.e., the achievable material throughput rate, is limited, particularly with the relatively low basis weights of the nonwovens produced. Overall, the chosen process routes for HiPerDiF and TUFF technology are similar in several aspects, resulting in several comparable restrictions.

[0010] While TUFF has demonstrated an almost freely selectable fiber orientation range from 90° (angle measurement relative to the take-up direction; seemingly optimal application) to approximately 30° (angle measurement relative to the take-up direction), a 0° orientation (angle measurement relative to the take-up direction – i.e., in the web direction) is not known and likely not feasible based on the technological principle used. The fiber orientation is uniform across the entire width of the nonwoven web and therefore cannot be locally modified.

[0011] The object of the present invention is therefore to provide, starting from the prior art, a device and a method for producing a nonwoven fabric with a non-isotropic fiber orientation that avoids the aforementioned disadvantages and restrictions. In particular, a continuously operating process for producing nonwoven fabrics should be enabled, and the restrictions encountered in the prior art, especially with regard to the web width of the produced nonwoven fabric web, the process window of the process, adjustable fiber orientation ratios or angular dimensions, and processable fiber templates, should be avoided.

[0012] This problem is solved with respect to a device having the features of claim 1, and with respect to a method having the features of claim 18. The respective dependent claims represent advantageous further developments.

[0013] According to a first aspect, the present invention thus relates to a screen belt (10) that can be guided in a transport direction (T), a nonwoven formation zone (20) arranged above the screen belt in which a suspension (S) of fibers (F) in a suspension medium can accumulate on the screen belt, a dewatering box (30) arranged below the screen belt in the area of ​​the nonwoven formation and dewatering zone (20), on the upper side of which a flow support (40) is arranged directly below the screen belt in an operating state of the device and which has a plurality of dewatering openings (41), and a device for generating a negative pressure in the dewatering box, characterized in that the dewatering openings (41) each have a length and a width (b) in projection onto the screen belt (10), wherein the ratio of length to width (b) is at least 2, wherein an angle which is from a direction,which is defined by the length of a drainage opening and includes the direction of transport, and has an amount between 0° and 65°.

[0014] The device according to the present invention is thus based on a nonwoven laying machine, which in the prior art is generally used to carry out a continuous wet nonwoven process. A characteristic feature of the device according to the invention is a flow support arranged directly below a screen belt in the nonwoven formation zone, which has a plurality of drainage openings. The drainage openings each have a length and a width, with the ratio of length to width being at least 2. The length of a drainage opening is understood to be the maximum dimension in a longitudinal direction, and the width is understood to be the maximum dimension in a transverse direction of the drainage opening.For example, if the drainage opening has a rectangular shape, the longitudinal direction corresponds to the orientation of the drainage opening along the long side, and the width corresponds to the orientation of the drainage opening along the short side. The drainage openings are therefore arranged at an angle between 0° and 65° relative to a transport direction, where this angle is the angle between the orientation of the long side and the transport direction.

[0015] During operation of the device, i.e., when a suspension of fibers is applied to the screen belt and, in the area of ​​the dewatering box, is drawn through the screen belt by applying a vacuum in the dewatering box and / or forced through it by applying a pressure gradient and / or flows through it due to other effects (e.g., gravity), the flow of liquid through the dewatering openings is influenced in such a way that the fibers contained in the suspension are oriented by the flow in a direction corresponding to the preferred direction of the dewatering opening. Thus, a non-isotropic deposition of the fibers occurs, resulting in a preferred direction that corresponds to the orientation of the dewatering openings. A completely isotropic deposition of the fibers is therefore avoided.The resulting fiber web (in which the individual fibers are not yet bound) can be solidified into a nonwoven fabric by binding the fibers, e.g. in a web binding step or by means of additives.

[0016] With a device according to the invention, the disadvantages known from the prior art can be effectively avoided: The practicality of the present invention has already been successfully demonstrated using a web width of 600 mm and can be scaled further relatively easily with regard to the laying width.

[0017] Furthermore, the present device and the inventive method described below are significantly more robust than the technology known from the prior art described above and can also be used for discontinuous fiber templates. This allows for a significantly more heterogeneous selection of processable fiber length distributions and also greater flexibility with regard to the generally processable fiber length, which can also be considerably higher.

[0018] The currently demonstrated productivity with regard to take-off speed (in addition to the reduced web width) is significantly lower for HiPerDiF and TUFF than for the process speed described in the present invention disclosure. Thus, a significantly higher material throughput is achieved.

[0019] Furthermore, the present invention allows manipulation of the fiber orientation with higher degrees of freedom and potentially also in locally different forms.

[0020] An advantageous embodiment of the present invention provides that the angle is a value of 0° to 65°, more preferably 0° to 45°, more preferably 0° to 30°, more preferably 0° to 15°, more preferably 0° to 10°, and in particular 0°.

[0021] It is further preferably provided that the ratio of length to width (b) of the drainage openings is 2 to 1200, preferably 5 to 500, more preferably 8 to 100, in particular 12 to 30.

[0022] In particular, the drainage openings (41) are arranged in at least one group of n successive rows in the transport direction (T), where n is an integer greater than or equal to 1, preferably 1 to 10, more preferably 1 to 6, more preferably 1 to 4, and in particular 1 to 3. The drainage openings can thus be arranged in one, but also in 2, 3, 4, 5, 6, 7, 8, 9 or 10 successive rows in the transport direction.

[0023] Preferably, the drainage openings (41) within each row are arranged equidistantly (d) perpendicular to the transport direction (T).

[0024] A further preferred embodiment provides that the drainage openings (41) within each row are arranged in an identical position in the transport direction (T).

[0025] In the event that multiple rows of drainage openings are present, the rows are spaced apart in the transport direction (T), the spacing preferably being 0.01 to 1.0 times, more preferably 0.02 to 0.5 times, further preferably 0.05 to 0.3 times, and in particular 0.08 to 0.15 times, the length of the drainage openings. The spacing of the rows is measured in the transport direction, e.g., the distance between the drainage openings of one row and the adjacent row.

[0026] It may also be preferable to provide that each row within a group has the same number of drainage openings.

[0027] According to a particularly preferred embodiment, drainage openings (41) are arranged in each row within a group, each having the same width (b) and arranged equidistantly perpendicular to the transport direction (T), wherein a dimension of an interval (a) of the drainage openings (41) relative to each other perpendicular to the transport direction is defined as a = n − 1 / n ⋅ B − b / x − 1 where x is an integer from 5 to 200, preferably 7 to 50, particularly preferably 10 to 40, n is the number of rows (at least 2), b is the width of a drainage opening, B is a total width of all drainage openings in each row.

[0028] This design allows the entire surface of the flow substrate to be mapped using multiple rows.

[0029] According to this preferred embodiment, it is preferably provided that b is defined as b = (y / n) · d, where d is a distance of a drainage opening to an adjacent drainage opening of a row perpendicular to the transport direction (T) and y is a real number between 1 and 2.

[0030] It is further advantageous that the drainage openings in a second row (i+1) following a first row (i) are arranged offset perpendicular to the transport direction (T) with respect to the positioning of the drainage openings of the first row (i).

[0031] Provided that the drainage openings are arranged in a staggered manner, several rows of fibers can be laid down in the transport direction, so that, with a suitably chosen offset, complete coverage of the screen belt with essentially non-isotropically oriented fibers is possible.

[0032] However, embodiments are also possible in which the sieve belt is not completely covered, for example by omitting one or more of the rows in which the flow openings are offset from each other, or by using a non-equidistant arrangement of the flow openings in the respective rows.

[0033] In particular, it is provided that the offset has an amount z / n·b perpendicular to the direction of transport, where z is an integer from 1 to n-1.

[0034] Particularly preferably, the drainage openings are arranged such that the projection of all drainage openings of a group of drainage openings onto a plane that intersects the transport direction (T) perpendicularly results in a recess.

[0035] Alternatively, it is also possible for the flow substrate to have only a series of drainage openings. For example, strip-shaped fiber fleeces can be produced, with the fibers in the strips exhibiting a preferred orientation.

[0036] The drainage openings may have a slit-shaped, oblong, elliptical, trapezoidal, triangular, curved or serpentine elevation when projected onto the screen belt, or an elevation in the form of a combination of the preceding features.

[0037] Preferably, all drainage openings have the same elevation, i.e., an identical amount of extension in the transport direction (T) and an identical amount of extension perpendicular to the transport direction (T).

[0038] This restriction can apply to all drainage openings within each group, but also to all drainage openings attached to the flow support.

[0039] The length of the drainage openings is preferably from 1 to 600 mm, preferably 5 to 400 mm, more preferably 7 to 200 mm, more preferably 10 to 100 mm, and in particular 15 to 70 mm.

[0040] Furthermore, it is possible that the width of the drainage openings is from 0.5 to 50 mm, preferably 1 to 40 mm, more preferably 1.5 to 25 mm, and in particular 2 to 10 mm.

[0041] The width of the screen belt can be variable, but a particular advantage of the present invention is that it is scalable to large nonwoven laying machines. For example, the width of the screen belt can be between 0.01 and 14 m, more preferably between 0.01 and 10 m, more preferably between 0.01 and 7 m, more preferably between 0.01 and 3 m, and in particular between 0.01 and 1.5 m, but is not limited to this.

[0042] In the area of ​​the fleece formation and drainage zone, the sieve belt and the flow support arranged below it are preferably arranged at an incline, so that the sieve belt runs upwards in the transport direction during operation, i.e. uphill, but the invention is not limited to this.

[0043] The present invention further relates to a method for producing a nonwoven fabric with a device described above, comprising the following steps: forming a fiber suspension (S) by suspending fibers (F) in a liquid dispersion medium, continuously accumulating the fiber dispersion onto a screen belt guided in a transport direction (T) in the nonwoven formation and dewatering zone, dewatering the dispersion medium by the moving screen belt in the nonwoven formation and dewatering zone, wherein the fibers (F) remain on the moving screen belt forming a fiber web (FV), drying and solidifying the fiber web (FV) to form the nonwoven fabric, wherein the solidification can also take place before drying.

[0044] The accumulation of the liquid dispersion medium on the screen belt can be such that, in the area of ​​the fleece formation and dewatering zone, the dispersion medium accumulates across the entire surface of the screen belt – and thus also completely within the area of ​​the flow support layer located below. However, it is also possible that only partial accumulation occurs, so that the dispersion medium may only accumulate on a portion of the flow support layer.

[0045] In particular, fiber dispersions are used in which the concentration of the fibers used is from 0.01 to 15 g / l, preferably 0.02 to 10 g / l, more preferably 0.05 to 5 g / l, and particularly preferably 0.1 to 2 g / l.

[0046] Drainage can be achieved, for example, by creating a negative pressure in the drainage box, or alternatively by creating a back pressure above the drainage box (or, if necessary, by both measures simultaneously).

[0047] The feed of the screen belt is set in the transport direction, particularly at speeds of 0.05 to 2500 m / s, more preferably from 0.1 to 800 m / s, more preferably from 0.1 to 300 m / s, more preferably from 0.1 to 150 m / s, more preferably from 0.1 to 80 m / s, more preferably from 0.1 to 30 m / s, and most preferably from 0.1 to 5 m / s.

[0048] Exemplary fibers that can be used for the purposes of the present invention are selected from the group consisting of carbon fibers, glass fibers and other mineral fibers (e.g. microglass fiber, rock wool), ceramic fibers, natural fibers (e.g. flax, hemp, cellulose, sisal, jute, kapok, abaca, cotton), viscose fibers, basalt fibers, aramid fibers, polymer fibers, metal fibers, recycled fibers (e.g. textile fibers, recycled carbon and glass fibers, short fiber dusts), as well as mixtures thereof and modifications thereof (e.g. fiber coatings, co-polymer fibers or split fibers).

[0049] The fiber lengths that can be selected can have an average length of 0.1 to 100 mm. Exemplary methods for determining the average fiber length include DIN EN ISO 22314:2023 (for fiber lengths up to 7.5 mm) or image analysis methods, for example according to ISO 13322-1:2014 or ISO 9276-2:2018.

[0050] Preferred diameters of the fibers used are in a range of 0.1 µm to 500 µm, which can also be determined using the aforementioned methods.

[0051] The present invention is described in more detail below, without limiting the invention to the specific parameters shown.

[0052] The present invention enables the manipulation of local flow conditions in the area of ​​the "headbox" of the wet nonwoven machine by means of a modified flow pad (also referred to as a "flow pad") located below the circulating screen of a wet nonwoven laying device. By locally adapting this flow pad to its geometry and material properties, the dispersing media flowing through it can be controlled in a wide range of degrees of freedom. The fibers transported in the dispersing medium can thus also be controlled along the local flow conditions. The dispersed fibers move along with the outflowing dispersing medium and are deposited at a specific point on the circulating screen. The deposited fibers form a cohesive structure in the form of a web. This can be, for example, a closed nonwoven surface or in the form of several parallel, individually produced nonwoven webs (e.g.,Non-woven fabric strips or tapes) are shown.

[0053] The fibers are fixed in a deposit position that is directly defined by the flow support located beneath the circulating screen. The relative force acting between the fiber-carrying dispersion and the circulating screen is explicitly not the primary focus or the sole manipulation effect.

[0054] The present invention allows for a significantly increased degree of freedom in structuring the laid-down discontinuous web material. In principle, a wide variety of flow states – i.e., local structuring – can be achieved across the length, thickness, and width of the nonwoven fabric at high local resolution. Simultaneously, the production of a homogeneous web material – uniformly oriented along an axis – is also feasible. An additional feature of high application relevance is the significantly greater robustness of this approach compared to alternative concepts. Thus, a high degree of freedom is also available with regard to processable material templates. This freedom relates both to the material class of the fiber (e.g., carbon, glass, polymer, ceramic, or natural fibers) and its properties (fiber length, fineness, surface area, ductility).As a result of this high flexibility, it is also possible to process material templates that intrinsically exhibit no variation range, such as recycled fiber templates (e.g., wide fiber length distribution) or natural fibers (e.g., naturally occurring variation in fineness, surface, length, etc.).

[0055] Using the selected process variant and the devices shown, individual filaments (or fiber bundles) dispersed in an aqueous medium can be selectively manipulated during the wet nonwoven fabric formation process. This allows for the controlled production of nonwovens with locally defined fiber orientations, i.e., nonwoven structure or even higher-level structuring. The advantage lies in the creation of a novel material structure with innovative structural and functional properties.

[0056] Since the focus is on a flexibly adjustable material structure with a high degree of freedom, a relatively wide range of applications across various fields is conceivable even from today's perspective. Some key areas of application are summarized below: Structural use:

[0057] The combination of discontinuous fibers and / or staple fibers in a macroscopic nonwoven structure with adapted structuring, i.e., local or global fiber orientation, opens up novel structural performance spectra, specifically, for example: Tailor-made properties along defined load paths close to the level of unidirectional local reinforcement; structural design not only layer by layer, but even adjustable within individual layers or potentially even at the filament level; increased elongation due to the flexibility of the non-continuous fiber filaments; increased drapability due to the flexibility of the non-continuous fiber filaments; innovative damping properties, e.g., under cyclic loading Functional use:

[0058] The functional properties are also adjustable in many areas and / or, based on the innovative material structure, possess novel profiles depending on the degree of anisotropy: Electrical conductivity / insulation, thermal conductivity / insulation, heat-dependent properties (e.g., thermal expansion), permeability and modifiable surface, compactibility

[0059] Specifically, various potential fields of application can already be derived from this today, including in the areas of nonwoven technology and fiber composite technology: Fiber-reinforced composites with a wide range of applications: High-quality processing of recycled fibers or discontinuous natural fiber templates, as well as primary fibers. Electrochemical applications, such as battery separators, gas diffusion layers, membranes, filters, transfer layers, reaction layers, electrodes. Electrical applications, such as EMI shielding, surface heating elements. Component structures with complex geometries requiring a high degree of drapability and / or ductility. High-volume production of components due to short cycle times resulting from potentially "metal-like" deep-drawing properties.

[0060] The present invention is explained in more detail with reference to the following figures.

[0061] Figure 1Figure 1 shows a section of a flow support 40 used in a device according to the invention for producing a nonwoven fabric with fiber orientation. A plurality of drainage openings 41 are shown, arranged successively in five rows (n=1...5) in the transport direction T. The drainage openings 41 each have a width b, which represents the recessed area. Within each row n, the drainage openings 41 are arranged equidistantly at a distance d from each other, the distance d being determined according to the design of the flow support 40. Figure 1 each measurement is taken from the left end of the drainage openings 41.

[0062] The drainage openings 41 are oriented with their longitudinal extent parallel to the transport direction T of a Figure 1The drainage openings are aligned with the sieve belt 10 (not shown). Each drainage opening has a rectangular cross-section, with the corresponding corners of the drainage openings being uniformly rounded. The total width over which the drainage openings 41 extend in the flow support 40 is determined according to... Figure 1 The area that extends is marked with B.

[0063] It can be seen that in each row n the equidistantly arranged drainage openings 41 are offset from the preceding row, with the exemplary offset in the case in Figure 1 twice the respective width b of each drainage opening 41.

[0064] The staggered arrangement of the drainage openings across the five rows ensures that the entire width of the sieve belt 10 is covered with drainage openings 41.

[0065] Figure 2shows the arrangement of a flow support 40 in a Figure 2 Schematically depicted device for the production of a nonwoven fabric. It is visible how the suspension S with fibers F is guided onto a screen belt 10 and accumulated there. The screen belt 10 is continuously guided in the transport direction T. Over the (in Figure 2 The suspension medium of the fibers (e.g., water) flows through the drainage openings 41 of the flow support 40 (not visible, as they are shown laterally) into the nonwoven formation and drainage zone 20, for example, a drainage box 30 located below the flow support 40. The fibers F remain on the screen belt 10 and form a fiber nonwoven FV there.

[0066] In Figure 3The flow situation that occurs at each drainage opening 41 in the flow support 40 is shown. The suspension S with the fibers F is thereby placed on the sieve belt 10 (in Figure 3 (not shown) accumulates, the suspension medium flows through the drainage openings 41 (in the example of the Figure 3 (Only one drainage opening 41 is shown) of the flow support 40 into the drainage box 30 below (see Figure 2 This results in flow conditions as shown by the grey arrows in Figure 3 This illustrates what – without being bound to a specific theory – leads to an anisotropic orientation of the fibers, and in the exemplary case of the Figure 3 This results in the fibers F being essentially oriented in the transport direction T.

[0067] In Figure 4 Exemplary geometric designs of drainage openings 41 are shown; the two on the left are preferred. Figure 4 The drainage openings shown are shown. The width b of each drainage opening is the maximum dimension of a drainage opening perpendicular to the longitudinal extent.

[0068] In Figure 5 Examples of nonwoven fibers are shown, which are combined with a flow-through substrate according to Figure 1 were produced. However, only a part that is purely filled with the suspension was produced (in the example case of the one in Figure 5 (The illustrated nonwovens: two to three rows) to illustrate the effect of the present invention. This allows linear rows of laid-down fibers to be produced in which the fibers are oriented essentially in the transport direction and thus have anisotropic orientation.

Claims

1. Device for producing a nonwoven fabric with fiber orientation, comprising a screen belt (10) that can be guided in a transport direction (T), a nonwoven formation zone (20) arranged above the screen belt in which a suspension (S) of fibers (F) in a suspension medium can accumulate on the screen belt, a drainage box (30) arranged below the screen belt in the area of ​​the nonwoven formation and drainage zone (20), on the upper side of which a flow support (40) is arranged directly below the screen belt in an operating state of the device, which has a plurality of drainage openings (41) so that the drainage of the suspension medium through the drainage openings into the drainage box is ensured, characterized by the fact thatthe drainage openings (41) each have a length and a width (b) in projection onto the screen belt (10), wherein the ratio of length to width (b) is at least 2, and wherein an angle between 0 and 65° enclosed by a direction defined by the length of a drainage opening and the transport direction is .

2. Device according to claim 1, characterized by the fact that the angle is a value of 0° to 65°, more preferably 0° to 45°, more preferably 0° to 30°, more preferably 0° to 15°, more preferably 0° to 10°, in particular 0°.

3. Device according to one of the preceding claims, characterized by the fact that the ratio of length to width (b) of the drainage openings is 2 to 1200, preferably 5 to 500, more preferably 8 to 100, in particular 12 to 30.

4. Device according to one of the preceding claims, characterized by the fact thatthe drainage openings (41) are arranged in at least one group of n successive rows in the transport direction (T), wherein n is an integer greater than or equal to 1, preferably 1 to 10, more preferably 1 to 6, more preferably 1 to 4, in particular 1 to 3.

5. Device according to the preceding claim, characterized by the fact that the drainage openings (41) within each row are arranged perpendicular to the transport direction (T) equidistant (d) and / or in the transport direction (T) at an identical position.

6. Device according to one of claims 4 to 5, characterized by the fact that the rows are spaced apart in the transport direction (T), the distance preferably corresponding to 0.01 to 1.0 times, more preferably 0.02 to 0.5 times, more preferably 0.05 to 0.3 times, in particular 0.08 to 0.15 times the length of the drainage openings.

7. Device according to one of claims 4 to 6, characterized by the fact thatEach row within a group has the same number of drainage openings.

8. Device according to any one of claims 4 to 7, characterized by the fact that in each row within a group x drainage openings (41) are arranged, each having the same width (b) and being equidistant perpendicular to the transport direction (T), wherein a dimension of an interval (a) of the drainage openings (41) to each other perpendicular to the transport direction is defined as a = n − 1 / n ⋅ B − b / x − 1 where x is an integer from 5 to 200, more preferably 7 to 50, particularly preferably 10 to 40, n is the number of rows, b is the width of a drainage opening (41), B is a total width of all drainage openings (41) in each row, where in particular b is defined as b = y / n ⋅ d where d is a distance of a drainage opening (41) to an adjacent drainage opening of a row perpendicular to the transport direction (T) and y is a real number between 1 and 2.

9. Device according to any one of claims 4 to 8, characterized by the fact that the drainage openings (41) in a second row (i+1) following a first row (i) are arranged offset perpendicular to the transport direction (T) with respect to the positioning of the drainage openings of the first row (i), wherein in particular the offset has an amount z / n·b perpendicular to the transport direction, where z is an integer from 1 to n-1.

10. Device according to any one of claims 4 to 9, characterized by the fact that the projection of all drainage openings (41) of a group of drainage openings (41) onto a plane that intersects the transport direction (T) perpendicularly, the drainage openings (41) being arranged in such a way results in a recess.

11. Device according to one of the preceding claims, characterized by the fact that the drainage openings (41) in projection onto the screen belt (10) have a slotted, oblong, elliptical, trapezoidal, triangular, curved or serpentine elevation or have an elevation in the form of a combination of the preceding features and / or within a group have an identical amount of extent in the transport direction (T) and an identical amount of extent perpendicular to the transport direction (T).

12. Device according to one of the preceding claims, characterized by the fact thatthe length of the drainage openings (41) is from 1 to 600 mm, preferably 5 to 400 mm, more preferably 7 to 200 mm, more preferably 10 to 100 mm, in particular 15 to 70 mm and / or the width (b) of the drainage openings (41) is from 0.5 to 50 mm, preferably 1 to 40 mm, more preferably 1.5 to 25 mm, in particular 2 to 10 mm, and / or the width of the sieve belt (10) and / or the flow support (40) is from 0.01 to 14 m, more preferably from 0.01 to 10 m, more preferably from 0.01 to 7 m, more preferably from 0.01 to 3 m, in particular from 0.01 to 1.5 m.

13. A method for producing a nonwoven fabric with a device according to one of the preceding claims, comprising the following steps: forming a fiber suspension (S) by suspending fibers (F) in a liquid dispersion medium, continuously accumulating the fiber dispersion onto a screen belt (10) guided in a transport direction (T) in the nonwoven formation and dewatering zone (20), dewatering the dispersion medium by the moving screen belt (10) in the nonwoven formation and dewatering zone (20), wherein the fibers (F) remain on the moving screen belt (10) forming a fiber web (FV), drying and solidifying the fiber web (FV) to form the nonwoven fabric, wherein the solidification can also take place before drying.

14. Procedure according to the preceding claim, characterized by the fact thatthe concentration of the fiber dispersion is from 0.01 to 15 g / l, preferably 0.02 to 10 g / l, more preferably 0.05 to 5 g / l, particularly preferably 0.1 to 2 g / l, the dewatering is carried out by creating a negative pressure in the dewatering box (30) and / or by creating a back pressure, and / or the feed of the screen belt in the transport direction (T) is set from 0.05 to 2500 m / min, more preferably from 0.1 to 800 m / min, more preferably from 0.1 to 300 m / min, more preferably from 0.1 to 150 m / min, more preferably from 0.1 to 80 m / min, more preferably from 0.1 to 30 m / min, particularly preferably from 0.1 to 5 m / min.

15. Method according to one of claims 13 to 14, characterized by the fact thatThe fibers are selected from the group consisting of carbon fibers, glass fibers and other mineral fibers (e.g., microglass fiber, rock wool), ceramic fibers, natural fibers (e.g., flax, hemp, cellulose, sisal, jute, kapok, abaca, cotton), viscose fibers, basalt fibers, aramid fibers, polymer fibers, metal fibers, recycled fibers (e.g., textile fibers, recycled carbon and glass fibers, short fiber dusts), as well as mixtures thereof and modifications thereof (e.g., fiber coatings, copolymer fibers, or split fibers) and / or have an average length of 0.1 to 100 mm (fiber length measurement e.g., according to DIN EN ISO 22314:2023, ISO 13322-1:2014, ISO 9276-2:2018 or comparable) and / or an average diameter of 0.1 exhibit dimensions from µm to 500 µm (e.g., determinable by the aforementioned methods).

Images