Seamed felt and use of the seamed felt in a tissue machine

Abstract

The invention relates to a seamed felt for use in a machine for producing a tissue web, comprising a single-layer or multilayer base structure which has a textile structure with MD threads that form seam loops on both end-face edges of the base structure. The fabric can be made continuous by connecting the end-face edges of the fabric by means of a seam, and the seam can be produced by interlocking the seam loops of both end-face edges and introducing a plug element. The seamed felt additionally comprises at least one layer of nonwoven fibers. The invention is characterized in that the MD threads predominantly or as a whole have a diameter ranging between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the thread density of the MD threads is more than 37%, in particular between 37% and 45%. The invention additionally relates to a corresponding machine and method for producing a tissue web.

Description

[0001] The invention relates to a seam felt for a machine for producing a tissue web according to the preamble of claim 1, as well as a machine and a method for producing a tissue web with such a covering.

[0002] The production of tissue and hygiene papers remains a rapidly growing market. A machine typically used in tissue production is described in EP 3 167 115 B1. As is generally the case in papermaking, a fiber suspension is applied between two sheets of paper and dewatered by suction. The fiber web is then further dewatered in a press and subsequently dried thermally.

[0003] The water squeezed out of the web is absorbed by the covering and removed again after the fiber web is removed. This is done, as described by way of example in EP 2 602 387 B1, by means of suction boxes, the so-called Uhle boxes.

[0004] The fiber web is formed on the same fabric in the former and then transported to the press. EP 3 167 115 refers to this fabric as a water-absorbing support belt. This support belt is usually a felt, also known as forming felt. These forming felts are now largely manufactured as continuous felts.

[0005] Patent applications US 2017 / 044718 A1 and US 2004 / 094281 A1 describe a seam felt. However, threading relatively long, continuous felt loops onto the tissue machine is very time-consuming and can lead to damage to the felt. Therefore, seam felts are increasingly used as press felts in the production of graphic and packaging papers. These are fed into the machine, and the seam is then closed within the machine. However, the use of such seam felts as forming felts in tissue machines is not yet possible. This is because the nonwoven fabric layer has a weak point at the seam. As it passes through the former, the stock jet from the headbox impacts this seam. Since tissue machines are typically operated at high production speeds, this stock jet also impacts the forming felt at high speed. The seam is thus subjected to considerable stress.Even after only a short period of use, damage occurs at the seam.

[0006] It is therefore an object of the invention to propose a seam felt that is suitable for use as a forming felt in a tissue machine.

[0007] It is further an object of the invention to propose a seam felt with increased service life when used as a forming felt in a tissue machine.

[0008] Furthermore, it is an object of the invention to propose a machine and a method for its operation that ensures the reliable production of a tissue web.

[0009] Another objective of the invention is to propose a conversion solution for existing systems that can be implemented with little or no effort.

[0010] The problems are completely solved by a seam felt according to the characterizing portion of claim 1, a machine according to claim 9, and a method according to claim 14. Further advantageous features of the embodiment according to the invention are found in the dependent claims.

[0011] With regard to the covering, the problem is solved by a seam felt for use in a machine for producing a tissue web. The seam felt comprises a single-layer or multi-layer—in particular, a two-layer—base structure, which has a textile structure with MD threads that form seam loops at the two end edges of the base structure. The seam felt can be made continuous by joining its end edges with a seam, and this seam can be executed by interlocking the seam loops of both end edges and inserting a plug-in element. Furthermore, the seam felt comprises at least one layer of nonwoven fibers. According to the invention, the MD threads have a diameter entirely or predominantly between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the thread density of the MD threads is more than 37%, in particular between 37% and 45%.In particular, a felt for use in a machine for producing a tissue web. The seam felt comprises a base structure having a textile structure with MD threads. Furthermore, the seam felt comprises at least one layer of nonwoven fibers. According to the invention, the MD threads have a diameter wholly or predominantly between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the thread density of the MD threads is more than 37%, in particular between 37% and 45%.

[0012] The term "wholly or predominantly" shall be understood to mean that at least 90% of the MD threads, preferably 95%, and in particular all MD threads, have a diameter within the specified range.

[0013] This application uses the term "diameter of a thread". For round threads, this term is well-defined.

[0014] For monofilaments that deviate from a round shape, or for threads twisted from several monofilaments, the diameter of the thread shall be understood to be the diameter of the smallest circle that encloses the cross-section of the thread.

[0015] To determine the thread density of the MD threads, the number of threads per unit length is multiplied by their diameter and the value is expressed as a ratio to the unit length.

[0016] Thus, with 10 threads / cm and a thread diameter of 0.40mm, the thread density is 10 * 0.4mm / 10mm= 40%.

[0017] In particular, a seam felt according to one aspect of the invention can be used as a forming felt in a tissue machine.

[0018] The short service life of conventional seam felts when used as forming felt stems from their comparatively thick nonwoven layer. At the seam, however, this nonwoven layer is not continuous, as it is in the rest of the felt, but rather segmented. This creates a butt joint or overlap, which is always a weak point. If the fabric jet of the headbox encounters this weak point, nonwoven fibers can detach. The further the nonwoven fibers are from the base structure, the weaker their anchoring becomes. The inventors discovered that by combining fine MD threads with a high MD thread density, the base structure can take over some of the functionality that is otherwise performed by one or more layers of nonwoven fabric in the covering, such as pressure distribution.This basic structure enables a uniform pressure distribution through the felt, which was previously impossible. Surprisingly, the applicant's experiments have shown that felts, particularly seam felts, with such basic structures can manage with a thinner nonwoven layer. As described, reducing the thickness of the nonwoven layer improves the stability of the seam. Firstly, the thinner nonwoven layer offers less surface area for the fabric jet to act upon. Secondly, the particularly vulnerable nonwoven fibers of the layers furthest from the basic structure are eliminated, and the service life of the forming felt in the tissue machine is significantly extended.

[0019] Another advantage is that, for example, a thinner felt allows for nipple dewatering in addition to Uhle-Box dewatering in the press of a tissue machine.

[0020] Preferably, the weight of the felt is between 750 g / m² and 1250 g / m², particularly between 900 g / m² and 1100 g / m². In special cases, weights of up to 1400 g / m² are also possible. This refers to the total weight of the base structure and any nonwoven layers.

[0021] It is very advantageous for the invention if the weight fraction of the nonwoven layers corresponds at most to the weight fraction of the base structure, in particular at most 2 / 3 of the weight fraction of the base structure.

[0022] Typically, in felts used for tissue production, the weight fraction of nonwoven fibers is greater than that of the base structure. Usually, 60% of the total weight consists of nonwoven fibers and 40% of the base structure.

[0023] Since the combination of MD thread density and MD thread diameter in the felts proposed here allows parts of the functionality of the nonwoven layer to be taken over by the base structure, it is possible to reduce the amount of nonwoven fibers. This makes lighter and thinner felts possible.

[0024] In preferred embodiments, the covering can have a thickness of 3.5 mm or less, preferably between 2.5 mm and 3 mm! The thickness is determined under a pressure of 0.1 MPa.

[0025] The relative proportion of nonwoven fibers in the total felt also decreases. Therefore, for example, felts can be used in which the base structure and nonwoven layers each make up 50% of the weight. The base structure can even constitute the larger proportion of the felt's weight. If 60% of the total weight comes from the base structure and only 40% from the nonwoven fibers, then the weight of the nonwoven layers corresponds to only 2 / 3 of the weight of the base structure.

[0026] Over the lifespan of the felt, the nonwoven layers become highly compressed, reducing essential covering properties such as permeability. A lower proportion of nonwoven fibers in the overall covering minimizes these losses due to fiber compression, allowing the covering properties to remain within an acceptable range for a longer period.

[0027] In particular, it can be advantageous for the weight of the nonwoven backing to be less than 600 g / m², especially less than 500 g / m², and specifically 450 g / m² or less. Alternatively or additionally, it can be advantageous for the weight of the nonwoven backing on the paper side of the felt to be less than 600 g / m², especially less than 500 g / m², and specifically 450 g / m² or less. Since the stock jet of the headbox impinges on the paper side, reducing the weight of the nonwoven backing on the paper side is particularly beneficial.

[0028] Advantageously, the textile structure can consist of, or comprise, a woven fabric or a twill weave.

[0029] In preferred embodiments, the textile structure may be a flat weave, wherein the warp threads of the loom are the MD threads of the seam felt. The flat weave may, for example, have a plain weave.

[0030] When using a woven fabric as the base structure, it should be noted that circular woven fabrics are typically used for the base structures of fabric coverings. These circular woven fabrics are rotated 90° for installation in the machine. This transforms the weft threads of the loom into the MD threads of the covering, and the warp threads into the CD threads. When producing a seam covering, a two-layer structure can be formed from the circular woven fabric by layering it on top of itself. Seam loops can be created at the end edges of the two-layer structure – for example, by removing one or more CD threads.

[0031] An alternative is to use a flat weave.

[0032] Paul Sudre describes in EP0425523 B1 the principle of producing a seam covering using a flat woven fabric. This technique can also be used for a seam felt according to one aspect of this invention.

[0033] For example, the flat fabric can be made endless by joining the end grains. By laying it on top of itself, a two-layer structure can be formed again. Seam loops can be created at the end grain edges of the two-layer structure by removing one or more CD threads.

[0034] Since the length of warp threads in the machine direction is generally significantly greater than their width in the CD direction, and the width of the loom is sufficiently large for the width of the machine, the required flat woven fabrics can most easily be produced by weaving a sufficiently long piece, whereby the warp threads then become MD threads in the warp. A 90° rotation, as with circular woven fabrics, is not necessary. This is very advantageous for a warp in the form of a seam felt according to one aspect of the present invention. While the warp threads in a loom can, in principle, be arranged arbitrarily close to one another, two adjacent weft threads are necessarily spaced apart from each other because the warp threads—e.g., in a plain weave—alternate between each pair of weft threads from top to bottom or vice versa.Due to this forced spacing of the weft threads, together with the 90° rotation, such a density of medium-density (MD) threads is not possible, or only with great difficulty, using conventional circular woven fabrics when employing very thin threads. In contrast, with flat woven fabrics, the warp threads serving as MD threads can be arranged arbitrarily close to one another, making it comparatively easy to produce fabrics with the properties described in the invention.

[0035] When using flat woven fabrics in the basic structure, the flat woven fabric can advantageously be made endless by joining the end faces. This joining can be achieved, in particular, by welding. Ultrasonic welding and laser welding, especially laser transmission welding, have proven to be suitable welding processes. It may also be advantageous to join the two end faces of the flat woven fabric using a connecting element. This element can, for example, be one or more threads arranged in the CD direction and connected, in particular welded, to the MD threads of the two ends.

[0036] The basic structure can consist of a textile structure or include other elements. In particular, the basic structure can contain further textile structures, such as additional fabrics.

[0037] Various materials can be used for the MD threads. Polyamides such as PA 6 and PA 6.6 are suitable, as are other polymers such as PET. If CD threads are present, they can be made from the same or a different polymer.

[0038] It is possible for all MD threads to be identical. However, different types of MD threads can also be used. This allows, for example, the fiber anchorage or dimensional stability to be influenced. Advantageously, MD threads are monofilaments.

[0039] There are also various options when choosing CD threads. In addition to monofilaments, multifilaments or yarns can also be used.

[0040] Suitable yarns can consist of 4 or 6 filaments. The filaments used can have a diameter of 0.15–0.25 mm. For example, 0.2 x 2 x 2 yarns are very suitable.

[0041] In advantageous designs, all CD threads can be made from yarn. All CD threads can be made from the same yarn, or different yarns can be used.

[0042] It can also be advantageous to use both yarns and monofilaments as CD threads. Preferably, around 50% or more of the CD threads are made of yarn.

[0043] In a preferred embodiment, yarns and monofilaments can be used alternately as CD threads. In this case, the proportion of yarns in the CD threads is 50% – or slightly less if, for technical reasons, individual CD threads have to be removed, e.g., to form the seam loops.

[0044] The high proportion of twisted CD threads has proven to be advantageous.

[0045] Surprisingly, it has been shown that the two-layer basic structure described above, based on a flat fabric, combined with a high thread density of thin MD threads - especially with diameters between 0.25 and 0.35 mm or 0.36 mm - and a proportion of 50% or more twisted CD threads, results in a basic structure for a covering, especially a seam felt, which can take over particularly effective parts of the function of the nonwoven layer.

[0046] In this way, it is very easy to produce coverings, especially seam felts, which are very thin (less than 3.5mm, or even between 2.5mm and 3mm) and yet have full functionality.

[0047] Due to their low thickness, such seam felts can also be used for challenging applications such as in tissue machines where conventional seam felts would wear out very quickly due to the thickness of the nonwoven layer.

[0048] A basic structure with more than two layers—e.g., with an additional inlay—is possible in principle, but leads to a greater thickness of the seam felt and is therefore not a preferred solution.

[0049] In advantageous embodiments, the felt can have one or more layers of nonwoven fabric. The layer(s) can be arranged on the paper side and / or the running side of the felt.

[0050] In most cases, it will be necessary for the paper side of the seam felt to contain a certain amount of nonwoven fibers. This amount should not be less than 10% of the total weight of the covering. It is also advantageous to use nonwoven fibers with a fineness between 11 and 22 dtex, at least on the paper-contacting top side of the felt.

[0051] The nonwoven fibers can be made of any suitable material, in particular a polyamide, but also an elastomer such as a thermoplastic polyurethane (TPU), melt fibers, two-component fibers or mixtures thereof.

[0052] With regard to the machine, the problem is solved by a machine for producing a tissue web, which includes a former. The machine has at least one seam felt according to one aspect of the invention. The seam felt is arranged such that it passes through the former during operation of the machine.

[0053] Tissue paper is typically made from wood pulp and is very lightweight. Its basis weight is usually between 15 g / m² and 30 g / m². However, values ​​as low as 10 g / m² or 5 g / m² are also possible, as are papers with more than 30 g / m².

[0054] In advantageous versions, the machine includes a so-called crescent former.

[0055] Furthermore, in advantageous embodiments, it can be provided that the machine has a pressing device with at least one press nip, and the seam felt is arranged so that it passes through the at least one press nip during operation of the pressing device.

[0056] After initial dewatering in the former, the fiber web can then be transported on the seam felt into a press device, where further dewatering takes place in the press nip.

[0057] Preferably, the press device features a long nip, in particular a shoe nip. Compared to a roller nip, which is also possible, the web's residence time in the nip is longer. This allows for the use of lower press pressures. This is important in the production of tissue papers, as it helps maintain the web's volume, which is a key quality parameter for tissue papers.

[0058] The seam felt according to one aspect of the invention can offer two advantages in a tissue machine. Firstly, the thinner nonwoven layer allows for a longer service life of the felt despite the stresses from the former. Additionally, the thinner felt enables further dewatering of the tissue web in the press.

[0059] Therefore, it can also be advantageous if the press has a wastewater collector designed to collect water that has been removed from the tissue web in at least one press nip. By using a felt according to one aspect of the invention, the dewatering capacity of the press can be increased—particularly in long nip or shoe presses—by incorporating nip dewatering in addition to the usual Uhle box dewatering. In this process, water (or a water-air mixture) from the tissue web is not only pressed into the felt but also through it. While the remaining portion of the pressed-out water is transported with the felt to a downstream Uhle box, this water escapes into the environment as splash water or spray mist after the press nip. It is also possible for splash water to escape forward against the direction of web travel.This portion of the drainage process is referred to as nozzle drainage. To prevent contamination of the press or uncontrolled wetting of the surrounding area, it is advantageous to incorporate one or more drainage traps into the press assembly. These are arranged so that the splash water can be collected and removed.

[0060] By means of a seam felt according to one aspect of the invention and optionally by installing a water catcher, the dewatering performance of the press device can be significantly increased with very little effort, even in existing tissue machines.

[0061] With regard to the method, the problem is solved by a method for producing a tissue web using a machine according to one aspect of the invention.

[0062] Advantageously, it can be provided that part of the dewatering in the pressing device takes place in the form of nipple drainage, and that this dewatered water is collected wholly or partially by a wastewater trap.

[0063] In particular, it may be provided that the nipple drainage accounts for more than 10%, especially between 20% and 50%, of the total drainage volume of the pressing device.

[0064] It is particularly advantageous if the tissue machine is operated at high speeds of more than 1200 m / min, especially more than 1500 m / min or 1800 m / min. Especially at high production speeds, an insufficient dry content after pressing is the limiting factor for increasing production speed.

[0065] Secondly, the high production speed of the tissue machine necessitates a high jet velocity in the stock head. In this case, the increased strength of the seam, or rather the nonwoven layer of the seam, is particularly advantageous.

[0066] The methods proposed here increase the dry content after pressing and simultaneously increase the service life of the seam felt, thus enabling stable and lasting high production speeds.

[0067] The invention will be explained in more detail below using schematic figures that are not to scale. Figure 1 shows a tissue machine according to one aspect of the invention. Figure 2 shows the seam area of ​​a seam felt according to one aspect of the invention.

[0068] Figure 1Figure 1 shows a tissue machine 1 according to one aspect of the invention. Using this typical design of a tissue machine 1 as an example, aspects of the idea described here will be explained. The invention is not limited to this embodiment. A fiber suspension is applied via a headbox onto a fabric 2, or between a fabric 2 and an outer screen 22. The fabric 2 is designed as a forming felt 2 in the form of a seam felt 2. Initial dewatering takes place in a former 20 with the aid of a suction forming roller 21, which is partially enclosed by the forming felt 2.

[0069] The Former 20 is in Figure 1 The forming process is carried out as a crescent former 20, although other former types are also possible. The resulting fiber mat is then transported, supported by the forming felt 2, into the press 30. Figure 1The press device 30 is designed as a shoe press 30. The press nip 31 is positioned between the shoe roller 34 and a Yankee cylinder 41. The forming felt 2 passes through the press nip 31 together with the tissue web 3. After passing through the press nip, the web 3 continues on the surface of the Yankee cylinder 41. A drying hood 42 is arranged on the Yankee cylinder 41. A crepe scraper 43 releases the web 3 from the Yankee cylinder 41 and transports it to a winding unit 60. As in Figure 1 As shown, a scanner 50 or another suitable measuring device 50 can be provided before the winding 60, with which important parameters of the fiber web 3, such as thickness, moisture content, or basis weight, can be recorded. If the scanner 50 is designed to traverse the web, cross-sectional profiles of these parameters can also be determined.

[0070] The covering 2 of the in Figure 1The machine 1 shown is advantageously a seam felt 2 according to one aspect of the invention. Advantageously, it can comprise a basic structure 100 made of a flat woven fabric 110, in particular a plain weave fabric, which is made endless by joining - e.g. welding - the end faces and is formed by layers on itself to form a two-layer structure 100.

[0071] The MD threads of this basic structure 100 all have a diameter between 0.25 mm and 0.45 mm, particularly between 0.3 mm and 0.35 mm. The thread density of the MD threads is more than 37%, preferably between 37% and 45%, and particularly preferably between 39% and 43%. With a preferred weight of the felt 2 between 750 g / m² and 1250 g / m², particularly between 900 g / m² and 1100 g / m², the nonwoven layer 200 can be reduced to half the weight or less of the felt 2. In particular, the weight of the nonwoven layer 200 on the paper side of the seam felt 2 or even of the entire seam felt 2 may be less than 600 g / m 2< , especially less than 500 g / m 2< , specifically 450 g / m 2< or less.

[0072] Since, according to one aspect of the invention, the base structure 100 of a covering 2 takes over parts of the function of the nonwoven layers 200, this covering 2 can be made very thin. As a result, the seam 150 or butt joint 210 offers less surface area for the fabric jet to act upon. Furthermore, the particularly vulnerable nonwoven fibers of the nonwoven layers located far from the base structure 100 are eliminated, and the service life of the forming felt 2 in the tissue machine 1 is significantly extended!

[0073] Furthermore, in contrast to tissue machines 1 known from the prior art, when using such a seam felt 2 in the press nip 31, particularly in a shoe press nip 31, nip dewatering can be achieved. This results in splashing water or spray mist, which usually occurs after the press nip 31, but can sometimes also occur in front of the nip 31. To prevent contamination of the press 30 or uncontrolled moistening of the surroundings, it is advantageous to provide one or more wastewater traps 33 in the press device 30. Figure 1A wastewater trap 33 is arranged downstream of the pressnip 31. Alternatively or additionally, a wastewater trap 33 can also be provided upstream of the pressnip 31. The wastewater trap(s) 33 collect the portion of the water that has been removed from the web 3 by the pressnip drainage. The remaining portion is stored in the covering 2 and transported away by the pressnip 31. To remove this water from the covering 2, a [missing information] is required in the [missing information]. Figure 1 In the system shown, a suction box 32, a so-called Uhle box 32, is provided between the press nipple 31 and the headbox 10. In a process according to one aspect of the invention, the proportion of nipple dewatering is more than 10%, preferably between 20% and 50% of the total dewatering of the press 30.

[0074] Figure 2Figure 1 shows a section of a seam felt 2 according to one aspect of the invention. The felt 2 shown here consists of a base structure 100 and a nonwoven layer 200 on the paper side of the felt 2. The nonwoven layer 200 can comprise one or more layers of nonwoven fibers. Likewise, a further nonwoven layer can be provided on the running side of the felt 2, which is Figure 2 not shown. In the basic structure 100 in Figure 2This involves a woven base structure 100. A flat fabric 100 can be folded over itself to create the two-layer base structure shown. The ends of the flat fabric 110 are advantageously joined together, for example, by a welded seam. Seam loops 120 are formed at the end edges of the resulting two-layer base structure 100. For this purpose, one or more CD threads can be removed from the fabric. To close the seam, the seam loops 120 are interlocked and can be connected by an element such as a connecting wire 130.

[0075] For the nonwoven layer 200 in such seam felts 2, the problem is that this nonwoven layer 200 cannot be continuous at the seam 150, but has a butt joint 210 (possibly in the form of an overlap joint 210). This butt joint 210 is particularly critical when used as a forming felt 2. The fabric jet of the headbox 10 can widen the butt joint or detach nonwoven fibers, since the anchoring of the outer nonwoven fibers in particular is reduced in the seam area 150.

[0076] In a seam felt according to one aspect of the invention, the base structure 100 can now take over parts of the function of the nonwoven layer 200, such as the evening of pressure. This has the effect, among others, that the nonwoven layer 200 can be made thinner. This makes it more difficult for the fabric jet to penetrate the seam 210. In addition, the nonwoven fibers are on average located closer to the fabric of the base structure 100, which improves anchoring. This enables the use of a seam felt 2 as a forming felt 2 of a tissue machine 1 with a significantly improved service life. Reference symbol list

[0077] 1 Tissue machine 2 Fabric, seam felt 3 Tissue web 10 Headbox 20 Former 21 Forming roller 22 Outer screen 30 Pressing device 31 Press nip 32 Suction box "Uhle Box" 33 Drainage catcher 34 Shoe roller 40 Drying device 41 Yankee cylinder 42 Hood 43 Crepe scraper 50 Scanner 60 Winder 100 Base structure 110 Flat weave 120 Seam loop 130 Connecting wire 150 Seam 200 Nonwoven layer

Claims

1. Seam felt (2) for use in a machine (1) for producing a tissue web (3), comprising at least one layer of nonwoven fibres (200) and a base structure (100) consisting of a fabric with MD threads and CD threads, which form seam loops (120) at the two front edges of the base structure, wherein the seam felt (2) can be made continuous by joining its front edges by means of a seam (150), and this seam (150) can be formed by interlocking the seam loops (120) of both front edges and inserting a stitching element (130), characterised in that the MD threads have a diameter of between 0.25 mm and 0.45 mm, in particular between 0.3 mm and 0.35 mm, and the thread density of the MD threads is more than 37%, in particular between 37% and 45%, whereby the term "entirely or predominantly" is to be understood as meaning that at least 90% of the MD threads, preferably 95%, in particular all MD threads, have a diameter within the specified range and wherein, to determine the thread density of the MD threads, the number of threads per unit length is multiplied by their diameter and the value is set in relation to the unit length.

2. Sewing felt (2) according to one of the previous claims, characterised in that the weight of the sewing felt (2) is between 750 g / m2 and 1250 g / m2, in particular between 900 g / m2 and 1100 g / m2.

3. Seam felt (2) according to one of the previous claims, characterised in that the weight proportion of the non-woven layers (200) corresponds at most to the weight proportion of the base structure (100), in particular at most to 2 / 3 of the weight proportion of the base structure (100).

4. Seam felt (2) according to one of the previous claims, characterised in that the weight of the non-woven layer (200) is less than 600 g / m2, in particular less than 500 g / m2, specifically 450 g / m2 or less.

5. Seam felt (2) according to one of the previous claims, characterised in that the fabric is a flat fabric (110), wherein the warp threads of the loom provide the MD threads of the seam felt (2) and the flat fabric (110) is made endless by joining the front ends, wherein a two-layer structure (100) is formed by layering on itself.

6. Seam felt (2) according to claim 5, characterised in that seam loops (120) are formed at the front edges of the two-layer structure (110) by removing one or more CD threads.

7. Seam felt (2) according to one of the previous claims, characterised in that at least some of the CD threads, in particular 50% or more of the CD threads, are listed as twisted yarn.

8. Seam felt (2) according to one of the previous claims, characterised in that the seam felt (2) has a thickness of 3.5 mm or less, in particular between 2.5 mm and 3 mm.

9. Machine (1) for producing a tissue web (3), comprising a former (20), characterised in that the machine (1) has at least one seam felt (2) according to one of claims 1-8 and the seam felt (2) passes through the former (20) during operation of the machine (1).

10. Machine (1) according to claim 9, characterised in that the former (20) is a crescent former (20).

11. Machine (1) according to one of claims 9 or 10, characterised in that the machine (1) has a pressing device (30) with at least one pressing nip (31), and the seam felt (2) passes through the at least one pressing nip (31) during operation of the pressing device (30).

12. Machine according to claim 11, characterised in that the pressing device (30) has a long nip (31), in particular a shoe nip (31).

13. Machine according to one of claims 11 or 12, characterised in that the pressing device (30) has a waste water collector (33) which is designed to collect splash water which has been removed from the tissue web (3) in the form of nip drainage in the at least one press nip (31).

14. Method for producing a tissue web (3), wherein a machine (1) according to one of claims 10 to 13 is used for the production.

15. Method according to claim 14, characterised in that in the pressing device (30), a portion, in particular more than 10% of the dewatering, takes place in the form of nip dewatering, and this dewatered water is collected in whole or in part as spray water by a waste water collector (33).

Images