Method for producing kraft paper

Abstract

The invention relates to a method for producing kraft paper, having the steps of: forming a fibrous web by applying a fibrous suspension onto a wire section (2); shaking the fibrous web transversely to the machine direction; pressing the partially dewatered fibrous web in a pressing section (5); further drying the fibrous web in a drying section (6); and winding up the paper web formed from the fibrous web; wherein the wire section (2) comprises an endlessly circulating dewatering screen (8); the wire section (2) has a first dewatering section (11); the shaking device (4) causes the dewatering screen (8) to oscillate in the transverse direction in the region of the breast roller (10); a second dewatering section (13) is provided downstream of the first dewatering section (11) in the running direction (23) of the fibrous web, said second dewatering section being equipped with a second dewatering device (15) which dewaters the fibrous web from above; and the material density of the fibrous suspension applied onto the wire section (2) is at most 0.46%. The invention further relates to a wire section, to the use of the wire section, to a kraft paper, and to an installation.

Description

[0001] Process for producing kraft paper

[0002] The present invention relates, in one aspect, to a process for producing kraft paper. In further aspects, the invention particularly relates to a kraft paper as such, a wire section for a kraft paper production plant, and the use of the wire section.

[0003] Various processes for producing kraft paper are known in the art. Kraft paper is a special type of paper characterized, among other things, by its particularly high strength. Due to this property, it is used for various packaging applications, such as the production of paper bags. In addition to strength, other parameters are also important, depending on the specific application of the kraft paper, such as stretchability or air permeability.

[0004] The properties of paper depend significantly on the conditions during its production. One object of the present invention can therefore be seen as creating a process that can produce kraft paper with an improved property profile compared to the prior art.

[0005] The long fibers typically used in the production of kraft paper tend to align preferentially in the direction of travel of the dewatering wire, i.e., in the machine direction, when applied to the wire section of the production line. This promotes the extensibility of the resulting paper web across the machine direction, which means that sufficient transverse strength cannot be achieved for certain applications.

[0006] Furthermore, it has been found that the extensibility of one and the same paper web varies. In particular, it has been observed that in state-of-the-art kraft paper production lines, an inhomogeneous extensibility profile is obtained in the transverse direction of the paper web, with the extensibility typically being higher at the edges of the paper web than in its center. These differences in extensibility between the center and the edge are also disadvantageous.

[0007] In particular, an object of the present invention can therefore be seen in overcoming these and other disadvantages of the prior art.

[0008] The invention therefore preferably relates to a process for producing kraft paper, in particular sack kraft paper, in which, in a first step, a fibrous web running in the machine direction is formed. This is carried out, in particular, by applying a fibrous suspension to a wire section by means of a headbox.

[0009] In particular, after the suspension is applied to the wire section, the fiber material is shaken or jolted with a high-frequency shaking device on the breast roll. This contributes to reducing fiber alignment in the machine direction and increasing it in the cross direction.

[0010] In the wire section, a fibrous band or sheet is formed by a filtration process, in particular using dewatering devices.

[0011] Following the wire section, a press section is typically arranged, where mechanical dewatering with simultaneous compaction of the fibrous web can take place. This can typically be achieved with several press nips, the first of which is usually designed as a suction press with double felt guides, and the others as roller presses or shoe presses with either double or single felt guides.

[0012] The mechanically extruded fibrous web can be subjected to one or more drying processes to achieve the desired dry content. Further manufacturing and / or processing steps, such as compressing or calendering the fibrous web, can be performed before, between, or after one or more drying processes.

[0013] Compressing the fibrous web can occur, in particular, between two drying steps, i.e., after a pre-drying step in a pre-drying section and before a post-drying step in a post-drying section. This can increase the paper's extensibility in the machine direction. This step can be performed, for example, in a so-called compression device, such as a Clupak device.

[0014] Calendering or embossing of the fibrous web can, for example, take place after the final drying step. Calendering or embossing can be performed using either thermal rolls or embossing rolls. Thermal rolls are used to provide the smoothest possible paper surface, while embossing rolls are used to give the paper surface a different appearance.

[0015] After the final processing step, the finished paper web can be wound up on the reel and then further processed to the desired finished roll width.

[0016] The wire section comprises, in particular, a continuously rotating dewatering wire driven by rollers. A breast roll may be located in the area where the fiber suspension is applied, with the suspension typically being applied to the outside of the dewatering wire. To consolidate the fiber sliver, the wire section comprises at least one dewatering device.

[0017] In particular, a first dewatering section is provided in which the fibrous web is dewatered downwards, i.e., toward the side resting on the dewatering wire. This dewatering can be carried out using vacuum suction devices that partially remove the water contained in the fibrous web. The first dewatering section can also comprise several different dewatering devices.

[0018] Preferably, in addition to the first dewatering section, a second dewatering section is provided, in which dewatering of the fibrous web takes place upwards, i.e., toward that side of the fibrous web that is not initially in contact with the dewatering screen. A system can also comprise several dewatering screens. If this is the case, this refers in particular to the dewatering screen onto which the fibrous suspension was applied, i.e., the main dewatering screen. The additional dewatering from the top side can also potentially improve the formation of the kraft paper.

[0019] It is preferably provided that the main dewatering screen is set into oscillation by means of a high-frequency shaking device in the region of the breast roller.

[0020] It is further preferably provided that the consistency of the fiber suspension when applied to the dewatering screen, i.e. in the area of ​​the shaking device, is at most 0.46%, preferably at most 0.3%, more preferably between 0.15% and 0.3%.

[0021] Surprisingly, it was found within the scope of the present invention that particularly advantageous extensibility properties of the resulting kraft paper, in particular in its transverse direction, can be achieved by combining upward drainage, also referred to as top former or hybrid former, the use of the shaking device and the specific adjustment of the stock density.

[0022] These effects are achieved in particular when the production speed of the kraft paper is greater than 400 m / min and when the width of the fibrous web or the paper web produced is greater than 3.5 m, in particular greater than 5.5 m, typically greater than 6.0 m.

[0023] Optionally, the dewatering screen has a width of at least 4.0 m, in particular of at least 7.0 m, typically of at least 8.0 m.

[0024] Where appropriate, the production speed is at least 600 m / min, in particular at least 1100 m / min.

[0025] In particular, the fiber used is pulp made from softwood or coniferous long fibers. The kappa number of the pulp can be at least 30. The kraft paper produced can, in particular, be unbleached, brown kraft paper.

[0026] If necessary, the shaking is carried out with an amplitude of at least 15 mm, for example between 20 mm and 70 mm, and / or with a frequency of between 5 Hz and 10 Hz.

[0027] In the area of ​​the second dewatering device, which dewaters the fibrous web from above, formation bars can be provided on the underside of the dewatering screen, which build up pressure on the fibrous web from below in the direction of the second dewatering device. Three, four or more formation bars can be provided, which are arranged one after the other in the running direction of the dewatering screen and optionally run parallel to one another. The formation of the paper can also be influenced by using the formation bars. The second dewatering device can optionally be designed with multiple zones, for example with three or four zones, in which case the suction zones are arranged one after the other in the running direction of the dewatering screen. The individual zones of the second dewatering device can be formed by suppression or vacuum suction boxes.

[0028] In the second dewatering section, an additional dewatering screen, also known as a top-former dewatering screen, can be placed between the second dewatering device and the fibrous web. The top-former dewatering screen can be continuously circulating and its outer surface can be in contact with the top side of the fibrous web. Typically, the top-former dewatering screen runs at the same speed as the main dewatering screen, so there is no speed difference between the top-former dewatering screen and the main dewatering screen.

[0029] Typically, drainage occurs exclusively downwards in the first drainage section and exclusively upwards in the second drainage section, or downwards again after the second drainage section.

[0030] Regarding the speed of the main dewatering screen, it should be noted that it can run at a different or the same speed as the suspension jet exiting the headbox. The speed difference can be up to 5%, with the dewatering screen running faster or slower than the suspension jet.

[0031] The process according to the invention can provide a kraft paper, in particular a sack kraft paper, which surprisingly has a property profile that is advantageous compared to the prior art. The invention therefore also relates to a kraft paper as such, which is obtainable in particular by a process according to the invention. The kraft paper according to the invention can optionally also be obtained by other production processes. The extensibility of the kraft paper, in particular according to ISO 1924-3:2005, is preferably greater than 5% in the transverse direction, preferably greater than 7.5%. These values ​​are optionally also met in the machine direction.

[0032] Preferably, the width of a paper web of the kraft paper is greater than 3.5 m and in particular greater than 5.5 m, for example greater than 6.0 m. In connection with the present invention, the width refers in particular to the dimension of a paper web in the transverse direction of the paper.

[0033] The difference in the extensibility of the paper in the transverse direction between the edge region and the middle region of the paper web is preferably a maximum of 4.0%, more preferably a maximum of 3.0% and even more preferably a maximum of 1.5%. In absolute terms, the extensibility of the paper web can be between 5% and 8% in the middle and between 7.5% and 12% at the edges, depending on the manufacturing process. In connection with the paper described here, the said difference is calculated in particular by subtracting the two extensibility values; it is therefore the absolute difference between these values. In a fictitious example of a paper web with an extensibility of 7% in the middle and 8.4% at the edges, the said difference is therefore 1.4%.

[0034] The edge area refers in particular to an area 50 cm wide, starting from each outer edge of the paper web. The center area refers in particular to an area 50 cm wide, extending 25 cm on either side of the geometric center of a paper web, determined in the width direction.

[0035] Alternatively or additionally, it can also be provided that the average extensibility of the paper in the middle third of the paper web differs by less than 0.8% from the extensibility in an outer third, in particular in both outer thirds, of the paper web. To determine the position of the two outer thirds and the middle third, the paper web is fictitiously divided into three sections of equal width in the width direction. The average extensibility in each third is then determined. The extensibility is measured in particular between 0.75 h and 1.5 h, typically 1.0 h, after the production of the kraft paper, i.e. after completion of the last manufacturing step.

[0036] Where applicable, the Ambertec formation of the paper is not more than 0.7 (g / m 2 ).

[0037] Where appropriate, the Gurley drag of the paper, in particular according to ISO 5636-5:2013, is not more than 15 s, preferably not more than 10 s.

[0038] Where appropriate, the tensile energy absorption index of the paper in the machine direction, in particular according to ISO 1924-3:2005, is at least 2.5 J / g, preferably at least 3.0 J / g. Where appropriate, these values ​​also apply to the machine direction of the paper.

[0039] The fiber contained in the paper may be unbleached pulp.

[0040] Where appropriate, the fiber contained in the paper consists of softwood long fibers with an average fiber length of at least 2 mm. Fiber analysis can be performed, in particular, according to ISO 16065-2:2014, for example, optically using the Fiber Tester L&W.

[0041] Where appropriate, the fibre contained in the paper has a kappa number of at least 30, in particular of at least 40.

[0042] The invention also particularly relates to a wire section for a plant for producing kraft paper. The wire section may have any features described in connection with the method with another aspect of the present invention.

[0043] The wire section preferably comprises a continuously running dewatering wire and a first and a second dewatering section. Furthermore, a shaking device is preferably provided, which is designed to cause the dewatering wire to oscillate in the region of the breast roll of the wire section. In the second dewatering section, a dewatering device is preferably provided, which is designed to dewater the passing fibrous web from above.

[0044] Optionally, the invention also relates to the use of such a wire section in the production of kraft paper.

[0045] Optionally, the invention also relates to a plant for producing kraft paper, i.e., a kraft paper production plant comprising a wire section according to the invention. Such a kraft paper production plant may comprise at least the following plant components: headbox, wire section, press section, dryer section, and reeling section. Optionally, the dryer section may comprise several separate dryer sections. Additionally, an upsetting device (e.g., a Clupak unit) and / or a calendering device or embossing device may be provided.

[0046] It should be noted that any features described in connection with other aspects of the invention may be provided in all aspects. For example, the wire section may have features described in connection with the method according to the invention, and vice versa.

[0047] Optionally, the invention relates to a process for producing kraft paper comprising the following steps:

[0048] - Forming a fibrous web running along the machine direction by continuously applying a fibrous suspension to a wire section through a headbox,

[0049] - Shaking the fibrous web transversely to the machine direction, i.e. in the transverse direction, by a shaking device,

[0050] - Pressing the fibrous web, previously partially dewatered in the wire section, in a press section,

[0051] - further drying of the fibrous web in a drying section,

[0052] - Winding up the paper web formed from the fibrous web in a winding station, wherein the wire section comprises an endlessly rotating dewatering wire and the application of the fibrous suspension to the outside of the dewatering wire takes place in the region of a breast roll of the wire section, wherein the wire section has a first dewatering section in which a first dewatering device is arranged on the inside of the dewatering wire, dewatering the fibrous web from below.

[0053] It is preferably provided that the shaking device causes the dewatering screen to oscillate in the transverse direction in the region of the breast roll, that a second dewatering section is arranged following the first dewatering section in the running direction of the fibrous web, in which second dewatering section a second dewatering device is provided which dewaters the fibrous web from above, and that the consistency of the fiber suspension applied to the screen section is at most 0.4%, preferably at most 0.3%, more preferably between 0.15% and 0.3%.

[0054] If necessary, the dewatering screen is designed to oscillate in the area of ​​the breast roller with an amplitude of at least 15 mm.

[0055] If necessary, the dewatering screen is designed to oscillate in the area of ​​the breast roller at a frequency of between 5 Hz and 10 Hz.

[0056] If appropriate, it is provided that in the second dewatering section on the inside of the dewatering screen at least four transversely extending formation strips are provided, which exert a pressure of between 2 and 25 kPa on the dewatering screen in the direction of the second dewatering device.

[0057] Optionally, it is provided that the second dewatering device comprises at least one, in particular at least three, suction zones arranged one after the other in the running direction of the fibrous web, which are / are operated in particular with a vacuum of between 5 and 25 kPa. Optionally, it is provided that in the second dewatering section, between the second dewatering device and the fibrous web, an endlessly rotating top-former dewatering screen is guided.

[0058] Where appropriate, the production speed shall be greater than 400 m / min and the width of the fibrous web shall be greater than 3.5 m and in particular greater than 5.5 m.

[0059] Where appropriate, it is provided that the extensibility of the paper web, in particular according to ISO 1924-3:2005, in the transverse direction is greater than 6.5%, preferably greater than 7.5%, and that the difference in the extensibility of the paper web in the transverse direction between the edge region and the central region of the paper web is a maximum of 1.5%.

[0060] Where appropriate, the fibre material shall be unbleached pulp.

[0061] Where appropriate, the pulp shall be made from softwood long fibres with an average fibre length of at least 2 mm in accordance with ISO 16065-2:2014.

[0062] Optionally, it is provided that the fiber material has a kappa number of at least 30, in particular of at least 45, preferably of at least 50.

[0063] Where appropriate, the speed of the dewatering wire of the wire section is intended to be between 97% and 99% of the jet speed of the headbox.

[0064] Where appropriate, it is intended that the Ambertec formation of the paper web should not exceed 0.7 (g / m 2 ) amounts.

[0065] Optionally, it is provided that the Gurley drag of the paper web, in particular according to ISO 5636-5:2013, is at most 15 s, preferably at most 10 s. Optionally, it is provided that the tensile energy absorption index of the paper web in the transverse direction, in particular according to ISO 1924-3:2005, is at least 2.5 J / g, preferably at least 3.0 J / g.

[0066] Where appropriate, it is provided that the drying section comprises a pre-drying section and a post-drying section, and that the fibrous web is compressed between the pre-drying section and the post-drying section by a compression device, in particular by a Clupak device.

[0067] If necessary, the fibrous web is calendered or embossed in a calendering device or in an embossing device after the drying section.

[0068] Optionally, the invention also relates to a kraft paper obtained from or obtainable from a process according to the invention.

[0069] Optionally, the invention also relates to a wire section for a plant for producing kraft paper, comprising an endlessly rotating dewatering wire, on the outside of which a fiber suspension can be applied in the region of a breast roll, wherein the wire section has a first dewatering section in which a first dewatering device for dewatering the fiber web from below is arranged on the inside of the dewatering wire.

[0070] It is preferably provided that a shaking device is provided which is designed to cause the breast roller to oscillate transversely to the running direction of the dewatering screen, and that in the running direction of the dewatering screen, a second dewatering section is arranged following the first dewatering section, in which a second dewatering device for dewatering the fibrous web from above is provided on the outside of the dewatering screen.

[0071] Optionally, it is provided that in the second dewatering section on the inside of the dewatering screen at least four transversely extending formation strips are provided, which are designed to exert a pressure of between 2 and 25 kPa on the dewatering screen in the direction of the second dewatering device.

[0072] Optionally, it is provided that the second dewatering device comprises at least one, in particular at least three, suction zones arranged one after the other in the running direction of the dewatering screen, which can be operated in particular with a vacuum of 5 - 25 kPa.

[0073] If necessary, it is provided that an endlessly rotating top former dewatering screen is arranged in the second dewatering section between the second dewatering device and the dewatering screen.

[0074] Optionally, the invention also relates to the use of a wire section according to the invention in a process for producing kraft paper, in particular in a process according to the invention.

[0075] Optionally, the invention also relates to a plant for producing kraft paper comprising the following plant components:

[0076] - a wire section for forming a fibrous web by continuously applying a fibrous suspension along the machine direction through a headbox,

[0077] - a shaking device for shaking the fibrous web transversely to the machine direction, i.e. in the transverse direction,

[0078] - a press section for pressing the fibrous web partially dewatered in the wire section,

[0079] - a drying section for drying the fibrous web,

[0080] - a winding station for winding up the paper web formed from the fibrous web.

[0081] It is preferably provided that the wire section is a wire section according to the invention, i.e. a wire section with one or more of the features described herein.

[0082] Further features of the invention will become apparent from the patent claims, the figures, and the description of the exemplary embodiment. The present invention will be explained in detail below using an exemplary embodiment.

[0083] They show:

[0084] Fig. 1a-c is a schematic overall view of a kraft paper manufacturing plant according to a first embodiment of the invention; and

[0085] Fig. 2 is a schematic detailed view of a sieve section according to the invention according to a second embodiment of the invention.

[0086] Unless otherwise indicated, the following features are shown in the figures: Machine direction 1, wire section 2, headbox 3, jogging device 4, press section 5, dryer section 6, reeling station 7, dewatering wire 8, outer side 9, breast roll 10, first dewatering section 11, inner side 12, second dewatering section 13, first dewatering device 14, second dewatering device 15, forming bar 16, suction zone 17, top former dewatering wire 18, pre-dryer section 19, after-dryer section 20, compression device 21, calendering device 22, direction of travel of the fibrous web 23, suction box 24, paper reel 25.

[0087] Fig. 1a-c show a schematic overall view of a kraft paper production plant according to a first embodiment of the invention. The plant comprises, in the machine direction 1, a headbox 3, a wire section 2, a press section 5, a pre-dryer section 19, an upsetting device 21, an after-dryer section 20, a calendering device 22, and a winding station 7. The calendering device 22 can alternatively be designed as an embossing device.

[0088] The headbox 3 serves, in a known manner, to apply a fiber suspension to the continuously rotating dewatering wire 8 of the wire section 2, thereby forming a fiber web. As the system progresses, the fiber web is continuously dewatered or dried, passing successively through the aforementioned system components. Finally, paper rolls 25 are formed, which can be transported away and / or fed to further processing steps. The production speed of the system in this exemplary embodiment is approximately 1100 m / min. The produced paper web has a paper width of approximately 6.4 m.

[0089] The function of the individual plant components is well known to a specialist in the field of paper production and will not be explained in detail here. The inventive features of the plant relate in particular to wire section 2.

[0090] Fig. 2 shows an enlarged view of a wire section according to a second embodiment of the invention in detail. The wire section according to this embodiment can be used in the plant shown in Fig. 1 to produce kraft paper.

[0091] The fiber suspension from headbox 3 is applied to the outside

[0092] 9 of the dewatering wire 8 of the wire section 2, forming a fibrous web. The machine direction 1 of the system or of the paper produced corresponds to the running direction 23 of the fibrous web.

[0093] The dewatering screen 8 is guided endlessly over an arrangement of several rollers, whereby the application of the fiber suspension in the area of ​​the breast roller

[0094] 10 of the screening section 2. The dewatering screen 8 has a width of approximately 7.2 m.

[0095] In this example, the fiber is softwood pulp with an average fiber length of approximately 2.2 mm. These are so-called long fibers. The pulp is unbleached and has a kappa number of approximately 65. The consistency of the fiber suspension when applied to the dewatering screen 8 is approximately 0.22%.

[0096] The speed of the fiber suspension emerging from the headbox 3 is approximately 2% higher than the running speed of the dewatering screen 8. The dewatering screen 8 has a speed of approximately 1100 m / min. The high-frequency shaking device 4 is designed to oscillate the breast roll 10 and thus also the dewatering screen 8 in the region of the breast roll 10. This reduces the longitudinal alignment of the fibers in the machine direction 1, which contributes to improving the properties of the produced paper in the transverse direction, i.e., transverse to the machine direction 1. In this exemplary embodiment, the oscillation occurs at a frequency of approximately 7 Hz and an amplitude of approximately 35 mm.

[0097] Viewed in the running direction 23, after the suspension has been applied to the dewatering screen 8, the fiber web enters a first dewatering area 11. Here, the fiber web is dewatered downwards, i.e., from the inner side 12 of the dewatering screen 8. A first dewatering device 14 is arranged in the first dewatering section 11, which initially enables a primarily gravity-driven dewatering of the fiber web, followed by a downward suction treatment. The suction treatment is carried out by means of suction boxes 24.

[0098] In the first dewatering section 11, the fibrous web is dewatered exclusively downwards.

[0099] The first dewatering section 11 is followed by a second dewatering section 13, in which the fibrous web is dewatered upwards, i.e., toward the top side of the fibrous web. For this purpose, a second dewatering device 15 is provided in the area of ​​the outer side 9 of the dewatering screen 8. This second dewatering device is designed as a suction dewatering device with four consecutive suction zones 17. A continuously circulating top-forming dewatering screen 18 is guided between the second dewatering device 15 and the fibrous web and moves at the same speed as the main dewatering screen 8.

[0100] Furthermore, four formation bars 16 are provided, arranged one after the other in the running direction 23 of the dewatering screen 8. These form the inner side 12 of the dewatering screen 8 and thereby press the fibrous web toward the top former dewatering screen 18 or the second dewatering device 15. The contact pressure exerted by the formation bars is adjustable between 5 and 25 kPa.

[0101] The fibrous web then exits the wire section and is further processed in the other parts of the plant, as shown in Fig. 1, to be further dewatered or dried and finally to form a paper web.

[0102] Due to the treatment in the wire section, the resulting kraft paper has a number of advantageous properties, particularly relating to the extensibility in the transverse direction and the formation of the paper.

[0103] The kraft paper produced according to the described embodiment has the following exemplary property profile:

[0104] 'measured in an area ±5 cm from the geometric center of the paper web in its transverse direction

[0105] “measured in an area not exceeding 10 cm from the edge of the paper web in its transverse direction

Claims

Patent claims 1. A process for producing kraft paper comprising the following steps: - forming a fibrous web running along the machine direction (1) by continuously applying a fibrous suspension to a wire section (2) through a headbox (3), - shaking the fibrous web transversely to the machine direction, i.e. in the transverse direction, by a shaking device (4), - pressing the fibrous web previously partially dewatered in the wire section (2) in a press section (5), - further drying of the fibrous web in a drying section (6), - Winding up the paper web formed from the fibrous web in a winding station (7), wherein the wire section (2) comprises an endlessly rotating dewatering wire (8) and the application of the fibrous suspension to the outer side (9) of the dewatering wire (8) takes place in the region of a breast roll (10) of the wire section (2), wherein the wire section (2) has a first dewatering section (11) in which a first dewatering device (14) is arranged on the inner side (12) of the dewatering wire (8) for dewatering the fibrous web from below, characterized in that - that the shaking device (4) causes the dewatering screen (8) to oscillate in the transverse direction in the area of the breast roller (10), - that in the running direction (23) of the fibrous web, a second dewatering section (13) is arranged following the first dewatering section (11), in which a second dewatering device (15) is provided which dewaters the fibrous web from above, - and that the consistency of the fiber suspension applied to the wire section (2) is at most 0.46%, preferably at most 0.3%, more preferably between 0.15% and 0.3%.

2. Method according to claim 1, characterized in that the dewatering screen (8) oscillates in the region of the breast roller (10) with an amplitude of at least 15 mm.

3. Method according to claim 1 or 2, characterized in that the dewatering screen (8) oscillates in the region of the breast roller (10) at a frequency of between 5 Hz and 10 Hz.

4. Method according to one of claims 1 to 3, characterized in that in the second dewatering section (13) on the inside (12) of the dewatering screen (8) at least four transversely extending formation strips (16) are provided, which exert a pressure of between 2 and 25 kPa on the dewatering screen (8) in the direction of the second dewatering device (15).

5. Method according to one of claims 1 to 4, characterized in that the second dewatering device (15) comprises at least one, in particular at least three, suction zones arranged one after the other in the running direction of the fibrous web (17) which is or are operated in particular with a vacuum of between 5 and 25 kPa.

6. Method according to one of claims 1 to 5, characterized in that in the second dewatering section (13) between the second dewatering device (15) and the fibrous web, an endlessly rotating top former dewatering screen (18).

7. Method according to one of claims 1 to 6, characterized in that - that the production speed is greater than 400 m / min, - and that the width of the fibrous web is greater than 3.5m and in particular greater than 5.5m.

8. Method according to one of claims 1 to 7, characterized in that - that the extensibility of the paper web, in particular according to ISO 1924-3:2005, in the transverse direction is greater than 6.5%, preferably greater than 7.5%, - and that the difference in the extensibility of the paper web in the transverse direction between the edge region and the central region of the paper web is a maximum of 1.5%.

9. Method according to one of claims 1 to 8, characterized in that - that the fibre is unbleached pulp, - and / or that the pulp is made of softwood long fibres with an average fibre length of at least 2 mm according to ISO 16065-2:2014, - and / or that the fiber material has a kappa number of at least 30, in particular of at least 45, preferably of at least 50.

10. Method according to one of claims 1 to 9, characterized in that - that the speed of the dewatering screen (8) of the screen section (2) is between 97% and 99% of the jet speed of the headbox (3), - and / or that the Ambertec formation of the paper web is not more than 0.7 (g / m 2 ) amounts, - and / or that the Gurley air resistance of the paper web, in particular according to ISO 5636-5:2013, is at most 15 s, preferably at most 10 s, - and / or that the tensile energy absorption index of the paper web in the transverse direction, in particular according to ISO 1924-3:2005, is at least 2.5 J / g, preferably at least 3.0 J / g. 11 . Method according to one of claims 1 to 10, characterized in that - that the drying section (6) comprises a pre-drying section (19) and a post-drying section (20), and - that the fibrous web is compressed between the pre-drying section (19) and the after-drying section (20) by a compression device (21), in particular by a Clupak device.

12. Method according to one of claims 1 to 11, characterized in that the fibrous web is calendered or embossed after the drying section (6) in a calendering device (22) or in an embossing device.

13. Kraft paper obtainable from a process according to any one of claims 1 to 12.

14. A wire section for a plant for producing kraft paper, comprising an endlessly rotating dewatering wire (8), on the outer side (9) of which a fiber suspension can be applied in the region of a breast roll (10), wherein the wire section (2) has a first dewatering section (11) in which a first dewatering device (14) for dewatering the fiber web from below is arranged on the inner side (12) of the dewatering wire (8), characterized in that - that a shaking device (4) is provided which is designed to oscillate the breast roller (10) transversely to the running direction (23) of the dewatering screen (8), and - that in the running direction (23) of the dewatering screen (8) a second dewatering section (13) is arranged following the first dewatering section (11), in which a second dewatering device (15) for dewatering the fibrous web from above is provided on the outer side (9) of the dewatering screen (8).

15. Screen section according to claim 14, characterized in that - that in the second dewatering section (13) on the inside (12) of the dewatering screen (8) at least four transversely extending formation strips (16) are provided, which are designed to exert a pressure of between 2 and 25 kPa on the dewatering screen (8) in the direction of the second dewatering device (15), - and / or that the second dewatering device (15) comprises at least one, in particular at least three, suction zones (17) arranged one after the other in the running direction of the dewatering screen, which can be operated in particular with a vacuum of 5 - 25 kPa, - and / or that an endlessly rotating top former dewatering screen (18) is arranged in the second dewatering section (13) between the second dewatering device (15) and the dewatering screen (8).

16. Use of a wire section according to claim 14 or 15 in a process for producing kraft paper, in particular in a process according to one of claims 1 to 12.

7. Plant for the production of kraft paper comprising the following plant components: - a wire section (2) for forming a fibrous web by continuous Application of a fiber suspension along the machine direction (1) through a headbox (3), - a shaking device (4) for shaking the fibrous web transversely to the Machine direction (1 ), i.e. in the transverse direction, - a press section (5) for pressing the partially dewatered in the wire section (2) fibrous web, - a drying section (6) for drying the fibrous web, - a winding station (7) for winding up the paper web formed from the fibrous web, characterized in that the wire section is a wire section according to claim 14 or 15.

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