Method and machine for producing a dry-laid fibrous web

Abstract

The invention relates to a machine (1) and to a corresponding method for producing a dry air-laid fibrous web (309). The machine (1) comprises: a) a low-water raw material preparation of cellulose-containing fibers (200), in particular fibrous material in the form of bales or sheets, in order to form individual fibers and / or fiber bundles (209); b) a dry-forming device (4) for dry-forming the individual fibers and / or fiber bundles (209) in an air stream in order to form a flat laid fibrous structure (300) on a forming belt (40); c) an application device (71) for applying a fluid, preferably water and / or a water-additive mixture, to the laid fibrous structure (300); d) a solidifying device (8) for solidifying the flat laid fibrous structure (300) by applying pressure and / or temperature, in particular in a press gap (81, 82, 83); and also a separating cutting device (55) having at least one compressed air nozzle (56) for cutting the laid fibrous structure (300, 305) by means of at least one compressed air jet (57), which forms a cutting wall (310) on at least one separating edge (311) of the separating cut (312) produced on the laid fibrous structure (300, 305) by means of the separating cutting device (55).

Description

[0001] Method and machine for producing a dry-elasticated fiber web

[0002] The invention relates to a method for producing a fibrous web, in particular a tissue, paper or cardboard web or a nonwoven web, comprising the following steps: a) low-water raw material preparation of cellulose-containing fibers to individual fibers and / or fiber bundles; b) forming the individual fibers and / or fiber bundles in an air stream to form a planar fiber layup on a forming belt by a dry forming process; c) application of a fluid, in particular water and / or a water-additive mixture, to the fiber layup; d) consolidation of the planar fiber layup by applying pressure and / or temperature in at least one consolidation device.

[0003] Many fiber webs, especially paper, cardboard, or tissue, were and still are produced almost exclusively using wet processes on an industrial scale. Cutting and separating devices are used to separate or cut the fiber web during production, for example, to trim the edges or to transfer the fiber web through the machine after a break or start-up. Such cutting and separating devices often have a mechanical cutting edge or are designed as water jet trimmers, which cut the fiber web with a jet of water. Since the fiber web produced using the wet process undergoes several drying stages during the manufacturing process anyway, the water introduced into the fiber web during cutting is removed from the paper web during this process.

[0004] In the production of dehydrated fiber webs, the use of water is largely reduced; in particular, the introduction of water not directly involved in the fiber web production process must be avoided, making the use of water jet trimmers for cutting the fiber web unfavorable. The use of mechanical cutting also has disadvantages, such as a narrow kerf width, which carries the risk of the cut edges rejoining or excessive cutting wear. Furthermore, cutting devices are known that, when cutting fiber webs using an air jet, produce comparatively frayed and unbound cut edges that are prone to tearing.

[0005] It is therefore an object of the present invention to provide a method and a machine for producing a dried fiber web, in particular a tissue web, with which the disadvantages described above can be avoided or at least reduced. In particular, it should be possible to separate or trim a fiber web in the desired manner during the production of a dried fiber web, whereby the strength of the fiber web is at least maintained at one of the two separation edges and no additional water or other liquid is introduced into the manufacturing process.

[0006] The problem described above is solved by the features of the independent claims. The dependent claims relate to advantageous embodiments of the present invention.

[0007] In particular, the problem is solved by the manufacturing process described at the outset, which is characterized in particular by the fact that the fiber fabric is cut by means of at least one air pressure jet, whereby a cut ridge is formed on at least one cutting edge of the cut on the fiber fabric by means of the air pressure jet.

[0008] The inventors have discovered that the fiber layup of a particularly dry fiber web can be separated using an air jet, thereby preventing water from being introduced into the fiber layup by the separation device. Furthermore, the inventors have discovered that fibers released or separated from the fiber layup by the air jet can be collected at at least one separation edge of the cut produced by the air jet, in order to form a cut ridge. This ridge is then solidified by a subsequent consolidation of the planar fiber layup in at least one consolidation device, as provided for in the manufacturing process of the fiber web, by applying pressure and / or temperature. This consolidation imparts additional strength, particularly to the at least one separation edge. A region with increased areal density, a cut ridge, is thus created at the separation edge.In this way, the tendency for the trimmed fiber web to tear at this cutting edge can be reduced, thereby enabling more reliable guidance of the fiber web or a transfer tape of the fiber web through the machine, particularly through the fiber web system. For industrial-scale production, a high, continuous production speed or fiber web speed of 300 m / min or more, in particular 400 m / min or more, in particular 500 m / min or more, in particular more than 600 m / min or more than 800 m / min, and a width of the continuously produced fiber web of 0.5 m or more, in particular 1 m or more, in particular 2.7 m or more up to 7.2 m or less, up to 10 m or less, is desired.An important factor in enabling such production speeds is the strength of the fiber web, especially in conjunction with preventing tearing at a separation edge.

[0009] Accordingly, a method for producing a fiber web of the type mentioned above is proposed, in which the fiber fabric is cut by means of at least one air jet, whereby a cut edge is formed on the fiber fabric at at least one cut edge. In one embodiment of the method, the cut edge of the fiber web has a density of at least 1.2 to 2 times the basis weight, in particular 1.3 to 1.8 times the basis weight, and in particular 1.4 to 1.6 times the basis weight of the fiber web. This increase in basis weight in the region of at least one cut edge can be achieved by collecting fibers from the fiber fabric, which are detached or separated by means of the air jet, at at least one cut edge of the fiber fabric.The at least one air pressure jet must be designed and / or directed towards the fiber fabric in such a way as to ensure reliable separation of the fiber fabric and / or to ensure that, on the one hand, the fibers released or cut from the fiber fabric collect at least one separation edge and form a cut ridge at the at least one separation edge of the separation cut.

[0010] In one embodiment of the method, the fiber layup is cut in the machine direction (MD) before a consolidation device. In this arrangement, the cut edge formed by the cutting process is consolidated by the consolidation device, particularly immediately after its formation. This creates bonds, especially in the form of mechanical connections, between the fibers of the fiber layup and the cut edge, thereby stabilizing the cut edge and the cut edge. The risk of tearing of the fiber layup at the cut edge, which arises during the cutting process, is thus subsequently eliminated.

[0011] In one embodiment of the method, the fiber fabric is cut in the machine direction MD upstream of an application device for applying a fluid, in particular water and / or a water-additive mixture, to the fiber fabric. The fluid creates bonds, particularly in the form of hydrogen bonds, between the fibers of the fiber fabric and / or the cut edge, thereby stabilizing the cut edge and the cut edge. Any potential risk of tearing of the fiber fabric at the cut edge during the cutting process can be further reduced or eliminated by applying a fluid to the fiber fabric via the application device after the cutting process.

[0012] In one embodiment of the method, the cut edge of the fiber fabric and / or the fiber web, after passing through at least one consolidation device, has a thickness at least 1.5 to 3 times that of the fiber fabric and / or the fiber web, in particular 1.8 to 2.6 times that of the fiber fabric and / or the fiber web, and in particular 2 to 2.4 times that of the fiber fabric and / or the fiber web. A cut edge that, after passing through at least one consolidation device, has a greater thickness than the fiber fabric and / or the fiber web, accordingly has a higher strength than the fiber fabric and / or the fiber web itself.Since higher forces can act in the area of ​​the separation edge, especially depending on further process steps of the manufacturing process, than in other areas of the fiber lay-up, the higher strength of the cut edge and thus of the separation edge can increase the safety against tearing of the separation edge and thus the reliability of the manufacturing process after the separation cutting operation.

[0013] In one embodiment of the method, the fiber fabric is cut as long as it has a lower strength than the produced fiber web. The strength during the cutting process is less than 80% of the strength of the produced fiber web, in particular less than 50%, and in particular less than 25%, and preferably less than 10%, preferably less than 5%, of the strength of the produced fiber web. The strength of the fiber fabric increases, in particular, with the number or density of bonding points between the fibers, especially with the number or density of hydrogen bonds formed. The lower the strength of the fiber fabric during cutting by the at least one compressed air jet, the easier it is to cut by at least one compressed air jet.In general, the strength of the fiber fabric increases with the progression of processing during the manufacturing process.

[0014] In one embodiment of the method, the separation cut is first made with a first compressed air jet and then widened with at least a second compressed air jet, which is arranged offset in the machine transverse direction (CD = Cross-Direction) relative to the first compressed air jet. For higher areal weights or strengths of the fiber fabric, at least two compressed air nozzles may be required to produce a suitable separation cut in the fiber fabric. Furthermore, wider separation cuts can also be made than when using a single compressed air jet. The width of the separation cut depends not only on the compressed air pressure used, but also on the geometry of the compressed air nozzle and thus on the cross-section of the compressed air jet acting on the fiber fabric, and especially on the distance between the at least two compressed air jets in the machine transverse direction. The mass of the fiber fabric detached or separated during the separation process determines the required separation width.The maximum mass of the cut ridge formed at at least one cutting edge of the separation cut is also determined by these separated fibers. It is also possible to vacuum up a fiber layer remaining, particularly in the transverse direction of the machine, between the air jets and thus especially between two separation cuts, or a portion of the detached fibers (which especially represent a mass surplus compared to the desired cut ridge) and reuse them, particularly as recycled material.

[0015] In one embodiment of the method, at least one air jet is arranged at an angle in the machine direction (MD), wherein the air jet is directed forward in the machine direction (MD), in particular in the direction of movement of the fiber layup or the fiber web. The angle of inclination relative to the vertical is 10° to 45°, in particular 20° to 35° and in particular 25° to 30°. An angle of inclination in the machine direction (MD) promotes the collection of loose fibers at at least one cutting edge and the formation of a corresponding cut ridge. The air jet directed forward in the machine direction (MD) can act similarly to a snowplow and lead to an accumulation and compaction of the fibers arranged at the cutting edges, in particular the collected fibers, even during the cutting process. An angle of inclination in the direction of movement of the fiber layup or the fiber web is also advantageous.The fiber web prevents excessive stirring of fibers from the composite and supports the deposition of the fibers to the left and right of the separation cut at the separation edge to form a cut ridge.

[0016] In one embodiment of the method, at least one air jet is arranged at an angle in the transverse direction (CD) of the machine, with the air jet directed towards a cutting edge of the section. The angle of inclination relative to the vertical is 1° to 20°, in particular 3° to 15° and in particular 5° to 10°. An angle of inclination in the transverse direction (CD) of the machine promotes the collection of detached fibers at the cutting edge of the section, towards which the air jet is inclined. Accordingly, by inclining the air jet in the transverse direction (CD) of the machine, improved compaction and accumulation of fibers at the cutting edge towards which the air jet is directed can be achieved.

[0017] In one embodiment of the method, the width of the separation cut corresponds at least to the average fiber length, in particular 1.5 times, preferably 2 times, the average fiber length of the fibers of the fiber layup. As the width of the separation cut increases beyond the average length of the fibers of the fiber layup, the probability decreases that fibers of the fiber layup will overlap the separation cut and form or exhibit bonds at both separation edges of the separation cut, and in particular that fibers extending from one separation edge of the separation cut will (re)connect with the fiber layup of the separation edge opposite the separation cut, thus creating an undesirable reconnection of the separation edges of the fiber layup on both sides of the separation cut.

[0018] The fiber webs or fibrous webs of tissue, paper, or cardboard produced using the proposed method predominantly have medium fiber lengths that are shorter than those of nonwoven webs, in particular usually no more than 5 mm. Accordingly, the width of the separation kerf for such fibrous webs is, for example, 4 to 6 mm.

[0019] In one embodiment of the method, the compressed air supplied to the at least one compressed air nozzle has a pressure in the range of 4 bar to 8 bar, in particular 5 bar to 7 bar, and in particular 6 bar. Such pressures, which are frequently provided by the air supply systems of machines for producing a fibrous web, are particularly suitable, in conjunction with suitable nozzle designs, for providing a compressed air jet suitable for separating a fiber layup.

[0020] In one embodiment of the process, the produced fibrous web is, in particular, a one-, two-, three-, four- or more-layered tissue web with a basis weight of 5 g / m². 2 up to 75 g / m² 2 , especially of 15 g / m² 2 up to 60 g / m² 2 , preferably of 25 g / m² 2 up to 45 g / m² 2 , particularly preferably 28 g / m² 2 up to 42 g / m. The proposed method is particularly suitable for the production of such fibrous webs.

[0021] Furthermore, the problem is solved by a machine for producing a fibrous web, in particular a tissue, paper or cardboard web or a nonwoven web, wherein the machine comprises: a) a raw material preparation plant for the low-water processing of cellulose-containing fibers into individual fibers and / or fiber bundles; b) a dry forming device for the dry forming of the individual fibers and / or fiber bundles in an air stream into a planar fiber layup on a forming belt; c) an application device for applying a fluid, in particular water and / or a water-additive mixture, to the fiber layup; d) a consolidation device for consolidating the planar fiber layup by applying pressure and / or temperature, in particular in a press gap.

[0022] The machine further comprises a cutting device with at least one compressed air nozzle for cutting the fiber fabric by means of at least one compressed air jet, which forms a cut ridge on at least one cutting edge of the cut produced by the cutting device on the fiber fabric.

[0023] The machine is specifically designed to carry out the method or embodiments of this method described above. Accordingly, the advantageous developments previously described for the method according to the invention also apply analogously to the machine according to the invention. In particular, the machine has a cutting device by which a cut ridge can be formed at at least one cutting edge of the fiber web by means of at least one jet of compressed air. In this way, it is possible to cut or trim a fiber web during the production of a dried fiber web in such a way that the strength of the fiber web is maintained or even increased at at least one of the two cutting edges, and no additional water is introduced into the manufacturing process.

[0024] In one embodiment of the machine, at least one compressed air nozzle of the cutting device is arranged at an angle in the machine direction (MD) such that the compressed air jet is directed forward in the machine direction (MD) and the angle of inclination of the compressed air jet generated by the nozzle relative to the vertical is 10° to 45°, in particular 20° to 35° and in particular 25° to 30°. As already described in the method, an angle of inclination in the machine direction (MD) promotes the accumulation of detached fibers at at least one cutting edge and the formation of a cut ridge at this cutting edge. The compressed air jet directed forward in the machine direction (MD) can act similarly to a snowplow and, even during the cutting process, lead to an accumulation and compaction of the fibers arranged at the at least one cutting edge, thus contributing to increased strength and stabilization of the cutting edge.

[0025] In one embodiment of the machine, the at least one compressed air nozzle has an aperture diameter between 0.5 mm and 1.8 mm, in particular between 0.8 mm and 1.2 mm. A compressed air nozzle with such a diameter is particularly suitable for separating a fiber fabric of the type and in the manner described herein by means of a jet of compressed air.

[0026] In one embodiment of the machine, the compressed air outlet of the at least one compressed air nozzle is located at a distance from the surface of the fiber fabric ranging from 1 mm to 60 mm, particularly from 10 mm to 45 mm, and especially from 20 mm to 30 mm. Depending on the fiber fabric and its current degree of consolidation, as well as the design of the compressed air jet, the distance of the compressed air outlet of the at least one compressed air nozzle from the surface of the fiber fabric is a relevant parameter for the cutting process and for the formation of a cut ridge at at least one cut edge of the fiber fabric.

[0027] In one embodiment of the machine, the cutting device, or at least one compressed air nozzle of the cutting device, can be movable in the transverse direction (CD) of the machine. The cutting device can also have two or more compressed air nozzles, which can be moved independently of one another, in order to achieve the desired cut. For example, when using at least two compressed air nozzles, a cut produced by a first nozzle can be widened by a second compressed air jet produced by a second nozzle. Similarly, the cut can be guided in the transverse direction of the machine. In particular, the cutting device can also have at least one extraction device that collects excess fibers released during the cutting process, especially those not used to build up a cut ridge, and removes them from the cutting area.

[0028] In one embodiment, the cutting device may also have at least two compressed air nozzles spaced apart from each other in the transverse direction of the machine (CD = Cross-Direction) to produce two adjacent cuts. In this way, a waste belt can be formed between the cuts, which can be removed from the fiber layup by means of a removal or, in particular, a suction device.

[0029] In the context of the present invention, the term "low-water" raw material processing also includes processing the raw material entirely without the targeted addition of water and / or other liquids. "Low-water" raw material processing is understood to mean that the amount of water already contained in the provided, air-dried raw material is sufficient for the processing process, and the processing can be carried out without any further addition of water or moisture. The water content of the air-dried raw material is typically between 1% and 30%, particularly between 1% and 20%, and especially between 1% and 10%, based on the mass of the raw material.

[0030] Alternatively, in a "low-water" processing method, a small amount of water or moisture can be added to the raw material during the processing, so that the water content of the raw material, chips, and / or individual fibers does not exceed a maximum limit of 30%, in particular 20%, and in particular 10%, based on the mass of the raw material, chips, or individual fibers in the individual processing steps. It must be taken into account that the raw material can absorb water or moisture from its environment during storage for at least several hours, with this maximum amount depending on the raw material, the storage conditions, and the environmental conditions.

[0031] The invention expressly extends to embodiments which are not given by combinations of features from explicit cross-references of the claims, whereby the disclosed features of the invention can be combined arbitrarily with one another - insofar as this is technically sensible.

[0032] To differentiate between the manufactured fiber webs, for example a tissue, paper or cardboard web, especially in a basis weight range of 5 g / m² 2 up to 600 g / m² 2 , on the one hand, or a non-woven fabric (in English "non-woven") on the other hand, the following distinction is made, which is based on fiber length, density and fiber bonding type:

[0033] A fibrous web with predominantly average fiber lengths that are shorter than the average fiber lengths of nonwoven webs, less than or equal to 5 mm, in particular less than or equal to 4 mm, in particular less than or equal to 3 mm, predominantly bonded by hydrogen bonds and with a bulk density greater than or equal to 0.4 g / cm³, is placed under a tissue, paper or cardboard web. 3The fibers used in a tissue, paper, or board web are further characterized by a fiber length-to-diameter ratio of less than or equal to 200, particularly less than or equal to 150, and especially less than or equal to 100. A nonwoven web, which also consists primarily of fibers, is defined, as a key distinction from a tissue, paper, or board web, by having a fiber content of at least 30% consisting of very long fibers with an average fiber length of more than 5 mm or continuous fibers, which determine the nonwoven characteristics. Furthermore, a fiber length-to-diameter ratio of greater than or equal to 300 is targeted for a nonwoven web. The remaining fiber content of a nonwoven web may be of a different composition, and the bulk density should be less than 0.40 g / cm³. 3to classify a fibrous web as a nonwoven fabric.

[0034] Furthermore, in the present invention, the manufactured fiber web is free of artificial fibers as raw material, for example, binding fibers such as bicomponent fibers, melt fibers and other fibers available on the market that are synthetically or industrially produced.

[0035] The dry-formed fiber web thus consists solely of natural fibers from plant, animal, or mineral sources as raw material, with cellulose-containing fibers, i.e., from plant sources, being used preferentially. This allows a basic strength to be created through hydrogen bonds between the cellulose-containing fibers when water is applied.

[0036] Furthermore, when using exclusively cellulose-based fibers as raw material, a specific, preferably small, proportion of chemical binders in the form of a water-additive mixture can be applied to the fiber web to adjust the quality factors of the manufactured fiber web, such as strength, feel, and appearance. These water-additive mixtures can contain a certain proportion of synthetically or industrially produced components, such as polymers, in dissolved form, which are present in the final manufactured fiber web in a cured form. Moreover, the dry-formed fiber web is produced without complex bonding methods such as needling or waterjet needling, which are typically used in the production of nonwoven webs.

[0037] Further features and advantages of the invention will become apparent from the following description of a preferred embodiment with reference to the drawing.

[0038] The following are exemplary embodiments of the invention explained with reference to the following figures.

[0039] Fig. 1 shows a schematic representation of the construction of an exemplary machine 1 for the production of a fibrous web 309;

[0040] Figures 2a to c show schematic views of a section of an exemplary machine 1 for producing a fibrous web 309 in a front view, from the left and in a top view; and

[0041] Fig. 3 shows an example of a schematic sectional view through a fiber fabric 300 according to section llc - llc from Fig. 2c.

[0042] To clarify the individual directions, a higher-level Cartesian coordinate system is used in the figures. The x-direction corresponds to a longitudinal extent, also known as the machine direction (MD). The y-direction corresponds to a direction orthogonal to the machine direction (MD) and is also known as the cross-direction (CD). The z-direction corresponds to the vertical direction.

[0043] Figure 1 and Figures 2a to 2c show, by means of a schematic representation, a possible embodiment of the manufacturing process according to the invention or of the structure of the machine 1 according to the invention, which can include a raw material preparation plant 2 and a fiber web plant 3. In the upper left of Figure 1, a possible embodiment of a low-water processing system or a low-water raw material preparation plant 2 is shown schematically, in which individual fibers and / or fiber bundles can be produced, for example, from fiber-containing recycled material and / or from virgin fiber pulp, particularly as bales, by means of comminution devices and / or fiber fiber separators. The individual fibers and / or fiber bundles can be transported in an air stream after successful comminution or fiber separation.The air / fiber mixture can be supplied via one or more distribution channels to at least one dry forming device 4 of a fiber web plant 3 for the production of a dry formed fiber web 309.

[0044] The two manufacturing processes of the low-water raw material preparation 2 and the fiber web plant 3 can be coupled for the production of high-quality fiber webs 309, whereby both can be coordinated or controlled and / or regulated via a higher-level control and / or regulating device 60.

[0045] Optionally, conditioning can be performed after cleaning the raw material. During conditioning, a small amount of moisture can be added to the cleaned raw material, for example, to minimize or prevent dust formation and / or electrostatic charging. Additives can also be added during conditioning. Recycled material from other fiber web production plants or waste paper can be mixed into the raw material. Furthermore, machine rejects or scrap from fiber web plant 3 can also be added. These rejects could be, for example, waste parts 302 or edge trimming or edge extraction, in which fibers from a fiber layup 300 are extracted from the edge after at least one dry forming device 4.Furthermore, individual fibers and / or fiber bundles filtered from the ambient air that have not been deposited can also be added back in as rejects. It is advantageous if the recycled material and / or rejects contain no additives and thus meet the specified quality requirements without further processing steps.

[0046] In the embodiment shown in Figure 1, only one exemplary dry forming device 4 is depicted. The fiber web system 3 can also have several dry forming devices, in particular to produce superimposed layers of the finished fiber web 309. The individual fibers and / or fiber bundles 209 processed from the raw material can be fed to at least one dry forming device 4 of the fiber web system 3 and, in particular, distributed as uniformly as possible transversely to the machine direction MD or in the machine transverse direction CD of the fiber web system 3.

[0047] Following at least one dry forming device 4, two application devices 7 can be provided, which can apply a fluid, in particular water or a water-additive mixture, to the fiber fabric 300 or the consolidated fiber fabric 305. The at least two application devices 7 can be configured as a first application device 71 and at least one further application device 72, 73.

[0048] It may be provided that in one embodiment a first application device 71 applies a fluid in the form of water, in particular free of, preferably chemical, additives, to the fiber fabric 300.

[0049] Furthermore, the first application device 71 can be provided after a pre-solidification device 83.

[0050] The first application device 71 can preferably apply a quantity of water of 1 to 20% based on the mass or basis weight of the fiber fabric 300. The first application device 71 can be activated before or after the transfer of the transfer belt 301. If activated before the transfer, the transfer belt 301 and the cut edge 310 can additionally form bonds in the form of hydrogen bonds, thus exhibiting increased strength. Contamination of the support elements, in particular the forming belt 40, the pressing belt 41, the transfer belts 102 and 103, and / or the drying belt 42, cannot occur with a pure application of water.

[0051] Furthermore, at least one consolidation device 8 can be provided after the at least one dry forming device 4, which can consolidate the fiber fabric 300. The embodiment shown in Fig. 1 has, by way of example, three consolidation devices 8. In particular, at least one consolidation device 8 can be designed such that, in addition to consolidating the fiber fabric 300, it can also structure and / or heat it. The structuring by at least one of the consolidation devices 8 can be used in particular for the production of a tissue web with low- and high-pressure zones, especially a tissue web with a basis weight of 28 g / m². 2 up to 42g / m² 2 , be important.

[0052] Furthermore, it may be provided that, in the case of several consolidation devices, for example a pre-consolidation device 83, a press gap 81 and / or a further press gap 82, the applied pressures or line loads for consolidation of the fiber fabric by the pre-consolidation device 83 are lower than the line loads in the press gap 81. Furthermore, the line load in the press gap 81 may be less than or equal to the line load in the further press gap 82.

[0053] Furthermore, the consolidation device 8 can be configured as at least one press gap with at least two pressing elements. It is also possible for three or four pressing elements to be provided in one press gap. For example, the press gap 81 is configured with three pressing elements, wherein the press gap is formed by a press belt 42 and two press rollers. For example, the further press gap 82 is configured with two pressing elements as two press rollers.

[0054] Furthermore, a multi-press roller arrangement can be provided, whereby one, two or three press gaps can be formed in combination with the same press rollers.

[0055] To complete the continuously produced fiber web 309, a web-width winding unit 12 can be arranged at the end of the fiber web system 3.

[0056] The fiber web system 3 can have at least one drying device 10. It is advantageous if the at least one drying device 10 is arranged downstream of the application devices 7 in order to dry the fiber web 305, onto which a fluid, in particular in a metered quantity, has been applied. In particular, the at least one drying device 10 can be arranged upstream of the winding 12 of the finished fiber web 309.

[0057] The dry forming step in the at least one dry forming device 4 can be controlled and / or regulated by at least one control and / or regulating means 60, wherein the individual fibers and / or fiber bundles 209 in the dry forming device 4 can be laid down, in particular partially, by weight force onto a circulating, in particular permeable, forming belt 40 and can form a fiber web 300 that is still substantially unconsolidated. Furthermore, the dry forming device 4 can include a suction device 30, which can assist in laying the individual fibers 209 down onto the permeable forming belt 40 and can also influence this process as a control and / or regulating means. In the area of ​​the forming belt 40, at least one cutting device 55 for cutting the fiber web 300 can also be arranged, for example, for trimming the side edges of the fiber web 309 or for example, for cutting a transfer belt 301.In particular, the fiber layup 300 can be measured with respect to its mass distribution or basis weight distribution by at least one enclosed measuring device 61, in particular a mass measuring device extending in the transverse direction CD of the machine. The measurement signal can act as a control variable, in particular via the higher-level control and / or regulating device 60, on the feed of the individual fibers from the raw material preparation plant 2 and / or on the suction device 30.

[0058] The air 39 extracted by the suction device 30 may contain a certain quantity of individual fibers 209. Therefore, it is advantageous if a large proportion, in particular up to 95%, of the air volume extracted by the respective suction device 30 can be returned directly to the dry forming device 4 in a recirculation circuit. This makes it possible to break down the continuously added individual fibers 209 even better in order to achieve good formation on the forming belt 40, while the extracted individual fibers can be immediately fed back into the corresponding production step.

[0059] As shown in Fig. 1, the fiber fabric 300 can pass through a consolidation device 8 in the form of a pre-consolidation device 83 before the first application device 71, in which the still unconsolidated fiber fabric 300 including any separating edges 311 can receive a first, full-surface pre-consolidation or pre-compacting over the entire machine transverse direction CD.

[0060] Immediately before winding 12, the fiber web 309 can be guided through a drying device 10. The properties of the fiber web 309, with regard to its thickness, its feel, and / or its absorption capacity, can be advantageously maintained by means of, for example, a contactless drying device 10. The application devices 71, 72, 73 can be designed such that the fiber web 300 can be wetted over its entire surface with the fluid. In the first, second, and / or third application device 71, 72, 73, a vacuum box 31 can be arranged on the side of the fiber web 300 opposite the side to be wetted.This can be implemented in particular by drawing ambient air through the fiber fabric 300 and through a support element supporting the fiber fabric 300 and designed to be permeable, preferably through a press belt 41 and / or a transfer belt 103 and / or a drying screen 42, by means of a negative pressure applied, especially during application. The reference numeral 22 indicates the respective direction of travel of the press belt 41 and other coverings in Fig. 1.

[0061] Optionally, at least one moisture measuring device 63 and / or a measuring device for monitoring the fluid application may be provided. The at least one moisture measuring device 63 may be arranged such that it can measure before and / or after the heating device 10.

[0062] The connecting belt 102 can guide the fiber fabric 300 from the press belt 41 to just before a further consolidation device 8 in the form of a further press gap 82, through which the fiber fabric 300 can then be guided unsupported. In the further press gap 82, the fiber fabric 300, including any parting edges 311 with cut ridges 310 formed thereon, can be further consolidated by pressure and / or temperature before it can be guided as a further consolidated fiber fabric 305 to the dryer device 10. The further press gap 82, like the press gap 81, which also constitutes a consolidation device 8, can be provided by the nip between two rollers.Because the fiber fabric 300 can be guided unsupported through the wider press gap 82, unlike in the previous press gap 81, no consideration needs to be given to the stability of a covering supporting the fiber fabric 300. This makes it possible to apply significantly higher pressures to the fiber fabric 300 in the wider press gap 82 than in the press gap itself.

[0063] 81 is the case. The higher pressures allow for significantly greater strength in the finished fiber web 309. The rollers should be designed to be correspondingly robust. For example, the rollers can be made primarily of steel. At least one of the two rollers forming the further press gap 82 between them can also be designed to provide the fiber fabric 300 with a multitude of high-pressure and low-pressure zones.

[0064] The connecting belt 102 can be designed, in particular, to guide the fiber fabric 300 as close as possible to the further press gap 82 in order to keep the free tension, i.e., the distance that the fiber fabric 300 must travel unsupported between the connecting belt 102 and the further press gap 82, as short as possible. For this purpose, a final connecting belt deflection roller, i.e., the deflection roller at the end of the conveying section of the connecting belt 102, can have a relatively small diameter, and the connecting belt 102 itself can be designed to be sufficiently flexible to follow the correspondingly strong surface curvature of the final connecting belt deflection roller.

[0065] After leaving the further solidification device 8 in the form of the press gap

[0066] 82 The further consolidated fiber fabric 305 can be picked up by a transfer belt 103, which can transfer the further consolidated fiber fabric 305 onto the drying screen 42. For similar reasons as before, the transfer belt 103 can be designed similarly to or identically with the connecting belt 102.

[0067] After the further consolidated fiber fabric 305 is transferred to the drying screen 42, fluid can be applied again to the side of the further consolidated fiber fabric 305 facing away from the drying screen 42 by the third application device 73. Thus, the further consolidated fiber fabric 305 can be moistened from both sides by the second application device 72 and / or the third application device 73 before it is dried in the drying device 10 and subsequently wound onto the winding unit 12 to form a coil.

[0068] The machine 1, in particular the fiber web system 3, can further comprise one or more cutting devices 55 for cutting the fiber fabric 300, 305 by means of at least one compressed air jet 56, which forms a cut ridge 310 at at least one cutting edge 311 of the cut 312 produced by the cutting device 55 on the fiber fabric 300, 305. A cutting device 55 and examples of its arrangement in the machine 1 or in the manufacturing process are shown and described in more detail in Figures 2a to 2c. An exemplary cut 311 with cut ridge 310 is shown and described in more detail in Figure 3 with reference to a detail from Figure 2c (section 11c-11c).

[0069] A cutting device 55 can be positioned at several locations in the fiber web system 3. Figure 1 shows three cutting devices 55 at three exemplary positions where the fiber layup 300 could be cut, particularly upstream of a pre-hardening device 8. At least one of the cutting devices 55 shown can be used to trim the edges of the fiber web 300. Likewise, at least one of the cutting devices 55 shown can be used to produce a transfer strip 301, whereby the fiber web 300 is cut, for example, after a break or machine start-up, particularly by a longitudinal cut, to form a transfer strip 301 and a waste section 302.

[0070] Figures 2a to 2c show schematic views of a section of an exemplary machine 1 for producing a fibrous web 309 from the front, from the left, and in a top view, for example, in the area of ​​the forming belt 40. In the machine direction MD, cutting devices 55a, 55c with at least one compressed air nozzle 56a, 56c can be arranged in both edge regions of the fiber web 300 upstream of a consolidation device 8, for edge trimming or trimming the fiber web 300 by means of at least one compressed air jet 57a, 57c. As shown in the sectional view of the fiber web 300 in Fig. 3, the respective compressed air jet 57a, 57c forms a cut ridge 310 at the respective cutting edge 311 of the cut 312 produced by the cutting device 55a, 55c on the fiber web 300.In particular, it can be advantageous, as in the exemplary embodiment, to cut the fiber fabric 300 as long as it has a lower strength than the produced fiber web 309. It is particularly advantageous if the strength of the fiber fabric 300 during the cutting process is less than 80%, in particular less than 50%, and in particular less than 25%, and preferably less than 10%, preferably less than 5%, of the strength of the produced fiber web 309.

[0071] In the machine direction MD of the exemplary machine 1, as shown in Figs. 2a to 2c, a further cutting device 55b with at least one compressed air nozzle 56b can be arranged behind the consolidation device 8 in order to separate or cut the fiber fabric 300, 305 longitudinally into a transfer strip 301 and a waste part 302 if necessary, for example after a web break or when starting the machine to guide the fiber fabric 300, 305 through the machine 1 or through the fiber web system 3. For example, once the fiber fabric 300 has been guided through the machine 1 and in particular up to the winding 12, the at least one compressed air nozzle 56b of the cutting device 55b can be guided in the machine transverse direction CD to the edge of the fiber fabric 300 (see dashed arrow shown in Fig. 2c), which is arranged on the other side of the fiber fabric 300 than the transfer tape 301 .The waste part 302 can thus be separated from the fiber fabric 300 so that the fiber fabric 300 can subsequently be fed through the machine 1 in its full width. As shown in Fig. 3, the respective air jets 57a, 57b form a cut ridge 310 at the separation edges 311 of the separation cuts 312 produced on the fiber fabric 300 by the cutting devices 55a, 55b. In the embodiment shown in Fig. 2a, the compressed air nozzles 56a, 56b of the separation cutting devices 55a, 55b are shown inclined in the machine direction MD, so that the air jet 57a, 57b is directed forward in the machine direction MD. The angle of inclination α of the compressed air jet 57a, 57b generated by such a compressed air nozzle 56a, 56b can be 10° to 45° relative to the vertical z, in particular 20° to 35° and especially 25° to 30°. It is also possible, as shown in Fig.Figure 2b shows how to arrange the air jet 57c of a compressed air nozzle 56c at an angle in the machine transverse direction CD, such that the air jet 57c is directed towards a parting edge 311 of the parting cut 312. The angle of inclination β relative to the vertical z can be 1° to 20°, in particular 3° to 15° and in particular 5° to 10°.

[0072] An exemplary aperture diameter of a compressed air nozzle 56 is between 0.5 mm and 1.8 mm, particularly between 0.8 mm and 1.2 mm. The compressed air supplied to the at least one compressed air nozzle 56 can have a pressure in the range of 4 bar to 8 bar, particularly 5 bar to 7 bar, and particularly 6 bar. Figure 2a shows the distance a of the exit of the compressed air jet 57b from the compressed air nozzle 56b and the surface of the fiber fabric 300. This distance can be in the range of 1 mm to 60 mm, particularly 10 mm to 45 mm, and particularly 20 mm to 30 mm.

[0073] Fig. 3 shows an exemplary schematic section through a fiber fabric 300 according to section 11c-11c from Fig. 2c. The sectional view shows the separation edge 311 produced as a result of cutting the fiber fabric 300 using the cutting device 55a, on which a cut ridge 310 has formed during cutting with the air jet 56a. Furthermore, the sectional view in Fig. 3 shows the separation cut 312 produced by cutting the fiber fabric 300 using the cutting device 55b, the width b of which corresponds in particular to at least the average fiber length of the fibers of the fiber fabric 300, especially to prevent the two separation edges 311 from rejoining by fibers of the fiber fabric 300 that could overlap the separation step 312.Particularly in the case of fiber fabrics 300 with larger average fiber lengths, a separation cut 312 with the desired width b can, for example, first be made with a first compressed air jet 57b and then expanded with at least a second compressed air jet 57b, which is arranged offset in the machine transverse direction CD relative to the first compressed air jet 57. An embodiment for expanding the separation cut 312 in this way is shown on the right in Fig. 2b. The separation cutting device 55b has two compressed air nozzles 56b arranged offset both in the machine direction MD and in the machine transverse direction CD, so that the fiber fabric 300 can first be separated with the first compressed air jet 57b as it passes through the compressed air jets 57b and then expanded with the second compressed air jet 57b.

[0074] An exemplary separation step 312, producible in this manner, is shown in Fig. 3. After the separation cutting process, each separation edge 310 has a cut ridge 310 arranged thereon, which consists in particular of fibers released, especially accumulated, during the separation process. The cut ridges 310 shown on the left side of the separation cut 312 in Fig. 3 show the cut immediately after the separation cutting process by the separation cutting device 55b. The edge of the fiber layup 300 shown on the right in Fig. 3 was produced by means of the separation cutting device 55a. The fiber layup separated during edge trimming can be removed by means of a suction device 58. An example of a cut ridge 310 formed during edge trimming is shown in Fig. 3 after passing through the consolidation device 8.As can be seen, the already solidified cut edge 310 has a lower height dw and higher strength than a cut edge 310 immediately after its formation by an air jet 57 during the cutting process. A cut edge 310 can pass through one or more solidification devices 8 during the manufacturing process of the fiber web 309, which can further increase its strength. In particular, a cut edge 310 of the fiber web 309 can have a strength at least 1.2 to 2 times the basis weight, in particular 1.3 to 1.8 times the basis weight, and in particular 1.4 to 1.6 times the basis weight of the fiber web 309.The cut edge 310 of the fiber web 309 can, after passing through at least one consolidation device, have a thickness at least 1.5 to 3 times the fiber web thickness dp, in particular 1.8 to 2.6 times the fiber web thickness dF and in particular 2 to 2.4 times the fiber web thickness dF.

[0075] List of reference signs

[0076] 1 machine

[0077] 2 Raw material processing plant

[0078] 3 Fiber web plant

[0079] 4 Dry forming device

[0080] 7 Application device

[0081] 8 Solidification device

[0082] 10 T dryer device

[0083] 12 Roll-up

[0084] 22 Direction of travel

[0085] 30 Suction device of the dry forming device

[0086] 31 Vacuum Box - Application Device

[0087] 32 vacuum boxes

[0088] 39 extracted air

[0089] 40 support element, forming belt

[0090] 41 Support element, press band

[0091] 42 Support element, drying sieve

[0092] 55 Cutting device

[0093] 56 Compressed air nozzle

[0094] 57 Air jet 58 Extraction device 60 Control and / or regulating device 61 Measuring device 63 Moisture measuring device 71 First application device 72 Second application device 73 Third application device 81 Press gap

[0095] 82 further press gap 83 pre-solidification device

[0096] 102 Connecting strip 103 Transfer strip 209 Individual fibers and / or fiber bundles 300 Fiber fabric after dry forming device 301 Transfer strip 302 Waste section 305 Consolidated fiber fabric 309 Fiber web 310 Cutting edge 311 Separating edge

[0097] 312 Separation cut

[0098] MD Machine direction CD Machine transverse direction a Distance air jet from surface fiber layup b Width of separation cut a Angle of inclination forward ß Angle of inclination to a separation edge z Vertical direction dF Fiber web thickness dw Cut-off wall thickness

Claims

- 28 - 1. A method for producing a fibrous web (309), in particular a tissue, paper or board web or a nonwoven web, comprising the following steps: a) low-water raw material preparation of cellulose-containing fibers (200) to individual fibers and / or fiber bundles (209); b) forming the individual fibers and / or fiber bundles (209) in an air stream to form a planar fiber layup (300) on a forming belt (40) by a dry forming process; c) application of a fluid, in particular water and / or a water-additive mixture, to the fiber layup (300, 305); d) consolidation of the planar fiber layup (300) by applying pressure and / or temperature in at least one consolidation device (8);characterized by the further step: e) separating the fiber layup (300, 305) by means of at least one air pressure jet (56), wherein a cutting ridge (310) is formed on at least one separation edge (311) of the separation cut (312) on the fiber layup (300, 305) by means of the air pressure jet (56).

2. Method according to claim 1, characterized in that the cut edge (310) of the fiber web (309) has at least 1.2 to 2 times the basis weight, in particular 1.3 to 1.8 times the basis weight, in particular 1.4 to 1.6 times the basis weight of the fiber web (309).

3. Method according to at least one of the preceding claims, characterized in that the separation cutting of the fiber layup (300) in machine direction (MD) takes place before a consolidation device (8).

4. Method according to at least one of the preceding claims, characterized in that the separation cutting of the fiber fabric (300, 305) in machine direction (MD) takes place in front of an application device (71 , 72, 73) for applying a fluid, in particular water and / or a water-additive mixture, to the fiber fabric (300, 305).

5. Method according to at least one of the preceding claims, characterized in that the cut edge (310) of the fiber fabric (300, 305) and / or the fiber web (309) has, after passing through the fiber fabric (300, 305) through at least one consolidation device (8), at least 1.5 to 3 times the fiber fabric and / or fiber web thickness (dp), in particular 1.8 to 2.6 times the fiber fabric and / or fiber web thickness (dp), in particular 2 to 2.4 times the fiber fabric and / or fiber web thickness (dr).

6. Method according to at least one of the preceding claims, characterized in that the fiber fabric (300, 305) is cut while it has a lower strength than the produced fiber web (309), wherein the strength of the fiber fabric (300, 305) during the cutting process is less than 80%, in particular less than 50%, in particular less than 25%, preferably less than 10%, preferably less than 5%, of the strength of the produced fiber web (309).

7. Method according to at least one of the preceding claims, characterized in that the separation cut (312) is first carried out with a first air pressure jet (57) and subsequently widened with at least a second air pressure jet (57), which is arranged offset in the machine transverse direction (CD) to the first air pressure jet (57).

8. Method according to at least one of the preceding claims, characterized in that at least one air pressure jet (57) is arranged inclined in the machine direction (MD), wherein the air pressure jet (57) is directed forward in the machine direction (MD) and the angle of inclination (a) relative to the vertical (z) is 10° to 45°, in particular 20° to 35° and in particular 25° to 30°.

9. Method according to at least one of the preceding claims, characterized in that at least one air pressure jet (57) is arranged inclined in the machine transverse direction (CD), wherein the air pressure jet (57) is directed towards a separating edge (311) of the separating cut (312) and the angle of inclination (β) relative to the vertical (z) is 1° to 20°, in particular 3° to 15° and in particular 5° to 10°.

10. Method according to at least one of the preceding claims, characterized in that the width of the separation cut (312) corresponds at least to the average fiber length, in particular at least 1.5 times, preferably 2 times, the average fiber length of the fibers of the fiber layup (300).

11. Method according to at least one of the preceding claims, characterized in that the compressed air supplied to the at least one compressed air nozzle (56) has a pressure in a range of 4 bar to 8 bar, in particular 5 bar to 7 bar and in particular 6 bar.

12. Machine (1) for the production of a fibrous web (309), in particular a tissue, paper or board web or a nonwoven web, comprising: a) a raw material preparation plant (2) for the low-water processing of cellulose-containing fibers (200) into single fibers and / or fiber bundles (209); b) a dry forming device (4) for dry forming the individual fibers and / or fiber bundles (209) in an air stream to form a planar fiber fabric (300) on a forming belt (40); c) an application device (71) for applying a fluid, in particular water and / or a water-additive mixture, to the fiber fabric (300); d) a consolidation device (8) for consolidating the planar fiber fabric (300) by applying pressure and / or temperature, in particular in a press gap (81, 82, 83); characterized by a cutting device (55) with at least one, in particular two, compressed air nozzle (56) for cutting the fiber fabric (300, 305) by means of at least one compressed air jet (57), which forms a cutting ridge (310) on at least one cutting edge (311) of the cutting cut (312) produced by means of the cutting device (55) on the fiber fabric (300, 305).

13. Machine according to claim 12, characterized in that at least one compressed air nozzle (56) of the cutting device (55) is arranged inclined in the machine direction (MD), so that the compressed air jet (56a) is directed forward in the machine direction (MD) and the angle of inclination (a) of the compressed air jet (57) generated by the compressed air nozzle (56) relative to the vertical (z) is 10° to 45°, in particular 20° to 35° and in particular 25° to 30°.

14. Machine according to at least one of claims 12 or 13, characterized in that the at least one compressed air nozzle (56) has an aperture diameter between 0.5 mm and 1.8 mm, in particular between 0.8 mm and 1.2 mm. - 32 - 15. Machine according to at least one of claims 12 to 14, characterized in that the exit of the air pressure jet (57) of the at least one compressed air nozzle has a distance (a) from the surface of the fiber fabric (300) which is in the range of 1 mm to 60 mm, in particular from 10 mm to 45 mm and in particular from 20 mm to 30 mm.

16. Fibre web (309) produced by a process for producing a fibrous web (309) according to any one of claims 1 to 11.

17. Fibre web (309) according to claim 16, characterized in that the fibrous web (309) has at least one cut edge (310) which, after passing through the fiber fabric (300, 305) by at least one consolidation device (8), has at least 1.5 to 3 times the thickness of the fiber fabric and / or the fibrous web (dp), in particular 1.8 to 2.6 times the thickness of the fiber fabric and / or the fibrous web (dp), in particular 2 to 2.4 times the thickness of the fiber fabric and / or the fibrous web (dr).

Images