Method for increasing the strength of a dry-laid single-layer fibrous web by means of a special press
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- VOITH PATENT GMBH
- Filing Date
- 2025-02-12
- Publication Date
- 2026-05-27
AI Technical Summary
Existing dry-laying processes for fibrous webs, such as tissue webs, struggle to achieve sufficient strength and extensibility without the use of expensive and environmentally harmful strength-enhancing agents like latex polymers or synthetic fibers, while minimizing energy consumption and emissions.
A method involving pressing elements with zigzag and/or wavy lines that are interrupted, allowing fibers to be pressed at multiple points, enhancing strength and equalizing strength properties in both machine and cross-machine directions without compromising extensibility.
The method significantly increases tensile strength and maintains extensibility, achieving uniform mechanical properties across directions while reducing the need for additional binders and energy consumption.
Smart Images
Figure EP2025053621_04092025_PF_FP_ABST
Abstract
Description
[0001] Method for increasing the strength of a dry-laid single-layer fibrous web using a special press
[0002] The invention relates to a method for increasing the strength of a single-layer fibrous web, in particular a tissue web, wherein the fibrous web is formed by a dry-laying process, in particular an air-laying process, and wherein the fibrous web is guided through a press nip in a production direction MD in a pressing step, wherein the fibrous web is locally pressed and consolidated in the press nip between a first pressing element and a second pressing element, wherein the first pressing element comprises an upper side facing the fibrous web with a plurality of press webs which have the shape of a plurality of zigzag and / or wavy lines aligned substantially parallel to one another, wherein each
[0003] Zig-zag and / or wavy line has a main extension center line and wherein a smallest repeating unit of the respective zig-zag and / or wavy line comprises at least two deflection points, of which at least one deflection point is arranged on each side of the respective main extension center line.
[0004] The wet-laid process is the most commonly used method for producing fibrous webs, such as tissue webs. The solids in these fibrous webs are suspended in water at the beginning of the production process and fed into a forming section via the headbox of a paper machine. There and in a downstream press section, they are mechanically dewatered, and then thermally dried in a drying section. The presence of water creates hydrogen bonds, which lead to the basic strength of the fibrous web. To further increase this basic strength, strength-enhancing agents are typically added to the fibrous web.
[0005] In the course of efforts to optimize the manufacturing processes for fibrous webs with a view to reducing energy consumption and CO2 emissions, dry-laying processes are being used more and more. In these processes, the strength of the fibrous webs can no longer be sufficiently achieved through the formation of hydrogen bonds, as little or no water is used and the fibers are therefore almost completely dry-laid to form the web. In the production of fibrous webs, such as tissue webs, latex polymers are sprayed onto the paper surface or synthetic melt fibers are mixed into the fibers before dry-laying. The fibrous web with the melt fibers is then heated. The melt fibers melt and bond with the cellulose fibers of the fibrous web, thereby increasing or creating the strength of the fibrous web.However, these strength-enhancing agents are expensive and account for a significant portion of the production costs of these papers. In addition, latex polymers and melt-bonded fibers exhibit poor or even no biodegradability and require significant amounts of thermal energy for polymerization and drying of latex or melting of the plastic fibers.
[0006] The consolidation process is of great importance for achieving good mechanical properties, such as elongation and tensile stress behavior, of the dry-laid fibrous web.
[0007] A generic method described above is already known from the document US 2007 / 0126141 A1, to which Figures 1 and 2 refer. In this case, a wave-shaped pattern is embossed into an air-laid fibrous web by guiding the fibrous web in a production direction MD through a press nip 14 formed by two press elements 10 and 12. The two press elements 10 and 12 here have the form of press rolls. The axes of the two press rolls are oriented parallel to the cross-machine direction CD. While an upper side of the second press element 12 facing the fibrous web in the press nip 14 is smooth, the first press element 10 has an upper side facing the fibrous web in the press nip 14 with a plurality of wave-shaped, in particular sine-wave-shaped press webs 16. The press webs 16 extend continuously and parallel to one another in the circumferential direction of the first press roll.The press bars 16 have a width 18 of 0.635 mm or 0.025 inches and a height 20 above a flat base 22 of between 0.635 mm or 0.025 inches and 1.27 mm or 0.5 inches. Furthermore, two directly adjacent press bars 16 are separated from each other by a distance 24 of 7.62 mm or 0.3 inches.
[0008] Figure 2 shows a portion of the upper side of the first pressing element 10 in an unwound state. This essentially corresponds to the embossing in the fibrous web after it has passed through the press nip in the production direction MD. The sine-wave-shaped pressing bars 16 have an amplitude 26 of approximately 3.5 mm and a repetition frequency 28 of approximately two oscillations per 25.4 mm or per inch. In other words, there are two oscillations or two smallest repetition units per 25.4 mm or per inch in the production direction MD. The individual sine-wave-shaped pressing bars 16 each have a main extension center line 30 which extends in the production direction MD. For reasons of clarity, only one such main extension center line 30 is shown in Figure 2. Relative to the main extension center line 30 of the respective pressing bar 16, each smallest repetition unit of the pressing bar 16 has two deflection points 32, orin this example, two vertices of the sine wave, namely one on each of the two opposite sides of the main extension center line 30.
[0009] Even though the process known from US 2007 / 0126141 A1 already offers advantages over previous processes with other press bars, especially those extending in a straight line, the results regarding the strength and extensibility of the fibrous web after it has passed through the press nip still have room for improvement. The fibrous web should exhibit both the greatest possible strength and the greatest possible extensibility, and this should be as uniform as possible in all directions, not only in the production direction but also in the cross-machine direction. There is still room for improvement in this regard in particular.
[0010] It is therefore an object of the present invention to solve or at least reduce the aforementioned problems. In particular, a method and a corresponding device are to be provided with which the fibrous web can be given the greatest possible strength when it passes through the press nip. A secondary objective is to keep the extensibility of the fibrous web at the highest possible level. In particular, the fibrous web should have sufficiently good properties with regard to strength and extensibility even when the fibrous web, such as tissue webs, is produced using only very small amounts of water in order to use as little energy as possible for drying the fibrous web and when the addition of thermally activated binders is largely or entirely dispensed with. The present invention relates exclusively to single-layer fibrous webs.This refers to fibrous webs that are formed on a single fabric. This is usually done by so-called air-laying units. The fibrous web can be formed by more than one air-laying unit, so that first fibrous material is laid onto the fabric by a first air-laying unit and then further fibrous material is laid onto the previously laid fibrous material by further air-laying units until the fibrous web has the desired basis weight. Multi-layer fibrous webs, to which this document does not refer, on the other hand, are laid on several fabrics, for example, and the layers thus formed are then couched together. Another example of multi-layer fibrous webs is that the individually formed layers are joined together in a part of the machine arranged downstream of the forming unit.In the case of wet-laid fibrous webs, to which this document does not refer anyway, there is still the possibility of forming multi-layer webs directly in the headbox (multi-channel headboxes).
[0011] This object is achieved by the subject matter of the independent claims. The dependent claims describe advantageous developments of the present invention.
[0012] In particular, the present object is achieved by a generic method as described at the outset, which is particularly characterized in that each of the zigzag and / or wavy lines has a plurality of interruptions. Tests have shown that it is advantageous not to form the press webs continuously in the circumferential direction of the press roll, but to divide them into a plurality of discrete elements or sections by the interruptions. Although this may slightly reduce the strength of the fibrous web in the production direction, it results in an equalization of the strengths of the fibrous web in the production or machine direction and in the cross-machine direction. In addition, the extensibility of the fibrous web increases significantly, in particular in the production direction. With regard to the extensibility of the fibrous web, there is also a noticeable standardization in the production or machine direction.Machine direction and cross-machine direction. The invention increases strength, for example, tensile strength, without compromising the required properties of the fibrous web, such as thickness, water absorption capacity, softness, and specific bulk.
[0013] The term "zig-zag and / or wavy lines" in the context of the present invention means that the pressing webs do not necessarily have to have a purely wavy shape, as is the case with the sinusoidal wave-shaped pressing webs described above, which are known from the document US 2007 / 0126141 A1. Instead, this line can also be formed from several straight sections, each arranged at a specific angle to one another, i.e. a pure zig-zag line, or the line can consist of a combination of straight sections and rounded sections connecting them, i.e. a combination of zig-zag line and wavy line. All three variants are conceivable, whereby the combination of zig-zag line and wavy line has proven particularly advantageous in practice by avoiding discontinuous changes in direction and the associated notch effect under tensile stress.Preferably, the zigzag and / or wavy lines are point-symmetrical to at least one point on their respective main extension line and / or axially symmetrical to at least one axis extending orthogonally to the respective main extension line.
[0014] The term "zigzag and / or wavy lines aligned substantially parallel to one another" in the context of the present invention means that the respective main extension center lines of the zigzag and / or wavy lines run substantially, preferably exactly, parallel to one another. In this context, "substantially" means that small angular deviations, in particular angular deviations of less than 10°, preferably of less than 5°, should be permissible in sections or over the entire length of the respective main extension center lines. The zigzag and / or wavy lines are preferably oriented "in phase", i.e., their deflection points are all at the same height when viewed in the direction of production.
[0015] The term "dry-laying process, in particular air-laying process" means that the fibers are not applied to a screen in a suspension of fibers and liquid, but in a dry state, in particular by means of an air stream. Preferably, only very small amounts of water are added to the fibers, in particular less than 20 wt. %, more preferably less than 10 wt. %, even more preferably less than 7 wt. % water, before the press nip with the first and second press elements. Even after the press nip, no large amounts of water, and in any case less than 10 wt. % water, should be added to the fibrous web before it is preferably wound up at the end. The addition of other wet strength agents, such as thermally activatable melt fibers, should also be largely, preferably entirely, avoided.If they are added in small quantities, they should only be added after the press nip to avoid contamination of the first and / or second pressing element.
[0016] The first and second pressing elements can be rollers, as is the case in the document US 2007 / 0126141 A1 described above. The two rollers form an approximately linear press nip between them, assuming the press webs are ignored. However, this configuration is not mandatory. Configurations are also conceivable in which the two pressing elements form a substantially flat press nip between them. For example, the two pressing elements can be formed by two plates or by a roller and a shoe press resting against the roller.
[0017] Furthermore, the fibrous web can be guided through the press nip supported by at least one fabric. However, in order to apply the greatest possible pressing pressures to the fibrous web, it is preferred for the fibrous web to be guided through the press nip alone, i.e., unsupported. For this to happen, the fibrous web requires a certain minimum strength beforehand. This minimum strength can be achieved, for example, by at least one upstream press, through which the fibrous web is guided supported and subjected to lower pressing pressures.
[0018] Preferably, the interruptions are essentially all the same length and the distances between two immediately adjacent zigzag and / or wavy lines are essentially all the same, with the length of the interruptions corresponding to between 50% and 200%, preferably between 70% and 150%, of the distance between two immediately adjacent zigzag and / or wavy lines. The length of the interruptions should preferably be selected as a function of the average fiber length of the fibers from which the fibrous web is formed. It is advantageous if as many fibers as possible are pressed at exactly two points of two different discrete segments of the zigzag and / or wavy lines. It would be optimal if these two pressing points were as close as possible to the two longitudinal ends of the fibers. During the manufacturing process, the fibers are more or less randomly oriented. In addition, they are often curved and do not always extend in a straight line.Through the two pressing points, the corresponding fibers contribute to the strength of the fibrous web, with the unpressed and often curved section of the fiber between the two pressing points contributing to the extensibility. In this respect, it is particularly advantageous if the length of the interruptions does not exceed 100% of the average fiber length, but preferably is at least 50% of the average fiber length. For example, the length of the interruptions can be between 50% and 70% of the average fiber length. The same considerations also apply to the distance between two immediately adjacent zigzag and / or wavy lines. The term "average fiber length" refers to the average length of the actual fibers, whereby tiny particles such as dust particles or the like, which may be present in large numbers between the fibers, are to be disregarded.
[0019] The press webs preferably have a width that is between 20% and 80%, more preferably between 30% and 70%, and even more preferably between 40% and 60%, of the distance between two immediately adjacent zigzag and / or wavy lines. This distance can be understood as the distance between the main extension center lines associated with these two zigzag and / or wavy lines.
[0020] To produce the fibrous web, fluff pulp can be used as a raw material in rolls. Alternatively, pulp in bales can also be used, which is generally significantly more cost-effective and therefore preferred.
[0021] Furthermore, it has proven advantageous if connecting lines between any two consecutive deflection points of a zigzag and / or wavy line all have the same length and / or the same absolute angle to the main extension center line. Preferably, both are true, so that the zigzag and / or wavy line on one side of the main extension center line is an image of the zigzag and / or wavy line on the other side of the main extension center line, mirrored at the main extension center line and shifted by half a phase. Tests have shown that the previously described angle of the connecting lines between the deflection points to the main extension center line is preferably between 20° and 40°, more preferably between 25° and 35°.
[0022] The respective main center lines of extension can be oriented essentially parallel to the production direction in the press nip. Preferably, they are oriented exactly parallel to the production direction.
[0023] It has proven particularly advantageous if the zigzag and / or wavy lines are interrupted at regular intervals. Preferably, the distances between two consecutive interruptions of a zigzag and / or wavy line are essentially identical for all zigzag and / or wavy lines. In other words, for each zigzag and / or wavy line, there is one and the same fixed distance, for example, measured in the direction of the main extension center line, between each two immediately consecutive interruptions of the zigzag and / or wavy line.
[0024] The distance between two consecutive interruptions of a zigzag and / or wavy line measured in the direction of the main extension center line can be equal to the distance between two consecutive deflection points of the zigzag and / or wavy line measured in the direction of the main extension center line.
[0025] Furthermore, it is preferred if a maximum of one deflection point is present between two consecutive interruptions of a respective zigzag and / or wavy line. In other words, the discrete segment between two consecutive interruptions can comprise either exactly one or no deflection point of the zigzag and / or wavy line.
[0026] With at least one zigzag and / or wavy line, the interruptions can be located precisely at the deflection points of the zigzag and / or wavy line. In this case, with a pure zigzag line or a combination of zigzag and wavy lines, the individual discrete segments of this line can consist only of straight sections.
[0027] Furthermore, it can be provided that two immediately adjacent zigzag and / or wavy lines have their respective interruptions offset from one another. In other words, two immediately adjacent zigzag and / or wavy lines do not have their respective interruptions at the same height in the direction of their respective main extension center lines.
[0028] However, each n-th zigzag and / or wavy line may be formed without offsetting its respective interruptions relative to the interruptions of the first zigzag and / or wavy line, where n is an integer greater than 2, preferably between 3 and 10. In particular, a specific sequence of zigzag and / or wavy lines may repeat periodically in the cross-machine direction.
[0029] The press bars can all rise to the same height above a flat base. If the second press element has a flat upper side, this generally results in two different levels of press zones, namely a high-pressure press zone where the press bars are arranged, and a low-pressure press zone where no press bars are present. In the region of the low-pressure press zone, the fibrous web can either not be compressed at all in the press nip between the first and second press elements or, as is preferred, it is also compressed there, but with a noticeably lower pressure than in the region of the high-pressure press zone or high-pressure press zones. In the high-pressure press zone, pressures of at least 10 MPa, more preferably at least 15 MPa, even more preferably at least 20 MPa are applied locally to the fibrous web.In the low-pressure pressing zone, however, the pressure should be significantly lower, preferably noticeably below 10 MPa, preferably below 5 MPa.
[0030] Furthermore, to improve the strength increase, the press bars can be heated to a temperature of 50°C to 300°C, preferably 100°C to 250°C. Advantageously, the strength and elongation properties of the produced fibrous web can be increased by a specific area proportion of the high-pressure press zones. A range between 20% and 60%, preferably between 30% and 50%, is ideal for significantly increasing the strength and elongation properties.
[0031] Preferably, a straight connecting line from any point on one side edge of the first pressing element to any point on a second side edge of the first pressing element opposite the first side edge always intersects at least one pressing web. If the first pressing element is a cylindrical roller, "straight connecting line" means a line that lies as a straight line in the unwound plane of the upper side of the roller facing the fibrous web. In other words, it is advantageous, particularly with regard to the strength of the fibrous web, if there is no low-pressure pressing zone extending in a straight line across the fibrous web. Otherwise, the fibrous web could tear more easily along this line.
[0032] A further aspect of the present invention relates to a press for a machine for producing a fibrous web, in particular a tissue web, in a dry-laying process, in particular an air-laying process, wherein the press comprises a first pressing element and a second pressing element, which form a press nip between them in order to locally press and consolidate the fibrous web, wherein the first pressing element comprises an upper side facing the fibrous web with a plurality of press bars, which have the shape of several zigzag and / or wavy lines aligned substantially parallel to one another, wherein each zigzag and / or wavy line has a main extension center line and wherein a smallest repeat unit of the respective zigzag and / or wavy line comprises at least two deflection points, of which at least one deflection point is arranged on each side of the respective main extension center line,wherein each of the zigzag and / or wavy lines has several interruptions.,
[0033] The advantages described above with regard to the method according to the invention, as well as the advantageous developments of the method according to the invention, also apply mutatis mutandis to the press according to the invention, and vice versa. The present invention also relates to a machine for producing a fibrous web, in particular a tissue web, comprising the press according to the invention described above.
[0034] Furthermore, the present invention relates to a fibrous web which has been produced according to the method according to the invention described above.
[0035] The fibrous web produced is preferably a tissue web. The fibrous web can have a specific basis weight of 10 g / m 2 up to 60g / m 2 , preferably 20g / m 2 up to 50g / m 2and especially preferably 25g / m 2 up to 45g / m 2 , have. The manufacturing process according to the invention works particularly well for such lightweight fibrous webs.
[0036] The invention is explained in more detail below using an exemplary embodiment illustrated in a schematic figure. It shows:
[0037] Fig. 3 shows a section of an upper side of a first pressing element facing the fibrous web, said first pressing element having a plurality of pressing webs, the first pressing element being a component of a press according to the invention.
[0038] The basic structure of the press according to the invention can correspond to that shown in Figure 1, namely with two pressing elements 10, 12 designed as press rollers, which form a press nip 14 between them, through which the dry-laid, in particular air-laid, fibrous web, in particular tissue web, is guided to be locally pressed and consolidated. The upper side of the second pressing element 12 facing the fibrous web can be smooth, whereas the upper side of the first pressing element 10 facing the fibrous web has a plurality of press webs 16 running parallel to one another. Figure 3 shows a flat, unwound section of the first pressing element 10 with fifteen press webs 16 running parallel to one another. The press webs 16 each have a main extension center line 30, which here is oriented in the production direction MD.In contrast to the prior art embodiment shown in Figures 1 and 2, the press webs 16 here are not sinusoidal in shape. Instead, they have a combination of zigzag and wave lines, with straight sections 34 extending between two consecutive deflection points 32, which are formed as rounded sections, if present.
[0039] More important than the difference that the press webs 16 are not wavy but rather a combination of zigzag and wavy lines, is the difference that in the embodiment according to the invention shown in Figure 3, the lines of the press webs 16 each have a plurality of interruptions 36. For reasons of better clarity, only two of these interruptions 36 are provided with reference symbols in Figure 3. The distances between two immediately consecutive interruptions 36, measured in the production direction MD, are the same everywhere. As can be seen from the first zigzag and wavy line (far left in Figure 3), the interruptions 36 can be located precisely at the deflection points 32. Thus, in this case, the first zigzag and wavy line consists only of straight sections 34, whereas the rounded deflection points 32 are missing in this zigzag and wavy line.In this case, the individual segments between two consecutive interruptions 36 do not have any deflection points 32.
[0040] The second zigzag and wavy line, which is immediately adjacent to the first zigzag and wavy line (to the right of the first zigzag and wavy line in Figure 3), also has a plurality of interruptions 36, which are also the same distance apart as the interruptions 36 of the first zigzag and wavy line. However, the interruptions 16 of the second zigzag and wavy line are offset relative to the interruptions 16 of the first zigzag and wavy line when viewed in the production direction MD. They therefore do not lie on the deflection points 32 but on the straight sections 34 that connect the deflection points 32 to one another. The segments of the second zigzag and wavy line therefore have exactly one rounded deflection point 32 between two immediately consecutive interruptions 36, from which straight sections 34 extend on both sides.
[0041] Furthermore, the interruptions 36 of the third zigzag and wave line, which is immediately adjacent to the second zigzag and wave line (to the right of the second zigzag and wave line in Figure 3), also exhibit an offset in the production direction MD relative to the interruptions 36 of the second zigzag and wave line. The interruptions 36 of the third zigzag and wave line also do not lie on the deflection points 32, but rather on the straight sections 34.
[0042] The situation is similar with the remaining zigzag and wavy lines. The interruptions 36 of any zigzag and wavy line, viewed in the production direction MD, always exhibit an offset relative to the interruptions 36 of the two immediately adjacent zigzag and wavy lines. However, the pattern repeats itself at regular intervals. In the exemplary embodiment shown in Figure 3, the interruptions 36 of the sixth zigzag and wavy line again lie exactly on the deflection points 32, so that the sixth zigzag and wavy line corresponds in appearance to the first zigzag and wavy line. With this arrangement, it is not possible to travel in a straight line from any point on the left page edge (left in Figure 3) to any point on the right page edge (right in Figure 3) without encountering at least one press land segment of the zigzag and wavy lines.
[0043] The lengths of the interruptions 36 and / or the distances between two immediately adjacent zigzag and wavy lines are preferably dimensioned such that they amount to between 50% and 100%, preferably between 50% and 70%, of the average fiber length of which the fibrous web is composed. The distances between two immediately adjacent zigzag and wavy lines can be somewhat larger than the lengths of the interruptions 36.
[0044] The inventors tested the method according to the invention. A pressing element with the corrugated lines according to the invention was used, and the strength and extensibility of a fibrous web pressed with it were compared with the corresponding values of a fibrous web pressed with an unstructured pressing element.
[0045] The following values were obtained for the unstructured pressing element:
[0046] Strength MD: 1.11 Nm / g Strength CD: 1.13 Nm / g
[0047] Extensibility MD: 12.05%
[0048] Extensibility CD: 14.18% The following values were obtained for the pressing element designed according to the invention:
[0049] Strength MD: 2.81 Nm / g
[0050] Strength CD: 2.16 Nm / g
[0051] Stretchability MD: 6.35% Stretchability CD: 8.02%
[0052] The results show that the strength could be significantly increased by the process according to the invention, while the extensibility could be kept at an acceptable level.
[0053] List of reference symbols:
[0054] 10 first pressing element
[0055] 12 second pressing element
[0056] 14 Press nip
[0057] 16 press bars
[0058] 18 Width of the press bars
[0059] 20 Height of the press bars
[0060] 22 Reason
[0061] 24 Distance between two adjacent press bars
[0062] 26 amplitude
[0063] 28 Refresh rate
[0064] 30 Main extension center line
[0065] 32 deflection point
[0066] 34 straight sections
[0067] 36 Interruption
[0068] CD cross machine direction
[0069] MD Machine direction or production direction
Claims
1. A method for increasing the strength of a single-layer fibrous web, in particular a tissue web, wherein the fibrous web is formed by a dry-laying process, in particular an air-laying process, and wherein the fibrous web is guided through a press nip (14) in a production direction (MD) in a pressing step, wherein the fibrous web is locally pressed and consolidated in the press nip (14) between a first pressing element (10) and a second pressing element (12), wherein the first pressing element (10) comprises an upper side facing the fibrous web with a plurality of press bars (16) which have the shape of several zigzag and / or wavy lines aligned substantially parallel to one another, wherein each zigzag and / or wavy line has a main extension center line (30) and wherein a smallest repeat unit of the respective zigzag and / or wavy line comprises at least two deflection points (32),of which at least one deflection point (32) is arranged on each side of the respective main extension center line (30), characterized in that each of the zigzag and / or wavy lines has a plurality of interruptions (36).
2. Method according to claim 1, characterized in that the interruptions (36) are essentially all of the same length and that the distances between two immediately adjacent zigzag and / or wavy lines are essentially all the same, the length of the interruptions (36) corresponding to between 50% and 150%, preferably between 70% and 130%, of the distance between two immediately adjacent zigzag and / or wavy lines.
3. Method according to claim 1 or 2, characterized in that connecting lines between each two successive deflection points (32) of a zigzag and / or wavy line all have the same length and / or the same angle to the main extension center line (30).
4. Method according to one of the preceding claims, characterized in that the respective main extension center lines (30) in the press nip (14) are oriented substantially, preferably exactly, parallel to the production direction (MD).
5. Method according to one of the preceding claims, characterized in that the zigzag and / or wavy lines are interrupted at regular intervals.
6. Method according to claim 5, characterized in that the distances between two consecutive interruptions (36) of a zigzag and / or wavy line are substantially identical for all zigzag and / or wavy lines.
7. Method according to claim 5 or 6, characterized in that the distance between two successive interruptions (36) of a zigzag and / or wavy line measured in the direction of the main extension center line (30) is equal to the distance between two successive deflection points (32) of the zigzag and / or wavy line measured in the direction of the main extension means (30).
8. Method according to one of the preceding claims, characterized in that between two successive interruptions (36) of a respective zigzag and / or wavy line there is a maximum of one deflection point (32).
9. Method according to one of the preceding claims, characterized in that in at least one zigzag and / or wavy line the interruptions (36) are arranged exactly at the deflection points (32) of the zigzag and / or wavy line.
10. Method according to one of the preceding claims, characterized in that two immediately adjacent zigzag and / or wavy lines have their respective interruptions (36) arranged with an offset to one another.
11. Method according to claim 10, characterized in that each nth zigzag and / or wavy line is formed without offsetting its respective interruptions (36) relative to the interruptions (36) of the first zigzag and / or wavy line, where n is an integer greater than 2, preferably between 3 and 10.
12. Method according to one of the preceding claims, characterized in that the pressing webs (16) all rise to the same height above a flat base.
13. Method according to one of the preceding claims, characterized in that a straight connecting line from any point of a side edge of the first pressing element (10) to any point of a second side edge of the first pressing element (10) opposite the first side edge always intersects at least one pressing web (16).
14. Method according to one of the preceding claims, characterized in that the fibrous web has a basis weight of 10g / m 2 up to 60g / m 2 has.
15. Fibrous web produced by a process according to any one of the preceding claims.