Method and device for producing a fibrous web

Abstract

A device (1) for producing a fibrous web (2) is proposed, the device having a swirl chamber (3) with an inlet (8) for introducing a fibre foam into the swirl chamber (3) and having an outlet side (7) for discharging the fibre foam from the swirl chamber (3), wherein a shear rate of at least 1 / sec and preferably at least 50 1 / sec is produced throughout the swirl chamber (3). A further device (1) for producing a fibrous web (2) and a method for producing a fibrous web (2) are also proposed.

Description

[0001] Method and device for producing a fiber web

[0002] The invention relates to a method and a device for producing a fiber web.

[0003] Processes for producing a fiber web are known from the prior art. The so-called wetlaid process, in which an aqueous fiber suspension is laid to form a nonwoven web, is frequently used. A nonwoven, as defined in the present invention, is also referred to as a nonwoven. In this case, it is difficult to achieve a good distribution of strength properties in the MD / CD direction and to the right, left, and center of the fabric direction. Flocking, in particular, leads to inhomogeneities in wetlaid processes.

[0004] An alternative to the wet-laid process is the foam-laying process. Instead of a fiber suspension, a fiber foam is applied. A fiber foam is a mixture of fiber, water, and air. The fibers adhere to the surfaces of the air bubbles in the fiber foam. The air bubbles space the fibers apart. The finer the foam, the better the individual fibers are separated from one another. The advantage of the foam-laying process is that the separation of the fibers with the help of the air bubbles prevents flaking.

[0005] This makes it possible to use much longer fibers than is possible with the conventional wet-laid processes. It is also possible to use a much higher fiber content. Both of these factors allow for the production of high-strength products.

[0006] Further advantages of the foam laying process compared to the wet laid process are significantly reduced water consumption, the possibility of using different combinations of fiber types and a significantly higher dry content of the fiber web, which saves energy when drying the fiber web.

[0007] The problem with applying the fiber foam is that conventional headboxes for applying the fiber foam, for example, on inclined wire or fourdrinier wire formers, do not maintain the dispersion of the fiber foam bubbles. This causes the bubbles to grow and foam separation. The fibers form flakes, resulting in fiber accumulation and thus inhomogeneity.

[0008] Furthermore, the state-of-the-art foam laying process is associated with strongly different exit velocities of the fiber foam in the MD direction along the CD direction, which can lead to inhomogeneous end products.

[0009] It is an object of the present invention to provide an apparatus and a method for producing a fiber web, by means of which the described disadvantages in the foam laying process are avoided and a good foam dispersion is achieved.

[0010] This problem is solved by the subject matter of the independent patent claims.

[0011] The device according to the invention for producing a fiber web has a vortex chamber with an inlet for introducing a fiber foam into the vortex chamber and an outlet side for discharging the fiber foam from the vortex chamber. According to the invention, a shear rate of at least 10 1 / sec and preferably at least 50 1 / sec is generated throughout the vortex chamber. This ensures optimal consistency of the fiber foam upon exiting the vortex chamber. Furthermore, the distribution of the exit velocity of the fiber foam in the MD direction along the CD direction is very uniform and has deviations of preferably less than 5% and particularly preferably less than 2.5%. A velocity deviation within the meaning of the present invention is calculated as: (maximum velocity - minimum velocity) / average velocity. Another particular advantage is an isotropic fiber orientation upon exiting the vortex chamber.These advantages make it particularly easy to specifically adjust different strengths of the fiber web in the MD and CD directions. In particular, it is possible to achieve very high strengths in the CD direction.

[0012] For the purposes of the present invention, MD direction is the direction in the machine direction. CD direction for the purposes of the present invention is the direction transverse to the machine direction.

[0013] A further object for solving the problem posed at the outset is a device for producing a fiber web, comprising a vortex chamber. The vortex chamber is part of the headbox and has at least one inlet on an inlet side for introducing a fiber foam into the vortex chamber. The fiber foam is introduced into the vortex chamber as a stream, i.e. the introduced fiber foam flows into the vortex chamber. The fiber foam is preferably introduced into the vortex chamber along an inflow direction. It is preferably provided that the inlet side is arranged at an angle of 45° to 135° to the inflow direction. A guide side is arranged opposite the inlet side, and a closing side is arranged between the inlet side and the guide side. An outlet side for discharging the fiber foam from the vortex chamber is arranged opposite the closing side.According to the invention, the guide side and / or the end side are at least partially curved to redirect the fiber foam.

[0014] The fiber foam impinges on an inner wall of the vortex chamber, dividing the flow into substreams. The curvature forces the fiber foam to move in all directions. This generates high shear rates, maintaining optimal consistency. In the context of the present invention, "curved" means that the surface is curved. The surface is, in particular, the surface of the guide side or the end side facing the interior of the vortex chamber.

[0015] In particular, a partial flow is directed along the inlet side to the outlet side. By splitting the flow of fiber foam opposite the inlet side and redirecting it along the inlet side to the outlet side, dead zones in the vortex chamber are avoided. The fiber foam is constantly in motion at every point in the vortex chamber, preventing fiber foam from disintegrating and achieving excellent foam dispersion.

[0016] Preferably, the fiber foam comprises fibers made of viscose and / or lyocell and / or natural fibers and / or recycled fibers and / or synthetic fibers and / or inorganic fibers such as glass fibers and / or man-made fibers and / or fibers made of pulp, northern (bleached) softwood pulp, and / or southern (bleached) softwood pulp. It is conceivable that the fiber foam comprises 10-100% man-made fibers.

[0017] The fiber foam preferably has an air content of 50% to 70% and a bubble size of 10 pm to 20 pm.

[0018] It is conceivable that the device could include a circular distributor that feeds the fiber foam into the swirl chamber. This further counteracts the separation of the fiber foam.

[0019] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0020] Preferably, the guide side has a curved impact area for redirecting the flow. In other words, a portion of the guide side is curved. Particularly preferably, the flow impacts the guide side or end side at a transition from a non-curved area of ​​the guide side or end side to a curved area of ​​the guide side or end side. This is particularly effective, increases the shear rates in the vortex chamber, and prevents dead spaces.

[0021] According to a preferred embodiment of the present invention, the end side is at least partially curved. This allows the partial flow to be advantageously directed to the feed side. Sedimentation on the sides is thus avoided.

[0022] According to a further preferred embodiment of the present invention, the distance between the feed side and the guide side decreases toward the outlet side, or the feed side is at least partially arranged such that the distance between the feed side and the guide side decreases toward the outlet side. By reducing the distance, the fiber foam is accelerated toward the outlet side, which promotes a particularly advantageous exit of the fiber foam from the vortex chamber.

[0023] Particularly preferably, the feed side and the guide side enclose a first chamber angle. The first chamber angle is between 10° and 45°, and preferably between 15° and 25°. This results in optimal outflow of the fiber foam from the vortex chamber.

[0024] Furthermore, it is preferably provided that the feed side and the end side enclose a second chamber angle. The second chamber angle is between 90° and 150°, and preferably between 100° and 120°. This advantageously ensures high shear rates in the region of the end side.

[0025] According to a further preferred embodiment of the present invention, several inlets arranged in a row are provided on the feed side. Preferably, several inlets arranged in two rows are provided on the feed side. The fiber foam is thus fed into the vortex chamber through several individual sections. It is conceivable that the inlets are connected to a circular distributor.

[0026] Preferably, the inlet has a diameter of 10 mm to 100 mm, and preferably 30 mm to 60 mm. It is conceivable that each of the inlets has a diameter of 10 mm to 100 mm, and preferably 30 mm to 60 mm.

[0027] According to a further preferred embodiment of the present invention, a shear rate of at least 10 1 / sec and preferably at least 50 1 / sec is generated throughout the entire vortex chamber. This ensures an optimal consistency of the fiber foam upon exiting the vortex chamber.

[0028] In particular, the device is intended for use with an inclined screen, meaning that the fiber foam is deposited onto an inclined screen. However, it is also conceivable that the device is intended for use with a fourdrinier screen.

[0029] A further object of the present invention to achieve the object mentioned at the outset is a method for producing a fiber web, wherein a fiber foam is introduced into a vortex chamber according to the invention, the fiber foam is redirected in the vortex chamber and is discharged at the outlet side of the vortex chamber.

[0030] According to a further preferred embodiment of the present invention, a shear rate of at least 10 1 / sec and preferably at least 50 1 / sec is generated throughout the entire vortex chamber. This ensures an optimal consistency of the fiber foam upon exiting the vortex chamber.

[0031] Preferably, the fiber foam is introduced into the vortex chamber in one stream, and the stream is divided into a partial stream and a further partial stream at the leading end and then redirected. The further partial stream flows along the leading end toward the outlet side, and the partial stream flows along the end side to the feed side and along the feed side toward the outlet side. This eliminates dead space. High shear rates prevail throughout the vortex chamber.

[0032] In particular, it is intended that the fiber foam is deposited on an inclined sieve or a fourdrinier sieve after leaving the vortex chamber.

[0033] All details, features and advantages previously disclosed in connection with the device according to the invention also relate to the method according to the invention and to the respective other device according to the invention and vice versa.

[0034] Further details, features, and advantages of the invention will become apparent from the drawings and the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the scope of the invention.

[0035] They show:

[0036] Fig. 1 : a schematic view of a device according to an exemplary embodiment of the present invention and of a method device according to an exemplary embodiment of the present invention,

[0037] Fig. 2: a schematic view of a device according to an exemplary embodiment of the present invention,

[0038] Fig. 3: a schematic view of a device according to an exemplary embodiment of the present invention,

[0039] Fig. 4: a schematic view of a device according to an exemplary embodiment of the present invention and Fig. 5: a schematic view of a device according to an exemplary embodiment of the present invention.

[0040] Figures 1, 2, 3, 4 and 5 each show a schematic view of a device 1 according to an exemplary embodiment of the present invention. The device 1 is a device 1 for producing a fiber web 2 using the foam laying process. For this purpose, the device 1 has a vortex chamber 3 with a feed side 4. On the feed side 4, an inlet 8 is provided for introducing a fiber foam into the vortex chamber 3. The inlet 8 shown is one of several inlets (not shown) arranged in a row orthogonal to the plane of the page shown. Preferably, the device 1 has two rows of inlets. The inlet 8 and preferably all inlets have a diameter of 30 mm to 60 mm. Figure 5 shows that the inlet 8 is connected to a line 10 through which the fiber foam flows into the vortex chamber 3.

[0041] The fiber foam is a water-air-fiber mixture in which the fibers are spaced apart by air bubbles in the fiber foam. This results in excellent homogeneity of the fiber distribution, as long as good foam dispersion is maintained.

[0042] The fibers can be made of viscose and / or lyocell. It is conceivable that the fibers are natural fibers and / or recycled fibers and / or synthetic fibers and / or inorganic fibers such as glass fibers and / or man-made fibers and / or fibers from pulp, northern (bleached) softwood pulp, and / or southern (bleached) softwood pulp. It is conceivable that the fiber foam contains 10-100% man-made fibers. The fiber foam preferably has an air content of 50% to 70% and a bubble size of 10 to 20 μm.

[0043] To ensure that the fiber foam remains dispersed and to prevent the formation of larger air bubbles, which could lead to inhomogeneities and floc formation, the device 1 is designed to generate a shear rate of at least 10 1 / sec and preferably at least 50 1 / sec throughout the entire vortex chamber 3. This requires that no dead spots, i.e., no spots with very low fiber foam speed, are created in the vortex chamber 3.

[0044] To achieve this, the incoming flow A of the fiber foam first encounters an impact area 5' of a guide side 5 opposite the feed side 4. At the impact area 5', the flow is split into a partial flow B and a further partial flow C and diverted. The guide side 5 and the feed side 4 are connected by a terminal side 6. The guide side 5 and / or the terminal side 6, preferably the guide side 5 and the terminal side 6, have a bend. The partial flow B flows from the impact area 5' along the bend past the terminal side 6. The partial flow B is then guided along the feed side 4 to an outlet side 7. The outlet side 7 is arranged opposite the terminal side 6 and has an outlet gap through which the fiber foam is deposited as a fiber web 2 on a screen 9, for example an inclined screen or a fourdrinier screen.

[0045] The end side 6 is partially curved and connects with the curved region of the guide side 5 with a flowing contour. Figures 1, 2, 3 and 5 show embodiments in which the feed side 4 and the guide side 5 are not arranged parallel to one another. Rather, the distance between the feed side 4 and the guide side 5 decreases towards the outlet side 7. The feed side 4 and the guide side 5 here enclose a first chamber angle α of 15° to 25°. Figure 4 shows an embodiment in which the feed side is partially arranged such that the distance between the feed side and the guide side decreases towards the outlet side. The part of the feed side 4 that is not parallel to the guide side and the guide side 5 here enclose a first chamber angle α of 15° to 25°.Reducing the distance between the guide side 5 and the feed side 4 to the outlet side 7 accelerates the fiber foam on its way to the outlet gap. To increase the shear rates, the feed side 4 and the end side 6 enclose a second chamber angle ß of 100° to 120°. List of reference symbols:

[0046] 1 Device 2 Fiber web

[0047] 3 vortex chamber

[0048] 4 Feed side

[0049] 5 Home page

[0050] 5' impact area

[0051] 6 Final page

[0052] 7 Outlet side

[0053] 8 Entrance

[0054] 9 Sieve

[0055] 10 Line

Claims

Patent claims: Device (1) for producing a fiber web (2) comprising a vortex chamber (3) with an inlet (8) for introducing a fiber foam into the vortex chamber (3) and an outlet side (7) for discharging the fiber foam from the vortex chamber (3), wherein a shear rate of at least 10 1 / sec and preferably at least 50 1 / sec is generated in the entire vortex chamber (3).A device (1) for producing a fiber web (2), comprising a vortex chamber (3), wherein the vortex chamber (3) has an inlet (8) on an inlet side (4) for introducing a fiber foam in a stream (A) into the vortex chamber (3), wherein a guide side (5) is arranged opposite the inlet side (4), wherein a terminal side (6) is arranged between the inlet side (4) and the guide side (5), wherein an outlet side (7) for discharging the fiber foam from the vortex chamber (3) is arranged opposite the terminal side (6), wherein the guide side (5) and / or the terminal side (6) are at least partially curved for diverting the fiber foam, wherein the device (1) is preferably a device (1) according to claim 1. Device (1) according to claim 2, characterized in that the guide side (5) has a curved impact region (5') for diverting the stream.Device (1) according to one of claims 2 to 3, characterized in that the end side (6) is at least partially curved. Device (1) according to one of claims 2 to 4, characterized in that the distance between the feed side (4) and the guide side (5) decreases towards the outlet side (7) or that the feed side (5) is at least partially arranged such that the outlet. The distance between the feed side (4) and the guide side (5) decreases towards the outlet side (7). Device (1) according to one of claims 2 to 5, characterized in that the feed side (4) and the guide side (5) enclose a first chamber angle (α), the first chamber angle (α) being between 10° and 45°, the first chamber angle (α) preferably being between 15° and 25°. Device (1) according to one of claims 2 to 6, characterized in that the feed side (4) and the end side (6) enclose a second chamber angle (β), the second chamber angle (β) being between 90° and 150°, the second chamber angle (β) preferably being between 100° and 120°. Device (1) according to one of the preceding claims, characterized in that a plurality of inlets (8) arranged in a row are provided on the feed side (4), wherein a plurality of inlets (8) arranged in two rows are preferably provided on the feed side (4).Device (1) according to one of the preceding claims, characterized in that the inlet (8) has a diameter of 10 mm to 100 mm and preferably of 30 mm to 60 mm. Device (1) according to one of claims 2 to 9, characterized in that a shear rate of at least 10 1 / sec and preferably at least 50 1 / sec is generated in the entire vortex chamber (3). Device (1) according to one of the preceding claims, characterized in that the device (1) is intended for use with an inclined screen (9).

12. A method for producing a fiber web (2), wherein a fiber foam is introduced into a vortex chamber (3) according to one of the preceding claims, wherein the fiber foam is redirected in the vortex chamber (3) and discharged at the outlet side (7) of the vortex chamber.

13. Method according to claim 12, characterized in that a shear rate of at least 10 1 / sec and preferably at least 50 1 / sec is generated in the entire vortex chamber (3).

14. The method according to one of claims 12 to 13, characterized in that the fiber foam is introduced into the vortex chamber (3) in a stream (A), the stream (A) is divided at the guide side (5) into a partial stream (B) and a further partial stream (C) and is diverted, the further partial stream (C) flowing along the guide side (5) in the direction of the outlet side (7), the partial stream (A) flowing along the end side (6) to the feed side (4) and along the feed side (4) in the direction of the outlet side (7).

15. Method according to one of claims 12 to 14, wherein the fiber foam is deposited on an inclined sieve or a fourdrinier sieve after leaving the vortex chamber (3).

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