Production of filaments with controlled gas flow

Abstract

The present invention relates to a device suitable for producing material filaments by extruding a material fluid and solidifying the material fluid, comprising an extrusion head (1) with a plurality of extrusion openings, a collecting bath (2) for receiving extruded fluid filaments (5) from the extrusion openings, a gas gap (A) between the extrusion openings and the collecting bath, thereby forming a gas treatment area (4') for extruded material fluid, a gas flow device (3, 6) for generating a gas flow in the gas gap, characterized in that at least one gas flow limit (4) is provided laterally to the gas treatment area and in the direction of the gas flow; and a method for producing solid material filaments from a material fluid by extruding the material fluid.

Description

[0001] The present invention relates to the shaping and treatment of extruded synthetic fibers before and during their consolidation. Background of the invention

[0002] Cellulose can be dissolved in aqueous solutions of amine oxides, particularly solutions of N-methylmorpholine-N-oxide (NMMO), to produce spinning products such as filaments, staple fibers, films, etc. from the resulting spinning solution. This is done by precipitating the extrudates in water or diluted amine oxide solutions after the extrudates are fed from the extruder through a gas gap into the precipitation bath. Cellulose solutions in the range of 4% to 23% are typically used for processing into extruded products. This process is also called the lyocell process, and the resulting cellulose filaments are also called lyocell filaments.

[0003] Depending on the required end product, the spinning process can be carried out through a single extrusion channel or multiple extrusion channels mounted in an extruder. A single-channel extrusion process, depending on the extrusion orifice diameter, is described in the article "Spinning of Fibres through the N-Methyl-Morpholine-N-Oxide Process" (S.A. Mortimer and A. Peguy; in Cellulose and Cellulose Derivatives: Physico - Chemical Aspects and Industrial Applications; Woodhead Publishing Ltd., 1995). In it, the authors describe the effects of spinneret diameter and spinning draft ratio, as well as their impact on fibre fibrillation in the NMMO process, which was carried out as a monofilament spinning process in an air gap.

[0004] An industrial NMMO multifilament plant is described in US 4,246,221 and consists of an extruder with an extrusion plate with several extrusion orifices, a gas gap and a collecting tank with a recovery medium.

[0005] EP 0 430 926 B1 describes extrusion openings with capillaries, which allows a higher hole density of the extrusion openings.

[0006] WO 93 / 19230 A, WO 94 / 28218 A, and EP 0 700 463 B1 describe cooling the extruded filaments after extrusion by blowing them with a gas stream. According to WO 94 / 282218, air is also extracted in addition to the blowing.

[0007] WO 94 / 28210 and WO 98 / 18983 describe spinnerets for the production of lyocell fiber, with the extrusion orifices provided in several plates welded into a frame structure. The plates as a whole result in a cluster-like arrangement of extrusion nozzles corresponding to the respective plates.

[0008] DE 10 200 405 A1 describes a lyocell process in which a filament curtain is cooled with a wide nozzle in an air gap with a widely fanned gas stream.

[0009] WO 2013 / 030399 A1 describes a lyocell process in which the gas stream is divided into a heating sub-stream and a cooling sub-stream.

[0010] WO 02 / 12600 describes a lyocell process which has been adjusted with regard to the withdrawal speed of the lyocell filaments.

[0011] In the area of melt spinning, which is different from the lyocell process, where the filaments are solidified in the gaseous state immediately after extrusion of a melt, an extrusion plate for small systems with channels is known according to US Pat. No. 4,283,364. The channels are intended to improve the yarn count with fewer irregularities in this system. However, the processes in the gaseous state after extrusion are not comparable between melt spinning and lyocell spinning: While solidification occurs in melt spinning, in the lyocell process, this only occurs in the solidification medium. e.g. in a precipitation bath, while the fluid filaments are pretreated in the gas gap e.g. to stretch them, to set a certain humidity (US 4,246,221), to pre-cool them or to remove harmful particles (WO 2013 / 030399 A1).

[0012] JP 05044104 A2 describes a dry-jet wet spinning process for producing filaments. A gas is forced to flow through the air gap below the spinneret in a direction perpendicular to the filament travel direction to remove residual solvent vapor from the extruded filaments. As a result, filament breakage, adherent filaments, unusually thick pieces, and size irregularities are prevented, significantly improving fiber quality and productivity. Additionally, after passing through the air gap, the gas is captured by an exhaust device. The gas is deflected by 90° so that the exhaust air flow is discharged approximately parallel to and opposite to the filament travel direction.

[0013] WO 03 / 014436 A1 describes a process for producing cellulosic molded articles, in which a solution of cellulose in a tertiary amine N-oxide and optionally water is molded in a hot state, and the molded solution is cooled by a gaseous medium in a gas gap before being introduced into a coagulation bath, wherein the gaseous medium flows through the molded solution from a gas inlet side to a gas outlet side. The process is characterized in that the gaseous medium is sucked off on the gas outlet side in a direction substantially parallel or substantially opposite to the direction of movement of the molding solution. Summary of the invention

[0014] The present invention relates to a filament spinning process or a wet spinning process in which extruded filaments are solidified in a solidification medium after being pretreated in a gas gap. One aim of the invention is to achieve the highest possible material throughput with optimal treatment in the gas gap and high quality of the resulting filaments. The qualities of a monofilament process are sought for multifilament processes.

[0015] Another goal is to keep productivity as high as possible. Another invention goal is to achieve the highest possible spinning speeds while maintaining spinning reliability and product quality (no clumping, consistent fiber fineness).

[0016] The present invention relates to a device suitable for producing material filaments by extruding a material fluid and solidifying the material fluid. The device has an extrusion head 1 with a plurality of extrusion openings, a collecting bath 2 for receiving extruded fluid filaments 5 from the extrusion openings, a gas gap A between the extrusion openings and the collecting bath, forming a gas treatment area 4' for extruded material fluid, and a gas flow device 3, 6 for generating a gas flow in the gas gap. At least one gas flow restriction 4 is provided laterally of the gas treatment area and in the direction of the gas flow.

[0017] Furthermore, the invention relates to a method for producing solid material filaments from a material fluid by extruding the material fluid through a plurality of extrusion openings, thereby forming fluid filaments 5, passing the fluid filaments through a gas gap A, and solidifying the filaments in a coagulation liquid in a collecting bath 2. A gas stream 6, 7 flows through the gas gap A, the gas stream being guided by at least one gas flow restrictor 4, the gas flow restrictor laterally defining a gas treatment area 4' in which the filaments are treated with the gas stream. Due to the partially open design of the spinning system to the environment, so-called "false air streams" 8 are introduced into the spinning system.

[0018] All details and embodiments described herein apply equally to all aspects of the invention, the device and the method. The device or parts thereof can be used in the method. Details of the method can preferably be the suitability of the device for carrying out these methods. Character description

[0019] In Fig.1 an extrusion device for producing material filaments by extruding a material fluid and solidifying the material fluid with a gas flow restriction 4, 4', 4" is shown in side view. In Fig. 2 an arrangement of the extrusion device is made of Fig. 1 in the front view (view of Fig. 1 from left). The filament curtain 5 is formed by individual filaments. The gas flow restriction 4 is located on the side. Fig. 3shows an embodiment of a gas flow restriction 4 according to the invention in detail. The gas flow restriction 4 has a perforation, here slots, in a partial area. Fig. 4 represents an alternative design of a gas flow restriction 4. The gas flow restriction 4 is basically the same as the design in Fig. 3 Instead of slits, the perforation is designed with a sieve mesh or grid. Fig. 5 represents another alternative design of a gas flow restriction 4. The gas flow restriction 4 is basically the same as the design in Fig. 3 Instead of slits, the perforation is made with regularly spaced recesses. The recesses can be round, square, rectangular, rhombic, triangular, or any other shape. Fig. 6represents a further alternative. In this case, the gas flow restriction 4 is not designed as a flat surface throughout, but has at least in a partial area a three-dimensional structured surface, in particular a grooved riblet surface (in Fig. 6 shown in dashed lines). Fig. 7 shows a sectional view from above (top view) of the edge region. The filament curtain 5 is flowed through by the gas flow 6. In the edge zone, additional "secondary gas" 8' is sucked in by the primary gas flow 6, which is swirled due to the three-dimensionally structured surface of the gas flow boundary 4. Fig. 8 describes a similar system as Fig. 7 . The difference to Fig.7is that the three-dimensionally structured surface of the gas flow restriction 4 is partially perforated, so that the suction effect of the secondary gas 8' sucked in at the edge area also introduces further "secondary gas" 8‴ into the system. Fig. 9 is identical to Fig. 8 However, the gas flow restriction 4 is designed as a flow chamber, whereby the "secondary gas" 8‴ is introduced as a forced flow in a metered manner. Fig. 10 represents a special form of execution compared to Fig. 6 The gas flow restriction 4 in this case is a restriction which has indentations at regular intervals which contain openings in the air flow direction which allow an air flow from the outside to the inside into the gas treatment area. Fig. 11 represents a sectional view from above (top view) of the edge area of Fig. 10The filament curtain 5 is flowed through by the gas flow 6. In the peripheral zone, additional "secondary gas" 8' is drawn in by the gas flow 6, which is swirled due to the three-dimensionally structured surface of the gas flow restriction 4. Due to the suction effect of the secondary gas 8' drawn in at the peripheral area, additional "secondary gas" 8‴ is introduced into the system from the outside through the gas flow restriction 4. Detailed description of the invention

[0020] The invention relates to a device comprising an extrusion head 1 with a plurality of extrusion openings, a collecting bath 2 for receiving extruded fluid filaments 5 from the extrusion openings, a gas gap A between the extrusion openings and the collecting bath, forming a gas treatment area 4' for extruded material fluid, and a gas flow device 3, 6 for generating a gas flow in the gas gap, with at least one gas flow restriction 4 being provided laterally of the gas treatment area and in the direction of the gas flow. The device can be used to produce material filaments by extruding a material fluid and solidifying the material fluid. For solidification, a coagulation liquid is typically provided in the collecting bath (the container therefor).This coagulation liquid is not a solvent in its composition for the material fluid, with which it coagulates and forms coagulated filaments which are essentially solid.

[0021] The gas gap is an essential treatment zone for the extruded filaments, in which the still-fluid filaments are, for example, stretched or surface-treated (volatilization of solvent components). The treatment zone in the gas gap is defined by the distance between the extrusion openings and the surface of the coagulation bath. In the device according to the invention, this surface level can be marked in the collecting bath, which is essentially a trough. In particular, this surface level is defined by an overflow, above which the level of the coagulation liquid cannot rise during operation. Therefore, in preferred embodiments, the collecting bath has a designated liquid level for a coagulation liquid that can be absorbed in the collecting bath.

[0022] Furthermore, the invention relates to a method for producing solid material filaments from a material fluid by extruding the material fluid through a plurality of extrusion openings, whereby fluid filaments 5 are formed, passing the fluid filaments through a gas gap A, and solidifying the filaments in a coagulation liquid in a collecting bath 2, wherein a gas stream 6, 7 flows through the gas gap A, wherein the gas stream is guided with at least one gas flow restriction 4, wherein the gas flow restriction laterally delimits a gas treatment region (4') in which the filaments are treated with the gas stream.

[0023] The invention relates to the production of material filaments, e.g. as continuous molded bodies, from a molding compound, such as a spinning solution. The process is preferably a lyocell process, i.e. a spinning process of a cellulose solution, such as a spinning solution containing cellulose, water, and tertiary amine oxide. Lyocell is a generic name assigned by BISFA (The International Bureau for the Standardization of Man-Made Fibres) for cellulose fibers produced from cellulose without the formation of a derivative. Extrusion takes place from a plurality of extrusion orifices through which the molding compound (material fluid) is extruded to form the fluid filaments. The fluid filaments are solidified in the coagulation liquid, which is also referred to as the solidification medium or coagulation bath. A gas treatment area for the filaments is located in the gas gap between the extrusion orifices and the coagulation liquid.

[0024] The gas treatment area is spatially defined by the height of the gas gap (distance between the extrusion orifices and the coagulation liquid, in particular the intended liquid level in the collection bath) and laterally by the dimensions of the arranged extrusion orifices. The extruded filaments flow from these extrusion orifices into the coagulation liquid (the collection bath) during operation. The area defined by the (outer) extruded filaments is called the gas treatment area, since the filaments are treated by the gas flow there. It is therefore the space formed by the area of the arrangement of extrusion orifices (limited by the extrusion orifices at the edge of the arrangement) times the height of the gas gap at the location of the extrusion orifices. The multitude of filaments in the gas gap is also called the extrudate curtain. This determines the gas treatment area.

[0025] A gas stream is moved through the gas gap, usually in a linear fashion, at least in plan view. The gas stream enters the gas treatment area at one inlet side and exits at the opposite outlet side. In the gas treatment area itself, the gas stream flows around the filaments.

[0026] According to the invention, at least one gas flow barrier is provided laterally of the gas treatment area. "Lateral" typically means essentially perpendicular to the extrusion direction or essentially parallel to the surface of the coagulation bath, and also laterally of the gas treatment area with respect to the continuous gas flow, i.e., essentially parallel to it, but offset to the edge of the gas treatment area. The gas flow barrier is a physical barrier that forms an area between the extrusion openings and the coagulation bath and along the boundary of the gas treatment area running in the direction of the gas flow. The gas flow barrier is, for example, a wall adjacent to the side of the gas treatment area. It is typically only a short distance from it.Of course, the gas flow restriction must not touch the extruded filaments to avoid impeding their flow from the extrusion openings into the collection bath. The gas flow restriction merely changes the gas flow, particularly in the peripheral areas of the gas treatment zone. These changes affect any turbulence that would otherwise occur and / or any lateral inflow or outflow to / from the gas stream.

[0027] In particular, the use of the gas flow limitation according to the invention creates conditions for guiding the gas through the filaments in the gas gap which represent a significant advancement compared to previous spinning systems in terms of filament quality, productivity and maintenance of trouble-free operation.

[0028] The gas flow restriction according to the invention influences the gas flow in the peripheral zones of the gas treatment area. The gas flow restriction according to the invention influences the streamlines of the gas flow; depending on the design of the restriction, they can be deflected, compressed, swirled, and / or mixed with secondary gas. Gas that flows in a direct line from the inlet side to the outlet side to and through the gas treatment area is called primary gas. It is usually blown into the gas treatment area by a fan. Secondary gas is indirectly introduced gas that is entrained, for example, by the primary gas. According to the invention, it was found that this secondary gas can lead to disruptions in the spinning process at the peripheral regions of the gas treatment area, such as sticking or breaking of the filaments. Recirculation gas is also disruptive.This is gas that has already passed through the filament curtain once. As a result, it has already absorbed solvent from its initial contact with the filaments or the coagulation bath and / or has been heated (extrusion typically occurs under heat, e.g., 80°C or more), making it less suitable for further treatment of the filaments and destabilizing the spinning process. Gas flow restriction minimizes the proportion of secondary air and the supply of recirculation gas. The purpose of gas flow restriction is, on the one hand, to ensure that the gas flow can be passed through the filaments under as uniform conditions as possible across the entire length and width of the gas treatment area. In addition, gas flow restriction also calms the surface of the solidification bath.

[0029] Closed, circumferentially unsectioned round or ring dies, i.e., extrusion openings arranged in a ring, achieve uniform gas flow conditions across the entire circumference due to their inherent "infinity." A specific feature of ring dies, however, is that eddies or backflows occur within the solidification bath inside the closed filament curtain, causing significant turbulence on the solidification bath surface. Therefore, the maximum take-off speed of ring dies must be kept low, as higher take-off speeds (as is common with "open" filament curtains) lead to severe spinning disruptions due to the bath turbulence.

[0030] Therefore, rectangular nozzles (extrusion openings arranged in a rectangle) or sectional nozzles, split ring nozzles, or other extrusion devices that form "open" (not closed) filament curtains are preferred. These arrangements allow for faster operation, and the gas flow restrictors according to the invention can contribute to significant advantages, as they minimize or prevent the "edge penetration" of the gas flow and turbulence at the solidification bath surface. The extrusion openings are preferably arranged in a rectangular shape, with the narrow side of the rectangular shape facing the gas flow restrictor. The long side is exposed to the gas flow or faces a fan. Possible arrangements of the extrusion openings include rectangular, curved, ring, or ring-segment shapes. The elongated shape may have a length to width ratio of 100:1 to 2:1, preferably 60:1 to 5:1 or 40:1 to 10:1.Preferably, a gas flow restriction as described herein is used on both sides of the gas treatment area (left and right, viewed from the gas flow).

[0031] In the case of a rectangular shape, the lateral gas flow restriction can be connected to the side of the gas flow supply (usually the long side - as described above, the side of the blower or the side against the gas flow direction). With gas flow restrictions attached to both sides of the gas treatment area, this creates a U-shaped restriction, collectively also referred to as a blower air box. The connecting part (on the side of the gas flow device) can be designed in the same way as the lateral gas flow restrictions and can protrude into the coagulation liquid in the collecting bath (or into the level provided for this purpose in the device according to the invention), for example to prevent secondary air from being drawn in. It is also possible for one end of the connecting part (like the lateral gas flow restriction) to protrude into the coagulation liquid in the collecting bath (or into the level provided for this purpose in the device according to the invention) without protruding into the coagulation liquid in the collecting bath (orinto the level provided for this purpose in the device according to the invention), i.e. one end above this level.

[0032] Gas flow restriction (and / or the connecting part) can be arranged perpendicular to the collecting bath (coagulation liquid level) or at an angle deviating from the vertical, e.g. 0° to 30°. The inclination is preferably downward (toward the collecting tank), widening (i.e., away from the extruded material fluid) or narrowing (toward the extruded material fluid). The distances specified here from the gas flow restriction to the extruded material fluid / gas treatment area refer to the distance at the narrowest point.

[0033] Advantages of the invention are uniform gas flow temperature and gas flow humidity in the gas treatment area; uniform gas flow velocity; uniform gas flow velocity gradient along the filaments in the extrusion direction (from the extrusion openings to the collecting bath); uniform loading of the filaments by the flowing gas flow; reduction or avoidance of turbulence at the solidification bath surface.

[0034] The gas flow restriction at least partially limits the gas flow laterally across the gas gap height. The gas flow restriction can extend from the extrusion head toward the surface of the coagulation liquid over the entire height of the gas gap, or it can extend only partially across the gas gap height, so that part of the gas gap height is not restricted. The area not restricted by the gas gap height can be located directly above the surface of the coagulation liquid, in the area directly below the extrusion openings, or even between the coagulation liquid surface and the extrusion openings. According to the invention, the gas flow restriction can also be immersed in the coagulation liquid and end below the surface of the coagulation liquid according to an immersion depth.

[0035] The gas flow restrictor can be mounted directly on the extrusion head, the collecting tank, or on the gas flow device (extraction, blower). A combination of several gas flow restrictors is also possible; these can be separate, possibly with a gap (a full-surface barrier is not necessary and is not used in preferred embodiments, especially in the examples), or connected to each other.

[0036] Preferably, the gas flow restriction extends over the entire length B of the gas treatment area, ieThe length refers to all extrusion openings arranged in the longitudinal direction (the gas flow direction along which the gas flow restriction runs or is essentially parallel). The extension over the entire length B of the gas treatment area means that the area of the gas flow restriction covers this area; in particular, the edges of the gas flow restriction reach at least these dimensions. They can also extend beyond them. Furthermore, as mentioned, the gas flow restriction can be perforated; i.e., covering and extending does not necessarily mean completely closing off this area. It can also partially block the area.

[0037] Preferably, the gas flow restriction extends over an area L, 4"in the gas flow direction downstream of the gas treatment area. The gas flow limitation can thus extend beyond the gas treatment area, according to this feature, in the direction of the gas flow or toward the extraction device, if present. It is preferred if the length L of this downstream area in the gas flow direction is at least half the length B of the gas treatment area of all extrusion openings arranged in the longitudinal direction. Preferably, the length L is greater than or equal to the length B.

[0038] Furthermore, it is preferred that the gas flow restriction extends over a region K upstream of the gas treatment region, i.e., in the direction of a blower, if present. The length K of this upstream region, downstream of the gas flow direction, is preferably at least half the length B of the gas treatment region of all extrusion openings arranged in the longitudinal direction.

[0039] The gas flow in the gas gap can be effected or forced by a gas flow device. For this purpose, the gas flow device can comprise, for example, a blower or an extraction device, or both. Preferably, both are provided. Different flows can be set in both devices. Typically, a higher flow is set for the extraction device than for the blower, since secondary air is drawn in in addition to the primary air. According to the invention, this inequality can be reduced due to the reduction in secondary air.

[0040] In preferred embodiments of the device according to the invention or in the method according to the invention, a blower and / or a suction device 3 is provided as the gas flow device or for the gas flow. The suction device can have an exhaust duct which is preferably oriented at an angle X of 0° to 45° to the horizontal (collecting bath / coagulation bath surface). Likewise preferably, the suction device is arranged above the gas gap so that the gas treatment area is accessible in a horizontal plane. This accessibility allows the filament curtain to be viewed or a user of the device to intervene to make corrective adjustments. The angle X is preferably 10° to 40°, e.g. 20° to 35°. 0° corresponds to the horizontal or the coagulation bath surface.Thus, it is preferred that the extraction device allows uninterrupted direct visibility of the filaments in the gas gap, that the exhaust gas is deflected as little as possible upon removal from the gas gap, thereby achieving particularly efficient extraction, and that the amount of excess ambient air (secondary air) that is extracted can be kept as low as possible. Furthermore, in combination with the gas flow limitation, this allows the solidification bath to be kept as turbulence-free as possible. Due to the relatively short distance to the intake opening of the extraction device, there is a risk that the exhaust gas flow could also entrain solidification bath and thus contribute to turbulence in the solidification bath. This is reduced by the invention.

[0041] In the process, the gas flow can therefore be achieved by blowing in 6 and extracting 7, with the extracted gas flow preferably being greater than the injected gas flow. The ratio of extracted gas flow to injected gas flow is preferably greater than 1.2:1, e.g., greater than 1.4:1 or greater than 1.6:1. This inequality can also be limited by the invention; thus, the ratio is preferably less than 2:1, preferably less than 1.8:1, less than 1.6:1, less than 1.5:1, or even less than 1.4:1.

[0042] A gas stream can optionally be blown into and / or sucked out of the gas gap (and preferably is, particularly in large, industrially relevant systems). The gas stream entering the treatment zone (immediately upstream of the treatment zone, e.g., at the blower) preferably has a temperature of 5°C to 65°C, preferably 10°C to 40°C, in particular room temperature, e.g., 20°C to 25°C. The material fluid can be extruded at a temperature of 75°C to 160°C. The gas gap preferably has a lower temperature than that of the extruded material fluid. In particular, a gas stream is conducted in the gas gap at a lower temperature than that of the extruded material fluid.

[0043] Possible lengths of the gas gap, i.e. the distance between the extrusion openings and the coagulation bath surface, are preferably between 10 mm and 200 mm, in particular between 15 mm and 100 mm, or between 20 mm and 80 mm. Preferably, it is at least 15 mm. The gas in the gas gap is preferably air. The gas flow is preferably an air flow. Other inert gases are also possible. An inert gas is a gas that does not interact with the fluid filaments in the gas gap and preferably also not with the solidification medium, such as water or a diluted NMMO in water solution or other solvent components - depending on the extrusion medium used. -, reacts chemically.

[0044] The inflow into the gas treatment zone (blowing, blower) is preferably adjusted to achieve the desired cooling of the gas in the gas gap in the gas treatment zone (particularly at the gas outlet end). Preferably, especially in a lyocell process, the inflow is adjusted to cool the temperature in the gas treatment zone to 40°C to 80°C, preferably 50°C to 70°C or 55°C to 65°C.

[0045] By selecting the gas flow and the gas flow limitation, turbulence of the gas flow at the lateral edge of the gas treatment area can also be avoided.

[0046] To achieve the advantages of the invention, in particular to influence the gas flow behavior, the gas flow restriction does not have to cover the entire lateral surface. Preferably, the gas flow restriction has a height in the gas treatment region in the extrusion direction of at least 70% of the height of the gas gap. The height of the gas flow restriction corresponds to its dimension in the extrusion direction, i.e., essentially vertical or normal to the coagulation liquid surface; particularly in the gas treatment region, i.e., between the extrusion openings and the coagulation bath, it should, in preferred embodiments, extend over at least 70%, particularly preferably at least 80% or at least 90%, of this height.

[0047] The gas flow restriction can be completely closed, slotted or perforated, i.e. it can have openings that allow a gas flow through. The perforation can be over the entire surface or only on parts of the surface. The perforation can be implemented using screens, slots or holes or other openings in the surface. Preferably, the gas flow restriction has perforations in the region of the gas treatment area. In this area with perforations, preferably at least 25% of the area of the gas flow restriction in the region of the gas treatment area is closed, i.e. not permeable to gas flow. Thus, 75% or less of the area can be open. In particular, at least 35% of the area in this area is closed, preferably at least 45%, or at least 55%, at least 65%, at least 75% or at least 85% of the area in the area with the perforations can be closed.

[0048] The gas flow restriction can be flat, curved, single- or multiply corrugated, or folded. The bending, corrugation, or folding direction can be horizontal, vertical, or even diagonally between horizontal and vertical.

[0049] The perforations are preferably holes or strips, preferably strips in the extrusion direction. Particularly preferably, at least one strip is provided every 4 cm, preferably every 2 cm or every 3 cm, of the length of the gas flow restriction in the region of the gas treatment zone in the gas flow direction.

[0050] In further preferred embodiments, the gas flow restriction in the region of the gas treatment zone has a corrugated, grooved, or ribbed surface. Such a surface is, for example, a riblet or waveguide surface. The corrugated, grooved, ribbed, or riblet surface is preferably combined with the above-mentioned perforations. Thus, the corrugated, grooved, ribbed, or riblet surface can further have the above-mentioned perforations. A riblet surface is a surface geometry with ribs that cause flow separation. The ribs are preferably designed such that, in the direction of flow, the ribs protrude increasingly into the gas treatment zone, then break off and return to the wall level. They are essentially serrations or jagged indentations. The perforations can be in the continuous region or in the break-off region of the serrations.The gas flow restriction can be designed as a plate with regularly spaced openings that deflect the gas flow after it passes through the plate. Depending on the design of the openings, the gas flow can be deflected by 15° to 90° compared to the vertical flow with "open" holes. The corrugations, grooves, riblets, serrations, and the like preferably create turbulence on the surface of these grooves, riblets, serrations, and the like. These surfaces are used in particular to generate low air resistance. Alternatively, the gas flow restriction can also be smooth.

[0051] The gas flow restriction 4 can be designed as a flow chamber. This essentially means that the gas flow restriction is double-walled, forming the chamber. The wall facing the gas treatment area has perforations. The double-walled design allows a gas flow (secondary gas) through the chamber and thus through the perforations to be limited, controlled, or monitored.

[0052] Preferably, the gas flow restriction is temperature controlled. This can be done by a gas flowing through the gas flow restriction and / or by cooling or heating media different from the gas. e.g. an electric heater or a heat transfer fluid that can temper the gas flow restriction.

[0053] The gas flow restriction is located laterally on the gas treatment area and is spaced from it (distance to the filaments). This distance is e.g.2-20 times the distance between the filaments (or the extrusion openings). Thus, the gas flow boundary to the gas treatment region is preferably located at a distance J of at least twice the distance C between the extrusion openings in a direction transverse to the gas flow direction. Preferably, the gas flow boundary to the gas treatment region is located at a distance J of a maximum of 30 times the distance C between the extrusion openings in a direction transverse to the gas flow direction.

[0054] Suitable and optimal distances and sizes of the gas flow restriction from the gas treatment area (extruded material) can be determined experimentally by recording the spinning instabilities in the peripheral zones. Recording can typically be done visually or by video recording and flow simulation, where the flow is investigated with or without the presence of certain gas flow restrictions (such as riblet surfaces and the like, and / or perforations) at a selected gas flow velocity. Gas flow visualization can be achieved using artificially generated smoke mist to understand and replicate the flow and to design the spinning system as a whole.

[0055] The gas flow restriction can be selected from various materials, such as e.g. metal or plastic, e.g. thermoformed plastic.

[0056] An extrusion medium is used as the fluid in the process according to the invention. This is preferably a solution or mixture of cellulose and other medium components, such as solvents. The cellulose concentration is selected within the ranges customary for lyocell processes. Thus, the cellulose concentration of the extruded fluid can be 4% to 23%, preferably 6% to 20%, in particular 8% to 18% or 10% to 16% (all percentages are by mass). The extrusion medium in the lyocell process is usually a cellulose solution or melt with NMMO (N-methylmorpholine N-oxide) and water, as described in the introduction. Other cellulose solutions, in particular ionic cellulose solvents, can also be used. Alternatively or additionally, an ionic solvent can be used. Such ionic solvents are described, for example, in WO 03 / 029329; WO 2006 / 000197 A1; Parviainen et al., RSC Adv., 2015, 5, 69728-69737; Liu et al., Green Chem. 2017, DOI: 10.1039 / c7gc02880f; Hauru et al., Cellulose (2014) 21:4471-4481; Fernandez et al., J Membra Sci Technol 2011, p. 4; etc., and preferably contain organic cations, such as ammonium, pyrimidium, or imidazolium cations, preferably 1,3-dialkylimidazolium salts, such as halides. Water is also preferably used here as a non-solvent for cellulose. Particularly preferred is a solution of cellulose and butyl-3-methylimidazolium (BMIM), e.g., with chloride as counterion (BMIMCl), or 1-ethyl-3-methylimidazolium (also preferably as chloride, acetate, or diethyl phosphate), or 1-hexyl-3-methylimidazolium or 1-hexyl-1-methylpyrrolidinium (preferably with a bis(trifluoromethylsulfonyl)amide anion), and water. Other ionic solvents are 1,5-diazabicyclo[4.3].0]non-5-enium, preferably as acetate; 1-ethyl-3-methylimidazolium acetate, 1,3-dimethylimidazolium acetate, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium diethyl phosphate, 1-methyl-3-methylimidazolium dimethyl phosphate, 1-ethyl-3-methylimidazolium formate, 1-ethyl-3-methylimidazolium octanoate, 1,3-diethylimidazolium acetate, and 1-ethyl-3-methylimidazolium propionate. The material fluid preferably contains cellulose, preferably a solution or melt of cellulose, a solvent of cellulose, preferably an amine oxide, and water.

[0057] In dry-wet spinning, the treatment zone essentially consists of a gas or air gap and downstream liquid containers, liquid funnels, or liquid chutes. The extrudates exiting the extrusion orifices pass through a gas gap and then a coagulation bath, also known as a spinning bath. The moist (precipitated and / or cooled) extrudates are fed to the take-off unit through one or more wash baths and / or through a gas or air chamber.

[0058] In wet or dry-wet spinning processes, turbulence and vortexes occur at higher speeds due to displacement and dragging processes between the coagulation bath liquid and the extrudate. In addition, at deflection points with rigid deflectors, there is a risk of dry running at the contact points between the extrudate and deflector. The risk of dry running increases the higher the take-off speed and the more forcefully the extrudate curtains or bundles are pressed against the deflection device. Preferably, the filaments are deflected in the collecting bath. A deflection device can be provided for this purpose.

[0059] Preferably, the gas flow restriction is immersed in the coagulation bath or extends below the surface level of the coagulation bath (or the designated level in the collection bath). This immersion can reduce turbulence in the bath. This immersion depth is preferably 1 mm to 50 mm.

[0060] The extrusion orifices preferably have a diameter of 30 µm to 200 µm, preferably 50 µm to 150 µm or 60 µm to 100 µm. This allows the production of filaments suitable for textiles (woven and nonwovens).

[0061] Preferably, the extrusion throughput is adjusted so that, at the given take-off speed, the individual fibers have a fiber fineness of 1.3 dtex + / -50%, preferably + / -25% or + / -10%. The extrusion throughput can be adjusted by the pressure of the extruded mass, i.e., the cellulose solution. Possible pressures are, for example, 5 to 100 bar, preferably 8 to 40 bar.

[0062] The present invention is further described by the following figures and examples, without being limited to these embodiments of the invention.

[0063] In Fig.1A typical arrangement of a spinning device is shown in a side view. The filament curtain 5 emerging from the extrusion head 1 or the extrusion openings passes through the gas gap A and subsequently enters the coagulation bath 2. A gas flow inlet 6 supplies the gas gap A with a gas flow, which passes through the filament curtain 5 and then, deflected by the deflection angle X, exits the spinning area through the suction device 3 as the discharged gas flow 7.

[0064] In addition to the supplied gas 6, secondary gas 8' is supplied to the gas gap A. The secondary gas 8' enters the gas gap A both from the direction of the supplied gas 6 and from the side via the perforated gas flow restriction 4. An essential feature of the invention is to create conditions through the inventive design of the gas flow restriction 4 and the design of the perforation of the gas flow restriction 4 such that trouble-free spinning operation and high filament draw-off speeds can be achieved. A preferred design was determined through a series of tests, in which the spinning stability and the degree of turbulence of the coagulation bath surface 2 were evaluated.

[0065] The gas flow 7 extracted by the extraction device 3 is the sum of the supplied gas flow 6, secondary gas 8' and ambient gas 8", which are sucked in from the environment due to the open design.

[0066] The gas flow restriction 4 is designed as a flat, at least partially planar structure with a height M. The gas flow restriction 4 covers the gas gap A at least partially laterally in the vertical direction. The gas flow restriction shown in the figure is additionally immersed in the coagulation bath 2 by the amount of the immersion depth O. Also shown is the vertical distance N, which represents the vertical distance between the exit plane of the filament curtain and the upper edge of the gas flow restriction 4. This distance is preferably 0 mm to 20 mm.

[0067] The gas flow restriction 4 preferably extends horizontally across the width of the filament curtain B (dimension in the gas flow direction, e.g., 5 mm to 100 mm) and additionally over a projection to the gas treatment area on the gas inlet side K and additionally over a projection to the gas treatment area on the gas outlet side L. The projection of the gas flow restriction on the gas inlet side K is, e.g., 0 mm to 200 mm. The projection of the gas flow restriction on the gas outlet side L is preferably 0 mm to 400 mm.

[0068] The gas flow restriction 4 is in Figure 1 shown as a single piece. Possible embodiments of the gas flow restriction 4 are also designed in multiple parts; for example, the gas flow restriction can be divided horizontally, vertically, or in any other direction.

[0069] In Fig. 2A typical arrangement of a spinning device is shown in the front view. The filament curtain 5 is formed by individual filaments, which extends over the filament curtain length T (dimension transverse to the gas flow direction). The filaments are spaced from each other over the length T of the filament curtain 5 by the distance C. This distance between the filaments is e.g. 0.4 mm to 10 mm. The gas flow restriction 4 is spaced from the filament curtain in extension of the filament curtain length T by the dimension of the lateral distance of the gas flow restriction J. This distance is e.g. 1 mm to 20 mm.

[0070] Fig. 3 shows an inventive embodiment of a gas flow restriction 4 in detail. The gas flow restriction 4 has a perforation in a partial area.

[0071] The position of the perforation is determined horizontally by the horizontal distance from the gas upstream end of the gas flow restriction to the perforation P and the horizontal length of the perforation Q. P is, for example, 1 mm to 50 mm. The perforation is shown here for a gas treatment area and an overhang toward the gas flow inlet. It can also be present in only part of the gas treatment area. Q can be a fraction of the width of the gas treatment area. The length L of a perforated area can be selected depending on the intended gas flow, filament withdrawal speed, and number of filaments; e.g. Q can be between 20 mm and 200 mm.

[0072] The perforation is preferably not immersed in the coagulation liquid. The position of the perforation is determined in a vertical orientation by the vertical distance from the spinneret-side end of the gas flow restriction to the perforation R and the height of the area with the perforation S. The vertical position of the area with the perforation is designed such that the perforation is present in at least a partial area of the gas gap A. However, the perforation can also extend in a vertical orientation across the entire gas gap A and also into the coagulation bath 2.

[0073] In Fig. 3 The perforation is designed, for example, with vertical slits. Horizontal or angled slits are also possible, but curved or other non-straight slits are also possible. R, for example, is 1 mm to 15 mm; S is preferably 10 mm to 40 mm.

[0074] Fig. 4represents an alternative design of a gas flow restriction 4. The gas flow restriction 4 is basically the same as the design in Fig. 3 Instead of slits, the perforation is designed with a sieve mesh or grid.

[0075] Fig. 5 represents another alternative design of a gas flow restriction 4. The gas flow restriction 4 is basically the same as the design in Fig. 3 Instead of slits, the perforation is designed with a variety of openings. In addition to round holes, square holes, rectangular holes, rhombic holes, and any other possible geometric shapes can be used to create the perforation.

[0076] Fig. 6 shows in modification of Fig. 3a gas flow boundary with a 3-dimensional structure. The dashed area is provided with a vertically oriented 3-dimensional structure (grooves, ribs, riblets, spikes) that repeats in the gas flow direction.

[0077] Fig. 7 This is an enlarged sectional view (top view) of the 3-dimensional structure. The gas flow 6 flows through the treatment area 5. The space between the edge zone of the gas treatment area 5 and the gas flow restriction 4 is flowed through by secondary gas 8' entrained from the environment. The scale-like 3-dimensional structure of the gas flow restriction 4 ensures turbulence in the secondary gas flow 8'. The structure shown here is exemplary. It can be vertically continuous, as shown, but can also be vertically divided or offset.

[0078] Fig. 8 shows an identical version to Fig. 7However, additional openings are incorporated into the 3-dimensional structure. The additional perforation ensures that, in addition to the secondary gas flow 8', secondary gas 8‴ is also drawn in from the outside. Depending on the design of the 3-dimensional structure and the selected gas flow rates 6, either secondary gas 8‴ can be drawn inward or secondary gas 8' can be forced outward. It can also be drawn in in some areas of the gas guide device 4 and forced in other areas of the gas flow restriction 4.

[0079] Fig. 9 shows an identical version to Fig. 8 However, in this case, the gas stream 8‴ is supplied as a forced gas stream. In an alternative mode, the gas stream 8‴ can also be extracted. Designs according to Fig. 9 are not limited to 3-dimensional structures, but can also be used for "flat" gas guiding devices according to Fig. 2 to 5 be used.

[0080] Fig. 10 represents an alternative design to the aforementioned 3-dimensional structures. In this case, the gas flow restriction 4 is a flat structure with indentations (dents) at regular intervals. The indentations can be triangular, as shown here, but can also be of any size and shape. The surface imprinted by the indentations leads to mixing or swirling of the secondary air. Alternatively, the indentations can also have an opening to enable secondary gas flow exchange.

[0081] Fig. 11 represents a sectional view from above (top view) of the edge area of Fig. 10In this case, the indentations have an opening that allows for secondary gas flow exchange. The filament curtain 5 is flowed through by the gas flow 6. In the edge zone, additional "secondary gas" 8' is sucked in by the gas flow 6, which is swirled due to the three-dimensionally structured surface of the gas flow restriction 4. Due to the suction effect of the secondary gas 8' sucked in in the edge region, additional "secondary gas" 8‴ is introduced from the outside through the gas flow restriction 4 into the system. Examples: Example 1 (comparative example): Simple device

[0082] An NMMO spinning dope consisting of 12.8% cellulose type MoDo Crown Dissolving-DP 510-550, 76% NMMO, and 11% water was fed at a temperature of 91°C and stabilized with propyl gallate into a rectangular spinneret with a bore length L of approximately 250 mm. The spinneret's extrusion orifices were arranged in staggered rows along the long side of the orifice (zigzag arrangement). The spinneret had a total of 10,384 orifices.

[0083] The spinneret was inserted into a housing that was heated to a temperature of approximately 95°C during the test. The space between the solidification bath surface and the spinneret exit surface was formed by a gas gap approximately 25 mm high. The resulting filament curtain passed through the gas gap under a gas flow feed essentially along the drilled width of the spinneret. The gas flow was generated by several multi-channel compressed air nozzles arranged side by side in a row. The diameter of each compressed air nozzle was approximately 0.8 mm. The air flow was regulated such that an exhaust temperature of between 50 and 60°C was established after flowing through the rows of filaments. A gas extraction device was not used in this test setup. A lateral gas flow restriction was also not installed.

[0084] The coagulation of the individual filaments to form cellulosic molded bodies took place in a coagulation bath in which a collecting bath was arranged below the extrusion openings, spaced apart by the gas gap.

[0085] The assessment of spinning stability resulted in a value of "2 to 3", with 1 being very good and 5 being poor, i.e. not operable.

[0086] Recurring malfunctions occurred in the gas gap, particularly in the edge zones of the filament curtain. Although these malfunctions could be resolved by manual intervention, they recurred after a short time. These malfunctions manifested themselves in the occurrence of multiple filament stickings in the gas gap, which also caused a disruption of the gas flow, which in turn further deteriorated the spinning stability. These malfunctions could only be resolved by manual intervention, and the same malfunction recurred after a short time.

[0087] Observations of the coagulation bath surface also revealed significant bath turbulence, causing uncontrolled movement of the filament curtain. The gas flow agitated the coagulation bath, particularly in the peripheral zones. The described turbulence in the coagulation bath was at least partially responsible for the clogging in the gas gap. Example 2 (comparative example): Device with gas extraction

[0088] The arrangement in this test was basically the same as in Example 1, however, a gas extraction device was additionally provided, which was mounted on the gas downstream side of the gas gap as a suction bar, as in Fig.1The suction gas flow was generated by a speed-controlled suction fan. The gas flow was regulated in such a way that no elevated gas flow temperature was measured on the side of the gas extraction device facing away from the filament curtain. This measure ensured that the entire gas flow was captured by the gas extraction device.

[0089] The spinning stability assessment resulted in a value of "2 to 3," with the frequency of spinning defects slightly reduced compared to Example 1, but trouble-free operation could not be achieved. The use of gas extraction resulted in additional turbulence in the solidification bath. Example 3: Device with gas flow limitation in the gas treatment area

[0090] The setup for this experiment was basically the same as Example 2, except that a gas flow restriction was also provided, which was installed according to the invention at the side edges of the filament curtain in the gas gap. The "short" gas flow restriction extended essentially only below the extrusion nozzles and was not perforated. The gas flow restriction extended vertically across the entire gas gap and also dipped into the coagulation bath. The gas extraction was set up as described in Example 2.

[0091] The spinning stability assessment resulted in an improved score of "2." The frequency of spinning defects decreased noticeably. Turbulence was still evident in the coagulation bath, caused partly by the gas flow supply at the edges of the filament curtain and partly by the gas flow discharge in the gas extraction area. Example 3': extended gas flow restriction

[0092] The setup for this experiment was basically the same as in Example 3. In addition, the lateral gas flow restriction was modified in this experiment so that it extended not only below the extrusion openings but also laterally below the extraction device. The non-perforated gas flow restriction extended vertically across the entire gas gap and was also immersed in the coagulation bath. The gas extraction was set up as described in Example 2.

[0093] The assessment of spinning stability resulted in a further improved score of "1 to 2." The frequency of spinning defects decreased again, although minor disturbances still occurred. Turbulence in the coagulation bath was reduced compared to the preliminary tests, but not eliminated. Example 4: Gas flow limitation with perforation

[0094] Compared to Example 3', this example additionally incorporated vertical slots into the lateral gas flow barrier. The slots were located below the extrusion openings. No slots were provided in the area below the exhaust device. The perforation ratio (ratio of open area to total area) in this arrangement was 30%.

[0095] This measure made it possible to raise the spinning behavior to a stable level, as no significant turbulence was detectable either in the gas gap or on the coagulation bath surface. The filament curtain was essentially smooth, stable, and free of clumping. Example 4': Gas flow restriction with round holes

[0096] Compared to Example 4, in this example, holes were drilled instead of vertical slots, as in Fig. 5As shown, the holes were inserted into the lateral gas flow restriction. The holes were located below the extrusion openings. No holes were provided in the area below the exhaust device. The perforation rate (ratio of open area to total area) in this arrangement was 7%.

[0097] Compared to Example 4, this arrangement resulted in a reduction in spinning stability which was rated "1 to 2". Table 1: Summary of Examples 1-4 Example 1 2 3 3' 4 4' Rectangular nozzle Rectangular nozzle Rectangular nozzle Rectangular nozzle Rectangular nozzle Rectangular nozzle Gas flow limitation without gas flow restriction without gas flow restriction with "short" gas flow limitation with "long" gas flow restriction with "long" gas flow restriction with "long" gas flow restriction Gas flow limitation - horizontal position no no 4' below extrusion device 4' + 4" below extrusion and suction device 4' + 4" below extrusion and suction device 4' + 4" below extrusion and suction device Gas flow limitation - vertical position no no immersed in coagulation bath immersed in coagulation bath immersed in coagulation bath immersed in coagulation bath perforation - - no no vertical slots Vertical drilling Degree of perforation - - - - 30% 7% without extraction with extraction with extraction with extraction with extraction with extraction Fiber titer [dtex] 1,33 1,36 1,38 1,32 1,35 1,31 Spinning solution throughput per capillary [g / min] 0,038 0,039 0,040 0,043 0,049 0, 047 Gas gap (4) [mm] 25 25 25 25 25 25 Overall spinning stability (1... good, 5... bad) 2 to 3 2 to 3 2 to 3 2 1 to 2 2 Disturbance in the gas gap 2 1 to 2 1 to 2 2 0 to 1 2 0...none 1...very rare 2...recurring 3...Irreparable Coagulation bath turbulence (visual assessment) 2 to 3 2 to 3 2 to 3 2 1 2 0... none 1... slight - not disturbing 2...medium - cause filament movement 3...heavy - cause sticking of the filaments in the gas gap

Claims

1. A device which is suitable for the production of filament materials by extrusion of a fluid material and solidification of the fluid material, with an extrusion head (1) having a plurality of extrusion openings, a collecting bath (2) for receiving extruded fluid filaments (5) from the extrusion openings, a gas gap (A) between the extrusion openings and the collecting bath, whereupon a gas treatment zone (4') is formed for extruded fluid material, and a gas flow device (3, 6) for producing a flow of gas in the gas gap, characterized in that at least one gas flow baffle (4) is provided in the lateral direction of the gas treatment zone and in the direction of the gas flow.

2. The device as claimed in claim 1, characterized in that the gas flow baffle extends over the entire length (B) of the gas treatment zone for all of the extrusion openings arranged in the longitudinal direction.

3. The device as claimed in claim 1 or claim 2, characterized in that the gas flow baffle extends over a zone (L, 4") in the gas flow direction downstream of the gas treatment zone, wherein the length of this downstream zone in the gas flow direction is at least half the length (B) of the gas treatment zone for all of the extrusion openings arranged in the longitudinal direction.

4. The device as claimed in one of claims 1 to 3, characterized in that the gas flow baffle extends over a zone (K) against the gas flow direction upstream of the gas treatment zone, wherein the length of this upstream zone against the gas flow direction is at least half the length (B) of the gas treatment zone for all of the extrusion openings disposed in the longitudinal direction.

5. The device as claimed in one of claims 1 to 4, characterized in that the gas flow device contains a fan and / or a suction device (3), preferably wherein the suction device has a drain which is orientated at an angle (X) of 0° to 45° to the horizontal, and / or preferably wherein the suction device is arranged above the gas gap so that the gas treatment zone is horizontally accessible.

6. The device as claimed in one of claims 1 to 5, characterized in that the height of the gas flow baffle in the gas treatment zone in the extrusion direction is at least 70% of the height of the gas gap.

7. The device as claimed in one of claims 1 to 6, characterized in that gas flow baffles are connected to both sides of the gas treatment zone at the lateral direction of the gas flow device, in particular connected in a U-shape.

8. The device as claimed in one of claims 1 to 7, characterized in that the gas flow baffle has a grooved, corrugated or ribbed surface, preferably a riblet surface and / or perforations in the region of the gas treatment zone, wherein preferably, at least 25% of the surface of the gas flow barrier is closed in the zone of the gas treatment zone; and / or wherein preferably, the perforations are holes or striations, particularly preferably striations in the extrusion direction, particularly preferably wherein at least one striation is provided every 4 cm of the length of the gas flow baffle in the zone of the gas treatment zone in the gas flow direction.

9. The device as claimed in one of claims 1 to 8, characterized in that the gas flow baffle is at a distance (J) from the gas treatment zone of at least twice the separation (C) of the extrusion openings with respect to each other in the direction transversely to the gas flow direction and / or in that the gas flow baffle is at a maximum distance (J) from the gas treatment zone of 20 times the separation (C) of the extrusion openings with respect to each other in the direction transversely to the gas flow direction.

10. The device as claimed in one of claims 1 to 9, characterized in that the extrusion openings are arranged in a rectangular shape, wherein the narrow side of the rectangular shape faces the gas flow baffle.

11. A process for the production of solid filament materials from a fluid material by extruding the fluid material through a plurality of extrusion openings, whereupon fluid filaments (5) are formed, passing the fluid filaments through a gas gap (A) and solidifying the filaments in a coagulation liquid in a collecting bath (2), wherein a gas flow (6, 7) passes through the gas gap (8'), characterized in that the gas flow is controlled with at least one gas flow baffle (4), wherein the gas flow baffle laterally delimits a gas treatment zone (4') in which the filaments are treated with the gas flow.

12. The process as claimed in claim 11, with a device as claimed in one of claims 1 to 10.

13. The process as claimed in claim 11 or claim 12, characterized in that the fluid material contains cellulose, preferably a solution or melt of cellulose, a solvent for cellulose, preferably an amine oxide, and water.

14. The process as claimed in one of claims 11 to 13, characterized in that the gas flow is obtained by blowing in (6) and sucking off (7), wherein preferably, a sucked flow of gas is greater than a blown-in flow of gas, particularly preferably wherein the ratio of sucked gas flow to blown-in gas flow is greater than 1.2 : 1.

15. The process as claimed in one of claims 11 to 14, characterized in that by selecting the flow of gas and the gas flow baffle, turbulences of the gas flow at the lateral edge of the gas treatment zone are prevented.

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