Apparatus and method for producing cellulose fibres

Abstract

The invention relates to an apparatus for producing cellulose fibres in a wet-spinning process and to a method for producing cellulose fibres. To provide a method for producing cellulose that can be used on a large industrial scale and an associated apparatus, an apparatus which comprises the following is envisaged: - a kneading and evaporating apparatus, which is designed for receiving a spinning slurry based on cellulose and an ionic liquid and for turning the spinning slurry into a spinning solution, - a spinning unit for producing continuous preliminary cellulose fibres, - a coagulation bath for precipitating continuous cellulose fibres from the preliminary cellulose fibres, - a stretching unit for applying a preliminary tension to the cellulose fibres coming from the coagulation bath, - a stretching bath for stretching and pre-washing the cellulose fibres coming from the stretching unit, - a washing unit with at least one washing bath for washing the cellulose fibres after stretching, - at least one drying unit for drying the washed cellulose fibres, and - a winding unit for winding up the dried cellulose fibres.

Description

[0001] Technikum Laubholz GmbH

[0002] Description

[0003] Apparatus and method for producing cellulose fibers

[0004] The invention relates to an apparatus for producing cellulose fibers according to the preamble of claim 1 and a method for producing cellulose fibers according to the preamble of claim 18.

[0005] Cellulose is one of the most important raw materials for the industrial production of fibers. Various processes are known for producing cellulose fibers, such as the cupro process, the carbamate process, the viscose process, and the lyocell process. The viscose process and the lyocell process are used on a large industrial scale.

[0006] The viscose process produces a fiber that is suitable for both textile and technical applications. However, the disadvantages are the use of highly toxic chemicals and the high water consumption required. Fibers produced using the lyocell process tend to fibrillate and are therefore primarily used as staple fibers. Furthermore, the lyocell process involves side reactions that produce explosive chemicals, which poses a corresponding risk in the manufacturing process.

[0007] The invention is therefore based on the object of providing a large-scale industrially applicable process for producing cellulose and an associated device.

[0008] This object is achieved by a method according to claim 1 and a device according to claim 18. Advantageous developments of the invention are specified in the dependent claims. All described features, individually or in any combination, are fundamentally the subject of the invention, regardless of their summary in the claims or their dependence. According to the invention, the device for producing cellulose fibers using a wet spinning process comprises the following: a kneading and evaporation device for receiving a spinning slurry based on cellulose and an ionic liquid and for processing the spinning slurry into a spinning solution;

[0009] - a spinning unit for producing endless pre-cellulose fibers,

[0010] - a coagulation bath for precipitating cellulose fibres from the pre-cellulose fibres,

[0011] - a drafting device for applying a pre-tension to the cellulose fibres coming from the coagulation bath,

[0012] - a drawing bath for drawing and pre-washing the cellulose fibres coming from the drawing system,

[0013] - a washing unit with at least one washing bath for washing the cellulose fibres after drawing,

[0014] - at least one drying unit for drying the washed cellulose fibres,

[0015] - a winding unit for winding the dried cellulose fibers.

[0016] The inventive device is designed to carry out a wet spinning process, in particular an air-gap process for producing cellulose fibers. A key aspect for the successful implementation of such a process is the spinning dope. To produce the spinning dope, the device has a kneading and evaporation device. The actual spinning dope, the dope, is produced in this device. Crucial for the production of the dope is that the device can both knead and evaporate, as this is the only way to ensure that a suitable bubble- and water-free spinning dope is provided. The spinning unit has a spinneret. The finished spinning dope is taken up by the spinning unit and pressed out of the spinning unit through the spinneret. To produce cellulose fibers, the spinneret has numerous micro-holes so that the spinning dope emerges from the holes as continuous threads.These threads, referred to here as pre-cellulose fibers, are immersed in a coagulation medium in the coagulation bath. In the coagulation bath, a portion of the ionic liquid is washed out of the pre-cellulose fibers, causing the threads to solidify (precipitate) into cellulose fibers. The solidified cellulose fibers are applied to the drafting system and drawn from the coagulation bath. The drafting system can be controlled so that the tensile force of the drafting system not only pre-tensions the cellulose fibers, but also causes them to undergo initial drawing in the area of ​​the air gap between the spinneret surface and the coagulation medium in the coagulation bath, and possibly in the coagulation medium itself. Water is primarily used as the coagulation medium.

[0017] Coming from the drawing system, the cellulose threads are guided through a drawing bath. The drawing bath is preferably linear, so that the cellulose threads are not deflected within the drawing bath. In the drawing bath, the cellulose fibers are guided through a drawing bath liquid (e.g., water) and / or actively sprayed with a drawing bath liquid, which initially (partially) washes out the solvent still present in the cellulose fibers after the coagulation bath. In addition, tensile stress can be applied to the cellulose fibers in the drawing bath area, resulting in further longitudinal stretching of the cellulose fibers.

[0018] The movement of the cellulose fibers through the draw bath and the degree of stretching are typically controlled by at least one controllable godet. The godet can either be part of the draw bath or be part of the unit following the draw bath, e.g., a washing unit.

[0019] The washing unit is designed to (further) wash out additional solvent, in this case ionic liquid. For this purpose, the washing unit preferably has a washing bath through which the cellulose fibers are passed within the washing unit. In addition to or as an alternative to the washing bath, washing nozzles can also be arranged so that the cellulose fibers are sprayed with a jet of washing liquid (e.g. water) as they pass through the washing unit. For this purpose, the washing unit preferably has at least one washing duo. The washing duo preferably comprises at least two godets for transporting the cellulose fibers, which are preferably arranged vertically one below the other, and a washing bath for passing the cellulose fibers through. The lower godet is in contact with the washing bath in particular in sections, so that the cellulose fibers are guided through the washing bath as the lower godet rotates.In addition, the washing duo can include the aforementioned washing nozzles in addition to or as an alternative to the washing bath. Washing nozzles are arranged in particular so that the washing liquid is sprayed onto the cellulose fibers in the area of ​​the contact surfaces of the cellulose fibers using a godet, preferably the upper godet in the vertical direction, thus achieving an optimal washing effect.

[0020] The washing bath or washing unit is followed by a drying unit, which can be designed as a separate unit or as part of the washing unit. The washed and wet cellulose fibers are fed into the drying unit. The drying unit is designed to dry the wet cellulose fibers. The dried cellulose fibers are then wound up by the winding unit.

[0021] The device is preferably designed in a linear fashion, so that the individual units are arranged one behind the other in the working direction (running direction of the cellulose / cellulose fibers). A modular structure is also advantageous, so that the individual units (kneading and evaporation device, spinning unit, coagulation bath, drafting system, drafting bath, washing unit, drying unit, winding unit) are particularly easy to replace, and additional units (modules) can be added. The device is designed for continuous operation.

[0022] In principle, various ionic liquids can be used with the device and the process described below. However, both the device and the process are optimized for the use of i-ethyl 3-methylimidazolium octanoate (EMIM octanoate).

[0023] According to a further development of the invention, at least one treatment unit is arranged to receive the processed spinning solution coming from the kneading and evaporation device, wherein the treatment unit is designed to keep the spinning solution at a predetermined temperature and / or to heat it to this temperature and to stir the spinning solution and to create a vacuum.

[0024] The treatment unit thus enables additional processing of the spinning solution. Firstly, by precisely adjusting the temperature of the spinning solution, and secondly, by further optimising degassing of the spinning solution. The treatment unit is designed to create a negative pressure, in particular a vacuum, within its interior, so that the spinning solution does not come into contact with air / gas. It is also preferably designed to be pressurised with a gas, in particular nitrogen, for example to prevent the spinning solution from reacting with, for example, oxygen when it is transferred to the subsequent unit, e.g. the spinning unit. To transfer the spinning solution, the treatment unit is preferably also designed to create an overpressure, whereby the spinning solution is forced out of the treatment unit.The preferred arrangement of two treatment units significantly simplifies continuous operation of the spinning unit.

[0025] In order to further improve the degassing of the spinning solution, a further development of the invention provides that a device for degassing the spinning solution, in particular a correspondingly designed extruder, is arranged upstream of the spinning unit and thus downstream of the kneading and evaporation device or, if the treatment unit is arranged downstream of the treatment unit.

[0026] Spinning slurry is understood to be a mixture of substances comprising cellulose and ionic liquid, which can be further processed into spinning dope. The spinning slurry can be prepared separately. However, spinning slurry production is preferably integrated into the device (e.g., in a modular manner). For this purpose, according to a further development of the invention, a mixing unit for mixing cellulose particles with the ionic liquid is arranged upstream of the kneading and evaporation device. Optionally, the spinning slurry production can also include a comminution unit arranged upstream of the mixing unit for comminuting (grinding, tearing) dried cellulose. The spinning dope is understood to be a spinning slurry that has been processed to such an extent that it is spinnable. This includes, in particular, that the cellulose is at least largely dissolved, preferably completely dissolved, in the ionic liquid.

[0027] In order to improve the dissolving behavior of the cellulose in the ionic liquid, according to a development of the invention, at least one depolymerization unit is arranged to reduce the degree of polymerization of the cellulose. The depolymerization unit causes the cellulose chains to be broken down, thereby making it easier to dissolve the cellulose in the ionic liquid. Particularly preferably, a front depolymerization unit is arranged upstream of the mixing unit, which is designed to reduce the degree of polymerization of the cellulose, in particular in the dry state. Alternatively or additionally, at least one rear depolymerization unit is arranged such that it reduces the degree of polymerization of the cellulose in the kneading and evaporation device and / or upstream of the kneading and evaporation device. The depolymerization unit can, for example,It can be designed to reduce the degree of polymerization by means of acid, alkaline hydrolysis, or biological agents such as enzymes, but is preferably designed as a radiation unit for exposing the cellulose to electron beams and / or as an ozone unit for exposing the cellulose to ozone. The front and rear depolymerization units can also be of different types.

[0028] According to a further development of the invention, the kneading and evaporation device is designed to reduce the degree of polymerization of the cellulose. For this purpose, the kneading and evaporation device is designed to heat the substance contained therein, in this case the spinning slurry or the spinning solution formed therefrom. Furthermore, the kneading and evaporation device can preferably be operated without creating a vacuum / negative pressure inside. Since the reduction in the degree of polymerization of cellulose occurs particularly under the influence of oxygen in combination with heat, the kneading and evaporation device preferably has a gas supply in its working chamber. The gas supply can be designed as a simple supply line, but is preferably designed as a controllable unit with which the gas volume / time unit can be controllably introduced into the interior of the kneading and evaporation device.The gas supply is designed in particular to transport air, oxygen-containing gases or even pure oxygen into the kneading and evaporation device.

[0029] As already stated, the washing unit has at least one washing bath. To increase washing performance, however, at least two, particularly preferably three, washing baths are arranged. The washing baths can be arranged directly one after the other, for example within a washing unit or a washing duo. Preferably, however, the washing unit comprises several separate units (e.g. washing duos) arranged one behind the other in the working direction of the device and each comprising at least one washing bath and / or washing nozzles. The units, in particular several washing duos, are arranged one behind the other in the working direction of the device so that the cellulose fibers run from washing duo to washing duo.

[0030] The cellulose fibers are dried and wound up after washing. However, treatment, e.g. finishing of the cellulose fibers, is often necessary. For this purpose, according to a development of the invention, at least one drawing and / or finishing unit is arranged after the washing unit. This unit can be designed as a pure drawing unit, as a pure finishing unit, or as a unit that can both draw and finish. For finishing, the unit has at least one finishing agent application device, such as a corresponding spraying or coating unit and / or a finishing agent bath through which the cellulose fibers can be passed. For example, to secure the finishing agent to the cellulose fibers, the drawing and finishing unit can comprise at least one pre-dryer that pre-dries the cellulose fibers treated with a finishing agent.In addition to this first stretching and preparation unit, according to a further development of the invention, at least one second stretching and preparation unit is arranged downstream of the first stretching and preparation unit in the working direction. The second stretching and preparation unit preferably also has a pre-dryer. Advantageously, it is constructed identically to the first stretching and preparation unit. Of course, further stretching and preparation units can be arranged in the working direction. The stretching and preparation unit, as well as the pre-dryers, are preferably designed as a godet duo (at least two transport godets arranged in the vertical direction). The pre-dryers are also preferably designed as drying cabinets with heating godets and suction devices for extracting the moisture.

[0031] According to a further development of the invention, the drying unit is designed as a horizontal drying channel, which is particularly designed to dry the cellulose fibers from an initial moisture content of at least 100 wt.%, preferably at least 200 wt.%, to a residual moisture content of a maximum of 20 wt.%, preferably a maximum of 10 wt.% or less. The drying channel preferably has an air flow control and controlled air supply to achieve a uniform temperature profile in the channel.

[0032] From an environmental and cost perspective, a key aspect of the industrial use of ionic liquids is the processing and recovery of the ionic liquid from the manufacturing process. According to a further development of the invention, a solvent recycling unit is provided for processing the ionic liquid, which is designed to receive a coagulation medium from the coagulation bath, a draw bath liquid (e.g., water) from the draw bath, and / or the washing liquid from the washing unit. In order to create a circuit that is as closed as possible, a direct line for transferring the coagulation medium, the draw bath liquid, and / or the washing liquid to the solvent recycling unit is particularly preferably arranged between the solvent recycling unit and the coagulation bath, the draw bath, and / or the washing bath.

[0033] In its simplest form, the solvent recycling unit can be designed as a collecting container for the contaminated solvent, especially one mixed with water. The collecting container can be configured so that it can be transported to a treatment plant for processing the collected solvent. However, the solvent recycling unit particularly preferably also comprises a device for direct processing within the device, in particular a thin-film evaporator, with which the ionic liquid can be purified and, if necessary, directly reintroduced into the process cycle during mash production.

[0034] According to a further development of the invention, particularly economical operation is possible through the arrangement of a recycling cascade, by means of which washing liquid can be transferred from the washing unit to the drawing bath, drawing bath liquid from the drawing bath to the coagulation bath, and coagulation medium from the coagulation bath to the solvent recycling unit. The ionic liquid content decreases from the coagulation medium in the working direction of the device via the drawing bath liquid and the washing liquid. In addition, the respective functions tolerate different proportions of ionic liquid in their respective functional liquid (washing liquid, drawing bath liquid, coagulation medium). For example, the washing liquid should contain only a very low proportion of ionic liquid to ensure complete washing of the ionic liquid from the cellulose fibers.The extension bath liquid, on the other hand, can tolerate significantly more ionic liquid, and the coagulation medium can consist of up to a maximum of 70% to a maximum of 50% ionic liquid before the cellulose no longer precipitates. The recycling cascade makes it possible to use the wash liquid that can no longer be used as a wash liquid in the extension bath until the ionic liquid content has increased so much that it can no longer be used as an extension bath liquid. It is then transferred to the coagulation medium and reused there until its use as a coagulation medium is no longer possible. Only then is it transferred to the solvent recycling unit. The recycling cascade makes it possible for only the coagulation medium to be technically processed, while fresh liquid only needs to be added to the wash unit.An advantage of the process described below is that both the coagulation medium and the draw bath liquid, as well as the washing liquid, primarily comprise water. When multiple washing baths or washing duos with a washing bath are arranged, the recycling cascade is also continued within the washing unit, so that the washing baths are connected in the working direction in such a way that the washing liquid can be transferred from the last washing bath to the previous washing bath, etc., i.e., against the working direction (the direction of travel of the cellulose fibers in the device).

[0035] Furthermore, the object underlying the invention is achieved by a method for producing cellulose fibers in a wet spinning process with the steps:

[0036] Preparation of a spinning mash based on cellulose and ionic liquid in a kneading and evaporation device by applying a negative pressure to the spinning mash in the kneading and evaporation device for degassing the spinning mash, evaporating water present in the spinning mash and simultaneously kneading the spinning mash under the influence of high shear forces to form a spinning solution,

[0037] Transferring the spinning solution into a spinning unit, producing continuous pre-cellulose fibres by means of a spinneret and introducing the cellulose fibres into a coagulation medium to precipitate the cellulose fibres,

[0038] Removing the cellulose fibres from the coagulation medium and passing the cellulose fibres through a drawing device which applies a pre-tension to the cellulose fibres,

[0039] Transferring the cellulose fibres into a stretching bath and stretching the cellulose fibres in the longitudinal direction,

[0040] Washing the cellulose fibres in a washing unit, in particular to remove ionic liquid,

[0041] Drying the cellulose fibers to a residual moisture content of less than 20 wt.%, winding up the dried cellulose fibers.

[0042] The inventive method and the device described above enable the industrial production of regenerated cellulose fibers as continuous fibers using ionic liquids, particularly in a continuous process. Renewable raw materials, especially wood, but also recycled materials such as old textiles or the like, can be used as pulp sources. The inventive method is particularly advantageously suited for the use of hardwood cellulose. Due to the use of ionic liquids, in particular the aforementioned EMIM octanoate, and the potential for complete recycling of the ionic liquid, no environmental impact occurs. The method is also very safe, since no toxic or explosive products or byproducts are used or produced during the process or during the recovery of the ionic liquid.The cellulose fibers produced using this process also exhibit a very low tendency to fibrillation, are high-strength, and fully recyclable. They have a wide range of applications, including in the textile, technical, and hygiene sectors, for example, as staple fibers.

[0043] To improve the spinnability of the spinning solution and the cellulose fibers to be produced from the spinning solution, a further development of the invention provides for transferring the spinning solution to a treatment unit in which the spinning solution is kept at a predetermined temperature while simultaneously stirring and / or heated to a predetermined temperature. This particularly preferably takes place under negative pressure, preferably a vacuum, with simultaneous stirring in the treatment unit, thereby achieving further degassing. To transfer the spinning solution from the treatment unit to the spinning unit, for example, a nitrogen atmosphere, preferably at overpressure, is set in the area of ​​the spinning solution in order to press the spinning solution out of the treatment unit.

[0044] To produce the spinning slurry, particularly particulate cellulose is mixed with an ionic liquid at a temperature at which the ionic liquid is in the liquid state. To support or improve the dissolution of the cellulose in the ionic liquid, a further development of the invention provides for reducing the degree of polymerization of the cellulose. The reduction can be carried out on the particulate (dry) cellulose itself. Alternatively, it is possible to carry out the reduction in the spinning slurry, for example, in the mixing unit and thus before transfer to the kneading and evaporation device and / or in the kneading and stirring device for producing the spinning solution.

[0045] A reduction in the degree of polymerization before producing the spinning slurry is particularly preferably carried out by exposure to ozone and / or electron radiation.

[0046] According to a further development of the invention, the degree of polymerization is reduced under the influence of heat and oxygen. This can take place, for example, within the kneading and evaporation device. For this purpose, the spinning slurry and / or spinning solution present in the kneading and evaporation device is brought into contact with oxygen, for example in pure form, in the form of air or another oxygen-containing gas. For this purpose, the spinning slurry and / or spinning solution in contact with the oxygen is heated in the kneading and evaporation device, preferably while kneading at the same time. The oxygen and heat ensure a reduction in the degree of polymerization of the cellulose. After the degree of polymerization has been reduced, the spinning slurry and / or spinning solution can be treated again in the kneading and evaporation device, in particular under negative pressure / vacuum, in order to, if necessary,To remove air bubbles created during the reduction of the degree of polymerization in the spinning slurry and / or spinning solution (degassing). Alternatively or additionally, the repeated / supplementary degassing can also be carried out in the treatment unit and / or the extruder.

[0047] A decisive factor for the quality of the resulting cellulose fibers is the spinning solution used, which must be bubble-free, i.e. degassed as much as possible. An important factor here is the inventive use of the kneading and evaporation device, which both kneads and evaporates at the same time. To further improve the quality of the spinning solution, it is also possible to further degas the spinning solution coming from the kneading and evaporation device or from the treatment unit before it is transferred to the spinning unit. This can be done, for example, using a specially designed extruder through which the spinning solution coming from the kneading and evaporation device or from the treatment unit is passed. An extruder also has the advantage that it can be used to transport the spinning solution to the spinning unit. The extruder can also be used to adjust the spinning solution to a predetermined temperature.

[0048] A further improvement in the cellulose fibers, in particular their tensile strength in the longitudinal direction, is achieved by stretching the cellulose fibers. Stretching aligns the cellulose molecules in the cellulose fibers linearly, which explains the increased tensile strength. The cellulose fibers can be stretched in several sections of the device or during different process steps. An initial stretching can take place in the region of the air gap between the spinnerets and the coagulation medium, which is created in particular by the stretching device. A preferred stretching step is also carried out in the stretching bath. The cellulose fibers are particularly preferably stretched after washing. The stretching after washing can be supplemented by subsequent pre-drying. Final stretching can particularly preferably take place when the cellulose fibers are dried to a residual moisture content of no more than 20% by weight.-% or less and before wrapping.

[0049] Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the claimed method, so that a block or component of one of the described devices can also be understood as a corresponding method step or as a feature of a method step. Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device.

[0050] The invention will be explained in more detail below using an exemplary embodiment. It shows:

[0051] Fig. 1 shows schematically a structural design of the inventive device and the sequence of the inventive method;

[0052] Example 1: Description of a reduction in the degree of polymerization.

[0053] Figure 1 schematically shows the inventive device and the individual process steps of the inventive method. Visible is a kneading and evaporation device 4 which is designed to hold a spinning slurry (not shown here). Two treatment units 6.1, 6.2 are connected to the kneading and evaporation device 4 in the working direction. A spinning solution (not shown here) coming from the kneading and evaporation device 4 can be transferred directly to the two treatment units 6.1, 6.2 via lines (not shown here). Alternatively, it is possible to first introduce the spinning solution into a rear depolymerization unit 5, in which the degree of polymerization of the cellulose (not shown here) is reduced, and then to transfer it from the rear depolymerization unit 5 to the two treatment units 6.1, 6.2.The rear depolymerization unit 5 can also be designed integrally with the treatment unit(s) 6.1, 6.2, so that the reduction of the degree of polymerization is carried out directly in the treatment units 6.1, 6.2. Not shown here, an alternative or supplementary reduction of the degree of polymerization of the cellulose to the rear depolymerization unit 5 can be carried out in the kneading and evaporation device 4, for which the latter can also be designed accordingly or equipped with the rear depolymerization unit 5.

[0054] From the treatment units 6.1, 6.2, the spinning solution is transferred via lines to the spinning unit 8. Alternatively, this can also be done via an additional extruder 7. In the spinning unit 8, the spinning solution passes through a spinneret (not shown here), so that thin pre-cellulose fibers (not shown here) emerge from the spinneret. The pre-cellulose fibers are transferred directly into a coagulation medium (not shown here), in this case water, located in the coagulation bath 9. The cellulose precipitates in the coagulation medium, forming the cellulose fibers (not shown here). The cellulose fibers are transferred to a drafting system 10 via corresponding deflection units (not shown here).

[0055] The drafting system 10 applies pre-tension to the cellulose fibers and optionally ensures an initial drawing in the area of ​​an air gap between the spinneret and the coagulation medium. From the draw point 10, the cellulose fibers are transferred directly into a draw bath 11. The draw bath 11 is filled with a draw bath liquid (not shown here), so that the drawing of the cellulose fibers in the draw bath 11 takes place in the draw bath liquid (here, water). From the draw bath 11, the cellulose fibers are passed directly to a washing unit 12. The washing unit 12 comprises three washing duos 12.1, 12.2, 12.3, each with its own wash bath (not shown here) and wash nozzles (not shown here). In each wash duo 12.1, 12.2, 12.3, the cellulose fibers pass through the wash bath to wash out any remaining ionic liquid.Additionally, they can be washed out using a jet of washing liquid (not shown here) coming from the washing nozzles. From the washing unit 12, the cellulose fibers are fed directly to a drying unit 15 and then to a winding unit 17 for winding the cellulose fibers.

[0056] Depending on the intended use of the cellulose fibers, different treatment steps can be carried out alternatively with the cellulose fibers. For this purpose, a first drawing and preparation unit 13.1 with a first pre-dryer 14.1, followed by a second drawing and preparation unit 13.2 and a second pre-dryer 14.2, is arranged downstream of the washing unit 12. The drying unit 15 is arranged downstream of the second drawing and preparation unit 13.2 with a second pre-dryer 14.2. Following the drying unit 15 and upstream of the winding unit 17, another alternative drawing unit 16 is arranged, which enables the drawing of the cellulose fibers in the drying unit 15. In Figure 1, unmarked arrows are shown between the individual units (modules), indicating the possible paths of the cellulose fibers through the device.The running direction corresponds to the working direction of the device.

[0057] Also located upstream of the kneading and evaporation device 4 are a comminution unit 1 for comminuting (grinding, tearing) dried cellulose and a mixing unit 3 for mixing the cellulose transferred from the comminution unit 1 with the ionic liquid to form a spinning slurry (not shown here). The cellulose comminuted in the comminution unit 1 can be transferred directly to the mixing unit 3 via lines (not shown here).

[0058] Alternatively, the degree of polymerization of the shredded cellulose can be reduced before transfer to the mixing unit 4. A depolymerization unit 2 can be arranged for this purpose. Appropriate lines (not shown here) are arranged to transfer the shredded cellulose from the shredding unit 1 to a depolymerization unit 2 and / or to the mixing unit 3, or from the depolymerization unit 2 to the mixing unit 3.

[0059] Figure 1 also shows a solvent recycling unit 18 with numerous lines Ri to R11. It can be seen that a direct transfer of the coagulation medium, the extension bath liquid, and the washing liquid into the solvent recycling unit 18 is possible via various lines Ri to R6 (shown as arrows).

[0060] Alternatively or additionally, a recycling cascade 19 is also arranged. For this purpose, liquid lines R7, R8 are arranged within the washing unit 12 so that the washing liquid from the last washing duo 12.3 can be directed to the second washing duo 12.2 and the washing liquid from the second washing duo 12.2 can be directed to the first washing duo 12.1. Furthermore, the recycling cascade 19 comprises liquid lines R9, R10, R5, R6 for transferring the washing liquid from the first washing duo 12.1 to the stretching bath 11, the stretching bath liquid from the stretching bath 11 to the coagulation medium in the coagulation bath 9, and the coagulation medium from the coagulation bath 9 to the solvent recycling unit 18.

[0061] From the solvent recycling unit 18, a line R11 is arranged to the mixing tank 3, via which the treated ionic liquid can be fed into the mixing tank 3.

[0062] The path of the cellulose, the pre-cellulose fibers, and the cellulose fibers is shown in Figure 1 by unmarked arrows.

[0063] Example 1

[0064] To prepare the spinning solution, the spinning slurry is introduced into the kneading and evaporation device. To remove moisture from the cellulose and ionic liquid and to degas, the spinning slurry is kneaded in the kneading and evaporation device for 10 to 30 minutes at a temperature of 90°C to 120°C under reduced pressure. Subsequently, in a preferred embodiment, to reduce the degree of polymerization of the cellulose, the reduced pressure in the kneading and evaporation device is dissolved, and oxygen, for example in the form of outside air, is admitted into the kneading and evaporation device. The degree of polymerization is then reduced to a preferred degree of polymerization (DP) of 600 to 300 by kneading the spinning slurry / spinning solution for 10 to 30 minutes in the oxygen-containing atmosphere (here air atmosphere) at a temperature of preferably between 90°C and 120°C.

[0065] After reaching the specified DP, the resulting spinning solution is transferred to the storage tanks, the extruder, and / or directly to the spinning unit. Alternatively, after reducing the degree of polymerization, degassing can also be performed again in the kneading and evaporation device. For this purpose, the spinning solution can be kneaded again under reduced pressure / vacuum for 10 to 30 minutes in the kneading and evaporation device, preferably at 90°C to 120°C.

[0066] Preferably, the inlet of oxygen-containing gas / oxygen is controlled, with a predetermined volume / time unit, for example by means of a preferred controllable gas supply.

[0067] List of reference symbols

[0068] 1 shredding unit

[0069] 2 Depolymerization unit

[0070] 3 Mixing unit

[0071] 4 Kneading and evaporation device

[0072] 5 Depolymerization unit

[0073] 6.1 Treatment unit

[0074] 6.2 Treatment unit

[0075] 7 extruders

[0076] 8 spinning unit

[0077] 9 Coagulation bath

[0078] 10 Drafting system

[0079] 11 Stretching bath

[0080] 12 washing units

[0081] 12.1 Washing Duo

[0082] 12.2 Washing Duo

[0083] 12.3 Washing Duo

[0084] 13.1 Stretching and preparation unit

[0085] 13.2 Stretching and preparation unit

[0086] 14.1 Pre-dryer

[0087] 14.2 Pre-dryer

[0088] 15 drying units

[0089] 16 stretch duo

[0090] 17 Changing unit

[0091] 18 Solvent recycling unit

[0092] Ri to

[0093] R11 lines

Claims

Claims 1. Device for producing cellulose fibers in a wet spinning process, with - a kneading and evaporation device (4) for receiving a spinning slurry based on cellulose and an ionic liquid and for processing the spinning slurry into a spinning solution, - a spinning unit (8) for producing endless pre-cellulose fibres, - a coagulation bath (9) for precipitating continuous cellulose fibres from the pre-cellulose fibres, - a drafting device (10) for applying a pre-tension to the cellulose fibres coming from the coagulation bath (9), - a drawing bath (11) for drawing and pre-washing the cellulose fibres coming from the drawing device (10), - a washing unit (12) with at least one washing bath for washing the cellulose fibres after drawing, - at least one drying unit (15) for drying the washed cellulose fibres, - a winding unit (17) for winding the dried cellulose fibres.

2. Device according to claim 1, characterized in that at least one treatment unit (6.1, 6.2) is arranged to receive the processed spinning solution coming from the kneading and evaporation device (4), wherein the treatment unit (6.1, 6.2) is designed to keep the spinning solution at a predetermined temperature and / or to heat it to this temperature and to stir the spinning solution and to create a vacuum.

3. Device according to one of the preceding claims, characterized in that a device for degassing the spinning solution, in particular an extruder (7), is arranged in front of the spinning unit (8). 4- Device according to one of the preceding claims, characterized in that a mixing unit (3) for mixing cellulose particles with the ionic liquid is arranged in front of the kneading and evaporation device (4).

5. Device according to one of the preceding claims, characterized in that at least one depolymerization unit (2, 5) is arranged to reduce the degree of polymerization of the cellulose.

6. Device according to claim 5, characterized in that a front depolymerization unit (2) is arranged in front of the mixing unit (3), which is designed to reduce the degree of polymerization of the cellulose, in particular in the dry state.

7. Device according to at least one of the preceding claims 5 or 6, characterized in that at least one rear depolymerization unit (5) is arranged in the kneading and evaporation device and / or in front of the kneading and evaporation device.

8. Device according to claim 6 or 7, characterized in that the front and / or rear depolymerization unit (2, 5) comprises a radiation unit for exposing the cellulose to electron radiation and / or an ozone unit for exposing the cellulose to ozone.

9. Device according to one of the preceding claims, characterized in that the kneading and evaporation unit is designed to reduce a degree of polymerization of the cellulose.

10. Device according to one of the preceding claims, characterized in that the washing unit (12) comprises two, preferably three washing baths, which are arranged in particular directly one after the other.

11. Device according to one of the preceding claims, characterized in that at least one stretching and preparation unit (13.1, 13.2) is arranged after the washing unit (12).

12. Device according to claim 11, characterized in that at least one pre-dryer (14.1, 14.2) is arranged after the stretching and preparation unit (13.1, 13.2).

13. Device according to one of the preceding claims, characterized in that a second stretching and preparation unit (13.2) with a second pre-dryer (14.2) is arranged directly after a first stretching and preparation unit (13.1) with a first pre-dryer (14.1).

14. Device according to one of the preceding claims, characterized in that the drying unit (15) is designed as a horizontal drying channel, which is particularly designed to dry the cellulose fibers at an initial moisture content of at least 100 wt.%, preferably at least 200 wt.%, to a residual moisture content of 10 wt.% or less.

15. Device according to one of the preceding claims, characterized in that at least one solvent recycling unit (18) is arranged for processing the ionic liquid, wherein the solvent recycling unit (18) is designed to receive a coagulation medium from the coagulation bath (9), drawing bath liquid from the drawing bath (11) and / or the washing liquid from the washing unit (12).

16. Device according to claim 15, characterized in that between the solvent recycling unit (18) and the coagulation bath (9), the stretching bath (11) and / or the washing unit (12) direct lines (Ri to R6) for transferring the coagulation medium, the stretching bath liquid and / or the washing liquid into the solvent recycling unit (18) are formed.

17. Device according to one of claims 15 or 16, characterized in that a recycling cascade (19) is arranged, by means of which washing liquid can be transferred from the washing unit (12) into the stretching bath (11), stretching bath liquid from the stretching bath (11) into the coagulation bath (9) and coagulation medium from the coagulation bath (9) into the solvent recycling unit (18).

18. A process for producing cellulose fibers in a wet spinning process comprising the steps: - Preparation of a spinning mash based on cellulose and ionic liquid in a kneading and evaporation device (4) by applying a negative pressure to the spinning mash in the kneading and evaporation device (4), evaporation of water present in the spinning mash and simultaneous kneading of the spinning mash under the action of high shear forces to form a spinning solution, - transferring the spinning solution into a spinning unit (8), producing continuous pre-cellulose fibres by means of a spinneret and introducing the pre-cellulose fibres into a coagulation medium to precipitate continuous cellulose fibres, - removing the cellulose fibres from the coagulation medium and passing the cellulose fibres through a drawing device (10) which applies a pre-tension to the cellulose fibres, - transferring the cellulose fibres into a stretching bath (11) and stretching the cellulose fibres in the longitudinal direction in the stretching bath (11), - washing the cellulose fibres in a washing unit (12), in particular for removing ionic liquid, - drying the cellulose fibres to a residual moisture content of 20% by weight or less, - Winding up the dried cellulose fibers.

19. Method according to claim 18, characterized in that the spinning solution, before being introduced into a spinning unit (8), is introduced into a treatment unit (6.1, 6.2) in which the spinning solution is kept at a predetermined temperature while being stirred and / or heated to a predetermined temperature, in particular an additional degassing of the spinning solution is carried out.

20. Method according to at least one of claims 18 or 19, characterized in that the degree of polymerization of the cellulose is reduced, wherein the reduction is carried out on the dry cellulose before producing a spinning slurry, before transferring to the kneading and evaporation device (4) and / or directly in the Kneading and evaporation device (4) and thus in the spinning mash or spinning solution.

21. Process according to claim 19, characterized in that the reduction of the degree of polymerization is carried out in an oxygen-containing atmosphere and in particular additionally under the action of heat.

22. A process according to at least one of claims 20 or 22, characterized in that the reduction of the degree of polymerization of the cellulose is carried out before mixing the cellulose with the ionic liquid to form the spinning slurry by the action of ozone and / or electron radiation on a particulate cellulose.

23. Method according to at least one of claims 18 to 22, characterized in that the spinning solution is degassed before being transferred to the spinning unit (8) and in particular after the treatment in a treatment unit (6.1, 6.2), in particular by passing it through an extruder (7) with a degassing function.

24. A method according to at least one of claims 17 to 23, characterized in that the cellulose fibers are subjected to a final stretching during or after drying to a residual moisture content of at most 20% by weight, preferably up to a maximum of 10% by weight, and before winding.

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