PLANT AND METHOD FOR THE PRODUCTION OF HOLLOW FIBER MEMBRANES

Description

[0001] The invention relates to a system for the production of hollow fiber membranes. In particular, the invention relates to a system for the production of hollow fiber membranes, wherein the system comprises an improved drying unit.

[0002] In further aspects, the invention relates to methods for producing hollow fiber membranes. In particular, the invention relates to methods for producing hollow fiber membranes with improved drying of the hollow fiber membranes. BACKGROUND OF THE INVENTION

[0003] Hollow fiber membranes are widely used in filtration technology. They are particularly prevalent in medical technology, for example in dialysis, to remove harmful metabolites from the blood of patients with kidney disease. Hollow fiber membranes are also used in water treatment to purify contaminated water. For these applications, the hollow fiber membranes are integrated into so-called hollow fiber membrane filters. These filters contain numerous hollow fiber membranes arranged as a bundle within a cylindrical housing. A typical hollow fiber membrane filter for dialysis contains 10,000 hollow fiber membranes, each approximately 23 cm long. In the medical field, particularly in dialysis, these hollow fiber membrane filters are provided as single-use items for hygienic reasons.This results in an enormous need for hollow fiber membrane filters in dialysis alone, in order to provide patients with kidney disease with the vital dialysis therapy.

[0004] To meet the high demand for hollow fiber membranes for the production of hollow fiber membrane filters, enormous demands are placed on the productivity of the manufacturing processes for these membranes. Established methods include the so-called dry-wet spinning process, which starts with a fluid spinning mass that is extruded into a filament and then coagulated and precipitated into a hollow fiber membrane through a phase inversion process. These spinning processes are designed so that a large number of simultaneously produced hollow fiber membranes are gathered into a bundle and wound onto a reel. The bundles are then cut into individual hollow fiber membrane bundles of the required lengths, which are then used in hollow fiber membrane filters.

[0005] Prior art methods for the dry-wet production of hollow fiber membranes start with a prepared spinning compound. A typical spinning compound is generally produced as a polymer solution consisting of a hydrophobic polymer, a hydrophilic polymer, optionally further additives, and a polar aprotic solvent.

[0006] The spinning compound is extruded through spinnerets in a spinning unit. The spinning unit can have a plurality of spinnerets, allowing a swarm of hollow filaments to be extruded through them. Each individual spinneret is designed such that the cavity of the filaments is filled with a coagulation medium, which causes phase inversion of the spinning compound within the filament. In the present application, the terms "Cavity" and "Lumen"Used as synonyms. Corresponding spinnerets are known in the prior art. As an example, one in the Figs. 1 to 5 These are called spinnerets, as shown in WO 03 / 076701 A1. The individual filaments are guided vertically through a precipitation gap and introduced into a precipitation bath, for example, water, where the membrane structure of the hollow fiber membrane is further solidified. Subsequently, the individual hollow fiber membranes are guided out of the precipitation bath by deflection rollers and, via further deflection rollers and guides, usually into one or more rinsing baths to remove solvents and excess polymer from the membrane. The rinsing baths often contain water as the rinsing medium.

[0007] After passing through the precipitation and rinsing baths, the hollow fiber membranes are completely filled with liquid, especially water; that is, the cavity of the hollow fiber membranes and the pores of the membrane walls are filled with liquid, especially water. Thus, after exiting the precipitation or rinsing bath, the hollow fiber membrane transports, for example, several times its own weight in liquid.

[0008] After the rinsing bath, the hollow fiber membranes are dried according to known manufacturing processes by introducing the individually guided membranes into a drying chamber via deflection rollers and suitable guides. Within the drying chamber, the distance the membranes travel is determined by the deflection rollers and guides. Depending on the transport speed, this results in a predetermined residence time for the membranes in the drying chamber. Drying is achieved by applying an elevated temperature. The temperature is set so that the liquid transported in the hollow fiber membrane, particularly water, evaporates. The evaporated liquid is discharged from the drying chamber, so that the hollow fiber membrane exits the chamber in a dry state and can be processed further.

[0009] Within the manufacturing process, after drying the hollow fiber membranes, a wave-forming step can be performed. In this step, a wave shape is mechanically imprinted onto the hollow fiber membranes using suitable gears. Furthermore, it is known to assemble a set of hollow fiber membranes and wind them onto a reel. The hollow fiber membrane bundles required for manufacturing the hollow fiber membrane filters are obtained by cutting individual strands from the wound-up hollow fiber membranes.

[0010] The extrusion rate of the spinning mass, the deflection rollers and guides, and the reel for holding the hollow fiber membranes determine the speed at which the hollow fiber membranes can be transported through the hollow fiber membrane production system. In the prior art, transport speeds of approximately 450 mm / s are known for the production of hollow fiber membranes. The transport speed of the hollow fiber membranes is ultimately crucial for the productivity of the manufacturing process. However, the transport speed cannot be increased arbitrarily, as increasing mechanical stress on the hollow fiber membranes during transport leads to a higher number of damaged fibers. In particular, fiber breakage and the collapse of individual fibers are to be expected if the transport speed is set too high.Such damage to the hollow fiber membranes renders the bundled hollow fiber membranes picked up by the reel unusable for further processing into hollow fiber membrane filters in the form of their separated hollow fiber membrane bundles.

[0011] The drying process of known manufacturing methods can also have a damaging effect on hollow fiber membranes. Achieving high productivity requires the application of high temperatures in state-of-the-art processes to completely dry the fibers in the drying chamber at a given transport rate. Excessive temperatures cause deformation of the hollow fiber membranes, rendering them unusable for hollow fiber membrane filters. Furthermore, prolonged exposure to high temperatures can lead to thermo-oxidative damage of the hollow fibers. In addition, the high drying temperatures required in the drying chamber are energy-intensive, which in turn increases the cost of the manufacturing process.

[0012] GB 731,415 discloses a device for drying textile fibers, in particular rayon. GB 731,415 describes a drying channel through which a plurality of textile fibers, for example arranged in parallel, are passed. The drying channel has heating elements. It is further described that air is supplied to the drying channel for drying the textile fibers.

[0013] US Patent 2,509,279 describes devices for treating fibers with fluids or gases. The fibers are passed through tubes in which they can be exposed to the gases.

[0014] DE 509 429 discloses a device for drying spun rayon threads. The rayon threads are washed with cold water and passed through a tube supplied with hot air for drying. The threads are then passed over a heated plate and wound onto spools. EP2591847 A1 also discloses a system for producing hollow fiber membranes with a tubular pressure chamber as a drying unit. TASK OF INVENTION

[0015] The methods known in the prior art for manufacturing hollow fiber membrane filters are no longer satisfactory in terms of productivity and efficiency from today's perspective. In particular, from the production standpoint of hollow fiber membrane filters, there is a persistent need to increase the production speed of hollow fiber membranes. Furthermore, there is also a need to optimize the manufacturing process for energy efficiency and cost-effectiveness. SUMMARY OF THE INVENTION

[0016] In a first aspect, the problem is solved by a device having the features of claim 1. Subclaims 2 to 9 represent alternative embodiments.

[0017] In a second aspect, the problem is solved by a method with the features of claim 10. Subclaims 11-13 describe further preferred embodiments.

[0018] In a third aspect, the problem is solved by a method for producing a hollow fiber membrane, characterized in that the spinning speed of the hollow thread is set to over 550 mm / s, preferably over 650 mm / s, more preferably over 750 mm / s. DETAILED DESCRIPTION OF THE INVENTION

[0019] In a first aspect, the invention relates to a system for the production of at least one hollow fiber membrane as defined in claim 1, comprising A spinning unit comprising at least one annular die fluidically connected to a source of spinning compound and a source of coagulation medium for extruding at least one hollow filament from the spinning compound, the cavity of which is filled with the coagulation medium; a precipitation bath for precipitation of the at least one filament into at least one hollow fiber membrane; optionally, at least one rinsing unit for rinsing the at least one hollow fiber membrane; at least one drying unit for drying the at least one hollow fiber membrane; optionally, a receiving unit for receiving the at least one hollow fiber membrane onto a support, wherein the at least one drying unit comprises a pressure section configured such that an atmospheric overpressure can be set in the pressure section, wherein the pressure section of the drying unit comprises a pressure chamber having an interior space.The pressure chamber has an inlet for introducing the at least one hollow fiber membrane into the interior of the pressure chamber, an outlet for expelling the at least one hollow fiber membrane from the interior of the pressure chamber, and at least one gas inlet, wherein the at least one gas inlet is in fluid communication with a gas source, and the pressure section is further configured such that an overpressure can be generated via the gas source in the interior of the pressure chamber, and the clear width of the interior of the pressure chamber has, in cross-section parallel to the direction of travel of the at least one hollow fiber membrane, at least one cross-sectional enlargement and at least one cross-sectional reduction, wherein the cross-sectional enlargement preferably forms a conical shape on the inside of the pressure chamber.

[0020] The system is designed such that at least one filament is directed into the precipitating bath and precipitated into at least one hollow fiber membrane, whereby further The at least one hollow fiber membrane obtained from the precipitation bath is optionally introduced into a rinsing bath and rinsed, wherein the at least one hollow fiber membrane obtained from the precipitation bath or the at least one hollow fiber membrane obtained from the rinsing bath is further guided into the drying unit and dried, wherein the system can further be designed such that the at least one hollow fiber membrane dried in the drying unit is guided to a receiving unit and received on a carrier.

[0021] For the sake of simplicity, in the following explanations, the terms "at least one annular gap die" or "one annular gap die", "at least one filament" or "one filament", and "at least one hollow fiber membrane" or "one hollow fiber membrane" should always be understood to include the plural of "annular gap dies", "filaments", and "hollow fiber membranes", unless explicitly stated otherwise. Modern hollow fiber spinning plants can have more than 1000 or 2000 annular gap dies.

[0022] The walls of the at least one hollow fiber membrane, which can be produced using the above-described system, are preferably porous. The pores and the cavity, i.e., the lumen, of the hollow fiber membrane are filled with liquid, particularly water, as the membrane passes through the precipitation bath and any rinsing bath. The inventors have found that, as the produced hollow fiber membrane passes through the pressure section of the drying unit, at least some of the liquid, particularly the water, can be separated from the pores and the cavity, i.e., the lumen, of the hollow fiber membrane by the applied atmospheric overpressure. This significantly reduces the weight of the liquid-filled hollow fiber membrane.Surprisingly, it was possible to increase the transport speed of the hollow fiber membrane in the system without causing fiber breakage or other damage such as flattening. In particular, it was also possible to perform thermal drying at lower temperatures or with shorter section lengths of the hollow fiber membranes while maintaining the same degree of dryness. This resulted in significant energy savings in the manufacturing process of the hollow fiber membranes and reduced thermo-oxidative damage to the hollow fibers. Furthermore, the hollow fibers produced with the system according to the invention exhibit a particularly low residual solvent content in the spinning compound.

[0023] The term "Plant for the production of at least one hollow fiber membrane" For the purposes of this application, it is to be understood that the apparatus defined in claim 1 can be used to produce one or a plurality of hollow fiber membranes simultaneously. The term "Production of at least one hollow fiber membrane"For the purposes of this application, "spinning" refers to the process of forming one or more filaments from a spinning mass, the precipitation of one or more filaments into one or more hollow fiber membranes, and optionally, the rinsing, drying, and, optionally, the mounting of the one or more hollow fiber membranes onto a support. "Manufacturing" It may also include other, unmentioned intermediate steps.

[0024] The term "Spinning unit" For the purposes of this application, a component is understood to be an assembly with which a spinning mass is extruded into a spinning thread.

[0025] The term "Spinning mass"For the purposes of this application, a polymer solution is understood to be one in which at least one polymer is dissolved in a solvent. In particular, for the purposes of this application, a spinning mass may comprise a polymer solution of at least one hydrophobic polymer and at least one hydrophilic polymer. Furthermore, the hydrophobic polymer may be a polysulfone (PSU) and the hydrophilic polymer may be polyvinylpyrrolidone (PVP). The solvent may be a polar aprotic solvent, in particular N-methylpyrrolidone (NMP), N,N-dimethylacetamide, or dimethyl sulfoxide (DMSO). Such materials are preferred in the production of dialyzers, whereas, for example, highly hydrophobic materials such as polypropylene (PP) or polymethylpentene (PMP) are used in oxygenators.

[0026] The term "spider thread"For the purposes of this application, a yarn is understood to be a thread extruded from the spinning mass that has not yet assumed the porous structure of the hollow fiber membrane to be produced. In particular, for the purposes of this application, the spinning mass extruded into the yarn is understood to be in the "fall gap" referred to as spider silk before being introduced into the coking bath. "fall gap" The distance traveled by the spider silk from its extrusion to its entry into the coagulation bath is understood here. The speed at which the spider silk passes through the coagulation gap is, for the purposes of this application, defined as... "Trigger rate" designated. The "Transport speed" The feed rate is adjusted to the feed rate or can be slightly higher to ensure taut guidance of the hollow fiber membrane through the system. Therefore, if the feed rate is increased, the feed rate is also increased.

[0027] The spinning unit has one or more annular nozzles. The term "Annular gap nozzle" For the purposes of this application, an annular die is understood to be an extrusion die with which the spinning mass can be extruded into a hollow filament. The annular die has a central bore through which the coagulation medium can be extruded. Furthermore, the annular die has an annular gap concentric to the central bore through which the spinning mass is extruded. Corresponding annular dies are known in the prior art. The term annular die also includes extrusion dies that have several annular gaps concentric to the central bore.

[0028] The spinning unit further features feed channels to fluidically connect the source of the spinning compound to the concentrically arranged annular gap(s) of the annular gap die and the source of the coagulation medium to the central bore of the annular gap die. The spinning compound and coagulation medium are co-extruded through the annular gap die to form the hollow spinning thread, with the hollow space of the spinning thread being filled with the coagulation medium.

[0029] As "Coagulation medium"For the purposes of this application, a liquid medium is understood to be one that, upon contact with the inner surface of the hollow spider silk, causes a phase inversion of the spinning mass within the spider silk. For the process described in this application, a coagulation medium is selected that consists of a mixture of an aprotic polar solvent and a polar protic solvent. In particular embodiments according to the present invention, the coagulation medium consists of N-methylpyrrolidone (NMP), N,N-dimethylacetamide, or dimethyl sulfoxide (DMSO), and water. Coagulation of the spider silk initiated with this coagulation medium is also referred to as "non-solvent-induced phase separation" (NIPS). Furthermore, according to the present application, coagulation of the spider silk can also be initiated by a "temperature-induced phase separation" (TIPS) process.The phase inversion and coagulation of the spider silk is initiated by a decrease in temperature.

[0030] The term "Falling bath" For the purposes of this application, a "precipitating unit" is understood to be a structural unit comprising a reservoir of a precipitation medium into which the extruded spun yarn is introduced. In the precipitation bath, the spun yarn precipitates, and the coagulated structure of the spun yarn is further solidified to form a porous hollow fiber membrane. According to the present invention, a polar protic solvent, in particular water, is preferably used as the "precipitating medium." However, it can also alternatively contain alcohols or other protic liquids, either alone or in mixtures. The precipitation medium can also contain a proportion of a polar aprotic solvent. After the hollow fiber membrane has passed through the precipitation bath, the pores and the cavity of the hollow fiber membrane are filled with liquid.

[0031] The term "Flushing unit" The invention refers to a structural unit comprising a reservoir of rinsing fluid into which the hollow fiber membrane obtained from the precipitation bath is introduced. This process removes any residual solvent and adhering polymer components that may still be present on the hollow fiber membrane after the precipitation bath. Water is preferably used as the rinsing fluid in the present invention. However, the rinsing unit can also have several reservoirs containing different rinsing fluids. After the hollow fiber membrane has passed through the rinsing unit, its pores and cavity are filled with liquid, particularly water.

[0032] The term "Drying unit"A drying unit is understood to be a structural unit comprising a space into which the hollow fiber membrane is introduced and in which it can be dried. Preferably, the drying unit dries the hollow fiber membrane, obtained from the precipitation bath or, optionally, from the rinsing bath and filled with liquid, particularly water, to a residual liquid content of less than 10% by weight, and more preferably less than 3% by weight, based on the total weight of the fiber. The drying unit can comprise a space into which the hollow fiber membrane is introduced and in which a path for the hollow fiber membrane to travel is defined by means of deflection rollers and guides, so that the hollow fiber membrane remains in the drying unit for a predetermined time, depending on the transport speed.

[0033] The term "receiving unit" refers to a device comprising a carrier prepared to receive the hollow fiber membrane. In particular, this carrier may be a reel, a drum, a winder, or a roll.

[0034] The term "Print section" For the purposes of this application, a structural unit within the drying unit is understood to be one in which an overpressure relative to the ambient pressure of the system according to claim 1 can be set. The term "Overpressure" refers to the standard atmospheric pressure of 1013.25 hPa and, in the context of the present application, denotes a pressure above the standard atmospheric pressure.

[0035] The person skilled in the art is aware of further details of a plant for the production of a hollow fiber membrane. In particular, it is known to the person skilled in the art that a plant for the production of hollow fiber membranes includes means for guiding the spun yarn and the hollow fiber membrane in order to guide the spun yarn through the precipitation bath and to transport the resulting hollow fiber membrane through the precipitation bath, the rinsing bath, the drying unit and to the receiving unit. The person skilled in the art is aware of corresponding guide rollers, guide racks or guide plates in this context.

[0036] Furthermore, those skilled in the art are aware of corresponding process parameters and spinning conditions that influence the extrusion of the spinning mass and the formation of the hollow fiber membrane. In particular, it is known to those skilled in the art that the temperature of the annular dies, the relative atmospheric humidity in the precipitation gap, the height of the precipitation gap, the composition of the spinning mass and the coagulation medium, as well as the temperature of the precipitation bath, influence the formation of the membrane structure of the hollow fiber membrane, e.g., its porosity and its separation properties. The process parameters for a TIPS process are known, for example, from WO17184817A1.

[0037] The invention is characterized in that the pressure section of the drying unit has a pressure chamber which has an interior space, an inlet for introducing the at least one hollow fiber membrane into the interior space of the pressure chamber, an outlet for expelling the at least one hollow fiber membrane from the interior space of the pressure chamber and at least one gas inlet, wherein the at least one gas inlet is in fluid communication with at least one gas source and the pressure section is further designed in such a way that an overpressure can be generated via the gas source in the interior space of the pressure chamber.

[0038] According to this embodiment, an overpressure can be applied, which can act particularly effectively on the hollow fiber membranes guided through the pressure chamber. The pressure chamber can, for example, be designed as a channel, which is, for example, tubular or slot-shaped, and into which the gas is introduced to adjust the overpressure. According to the invention, the inner diameter of the pressure chamber is not constant, but is, for example, larger than at the inlet and outlet of the pressure chamber. It is provided that at least one hollow fiber membrane or a set of hollow fiber membranes is guided through the pressure chamber and that at least a portion of the water transported in the hollow fiber membranes is removed by the applied overpressure. The overpressure can be adjusted by the inflow of a gas that flows into the pressure chamber through the gas inlet.The removal of water is particularly effective when there is a discharge of liquid, especially water, from the pressure chamber, particularly against the conveying direction of the hollow fiber membrane, so that water separated from the hollow fiber membranes can be drained from the inlet of the pressure chamber.

[0039] The term "Pressure chamber" For the purposes of this application, a pressure chamber is defined as an enclosed space in which a pressure higher than the ambient pressure can be set. For the purposes of this application, the pressure chamber has an inlet opening and an outlet opening for the passage of hollow fiber membranes.

[0040] The term "Gas source"A gas source is understood to be a device capable of supplying gas at an overpressure relative to the ambient atmosphere. In particular, a gas source within the meaning of this application can be a pressurized gas container, e.g., a gas cylinder. Alternatively, the gas source can also be a compressor that supplies compressed air. According to the described design, the gas introduced into the pressure chamber can escape through the inlet and outlet of the pressure chamber.

[0041] The term "fluid connection" refers to a connection that allows gas to be conveyed from the gas source to the gas inlet of the pressure chamber. Such fluid connections can be pipes or hoses.

[0042] Another embodiment of the first aspect of the invention is characterized in that the system is designed such that the pressure in the pressure section of the drying system is 1100 hPa to 10,000 hPa, or 1200 hPa to 5000 hPa, or 1200 hPa to 4000 hPa. It has been shown that, depending on the membrane porosity and separation properties, the pressure in this range can be optimally adjusted, thus achieving good liquid removal.

[0043] Another embodiment of the first aspect of the invention is characterized in that the cross-sectional area of ​​the inlet for introducing the at least one hollow fiber membrane into the interior of the pressure chamber and of the outlet for expelling the at least one hollow fiber membrane from the pressure chamber is less than 30 times, preferably less than 20 times, more preferably less than 10 times, and more preferably less than 5 times, the cross-sectional area of ​​the single hollow fiber membrane or the sum of the cross-sectional areas of the multiple hollow fiber membranes. According to one embodiment, the cross-sectional area of ​​the inlet is greater than 1.1 times, or 2 times, or 3 times the cross-sectional area of ​​the single hollow fiber membrane or the sum of the cross-sectional areas of the multiple hollow fiber membranes.

[0044] The pressure build-up can be adjusted by changing the cross-sectional area of ​​the inlet and outlet of the pressure chamber, depending on the number of hollow fiber membranes passing through the chamber. If the cross-sectional area of ​​the inlet and outlet is too small, guiding the hollow fiber membranes through the pressure chamber becomes difficult. This can occur if the cross-sectional area of ​​the inlet or outlet is less than 1.1 times the cross-sectional area of ​​a single hollow fiber membrane or the sum of the cross-sectional areas of multiple hollow fiber membranes. If the cross-sectional area is too large, adjusting the overpressure becomes more difficult, and the amount of gas required to achieve a desired pressure increases.

[0045] The inlet and outlet of the pressure chamber can be designed to allow up to 128 fibers to pass through it. If a larger number of hollow fiber membranes are passed through the pressure chamber, partial liquid removal, particularly water removal, from the inner fibers of the set of hollow fiber membranes becomes more difficult. Preferably, a set of 2 to 64 hollow fiber membranes, alternatively a set of 5 to 32 hollow fiber membranes, and in a further alternative, a set of 10 to 20 hollow fiber membranes are passed through the pressure chamber. If it is necessary to simultaneously remove liquid from an even larger number of hollow fiber membranes by means of an overpressure gas atmosphere, several pressure chambers can be arranged simultaneously and in parallel in the system for manufacturing the hollow fiber membranes.

[0046] Another embodiment of the first aspect of the invention is characterized in that the drying unit has a temperature control section which has a heating device designed in such a way that a temperature of 50 to 230°C can be set in the temperature control section.

[0047] It has been shown that a drying unit comprising a combination of a pressure section and a temperature control section is particularly effective and efficient for drying hollow fiber membranes. Specifically, this embodiment provides for the partial removal of liquid, particularly water, from the hollow fiber membrane by the pressure section. This allows the fiber to be dried more efficiently in the temperature control section because hot air can penetrate the pores and the cavity of the hollow fiber membrane.

[0048] The term "Temperature control section"This refers to a section of the drying unit where the temperature is set between 50 and 230°C. The temperature range must be selected to prevent damage to the hollow fiber membrane while ensuring sufficient drying. In this regard, temperature ranges of 70°C or above, 90°C or above, 110°C or above and 210°C and below, 190°C and below, or 170°C and below, are particularly suitable for drying the hollow fiber membranes in this drying section. Alternatively, drying at temperatures between 170°C and 230°C can be used, resulting in particularly rapid drying.

[0049] Another embodiment of the first aspect of the invention is characterized in that the temperature control section of the drying unit has a temperature control chamber which has an inlet for introducing the at least one hollow fiber membrane and an outlet for removing the at least one hollow fiber membrane.

[0050] Another embodiment of the first aspect of the invention is characterized in that the pressure chamber and the temperature control chamber are separate chambers, and the system is further configured such that the at least one hollow fiber membrane obtained from the precipitation bath or, optionally, from the rinsing bath, is first passed through the pressure chamber and then through the temperature control chamber. Separating the pressure and drying chambers has the advantage that liquid can be removed in the upstream pressure chamber without having to evaporate it. The liquid can then be returned to the rinsing bath, which reduces liquid consumption in the rinsing bath, or collected separately and reused. After entering the drying chamber, significantly less liquid needs to be evaporated, which accelerates the drying process and / or reduces energy consumption by lowering the required enthalpy of vaporization.

[0051] Another embodiment of the first aspect of the invention is characterized in that the pressure chamber of the pressure section is divided into several compartments. Advantageously, different pressures can be set in the different compartments of the pressure chamber. According to this embodiment, a pressure gradient can be generated across the several compartments in the pressure chamber. The pressure gradient results in a particularly efficient discharge of liquid, especially water, from the pressure chamber and thus efficient liquid removal from the at least one hollow fiber membrane.

[0052] According to this embodiment, the gas inlet is arranged on at least one compartment of the pressure chamber. Water outlets for draining the water separated from the hollow fiber membranes can be arranged on further compartments of the pressure chamber. A compartment can be formed within the pressure chamber by suitable geometric configurations of the interior of the pressure chamber and can be separated from another compartment. The compartments can be separated from each other by partitions. In this context, the term "separate" means that different pressures are established in the compartments, and thus a first pressure in a first compartment differs from a second pressure in a second compartment of the pressure chamber. The compartments are open to the hollow fiber membranes via the central passage area.

[0053] According to the invention, the clear width of the interior of the pressure chamber is designed in cross-section parallel to the direction of travel of the hollow fiber membrane such that it has at least one cross-sectional enlargement and at least one cross-sectional reduction, wherein the cross-sectional enlargement and the cross-sectional reduction preferably form a cone shape of the inside of the pressure chamber.

[0054] The conical inner surface of the pressure chamber has the advantage that water separated from the hollow fiber membranes can be transported away particularly effectively. This effective water removal makes it possible to keep the overall length of the pressure chamber in the fiber direction below 50 cm, preferably below 20 cm, and more preferably below 12 cm, which allows for a more compact design of the hollow fiber membrane production system. According to a particular embodiment, the overall length of the pressure chamber is at least 5 cm.

[0055] According to a preferred embodiment, several cross-sectional enlargements and reductions are connected inside the pressure chamber, so that several compartments with a cone-shaped section are formed in the interior of the pressure chamber.

[0056] Another embodiment of the first aspect of the invention is characterized in that the at least one gas inlet of the pressure chamber is arranged at a cross-sectional maximum of the clear width of the interior of the pressure chamber, preferably centrally located between the inlet for introducing and the outlet for expelling the at least one hollow fiber membrane of the pressure chamber. This embodiment facilitates the flow of gas to the inlet and outlet of the hollow filament(s).

[0057] Another embodiment of the first aspect of the invention is characterized in that the pressure chamber has one or more outlets for draining liquid, in particular water, wherein the outlets are preferably arranged at a cross-sectional maximum of the clear width of the interior of the pressure chamber. The liquid, in particular water, separated from the at least one hollow fiber membrane can be discharged from the interior of the pressure chamber via the outlets. This improves the efficiency of the drying process in the pressure chamber, as the liquid can be drained particularly quickly and efficiently.

[0058] Another embodiment of the first aspect of the invention is characterized in that the pressure chamber has inlets and outlets for the hollow fiber(s), with a funnel-shaped opening adjoining the inlet. This protects the hollow fiber membrane or the set of hollow fiber membranes when introduced into the pressure chamber. It is also possible for the outlet to have a funnel-shaped opening. Preferably, all edges, in particular all edges of the inlet, are rounded.

[0059] In particular, in one embodiment of the first aspect of the invention, the apparatus for producing the at least one hollow fiber membrane is characterized in that it is designed to produce a "high-flux" hollow fiber membrane, a "mid cut-off" hollow fiber membrane, a "high cut-off" hollow fiber membrane or hollow fiber membranes for blood plasma separation for extracorporeal blood treatment.

[0060] The term "high-flux," as used here, refers to hollow fiber membranes with a molecular weight retention onset (MWRO) between 5 kDa and 10 kDa and a molecular weight cutoff (MWRO) between 25 kDa and 65 kDa, as determined by dextran sieve coefficient measurements according to Boschetti et al. (2013). The average pore radius is in the range of 3.5 to 5.5 nm, with the pore size determined by the MWRO based on the dextran sieve coefficients according to Boschetti-de-Fierro et al. (2013) and Granath et al. (1967), as well as by analysis of the molecular weight distribution by gel chromatography on Sephadex. J Chromatogr A. 1967; 28 (C): 69-81 becomes.The main difference between "high-flux" membranes and "low-flux" membranes lies in a higher water permeability and the ability to remove small to medium molecules such as β2-microglobulin.

[0061] The term "mid-cut-off" membranes is used for membranes whose separation properties lie between those of high-flux and high-cut-off membranes. "Low-flux" membranes exhibit separation properties characterized by a steeper sieve curve than high-flux membranes.

[0062] The term "high cut-off" used here refers to hollow fiber membranes with a MWRO between 15 and 20 kDa and a MWCO between 170 and 320 kDa. These hollow fiber membranes are characterized by a pore radius on the surface of the selective layer between 8 and 12 nm. The MWRO and MWCO of the "high cut-off" hollow fiber membrane described here are determined according to the methods of Boschetti-de-Fierro et al. (2013).

[0063] Hollow fiber membranes for blood plasma separation are characterized by a MWCO value above the value defined for "high cut-off" hollow fiber membranes. In particular, the pore size of hollow fiber membranes for blood plasma separation is such that only cellular components of the blood are retained by the membrane.

[0064] High-flux hollow fiber membranes, mid-cut-off hollow fiber membranes, high-cut-off hollow fiber membranes, or hollow fiber membranes for blood plasma separation can be manufactured particularly well according to the method described in the second aspect. These hollow fiber membranes exhibit high fluid permeability, especially high water permeability, so that the removal of fluid, particularly water, from the hollow fiber membrane in the pressure chamber can be carried out very effectively. This is especially true for high-cut-off hollow fiber membranes with a MWRO of 10–20 kDa.

[0065] According to the invention, two or more pressure chambers can also be connected in series. This is particularly advantageous when only a comparatively small portion of the liquid can be removed in the first pressure chamber. This may be necessary, for example, in the production of "low-flux" hollow fiber membranes, which require increased drying effort due to their small pore diameter.

[0066] In a second aspect, the invention relates to a method for producing one or more hollow fiber membranes according to claim 10, comprising the steps of providing a source of spinning mass, providing a source of a coagulation medium, co-extruding the spinning mass and the coagulation medium through at least one annular die to form at least one hollow spinning thread whose cavity is filled with the coagulation medium, introducing the at least one spinning thread into a precipitation bath containing a precipitating agent, and precipitating the at least one spinning thread into at least one hollow fiber membrane, optionally subsequently introducing the at least one hollow fiber membrane into a rinsing bath containing a rinsing agent, introducing the at least one hollow fiber membrane obtained from the precipitation bath or introducing the at least one hollow fiber membrane optionally obtained from the rinsing bath into a drying unit.Optionally, the at least one hollow fiber membrane obtained from the drying unit is placed on a support, wherein the at least one hollow fiber membrane passes through a pressure section in the drying unit in which atmospheric overpressure is generated by introducing a gas into the pressure section and in which at least a part of the precipitating agent or rinsing agent contained in the at least one hollow fiber membrane is separated from the at least one hollow fiber membrane, wherein the pressure section of the drying unit comprises a pressure chamber, and the at least one hollow fiber membrane is introduced through an inlet into an interior of the pressure chamber, wherein the clear width of the interior of the pressure chamber has, in cross-section parallel to the direction of travel of the at least one hollow fiber membrane, at least one cross-sectional enlargement and at least one cross-sectional reduction.wherein the cross-sectional enlargement and reduction preferably form a conical shape on the inside of the pressure chamber, and the hollow fiber membrane is discharged from the interior of the pressure chamber through an outlet.

[0067] Those skilled in the art are familiar with the basic procedures and details of a method for producing a hollow fiber membrane. In particular, it is known that in a method for producing hollow fiber membranes, means for guiding the spun yarn and the hollow fiber membrane serve to guide the spun yarn through and out of the precipitation bath and subsequently to the rinsing bath, the drying unit, and the receiving unit. Those skilled in the art are familiar with corresponding guide rollers, guide racks, guide plates, or undulating tools with which the method according to the invention can be carried out.

[0068] Furthermore, the process parameters and spinning conditions for extruding the spinning mass and forming the hollow fiber membrane are known to those skilled in the art. In particular, it is known to those skilled in the art that the temperature of the annular dies, the relative atmospheric humidity in the precipitation gap, the height of the precipitation gap, the composition of the spinning mass and the coagulation medium, as well as the temperature of the coagulation bath, influence the formation of the membrane structure of the hollow fiber membrane, e.g., its porosity. In particular, the process according to the second aspect is suitable for producing hollow fiber membranes for nano-, ultra-, and microfiltration. Preferably, the coagulation of the spinning filament is carried out according to the principle of non-solvent induced phase separation (NIPS). Alternatively, the coagulation of the spinning filament can also be controlled according to temperature induced phase separation (TPIS).TIPS processes using hydrophobic polymers are particularly suitable for the separation of gases, especially in oxygenators; this applies in particular to the polymer PMP (polymethylpentene) and polypropylene (PP).

[0069] Another embodiment of the second aspect of the invention is characterized in that an undulating tool is arranged downstream of the drying unit and optionally upstream of the receiving unit. In the context of this application, an "undulating tool" is understood to be a tool with which the hollow fiber membrane can be formed into a wave-like geometric shape. Such tools are known in the prior art; in particular, reference is made to the embodiments disclosed in DE 10 2017 204 524 A1.

[0070] The process according to the second aspect is suitable for the production of a hollow fiber membrane. The process is equally suitable for the simultaneous production of a set of (multiple) hollow fiber membranes. In this case, spinning mass and coagulation medium are extruded through a plurality of annular dies arranged in the spinning unit to form a set of filaments, which are then further processed into dried hollow fiber membranes analogously to the process according to the invention. In particular, the system for producing the hollow fiber membranes can be designed such that 1 to 64 hollow fiber membranes, or 5 to 32 hollow fiber membranes, or 10 to 20 hollow fiber membranes, or up to 128 hollow fiber membranes can be produced simultaneously.

[0071] As previously described, a hollow fiber membrane is filled with liquid, particularly water, during the manufacturing process as it passes through the precipitation bath and, if present, the rinsing bath. The weight of the hollow fiber membrane can be significantly reduced in the manufacturing process by the pressure section of the drying unit. In particular, this makes it possible to increase the transport speed of the hollow fiber membrane in the manufacturing system without causing fiber breakage or other fiber damage such as flattening. Furthermore, it is possible to perform thermal drying at a lower temperature or over a shorter distance while maintaining the same degree of dryness, resulting in significant energy savings in the manufacturing process and / or reducing or preventing thermo-oxidative damage to the hollow fibers.Furthermore, the hollow fibers produced according to the invention have a particularly low solvent content in the spinning mass.

[0072] Another embodiment of the second aspect of the invention is characterized in that the atmospheric overpressure in the pressure section is set to a pressure of 1100 hPa to 10,000 hPa, or 1200 to 5000 hPa, or 1200 to 4000 hPa. The specified pressure ranges have proven advantageous for at least partially removing the water contained in the pores and cavity of the hollow fiber membranes during the manufacturing process.

[0073] Another embodiment of the second aspect of the invention is characterized in that the gas is selected from the group consisting of air, nitrogen, argon, carbon dioxide, water vapor, or mixtures thereof. These gases have proven advantageous because they are inert to the materials of the hollow fiber membrane. Preferred gases are nitrogen and synthetic air.

[0074] Another embodiment of the second aspect of the invention is characterized in that the pressure section is temperature-controlled to 30 to 125 °C, preferably 30 to 110 °C, and more preferably 30 to 90 °C. Improved separation of water from the hollow fiber membrane was observed at elevated temperatures in the pressure section. In particular, the hollow fiber membrane can be partially sterilized at temperatures above 100 °C. In this case, it is advantageous to establish a water vapor atmosphere at overpressure and 120 °C in the pressure section.

[0075] Another embodiment of the second aspect of the invention is characterized in that a portion of the gas supplied to the pressure chamber escapes in the rinsing unit, particularly in the rinsing bath. According to the invention, this is controlled, depending on the type of hollow fiber membrane and the geometry of the pressure chamber, by adjusting the gas pressure until a sufficient number of gas bubbles escape into the rinsing bath. This ensures particularly effective liquid removal. A further embodiment of the second aspect is characterized in that the transport speed of the hollow fiber membrane is 550 mm / s to 1000 mm / s, preferably 650 mm / s to 900 mm / s, and more preferably 750 mm / s to 800 mm / s.

[0076] According to another embodiment of the second aspect, the manufactured hollow fiber membrane is a "high-flux", a "mid-cut-off", a "high cut-off" hollow fiber membrane, or a hollow fiber membrane for blood plasma separation.

[0077] According to a further embodiment of the second aspect of the invention, in the pressure chamber the majority, particularly preferably more than 75% or more than 90%, of the liquid is removed from the pores and the cavity, i.e., the lumen, of the membrane. Thus, efficient liquid removal is ensured.

[0078] In a third aspect, the invention relates to a method for producing one or more hollow fiber membranes, comprising the steps Providing a source of spinning compound, providing a source of a coagulation medium, co-extruding the spinning compound and the coagulation medium through at least one annular die to form at least one hollow spinning thread whose cavity is filled with the coagulation medium, introducing the at least one spinning thread into a precipitation bath containing a precipitating agent, and precipitating the at least one spinning thread into at least one hollow fiber membrane, optionally subsequently introducing the at least one hollow fiber membrane into a rinsing bath containing a rinsing agent, introducing the at least one hollow fiber membrane obtained from the precipitation bath or introducing the at least one hollow fiber membrane optionally obtained from the rinsing bath into at least one drying unit, optionally receiving the at least one hollow fiber membrane obtained from the drying unit onto a support, characterized in that,that the transport speed of the hollow fiber membrane is 550 mm / s to 1000 mm / s, preferably over 650 mm / s to 900 mm / s, more preferably 750 mm / s to 800 mm / s. An embodiment of the third aspect is characterized in that the at least one drying unit has a pressure section in which an atmospheric overpressure is set. At these spinning speeds, a particularly economical production of hollow fiber membranes is possible. The embodiments of the second aspect of the invention are also the subject of the third aspect of the invention. DESCRIPTION OF THE INVENTION BASED ON THE DRAWINGS

[0079] Further embodiments of the invention are explained below with reference to the figures. Fig. 1 Figure 1 shows a schematic representation of an embodiment of the apparatus 100 according to the invention for the production of at least one hollow fiber membrane. Fig. 1The cross-section of an annular gap nozzle 101 is shown in a schematic, simplified representation. The source of a spinning mass and the source of a coagulation medium are shown in Fig. 1 not shown. Fig. 1 The figure schematically shows the spun yarn 102, which is guided through the precipitation gap 102b and into the precipitation bath 103. Also schematically shown are deflection rollers 105a to 105l, which guide the spun yarn and the hollow fiber membrane through the system. The hollow fiber membrane 104, formed in the precipitation bath 103, is guided by deflection rollers into a rinsing bath 106. In alternative configurations, several rinsing baths can be arranged in series (not shown in the figure). Fig. 1 (shown). Furthermore, it shows Fig. 1 schematically a pressure chamber 200 with an inlet 201 and an outlet 202 for the one in Fig. 1The hollow fiber membrane 104 shown passes through the pressure chamber and is guided through the temperature control chamber 300 via an inlet 301, deflection rollers 105h to 105l, and an outlet 302. A reel 400, which receives the hollow fiber membrane 104 and bundles it into strands of hollow fiber membranes, is shown schematically. For simplification, the schematic representation of Fig. 1 The production of only one hollow fiber membrane was shown. The in Fig. 1 The system shown is equally suitable for the production of a large number of hollow fiber membranes. The pressure chamber 200 and the temperature control chamber 300 together form a drying unit 350. The temperature control chamber can be configured in the schematic embodiment shown. Fig. 1 It can be operated within a temperature range of 100 to 230°C. An undulating tool is not included. Fig. 1shown. An undulating tool can additionally be arranged between tempering chamber 300 and reel 400. Also not shown in the Fig. 1 The gas inlet is located on pressure chamber 200. This is shown in the following figures. Hollow fiber membranes according to the NIPS and TIPS principles can be produced using the system 100 shown. Fig. 2 Figure 2 shows a schematic cross-section of a pressure chamber 200 according to an illustrative embodiment. Fig. 2 A hollow fiber membrane 104 is shown, which passes through an inlet 201 and an outlet 202 in the pressure chamber 200. Also shown are a gas inlet 203 and a valve 204, which may be present to regulate the flow of gas into the pressure chamber. The pressure chamber has an interior space 205, which forms a cavity in the illustration. When gas is introduced through the gas inlet 203, atmospheric overpressure builds up in the interior space 205. Fig. 3Figure 2 shows a schematic cross-section of a pressure chamber 200 according to a further illustrative embodiment. Analogous to Fig. 2 shows Fig. 3 The pressure chamber comprises an inlet 201 for introducing at least one hollow fiber membrane, an outlet 202 for expelling at least one hollow fiber membrane 104, a gas inlet 203, a valve 204, and an interior space 205. According to this design, the pressure chamber can have a tubular or slit-shaped geometry. Fig. 4Figure 1 shows a schematic representation of a section of the apparatus 100 according to the invention. Shown are the rinsing bath 106, the hollow fiber membrane 104, which is guided through the rinsing bath and through the pressure chamber 200, the inlet 201 and outlet 202 of the pressure chamber, and the gas inlet 203 of the pressure chamber. By introducing gas through the gas inlet 203 into the interior, an atmospheric overpressure is built up in the pressure chamber, whereby a portion of the water or liquid transported in the hollow fiber membrane 104 is separated from the membrane. In particular, the gas penetrates the pores and the cavity of the hollow fiber membrane and spreads within the cavity of the hollow fiber membrane with and against the direction of transport of the membrane.At a pressure of 3000 hPa in the pressure chamber, the gas spreads in the hollow fiber membrane against the direction of transport to such an extent that gas bubble formation can be observed in the upstream rinsing bath or precipitation bath, if present. Fig. 5 Figure 1 schematically shows another illustrative embodiment of a pressure chamber 200, wherein the interior 205 is divided into two compartments 205a and 205b by two walls 206a and 206b, and the hollow fiber membrane 104 is guided through the pressure chamber 200 via the inlet 201 and the outlet 202. The gas inlet 203 is located at compartment 205b. The inflowing gas causes a first atmospheric overpressure with a pressure P1 in compartment 205b, while a second atmospheric overpressure with a pressure P2 is established in the second compartment 205a. According to the illustration in Fig. 5In the illustrated embodiment, P1 is greater than P2. The pressure P1 can be 3000 hPa. The pressure P2 can be 1500 hPa. The compartments create a pressure gradient within the pressure chamber. Fig. 6 Figure 1 schematically shows another illustrative embodiment of a pressure chamber 200, wherein the interior 205 is divided into compartments 205a, 205b, and 205c by four walls 206a, 206b, 206c, and 206d, and the hollow fiber membrane 104 is guided through the pressure chamber 200 via the inlet 201 and the outlet 202. The gas inlet 203 is located at compartment 205a. The inflowing gas causes a first atmospheric overpressure of pressure P1 in compartment 205a, a second atmospheric overpressure of pressure P2 is established in compartment 205b, and a third atmospheric overpressure of pressure P3 is created in compartment 205c. According to the illustration in Fig. 6In the illustrated embodiment, P1 is greater than P2. The pressure P1 can be 3000 hPa and is greater than the pressure P2. The pressure P2 is greater than the pressure P3, which can be 1500 hPa. Fig. 7Figure 1 schematically shows an embodiment of a pressure chamber 200 according to the invention, wherein the interior 205 has several cross-sectional enlargements and several cross-sectional reductions, the cross-sectional enlargements and reductions forming several cone-shaped sections on the inside of the pressure chamber. The cone-shaped sections in the interior of the pressure chamber 200 form three compartments 205a, 205b, and 205c, with the hollow fiber membrane 104 passing through the pressure chamber 200 via the inlet 201 and the outlet 202. The cone-shaped sections on the inside of the pressure chamber are arranged symmetrically with respect to the gas inlet 203. The gas inlet 203 is located at compartment 205a.The inflowing gas causes a first atmospheric overpressure with pressure P1 in compartment 205a, a second atmospheric overpressure with pressure P2 in compartment 205b, and a third atmospheric overpressure with pressure P3 in compartment 205c. According to the in . Fig. 6 In the illustrated embodiment, P1 is greater than P2. The pressure P1 can be 3000 hPa and is greater than the pressure P2. The pressure P2 is greater than the pressure P3, which can be 1500 hPa. According to Fig. 7 The at least one gas inlet 203 of the pressure chamber 200 is arranged at a cross-sectional maximum 207 of the clear width of the interior of the pressure chamber, wherein the gas inlet is arranged centrally between the inlet and the outlet of the pressure chamber. The in Fig. 7 The cross-sectional maxima of the clear width of the interior of pressure chamber 207, 207a and 207b shown are of the same size.

[0080] With the in the Figs. 5 to 7In the embodiments shown, a particularly efficient separation of water from the hollow fiber membrane is possible. It can be provided that the components in the Figs. 5 to 7 The compartments shown have an outlet opening for water. However, water can also be discharged via inlets 201 and outlets 202 of the pressure chamber. Fig. 8 Figure 2 shows a schematic representation of the cross-section of a pressure chamber 200 according to a further embodiment of the invention. Fig. 8 Figure 1 shows an inlet 201 for introducing the at least one hollow fiber membrane 104, an outlet 202 for expelling the at least one hollow fiber membrane 104, a gas inlet 203, and an interior space 205. According to this embodiment, the interior space 205 of the pressure chamber is divided into two asymmetrical cone-shaped sections.

[0081] Fig. 9Figure 1 schematically shows another embodiment of a pressure chamber 200 according to the invention, wherein the interior 205 forms cone-shaped sections through several cross-sectional enlargements and reductions, dividing the interior into two compartments 205a and 205b, with the hollow fiber membrane 104 passing through the pressure chamber 200 via the inlet 201 and the outlet 202. The cone-shaped sections are arranged asymmetrically within the interior of the pressure chamber. The gas inlet 203 is located at compartment 205a. The inflowing gas causes a first atmospheric overpressure with a pressure P1 in compartment 205a, while a second atmospheric overpressure with a pressure P2 is established in the second compartment 205b. According to the illustration in Figure 205a, the pressure is reduced by the pressure of the inlet 205a. Fig. 5In the illustrated embodiment, P1 is greater than P2. The pressure P1 can be 3000 hPa. The pressure P2 can be 1500 hPa. The compartments create a pressure gradient within the pressure chamber. The in Fig. 9 The cross-sectional maximum of the clear width of the interior space 207a shown is larger than the cross-sectional maximum of the clear width of the interior space 207.

[0082] In the Fig. 8 and 9 Embodiments are shown in which the conical shape adjoining the inlet 201 has an opening angle α. Furthermore, in the Fig. 8 and 9 Embodiments are shown in which the conical shape adjoining the outlet 202 has an opening angle β. According to the embodiments of the Fig. 8 and 9 α is greater than β.

[0083] Fig. 10Figure 1 schematically shows another embodiment of a pressure chamber 200 according to the invention, wherein the interior 205 has several cross-sectional enlargements and several cross-sectional reductions, the cross-sectional enlargements and reductions forming several cone-shaped sections on the inside of the pressure chamber. The cone-shaped sections in the interior of the pressure chamber 200 form three compartments 205a, 205b, and 205c, with the hollow fiber membrane 104 passing through the pressure chamber 200 via the inlet 201 and the outlet 202. The cone-shaped sections on the inside of the pressure chamber are arranged symmetrically with respect to the gas inlet 203. The gas inlet 203 is located at compartment 205a.The inflowing gas causes a first atmospheric overpressure with pressure P1 in compartment 205a, a second atmospheric overpressure with pressure P2 in compartment 205b, and a third atmospheric overpressure with pressure P3 in compartment 205c. According to the in . Fig. 6 In the illustrated embodiment, P1 is greater than P2. The pressure P1 can be 3000 hPa and is greater than the pressure P2. The pressure P2 is greater than the pressure P3, which can be 1500 hPa. According to Fig. 10 The at least one gas inlet 203 of the pressure chamber 200 is arranged at a cross-sectional maximum 207 of the clear width of the interior of the pressure chamber, wherein the gas inlet is arranged centrally between the inlet 201 and the outlet 202 of the pressure chamber. The in Fig. 10The cross-sectional maxima of the clear width of the interior of pressure chamber 207, 207a and 207b shown are of different sizes. In particular, the cross-sectional maximum 207 is smaller than the cross-sectional maxima 207b and 207a.

[0084] In Fig. 10 An embodiment is shown in which the conical shape adjoining the inlet 201 has an opening angle α. Furthermore, in Fig. 10 An embodiment is shown in which the conical shape adjoining the cross-sectional maximum 207b or 207a to the centrally arranged gas inlet 203 has an opening angle γ. In this embodiment, α is smaller than γ. This has the advantage that separated water can be transported away particularly well. This makes it possible to limit the total length of the pressure chamber 200 in the direction of extension of the hollow fiber membrane 104 to less than 50 cm, preferably less than 20 cm, and more preferably less than 12 cm.

[0085] Fig. 11Figure 1 shows a schematic representation of another embodiment of a pressure chamber 200 according to the invention. This embodiment is essentially the same as the one shown in Figure 2. Fig. 10 the embodiment shown, wherein, in contrast to the embodiment in Fig. 10 the cross-sectional maxima 207, 207a and 207b are of the same size and an outlet 208, 208a and 208b for liquid, in particular water, is arranged at each of the cross-sectional maxima 207, 207a and 207b, which is separated from the hollow fiber membrane 104 in the pressure chamber 200, with the gas inlet 203 additionally arranged at the cross-sectional maximum 207.

[0086] Fig. 12 Figure 1 shows a schematic representation of another non-inventive embodiment of a pressure chamber 200. This embodiment is essentially the same as the one shown in Figure 2. Fig. 6 the embodiment shown, wherein, in contrast to the embodiment in Fig. 6Outlets 208, 208a and 208b for water are arranged at compartments 205a, 205b and 205c, which is separated from the hollow fiber membrane 104 in the pressure chamber 200.

[0087] Fig. 13 The schematic representation shows an embodiment of the pressure chamber 20, which corresponds to the one described in Fig. 10 corresponds to the embodiment shown. Fig. 13 This clarifies further details of the design. Fig. 13Figure 1 is a schematic representation in which parts of the pressure chamber are shown semi-transparently. According to the embodiment shown, the pressure chamber is tubular. Furthermore, the pressure chamber, except for the gas inlet 200, is rotationally symmetrical about its longitudinal axis. The longitudinal axis corresponds to the straight line along which the hollow fiber membrane 104 is guided through the pressure chamber. In the schematic representation shown, the hollow fiber membrane 104 lies on the longitudinal axis. Fig. 13The surrounding tubular wall 212 of the pressure chamber and structural components of the gas inlet 203 are shown semi-transparently. The wall 217 has a larger diameter in a central region 217a of the pressure chamber than in an end region 217b, 217c. The interior 205 of the pressure chamber 200 is divided into conical sections, with the conical sections 211, 212, 213, 214, 215, and 216 adjoining each other. A first conical section 211 extends from the inlet 201 for hollow fiber membranes to a first cross-sectional maximum of the interior 205 of the pressure chamber 200. A second conical section 212 then extends from the first cross-sectional maximum 217b to a cross-sectional minimum 210a. Following this, a third cone-shaped section 213 runs from the first cross-sectional minimum 210a to a second cross-sectional maximum 207.A fourth cone-shaped section 214 extends from the second cross-sectional maximum 207 to a second cross-sectional minimum 210b. A fifth cone-shaped section 215 then extends from the second cross-sectional minimum 210b to a third cross-sectional maximum 207a. A sixth cone-shaped section 216 then extends from the third cross-sectional maximum to the outlet 202 for the hollow fiber membrane 104. The gas flowing in through the gas inlet creates an atmospheric overpressure in the interior 205 of the pressure chamber, extending from the inlet for the hollow fiber membrane 201 to the outlet 202 for the hollow fiber membrane. Funnel-shaped openings 201a and 202a are located at the inlet 201 and the outlet 202, respectively. This protects the hollow fiber membrane or the set of hollow fiber membranes during introduction into and removal from the pressure chamber.In particular, all edges in the interior 205 of the pressure chamber are rounded to prevent damage to the hollow fiber membrane(s). The opening angles of the conical sections α and β are defined by the orientation of the inner surface of the conical sections relative to the longitudinal axis of the pressure chamber. In the first and sixth conical sections 211, 216, the opening angle is denoted by α. In the second and fifth conical sections, the opening angle is denoted by β. Preferably, α is smaller than β, as shown in [reference]. Fig. 10The adjoining conical sections 211, 212, 213, 214, 215, 216 of the interior 205 of the pressure chamber 200 form three compartments 205a, 205b and 205c, such that a pressure gradient is built up from the gas inlet to the inlet for the hollow fiber membrane 201 and the outlet for the hollow fiber membrane 202 when gas flows into the interior 205, as shown for the embodiment according to Fig. 10 was described. EXAMPLES Comparative example 1

[0088] Sixteen hollow fiber membranes were produced simultaneously according to an embodiment disclosed in DE 10 2016 224 627. The following procedure was used for the production of a hollow fiber membrane: A spinning solution consisting of 16 parts by weight of polysulfone (P3500 from Solvay), 4.4 parts by weight of polyvinylpyrrolidone (K82-86 from Ashland), and 79.6 parts by weight of DMAC was processed into a homogeneous spinning mass by stirring, heating to 60°C, and degassing. The spinning mass was co-extruded into a filament through an annular die with a central bore through which coagulation medium was introduced. The coagulation medium, consisting of 35% DMAC and 65% water, was guided inside the hollow filament. The temperature of the annular die was 70°C. The extruded filament was passed through a precipitation gap whose atmosphere had a relative humidity of 100%.The height of the precipitation gap was 200 mm, and a residence time of 0.4 s was set. The take-off speed of the filament was therefore 650 mm / s. The residence time of the filament in the precipitation gap depends on the take-off speed and can be varied in alternative comparative examples. The filament was introduced into the precipitation bath, consisting of water heated to 80°C, and precipitated into a hollow fiber membrane. The hollow fiber membrane was then passed through rinsing baths heated to between 75°C and 90°C. Subsequently, the hollow fiber membrane passed through a temperature control chamber of a drying unit at a temperature of 100°C to 150°C and was thus dried. The transport speed of the hollow fiber membrane was adjusted to the take-off speed. The 16 hollow fiber membranes were then picked up by a reel and stacked.The coiled hollow fiber membranes were analyzed for possible fiber defects. An increased number of flattened fibers and fiber breaks were found in the coiled hollow fiber membranes. Comparative example 2

[0089] The conditions for producing the hollow fiber membranes were chosen according to comparative example 1. The take-off speed of the spun yarn and the hollow fiber membrane was reduced to 450 mm / s. The transport speed of the hollow fiber membrane was adjusted to the take-off speed. The resulting hollow fiber membranes were free of fiber flattening and fiber breakage. Example 1

[0090] In contrast to comparative example 1, in example 1 the set of 16 hollow fiber membranes was subjected to a pressure chamber after passing through the rinsing baths and before being introduced into the temperature control chamber, according to the design shown. Fig. 10The process was carried out by introducing air through the gas inlet of the pressure chamber, resulting in a pressure of 3000 hPa in the central conical cavity, 1500 hPa in the second conical cavity, and 1300 hPa in the third. The dried hollow fiber membranes were reeled and examined for possible defects. The production of the hollow fiber membranes according to Example 1 was carried out at various take-up speeds. No fiber damage was observed at a take-up speed of 650 mm / s. The term take-up speed refers to the throughput speed of the hollow fiber membrane through the production system. According to Example 1, the take-up speed can therefore be increased, resulting in a higher production speed compared to the comparative examples and thus the prior art.This also resulted in energy savings per 1 km of hollow fiber length. Alternatively, the distance in the temperature control section can be shortened, allowing the hollow fiber membrane production plant to be operated with reduced structural requirements.

Claims

1. An apparatus (100) for the manufacture of at least one hollow fiber membrane, comprising a spinning unit comprising at least one annular gap nozzle (101) which is fluidically connected to a source of a spinning mass and a source of a coagulation medium in order to extrude at least one hollow spinning thread (102) from the spinning mass, the cavity of which hollow spinning thread is filled with the coagulation medium, a precipitation bath (103) for precipitating the at least one spinning thread (102) to form at least one hollow fiber membrane (104), if necessary, at least one rinsing unit (106) for rinsing the at least one hollow fiber membrane (104), at least one drying unit (350) for drying the at least one hollow fiber membrane (104), if necessary, a receiving unit for receiving the at least one hollow fiber membrane on a support, wherein the at least one drying unit comprises a pressure section which is constructed in such a way that a positive pressure compared with atmospheric pressure can be set in the pressure section, wherein the pressure section of the drying unit comprises a pressure chamber(200) which comprises an interior space (205), an inlet (201) for introducing the at least one hollow fiber membrane (104) into the interior space (205) of the pressure chamber, an outlet (202) for discharging the at least one hollow fiber membrane (104) from the interior space (205) of the pressure chamber and at least one gas inlet (203), wherein the at least one gas inlet (203) is in fluid communication with a gas source and the pressure section is further constructed in such a way that a positive pressure can be generated in the interior space (205) of the pressure chamber (200) via the gas source, and wherein the clear width of the interior space (205) of the pressure chamber (200) has, in the cross section parallel to the direction of travel of the at least one hollow fiber membrane, at least one enlargement of the cross section and at least one reduction of the cross section, wherein the enlargement of the cross section and the reduction of the cross section result in a conical shape of the inner side of the pressure chamber.

2. The apparatus according to claim 1, wherein the apparatus is constructed in such a way that the pressure in the pressure section of the drying apparatus is 1100 hPa to 10000 hPa or 1200 to 5000 hPa, or 1200 to 4000 hPa.

3. The apparatus according to claim 1 or 2, wherein a cross-sectional area of the inlet (201) for introducing the at least one hollow fiber membrane (2014) into the interior space of the pressure chamber (200), and of the outlet (202) for discharging the at least one hollow fiber membrane (104) from the pressure chamber (200) is less than 30 times, preferably less than 20 times, preferably less than 10 times, further preferably less than 5 times and at least 1.1 times or more the cross-sectional area of the hollow fiber membrane (104) or the total of the cross-sectional areas of the plurality of hollow fiber membranes.

4. The apparatus according to at least one of claims 1 to 3, wherein the drying unit (350) further comprises a tempering section which has a heating device which is arranged so that a temperature of 50 to 230° C can be set in the tempering section.

5. The apparatus according to claim 5, wherein the tempering section of the drying unit comprises a tempering chamber (300) which has an inlet (301) for introducing the at least one hollow fiber membrane (104) and an outlet (302) for discharging the at least one hollow fiber membrane (104).

6. The apparatus according to claim 5, wherein the pressure chamber (200) and the tempering chamber (300) are separate chambers, and that the apparatus is further constructed in such a way that the at least one hollow fiber membrane or several hollow fiber membranes obtained from the precipitation bath or, if applicable, from the rinsing bath is / are first passed through the pressure chamber (200) and then through the tempering chamber (300).

7. The apparatus according to at least one of claims 1 to 6, wherein the pressure chamber (200) of the pressure section is divided into several compartments (205a), (205b), (205c).

8. The apparatus according to at least one of claims 1 to 7, wherein the clear width of the interior space (205) of the pressure chamber (200) has, in the cross section parallel to the direction of travel of the at least one hollow fiber membrane, at least one enlargement of the cross section and at least one reduction of the cross section, wherein the enlargement of the cross section and the reduction of the cross section result in a conical shape of the inner side of the pressure chamber.

9. The apparatus according to at least one of claims 1 to 8, wherein the pressure chamber (200) has one or more outlets (208, 208a, 208b) for discharging liquid, in particular water, wherein the outlets are arranged at a position where the cross section of the clear width of the interior space of the pressure chamber (200) has a maximum.

10. A method of producing at least one hollow fiber membrane comprising the steps of providing a source of a spinning mass, providing a source of a coagulation medium, co-extruding the spinning mass and the coagulation medium through at least one annular gap nozzle (101) into at least one hollow spinning thread (102), the cavity of which is filled with the coagulation medium, introducing the at least one spinning thread (102) into a precipitation bath (103) containing a precipitating agent and precipitating the at least one spinning thread (102) to at least one hollow fiber membrane (104), optionally subsequently introducing the at least one hollow fiber membrane (104) into a rinsing bath (106) containing a rinsing agent, introducing the at least one hollow fiber membrane (104) which has been obtained from the precipitation bath (103), or, if applicable, introducing the at least one hollow fiber membrane which has been obtained from the rinsing bath (106), into a drying unit (450), if applicable, receiving, on a support, the at least one hollow fiber membrane (104) obtained from the drying unit (350), wherein the at least one hollow fiber membrane (104) passes through a pressure section in the drying unit, in which pressure section a positive pressure compared with atmospheric pressure is generated by introducing a gas, which is selected from the group consisting of air, nitrogen, argon, carbon dioxide, water vapor or mixtures thereof, into the pressure section and in which at least part of the precipitating agent or rinsing agent contained in the at least one hollow fiber membrane (104) is separated from the at least one hollow fiber membrane, wherein the pressure section of the drying unit comprises a pressure chamber (200) and the at least one hollow fiber membrane (104) is introduced through an inlet (201) into the interior space (205) of the pressure chamber (200), wherein the clear width of the interior space (205) of the pressure chamber (200) has, in the cross section parallel to the direction of travel of the at least one hollow fiber membrane, at least one enlargement of the cross section and at least one reduction of the cross section, wherein the enlargement of the cross section and the reduction of the cross section result in a conical shape of the inner side of the pressure chamber, and the hollow fiber membrane (104) is discharged from the interior space (205) of the pressure chamber via an outlet (202).

11. The method according to claim 10, wherein the positive pressure - compared with atmospheric pressure - in the pressure section is set to a pressure of from 1100 hPa to 10,000 hPa or 1200 to 4000 hPa.

12. The method according to claim 10 or 11, wherein the pressure section is tempered to 30 to 125° C, preferably 20 to 110 °C, further preferably 30 to 90 °C.

13. The method according to at least one of claims 10 to 12, wherein the transport speed of the spinning thread is 550 mm / s to 1000 mm / s, preferably 650 mm / s to 90 mm / s, further preferably 750 mm / s to 800 mm / s.