Systems and methods for producing hollow fiber membranes

Abstract

The present invention relates to a system and a method for the production of at least one hollow fiber membrane, wherein a spinning mass is extruded through a spinning unit to form a spinning thread and precipitated in a precipitation tank to form hollow fiber membranes, the hollow fiber membranes are optionally washed in a washing tank, and the hollow fiber membranes are also guided through at least one drying unit, the drying unit having a pressure section designed so that a positive pressure can be set in the pressure section compared to atmospheric pressure, and at least a portion of the precipitation or washing agent contained in the at least one hollow fiber membrane (104) is removed from the at least one hollow fiber membrane.

Description

[Technical field]

[0001] The present invention relates to an apparatus for the production of hollow fiber membranes. In particular, the present invention relates to an apparatus including an improved drying unit for the production of hollow fiber membranes.

[0002] In yet another aspect, the present invention relates to a method for producing hollow fiber membranes. In particular, the present invention relates to a method for producing hollow fiber membranes having an improved drying step for the hollow fiber membranes. [Background technology]

[0003] Hollow fiber membranes are widely used in filtration technology. In particular, hollow fiber membranes are used in medical technology, for example in dialysis, to remove harmful metabolites from the blood of patients with kidney disease. Likewise, hollow fiber membranes are also used in water treatment to treat polluted water. In such applications, hollow fiber membranes are integrated into so-called hollow fiber membrane filters. In these hollow fiber membrane filters, a large number of hollow fiber membranes are arranged in a cylindrical housing of the hollow fiber membrane filter to form a hollow fiber membrane bundle. A hollow fiber membrane filter for dialysis contains 10,000 hollow fiber membranes, which in a typical version of such a filter have a length of about 23 cm. In the field of medical technology, especially in the field of dialysis, such hollow fiber membrane filters are provided as disposable articles with regard to their use for hygienic reasons. Thus, there is a great demand for hollow fiber membrane filters even for dialysis alone, so that patients with kidney disease can be provided with the essential dialysis treatment.

[0004] In order to meet the high demands on hollow fiber membranes for the production of hollow fiber membrane filters, great demands are placed on the productivity of the production process of hollow fiber membranes. Methods in the so-called dry-wet spinning process are well established in that a fluid spinning mass is first provided, which is extruded onto a spinning thread, which is agglomerated and precipitated into hollow fiber membranes in a phase inversion process. Such spinning processes are designed in such a way that a number of simultaneously produced hollow fiber membranes are combined to form a group of hollow fiber membranes and wound on a reel to form a bundle strand. The bundle strand is then divided into the required lengths into individual hollow fiber membrane bundles that are subsequently used in hollow fiber membrane filters.

[0005] The known methods from the prior art for the manufacture of hollow fiber membranes using a dry-wet process are based on a prepared spin mass, which is generally produced in the form of a polymer solution of a hydrophobic polymer, a hydrophilic polymer, if applicable further additives, and a polar aprotic solvent.

[0006] The spun mass is extruded in the spinning unit through a spinneret. The spinning unit can be equipped with multiple spinnerets so that a group of hollow spun threads can be extruded through the spinneret. A single spinneret is configured such that the cavity of the spinning thread is filled with a coalescing medium that causes a phase inversion of the spun mass in the spinning thread. In the present application, the terms "cavity" and "lumen" are used synonymously. Spinnerets of this type are known in the prior art. By way of example, reference is made here to the spinneret shown in Figures 1 to 5 of WO 03 / 076701 A1. The individual spinning threads are guided vertically through a deposition gap and are fed, for example, into water, into a deposition bath where the membrane structure of the hollow fiber membrane is further consolidated. The individual hollow fiber membranes are then pumped from the precipitation tank by pulleys and guided through further pulleys and guides to remove the solvent and excess polymer from the membranes, usually into one or more wash tanks, which often contain water as the wash medium.

[0007] After passing through the precipitation and washing tanks, the hollow fiber membranes are completely filled with liquid, in particular water, i.e. the cavities of the hollow fiber membranes and the pores in the walls of the hollow fiber membranes are filled with liquid, in particular water. The hollow fiber membranes thus carry, for example, several times their own weight of liquid after being guided out of the precipitation or washing tanks.

[0008] After leaving the washing tank, the hollow fiber membranes are dried according to known manufacturing methods by introducing the individually guided hollow fiber membranes through pulleys and suitable guiding means into a drying chamber. In the drying chamber, the distance to be covered by the hollow fiber membranes is determined by the pulleys and guiding means. Based on the conveying speed, this results in a predetermined residence time of the hollow fiber membranes in the drying chamber. Drying is achieved by applying an elevated temperature. Here, the temperature is set to a level such that the liquids conveyed in the hollow fiber membranes, in particular water, are vaporized. The vaporized liquid is discharged in a dry state from the drying chamber after the hollow fiber membranes have passed through it, so that it can be fed to further processing stages.

[0009] Within the manufacturing process, a corrugation step of the hollow fiber membranes can be carried out after drying of the hollow fiber membranes, where the hollow fiber membranes are mechanically embossed with corrugations using a suitable gear. It is further known that a group of hollow fiber membranes is brought together and wound up by a reel. The hollow fiber membrane bundles required for the manufacture of hollow fiber membrane filters are obtained by cutting out individual bundle strands from the hollow fiber membranes wound on a reel.

[0010] The extrusion speed of the spinning mass, the pulleys and guide means, as well as the reel for receiving the hollow fiber membranes, determine the speed at which the hollow fiber membranes can be conveyed through the device for producing hollow fiber membranes. Conveying speeds of about 450 mm / s are known from the prior art for the production of hollow fiber membranes. The conveying speed of the hollow fiber membranes ultimately determines the productivity of the production process. However, the conveying speed cannot be increased at will, since the increasing mechanical impact on the hollow fiber membranes during conveying is likely to result in an increasing number of damaged fibers (yarns). In particular, if the conveying speed is selected too high, it is to be expected that individual fibers (fibers, yarns) will break or break. Such damage to the hollow fiber membranes makes the hollow fiber membranes that have been brought together and wound up by the reel unusable in the form of separate hollow fiber membrane bundles for further processing into hollow fiber membrane filters.

[0011] The drying process of known manufacturing methods may also have a damaging effect on the hollow fiber membranes. To achieve the desired high productivity, the prior art methods require high temperatures to be used to completely dry the fibers (yarns) at a specified conveying speed in the drying chamber. If the temperature is too high, deformations may be observed on the hollow fiber membranes, making them unsuitable for use in the construction of hollow fiber membrane filters. In addition, if the exposure to high temperatures is too long, thermo-oxidative damage to the hollow fibers may occur. In addition, high drying temperatures in the drying chamber require a large amount of energy, which in turn makes the manufacturing process more expensive.

[0012] GB 731,415 discloses a device for drying textile fibers, particularly artificial silk. GB 731,415 describes a drying channel through which a plurality of textile fibers, for example arranged in parallel, pass. The drying channel includes a heating element. It also describes that air is supplied to the drying channel to dry the textile fibers.

[0013] US 2,509,279 describes a device for the treatment of fibres with a fluid or gas: the fibres pass through a tube through which the gas can be supplied.

[0014] DE 509 429 shows a device for drying spun artificial silk threads. The artificial silk threads are washed with cold water and passed through a tube into which hot air is fed for drying. The threads are then guided over a heated plate and wound onto a reel. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] WO 03 / 076701 A1 [Patent Document 2] GB 731,415 [Patent Document 3] US 2,509,279 [Patent Document 4] DE 509 429 [Patent Document 5] WO17184817A1 [Patent Document 6] DE 10 2017 204 524 A1 [Patent Document 7] DE 10 2016 224 627 [Non-patent literature]

[0016] [Non-Patent Document 1] Boschetti et al. (2013) [Non-Patent Document 2] Boschetti-de-Fierro et al. (2013) [Non-Patent Document 3] Granath et al. (1967) [Non-Patent Document 4] Sephadex.J Chromatogr A.1967, 28(C), 69~81 Summary of the Invention [Problem to be solved by the invention]

[0017] From the present point of view, the methods for producing hollow fiber membrane filters known from the prior art are no longer sufficient in terms of their productivity and efficiency.In particular, from the point of view of the production of hollow fiber membrane filters, there is a permanent need to increase the speed of production of hollow fiber membranes.In addition, there is a need to optimize the production process in the production of hollow fiber membranes in an energy-efficient and cost-effective manner. [Means for solving the problem]

[0018] In a first aspect, this object is solved by a device having the features of claim 1. Dependent claims 2 to 10 represent alternative embodiments.

[0019] In a second aspect, this object is solved by a method having the features of claim 11. Dependent claims 12 to 15 represent further preferred embodiments.

[0020] In a third aspect, this object is solved by a method for the production of hollow fiber membranes, characterized in that the spinning speed of the hollow thread is set to more than 550 mm / s, preferably more than 650 mm / s, more preferably more than 750 mm / s. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] In a first aspect, the present invention relates to an apparatus for the manufacture of at least one hollow fiber membrane comprising a spinning unit comprising at least one annular gap nozzle fluidly connected to a source of spinning mass and to a source of coalescence medium for extruding at least one hollow spun thread from the spinning mass and for filling the cavity of the hollow spun thread with coalescence medium, a precipitation bath for precipitating the at least one spinning thread to form at least one hollow fiber membrane, optionally at least one washing unit for washing the at least one hollow fiber membrane, at least one drying unit for drying the at least one hollow fiber membrane and optionally a receiving unit for receiving the at least one hollow fiber membrane on a support, characterized in that at least one drying unit comprises a pressure section, which is configured in such a way that a positive pressure can be set in the pressure section compared to atmospheric pressure.

[0022] The apparatus may be configured such that at least one spinning thread is fed into a precipitation tank and precipitated onto at least one hollow fiber membrane, and further the at least one hollow fiber membrane obtained from the precipitation tank is optionally introduced into a washing tank for washing, further the at least one hollow fiber membrane obtained from the precipitation tank or the at least one hollow fiber membrane obtained from the washing tank is introduced into a drying unit for drying, and further the apparatus may be configured such that the at least one hollow fiber membrane dried in the drying unit is guided to a receiving unit and received on a support.

[0023] For the sake of simplicity, in further descriptions, unless otherwise specified, the terms "at least one annular gap nozzle" or "annular gap nozzle", "at least one spinning thread" or "spinning thread", "at least one hollow fiber membrane" or "hollow fiber membrane" shall always be understood as including the plural, i.e. "multiple annular gap nozzles", "multiple spinning threads" and "multiple hollow fiber membranes". Modern hollow fiber spinning apparatuses can contain more than 1000 or even 2000 annular gap nozzles.

[0024] The walls of at least one hollow fiber membrane that can be produced using the above-mentioned device are preferably porous. When the hollow fiber membrane is passed through the precipitation bath and, if present, the washing bath, the pores and cavities, i.e. the lumen, of the hollow fiber membrane are filled with liquid, in particular water. The inventors have found that when the produced hollow fiber membrane is passed through the pressure section of the drying unit, at least a part of the liquid, in particular water, can be separated from the pores and cavities, i.e. the lumen, of the hollow fiber membrane by using a positive pressure set compared to atmospheric pressure. This significantly reduces the weight of the hollow fiber membrane containing the liquid. Surprisingly, the conveying speed of the hollow fiber membrane in this device could be increased without fiber breakage or other damage, such as the resulting flattening. In particular, thermal drying could be carried out at a lower temperature or with the same dryness within a shorter hollow fiber membrane section length, so that significant energy savings can be achieved overall in the production process of the hollow fiber membrane, and thermal oxidative damage of the hollow fiber is reduced. Furthermore, the hollow fibers produced using the device according to the invention have a particularly low residual content of solvent in the spinning mass.

[0025] The term "apparatus for the production of at least one hollow fiber membrane" shall be understood in the sense of the present application to mean that the apparatus as defined in claim 1 can be used to produce one hollow fiber membrane or several hollow fiber membranes at the same time. In the sense of the present application, the term "production of at least one hollow fiber membrane" refers to the steps of forming one or more spinning threads from a spinning mass, depositing one or more spinning threads into one or more hollow fiber membranes and, if applicable, washing one or more hollow fiber membranes, as well as drying one or more hollow fiber membranes and, if applicable, receiving one or more hollow fiber membranes on a support. The term "production" may also include further intermediate steps that are not mentioned.

[0026] The term "spinning unit" within the meaning of the present application shall be understood to mean an assembly of components used to extrude the spinning mass into a spinning thread.

[0027] The term "spun mass" in the sense of the present application shall be understood to mean a polymer solution in which at least one polymer is dissolved in a solvent. In particular, in the sense of the present application, the spun mass may comprise a polymer solution composed of at least one hydrophobic polymer and at least one hydrophilic polymer. Furthermore, the hydrophobic polymer may in particular be polysulfone (PSU) and the hydrophilic polymer may in particular be polyvinylpyrrolidone (PVP). The solvent may be a polar aprotic solvent, in particular N-methylpyrrolidone (NMP), N,N-dimethylacetamide or dimethylsulfoxide (DMSO). Such materials are preferred in the manufacture of dialyzers, whereas for example in heart-lung machines, highly hydrophobic materials such as polypropylene (PP) or polymethylpentene (PMP) are used.

[0028] The term "spun thread" in the sense of the present application shall be understood to mean the thread extruded from the spun mass and not yet assuming the pore structure of the resulting hollow fiber membrane. In particular, in the sense of the present application, the spun mass before being introduced into the precipitation bath, extruded into the thread in the "deposition gap", is called the spun thread. The "deposition gap" is understood to be the distance from the extrusion of the spinning thread to its entry into the precipitation bath. The speed at which the spinning thread passes through the deposition gap is called the "drawing speed" in the sense of the present application. The "conveying speed" can be adapted to the drawing speed or can be slightly higher than the drawing speed in order to guide the hollow fiber membrane through the device in a taut manner. If the conveying speed is increased, the drawing speed is also increased in a corresponding manner.

[0029] The spinning unit comprises one or more annular gap nozzles. The term "annular gap nozzle" in the sense of the present application shall be understood to mean an extrusion nozzle that allows the spinning mass to be extruded into a hollow spinning thread. The annular gap nozzle has a central bore through which the coalescing medium can be extruded. Furthermore, the annular gap nozzle has an annular gap, concentric with the central bore, through which the spinning mass is extruded. Annular gap nozzles of this type are known from the prior art. The term "annular gap nozzle" shall also be understood to encompass such an extrusion nozzle comprising several annular gaps arranged concentrically with the central bore.

[0030] The spinning unit further comprises a feed channel for fluidly connecting a source of the spinning mass with the annular gap or the concentrically arranged annular gaps of the annular gap nozzle and further for fluidly connecting a source of the coalescing medium with the central bore of the annular gap nozzle, the spinning mass and the coalescing medium being co-extruded through the annular gap nozzle to form a hollow spun thread, thereby filling the cavity of the spinning thread with the coalescing medium.

[0031] The term "coagulation medium" in the sense of the present application shall be understood to mean a liquid medium which, in connection with the inner surface of the hollow-spun thread, induces a phase inversion of the spun mass in the spinning thread. In the method described in the present application, a coagulation medium is selected which consists of a mixture of aprotic polar solvents and polar protic solvents. In a particular embodiment according to the present invention, the coagulation medium is composed of N-methylpyrrolidone (NMP), N,N dimethylacetamide or dimethylsulfoxide (DMSO) and water. Coagulation of the spinning thread initiated with this coagulation medium is also called "non-solvent induced phase separation" (NIPS). Furthermore, in the sense of the present application, the coagulation of the spinning thread can be initiated using the "temperature induced phase separation" (TIPS) method. Phase inversion and coagulation of the spinning thread are initiated by a temperature reduction.

[0032] The term "precipitation bath" in the sense of the present application shall be understood to mean a structural unit comprising a reservoir of a precipitation medium into which the extruded spinning thread is introduced. In the precipitation bath, the spinning thread is precipitated, whereby the cohesive structure of the spinning thread is further consolidated into a porous hollow fiber membrane. According to the invention, a polar protic solvent, in particular water, is preferably used as the "precipitation medium". However, as an alternative or as part of a mixture, the polar protic solvent may contain alcohols or other protic liquids. The precipitation medium may contain polar aprotic solvents as components. After the hollow fiber membrane has passed through the precipitation bath, the pores and cavities of the hollow fiber membrane are filled with liquid.

[0033] The term "washing unit" shall be understood to mean a structural unit comprising a reservoir of washing liquid into which the hollow fiber membranes obtained from the precipitation bath are introduced. Residual solvent and polymer components that may still adhere to the hollow fiber membranes after the precipitation bath are removed from the hollow fiber membranes. According to the invention, it is preferred to use water as washing liquid. However, the washing unit may comprise several reservoirs containing different washing liquids. After the hollow fiber membranes have passed through the washing unit, the pores and cavities of the hollow fiber membranes are filled with liquid, in particular water.

[0034] The term "drying unit" shall be understood to mean a structural unit comprising a space into which the hollow fiber membranes can be introduced and dried. Preferably, the hollow fiber membranes obtained from the precipitation bath or, where applicable, the washing bath and full of liquid, in particular water, are dried by means of the drying unit to a residual liquid content of less than 10% by weight, more preferably less than 3% by weight, based on the total weight of the fiber. The drying unit may comprise a space into which the hollow fiber membranes are introduced, and in which the distance over which the hollow fiber membranes will travel is specified by pulleys and guide means, so that they remain in the (space of) the drying unit for a specified period of time that depends on the conveying speed.

[0035] The term "receiving unit" is understood to mean a device comprising a support prepared to receive hollow fiber membranes. In particular, this support can be a reel, a drum, a winder or a roll.

[0036] The term "pressure section" in the sense of the present application shall be understood to mean a structural unit which is in the drying unit and in which a positive pressure can be set with respect to the ambient pressure of the installation device according to claim 1. The term "positive pressure" should be taken in relation to the normal atmospheric pressure of 1013.25 hPa and means in the context of the present application a pressure above normal atmospheric pressure.

[0037] The skilled person will know further details of the apparatus for the production of hollow fiber membranes. In particular, it will be known to the skilled person that the apparatus for the production of hollow fiber membranes comprises means for guiding the spinning thread through a precipitation bath and for guiding the spinning thread and the hollow fiber membranes obtained from the spinning thread by the precipitation bath through a washing bath, a drying unit and a receiving unit. In this connection, the skilled person will be considered to be familiar with the corresponding guide rollers, guide rakes or guide plates.

[0038] Moreover, the skilled person is assumed to be familiar with the corresponding process parameters and spinning conditions that affect the extrusion of the spinning mass and the formation of the hollow fiber membrane. In particular, the skilled person will know that the temperature of the annular gap nozzle, the relative atmospheric humidity in the deposition gap, the height of the deposition gap, the composition of the spinning mass and the coalescing medium, as well as the temperature of the deposition bath have an influence on the formation of the membrane structure of the hollow fiber membrane, for example, its porosity and separation properties. Process parameters for the TIPS method are known, for example, from WO17184817A1.

[0039] Yet another embodiment of the first aspect of the present invention is characterized in that the pressure section of the drying unit comprises a pressure chamber comprising an interior space, an inlet for introducing at least one hollow fiber membrane into the interior space of the pressure chamber, an outlet for discharging the at least one hollow fiber membrane from the interior space of the pressure chamber, and at least one gas inlet, the at least one gas inlet being in fluid communication with a gas source, and the pressure section is further configured to be capable of generating a positive pressure in the interior space of the pressure chamber through the gas source.

[0040] According to this embodiment, a positive pressure can be applied which can act particularly effectively on the hollow fiber membranes guided through the pressure chamber. For example, the pressure chamber can be, for example, tubular or slit-shaped and configured as a channel into which gas is introduced to set the positive pressure. In certain embodiments, it is possible to envisage that the inner diameter of the pressure chamber is not constant, in particular that this inner diameter is enlarged relative to the inlet and outlet of the pressure chamber. It is envisaged that at least one hollow fiber membrane or a group of hollow fiber membranes is guided through the pressure chamber, and that at least a part of the water transported in the hollow fiber membrane is removed by the set positive pressure. The positive pressure can be set by the inflow of gas through the gas inlet into the pressure chamber. The removal of water is particularly effective when the liquid, in particular the water, is discharged from the pressure chamber in a direction opposite to the transport direction of the hollow fiber membranes, in particular, so that the water separated from the hollow fiber membranes can be discharged from the inlet of the pressure chamber.

[0041] The term "pressure chamber" in the sense of the present application means a delimited space in which a higher pressure can be set when compared to the ambient pressure. In the sense of the present application, the pressure chamber comprises an inlet opening and an outlet opening for the passage of the hollow fiber membrane.

[0042] The term "gas source" shall be understood to mean a device capable of supplying gas at a positive pressure with respect to the surrounding atmosphere. In particular, a gas source in the sense of the present application may be a pressurized gas container, for example a gas cylinder. However, alternatively, the gas source may be a compressor used to supply compressed air. The gas introduced into the pressure chamber may escape through the inlet and the outlet of the pressure chamber according to the above-mentioned embodiments.

[0043] The term "fluid connection" shall be understood to mean a connection making it possible to guide gas from a gas source to a gas inlet of a pressure chamber. Such a fluid connection may be a pipe or a hose.

[0044] Further embodiments of the first aspect of the invention are characterized in that the apparatus is configured such that the pressure in the pressure section of the drying apparatus is 1100 hPa to 10,000 hPa, 1200 hPa to 5000 hPa, or 1200 hPa to 4000 hPa. It has been shown that the pressure can be optimally adjusted within this range based on the porosity and separation properties of the membrane, thereby providing good liquid removal.

[0045] Yet 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 internal space of the pressure chamber and the cross-sectional area of ​​the outlet for discharging the at least one hollow fiber membrane from the pressure chamber are smaller than 30 times, preferably smaller than 20 times, more preferably smaller than 10 times, more preferably smaller than 5 times the cross-sectional area of ​​the hollow fiber membrane or the sum of the cross-sectional areas of the hollow fiber membranes. According to some embodiments, the cross-sectional area of ​​the inlet is larger than 1.1 times, larger than 2 times, or larger than 3 times the cross-sectional area of ​​the hollow fiber membrane or the sum of the cross-sectional areas of the hollow fiber membranes.

[0046] The size of the cross-sectional area of ​​the inlet and outlet of the pressure chamber can be used to adjust the pressure increase depending on the number of hollow fiber membranes passed through the pressure chamber. If the cross-sectional area of ​​the inlet and outlet is too small, it becomes more difficult to guide the hollow fiber membrane through the pressure chamber. This may be the case when the cross-sectional area of ​​the inlet and outlet is smaller than 1.1 times the cross-sectional area of ​​the hollow fiber membrane or the sum of the cross-sectional areas of the hollow fiber membranes. If the cross-sectional area is too large, it becomes more difficult to set a positive pressure and the amount of gas required to obtain the desired gas pressure increases.

[0047] The inlet and outlet of the pressure chamber can be configured so that up to 128 fibers can be passed through the pressure chamber. If a large number of hollow fiber membranes are passed through the pressure chamber, the partial removal of liquid, especially water, from the fibers in the group of hollow fiber membranes becomes more difficult. Preferably, groups of 2 to 64 hollow fiber membranes, in an alternative embodiment groups of 5 to 32 hollow fiber membranes, in yet another alternative embodiment groups of 10 to 20 hollow fiber membranes are guided through the pressure chamber. If it is necessary to simultaneously remove liquid from a larger number of hollow fiber membranes by the positive pressure of the gas atmosphere, several pressure chambers can be arranged simultaneously and in parallel in the device for producing hollow fiber membranes.

[0048] A further embodiment of the first aspect of the present invention is characterized in that the drying unit comprises a tempering section, the tempering section having a heating device arranged such that a temperature of from 50°C to 230°C can be set in the tempering section.

[0049] Drying units including a combination of a pressure section and a tempering section have been shown to be particularly effective and efficient for drying hollow fiber membranes. In particular, according to this embodiment, it is envisaged that partial removal of liquid, in particular water, from the hollow fiber membranes is performed by the pressure section. This allows hot air to penetrate into the pores and cavities of the hollow fiber membranes, thereby allowing the yarns to be dried more efficiently in the tempering section.

[0050] The term "tempering section" means a section of the drying unit in which the temperature is set between 50°C and 230°C. This temperature range must be selected so that the hollow fiber membranes are not damaged, but on the other hand sufficient drying of the hollow fiber membranes can be achieved. In this respect, for drying of the hollow fiber membranes in the drying section, in particular temperature ranges of 70°C or higher, 90°C or higher, or 110°C or higher, and 210°C and lower, 190°C and lower, or 170°C and lower, in particular 70°C to 210°C, 90°C to 190°C, or 110°C to 170°C, are provided. Alternatively, drying at temperatures between 170°C and 230°C can also be provided, this range resulting in particularly fast drying.

[0051] Yet another embodiment of the first aspect of the present invention is characterized in that the tempering section of the drying unit comprises a tempering chamber having an inlet for introducing at least one hollow fiber membrane and an outlet for discharging at least one hollow fiber membrane.

[0052] A further embodiment of the first aspect of the invention is characterized in that the pressure chamber and the tempering chamber are separate chambers and the device is further configured such that at least one hollow fiber membrane obtained from the precipitation bath or, if applicable, the washing bath is first passed through the pressure chamber and then through the tempering chamber. The separation of the pressure chamber and the drying chamber has the advantage that the liquid can be removed beforehand in the upstream pressure chamber without the need to vaporize it. The liquid is then conveyed back into the washing bath, thereby reducing the liquid consumption in the washing bath or can be recovered separately and reused. After entering the drying chamber, significantly less liquid needs to be vaporized, thereby accelerating the drying process and / or reducing energy consumption by reducing the required enthalpy of evaporation.

[0053] A further 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 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 causes a particularly efficient drainage of liquid, in particular water, from the pressure chamber and thus an efficient removal of liquid from the at least one hollow fiber membrane.

[0054] According to this embodiment, the gas inlet is arranged in at least one compartment of the pressure chamber. A water outlet for the discharge of water separated from the hollow fiber membrane can be arranged in a further compartment of the pressure chamber. The compartments can be formed in the pressure chamber by a suitable geometric design in the pressure chamber and can be separated from the other compartments. The compartments can be separated from each other by a partition wall. In this context, the term "separation" means that different pressures are independently established in the compartments, such that a first pressure in a first compartment of the pressure chamber is different from a second pressure in a second compartment. The compartments open towards the central passage area of ​​the hollow fiber membrane.

[0055] Yet another embodiment of the first aspect of the present invention is characterized in that the clear width of the internal space of the pressure chamber has at least one enlarged cross-sectional area and at least one reduced cross-sectional area in a cross section parallel to the direction of travel of the hollow fiber membrane, the enlarged cross-sectional area and the reduced cross-sectional area preferably resulting in a cone-shaped inner surface of the pressure chamber.

[0056] The conical inner surface of the pressure chamber has the advantage that the water separated from the hollow fiber membranes can be removed particularly effectively. Due to the effective removal of water, the total length of the pressure chamber in the fiber direction can be kept shorter than 50 cm, preferably shorter than 20 cm, more preferably shorter than 12 cm, thereby allowing a more compact construction of the device for the production of hollow fiber membranes. According to a particular embodiment, the total length of the pressure chamber is at least 5 cm.

[0057] According to a preferred embodiment, several enlarged and reduced cross-sections follow one another alternatingly, so that several compartments with conical sections are formed in the internal space of the pressure chamber.

[0058] Yet 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 position where the cross section of the clear width of the inner space of the pressure chamber has a maximum, preferably in the center between the inlet for introducing at least one hollow fiber membrane into the pressure chamber and the outlet for discharging at least one hollow fiber membrane from the pressure chamber, this embodiment facilitating the flow of gas to the inlet and outlet of the one or more hollow threads.

[0059] A further embodiment of the first aspect of the present invention is characterized in that the pressure chamber has one or more outlets for discharging liquid, in particular water, which are preferably arranged at the position where the cross section of the clear width of the inner space of the pressure chamber has a maximum. The liquid, in particular water, separated from the at least one hollow fiber membrane can be discharged from the inner space of the pressure chamber through the outlet. This improves the efficiency of the drying process in the pressure chamber, since the liquid can be transported out particularly quickly and efficiently.

[0060] Yet another embodiment of the first aspect of the invention is characterized in that the pressure chamber has an inlet and an outlet for one or more hollow threads, and a funnel-shaped opening is bonded above the inlet. This protects the hollow fiber membrane or group of hollow fiber membranes when they are introduced into the pressure chamber. The outlet can have a funnel-shaped opening. All edges, especially all edges of the inlet, are preferably rounded.

[0061] In particular, in an embodiment of the first aspect of the present invention, the device for producing at least one hollow fiber membrane is characterized in that it is configured to produce "high flux" hollow fiber membranes, "intermediate cut-off" hollow fiber membranes, "high cut-off" hollow fiber membranes or hollow fiber membranes for plasma separation for extracorporeal blood processing.

[0062] The term "high flux" as used herein 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, which can be determined by measuring the dextran sieving coefficient according to Boschetti et al. (2013). The average pore radius is in the region of 3.5 nm to 5.5 nm, where the pore size is determined by the MWCO based on the analysis of the molecular weight distribution by gel chromatography as in Boschetti-de-Fierro et al. (2013) and Granath et al. (1967) and Sephadex. J Chromatogr A. 1967, 28(C), 69-81. The main difference between high flux and low flux membranes is the higher water permeability and the ability to remove small to medium molecules such as β2-microglobulin.

[0063] The term "intermediate cut-off" membranes is used for membranes that have separation properties that are between those of high-flux and high-cut-off membranes. "Low-flux" membranes have separation properties that are characterized by a steeper sieving curve than those of high-flux membranes.

[0064] The term "high cut-off" as used herein refers to hollow fiber membranes having a MWRO between 15 kDa and 20 kDa and a MWCO between 170 kDa and 320 kDa. The hollow fiber membranes are characterized by a pore radius between 8 nm and 12 nm on the face of the selective layer. The determination of the MWRO and MWCO of the "high cut-off" hollow fiber membranes referred to herein is determined according to the method of Boschetti-de-Fierro et al. (2013).

[0065] Hollow fiber membranes for plasma separation are characterized in that their MWCO is greater than the value defined for "high cut-off" hollow fiber membranes. In particular, the pore size of hollow fiber membranes for plasma separation is such that only the cellular components of blood are retained by the membrane.

[0066] "High flux", "medium cut-off", "high cut-off" or hollow fiber membranes for plasma separation can be produced particularly well according to what is described according to the second embodiment. The mentioned hollow fiber membranes have high liquid permeability, especially high water permeability, so that the removal of liquids, especially water, from the hollow fiber membrane in the pressure chamber can be carried out particularly effectively. This applies in particular to "high cut-off" hollow fiber membranes with a MWRO of 10 to 20 kDa.

[0067] According to the invention, two or more pressure chambers can be connected in series. This is especially advantageous when only a relatively small part 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 a lot of effort due to their small pore diameter.

[0068] In a second aspect, the present invention relates to a method for producing a hollow fiber membrane comprising the steps of: providing a source of a spun fiber mass; providing a source of a coalescing medium; co-extruding the spun fiber mass and the coalescing medium through at least one annular gap nozzle onto at least one hollow fiber thread, filling the cavity of the hollow fiber thread with the coalescing medium; introducing the at least one spun fiber thread into a precipitation bath containing a precipitation agent, precipitating the at least one spun fiber thread into at least one hollow fiber membrane, optionally thereafter introducing the at least one hollow fiber membrane into a washing bath containing a washing agent, and removing the at least one hollow fiber membrane obtained from the precipitation bath or, if applicable, the washing agent. The present invention relates to a method for producing at least one hollow fiber membrane, comprising the steps of introducing at least one hollow fiber membrane obtained from a purification tank into a drying unit and, if applicable, receiving on a support the at least one hollow fiber membrane obtained from the drying unit, characterized in that the at least one hollow fiber membrane passes through a pressure section in the drying unit, a positive pressure is generated in the pressure section compared to atmospheric pressure by introducing a gas into the pressure section, and at least a part of the precipitating agent or washing agent contained in the at least one hollow fiber membrane in the pressure section is separated from the at least one hollow fiber membrane.

[0069] The person skilled in the art will know the basic procedures and details of the method for the production of hollow fiber membranes. In particular, in the method for producing hollow fiber membranes, it is known to guide the spinning thread through and out of the deposition bath using means for guiding the spinning thread and the hollow fiber membrane, and then to convey it to a washing bath, a drying unit and a receiving unit. In this connection, the person skilled in the art will know the corresponding guide rollers, guide rakes, guide plates or corrugation tools that can be used to carry out the method according to the invention.

[0070] The skilled person will also know the process parameters and spinning conditions for extruding the spun mass and for forming the hollow fiber membrane. In particular, the skilled person will know that the formation of the membrane structure of the hollow fiber membrane, for example its porosity, is influenced by the temperature of the annular gap nozzle, the relative atmospheric humidity in the deposition gap, the height of the deposition gap, the composition of the spun mass and the coalescence medium, and the temperature of the deposition bath. In particular, the method according to the second aspect is suitable for producing hollow fiber membranes for nanofiltration, ultrafiltration and microfiltration. The coalescence of the spun threads preferably occurs according to the principle of "non-solvent induced phase separation" (NIPS). Alternatively, the coalescence of the spun threads can be controlled according to "temperature induced phase separation" (TIPS). The TIPS method with hydrophobic polymers is particularly suitable for the separation of gases, in particular in cardiopulmonary bypass. This applies in particular to the polymers PMP (polymethylpentene) and polypropylene (PP).

[0071] A further embodiment of the second aspect of the invention is characterized in that a corrugation tool is arranged downstream of the drying unit and potentially upstream of the receiving unit. In the context of the present application, "corrugation tool" is to be understood as meaning a tool that allows the hollow fiber membranes to be formed into a corrugated geometry. Corresponding tools are known from the prior art. See in particular the details disclosed in DE 10 2017 204 524 A1.

[0072] The method according to the second aspect is suitable for the production of hollow fiber membranes. The method is also suitable for the simultaneous production of a group of (several) hollow fiber membranes. In this case, the spinning mass and the agglomeration medium are extruded through several annular gap nozzles arranged in the spinning unit to form a spinning thread group, which is further processed into a dry hollow fiber membrane by the method according to the invention. In particular, the apparatus for the production of hollow fiber membranes can be configured so that 1 to 64 hollow fiber membranes, 5 to 32 hollow fiber membranes, 10 to 20 hollow fiber membranes or up to 128 hollow fiber membranes can be produced simultaneously.

[0073] In the above-mentioned production method, the hollow fiber membrane is filled with liquid, especially water, when it is passed through the precipitation bath and, if present, the washing bath. In this production method, the weight of the hollow fiber membrane can be significantly reduced by the pressure section of the drying unit. This makes it possible to increase the conveying speed of the hollow fiber membrane in the device for producing the hollow fiber membrane without fiber breakage or other fiber damage such as flattening occurring. In particular, thermal drying can be performed at a lower temperature or over a shorter distance, with the same degree of dryness being obtained, so that significant overall energy savings can be achieved in this production process and / or thermo-oxidative damage to the hollow fiber can be reduced or avoided. Furthermore, the hollow fiber produced according to the invention has only a particularly low content of spinning mass solvent.

[0074] Yet another embodiment of the second aspect of the invention is characterized in that the positive pressure in the pressure section (relative to atmospheric pressure) is set to a pressure of 1100 hPa to 10,000 hPa, 1200 hPa to 5000 hPa, or 1200 hPa to 4000 hPa. These specified pressure ranges have been found to be advantageous for removing at least a portion of the water contained in the pores and cavities of the hollow fiber membrane during this production method.

[0075] Yet 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 been found to be advantageous as they are inert to the material of the hollow fiber membrane. Preferred gases are nitrogen and synthetic air.

[0076] A further embodiment of the second aspect of the invention is characterized in that the pressure section is adjusted to 30° C. to 125° C., preferably 30° C. to 110° C., more preferably 30° C. to 90° C. In the pressure section, improved separation of water from the hollow fiber membranes is observed at high temperatures. In particular, the hollow fiber membranes can be partially sterilized at temperatures above 100° C. In this case, the water vapor atmosphere in the pressure section is advantageously set at positive pressure and 120° C.

[0077] A further embodiment of the second aspect of the invention is characterized in that a part of the gas applied to the pressure chamber flows out and enters the washing unit, in particular the washing tank. According to the invention, depending on the type of hollow fiber membrane and the geometry of the pressure chamber, this outflow is regulated by adjusting the gas pressure until gas bubbles appear to a sufficient extent in the washing tank. In this case, a particularly effective liquid removal is ensured.

[0078] Yet another embodiment of the second aspect is characterized in that the conveying speed of the hollow fiber membrane is from 550 mm / s to 1000 mm / s, preferably from more than 650 mm / s to 900 mm / s, more preferably from 750 mm / s to 800 mm / s.

[0079] According to yet another embodiment of the second aspect, the hollow fiber membrane produced is a "high flux", "medium cut-off", "high cut-off" hollow fiber membrane, or a hollow fiber membrane for plasma separation.

[0080] According to yet another embodiment of the second aspect of the invention, a large part of the liquid, particularly preferably more than 75% or more than 90%, is removed from the pores and cavities of the membrane, i.e. the lumen, in the pressure chamber, which ensures efficient liquid removal.

[0081] In a third aspect, the present invention provides a method for producing a hollow fiber membrane comprising the steps of providing a source of a spun fiber mass, providing a source of a coalescing medium, co-extruding the spun fiber mass and the coalescing medium through at least one annular gap nozzle onto at least one hollow fiber thread, filling the cavity of the hollow fiber thread with the coalescing medium, introducing the at least one spun fiber thread into a precipitation bath containing a precipitation agent, precipitating the at least one spun fiber thread to form at least one hollow fiber membrane, and, if applicable, subsequently introducing the at least one hollow fiber membrane into a washing bath containing a washing agent. introducing at least one hollow fiber membrane obtained from a precipitation bath or, if applicable, from a washing bath into at least one drying unit and, if applicable, receiving on a support at least one hollow fiber membrane obtained from the drying unit, characterized in that the conveying speed of the hollow fiber membranes is between 550 mm / s and 1000 mm / s, preferably between more than 650 mm / s and 900 mm / s, more preferably between 750 mm / s and 800 mm / s.

[0082] An embodiment of the third aspect is characterized in that at least one drying unit comprises a pressure section in which a positive pressure is set compared to atmospheric pressure.

[0083] These spinning speeds allow a particularly economical production of hollow fiber membranes.Embodiments of the second aspect of the invention are also the subject of the third aspect of the invention.

[0084] Description of the invention based on the drawings Further embodiments of the present invention will now be described with reference to the accompanying drawings.

[0085] FIG. 1 shows a schematic diagram of an embodiment of the device 100 according to the invention for the production of at least one hollow fiber membrane. FIG. 1 shows a schematic diagram of a cross section of an annular gap nozzle 101. The source of the spinning mass and the source of the coalescing medium are not shown in FIG. 1. Furthermore, FIG. 1 shows a spinning thread 102 passing through a deposition gap 102b and guided through a deposition tank 103. Furthermore, pulleys 105a to 105l are shown, which are used to guide the spinning thread and the hollow fiber membrane through the device. The hollow fiber membrane 104 formed in the deposition tank 103 is guided by pulleys into a washing tank 106. In an alternative embodiment, several washing tanks can be arranged in succession (not shown in FIG. 1). Furthermore, FIG. 1 shows a pressure chamber 200 with an inlet 201 and an outlet 202 for one hollow fiber membrane 104 shown therein. The hollow fiber membrane 104 passes through the pressure chamber and is guided through the tempering chamber 300 by the inlet 301, the pulleys 105h to 105l and the outlet 302. A reel 400 is shown which receives the hollow fiber membrane 104 and combines it into a bundle strand of hollow fiber membranes. For the sake of simplicity, the schematic diagram according to FIG. 1 shows the production of only one hollow fiber membrane. However, the device shown in FIG. 1 is equally suitable for the production of a large number of hollow fiber membranes. The pressure chamber 200 and the tempering chamber 300 together form a drying unit 350. In the schematic embodiment shown in FIG. 1, the tempering chamber can be operated in the temperature range from 100° C. to 230° C. A corrugation tool is not shown in FIG. 1. A corrugation tool can additionally be arranged between the tempering chamber 300 and the reel 400. Also not shown in FIG. 1 is a gas inlet of the pressure chamber 200. This gas inlet is shown in the subsequent figures. In the illustrated system 100, the hollow fiber membranes can be manufactured according to the NIPS principle and the TIPS principle.

[0086] Figure 2 shows a schematic diagram of a cross section of a pressure chamber 200 according to an embodiment. Figure 2 shows a hollow fiber membrane 104 guided through the pressure chamber 200 through an inlet 201 and an outlet 202. Additionally, a gas inlet 203 and a valve 204 that may be present to regulate the flow of gas into the pressure chamber are shown. The pressure chamber has an interior space 205 forming a cavity as shown in this figure. When gas is introduced through the gas inlet 203, a positive pressure (compared to atmospheric pressure) is built up in the interior space 205.

[0087] Figure 3 shows a schematic cross-sectional view of a pressure chamber 200 according to yet another embodiment. Similar to Figure 2, Figure 3 shows an inlet 201 for introducing at least one hollow fiber membrane, an outlet 202 for discharging at least one hollow fiber membrane 104, a gas inlet 203, a valve 204, and an interior space 205. The pressure chamber can have a tubular geometry or a slit-shaped geometry according to this embodiment.

[0088] 4 shows a schematic view of a part of the device 100 according to the invention. Shown are the washing tank 106, the hollow fiber membrane 104, which passes through the washing tank and is further guided through a pressure chamber 200, the inlet 201 and outlet 202 of the pressure chamber, and the gas inlet 203 of the pressure chamber. Due to the introduction of gas into the internal space through the gas inlet 203, a positive pressure (compared to atmospheric pressure) increases in the pressure chamber, as a result of which a part of the water or liquid transported in the hollow fiber membrane 104 is separated from the hollow fiber membrane. In particular, the gas penetrates into the pores and further into the cavity of the hollow fiber membrane and diffuses in the cavity of the hollow fiber membrane in the same direction as the transport direction of the hollow fiber membrane and against the transport direction of the hollow fiber membrane. Under a pressure of 3000 hPa in the pressure chamber, the gas in the hollow fiber membrane diffuses against the transport direction to such an extent that the development of bubbles can be observed in the washing tank, which may be located upstream, or in the precipitation tank, which is located upstream.

[0089] FIG. 5 shows a schematic diagram of yet another embodiment of a pressure chamber 200, in which the interior space 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 through the inlet 201 and the outlet 202. The gas inlet 203 is located on the compartment 205b. The incoming gas leads to a first positive pressure of pressure P1 (relative to atmospheric pressure) in the compartment 205b, which establishes a second positive pressure of pressure P2 (relative to atmospheric pressure) in the second compartment 205a. According to the embodiment shown in FIG. 5, P1 is higher than P2. The pressure P1 can be 3000 hPa. The pressure P2 can be 1500 hPa. These compartments set up a pressure gradient in the pressure chamber.

[0090] FIG. 6 shows a schematic diagram of yet another embodiment of a pressure chamber 200 in which the interior space 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 through the inlet 201 and the outlet 202. The gas inlet 203 is located on the compartment 205a. The incoming gas creates a first positive pressure of pressure P1 (relative to atmospheric pressure) in the compartment 205a, which establishes a second positive pressure of pressure P2 (relative to atmospheric pressure) in the second compartment 205b, and a third positive pressure of pressure P3 (relative to atmospheric pressure) in the third compartment 205c. According to the embodiment shown in FIG. 6, P1 is higher than P2. The pressure P1 can be 3000 hPa and is higher than the pressure P2. Pressure P2 is higher than pressure P3, which may be 1500 hPa.

[0091] FIG. 7 shows a schematic diagram of yet another embodiment of a pressure chamber 200 in which the interior space 205 has several enlarged and reduced cross-sectional areas, which form several conical sections in the pressure chamber. These conical sections form three compartments 205a, 205b, and 205c in the interior space of the pressure chamber 200, and the hollow fiber membrane 104 is passed through these compartments through the inlet 201 and the outlet 202 into the pressure chamber 200. The inner conical sections of the pressure chamber are arranged symmetrically with respect to the gas inlet 203. The gas inlet 203 is located on the compartment 205a. The inlet gas provides a first positive pressure of pressure P1 (relative to atmospheric pressure) in the compartment 205a, which establishes a second positive pressure of pressure P2 (relative to atmospheric pressure) in the second compartment 205b, and provides a third positive pressure of pressure P3 (relative to atmospheric pressure) in the third compartment 205c. According to the embodiment shown in Fig. 6, P1 is higher than P2. Pressure P1 may be 3000 hPa and is higher than pressure P2. Pressure P2 is higher than pressure P3, which may be 1500 hPa. According to Fig. 7, at least one gas inlet 203 of the pressure chamber 200 is arranged at a position where the cross section of the clear width of the internal space of the pressure chamber has a maximum part 207, which gas inlet is centrally located between the inlet and the outlet of the pressure chamber. The cross section maximum parts 207a and 207b of the clear width of the internal space of the pressure chamber 207 shown in Fig. 7 are of equal size.

[0092] A particularly efficient separation of water from the hollow fiber membranes is possible by the embodiment shown in Figures 5 to 7. It can be provided that the compartments shown in Figures 5 to 7 have outlet openings for water. However, the discharge of water can be made possible through the inlet 201 and outlet 202 of the pressure chamber.

[0093] Figure 8 shows a schematic cross-sectional view of a pressure chamber 200 according to yet another embodiment. Figure 8 shows an inlet 201 for introducing at least one hollow fiber membrane 104, an outlet 202 for discharging 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 subdivided into two asymmetric conical sections.

[0094] FIG. 9 shows a schematic diagram of yet another embodiment of a pressure chamber 200, in which the internal space 205 forms a conical section by several cross-sectional enlargements and cross-sectional reductions, whereby the internal space is subdivided into two compartments 205a and 205b, and the hollow fiber membrane 104 is guided through the pressure chamber 200 through the inlet 201 and the outlet 202. The conical sections are arranged asymmetrically in the internal space of the pressure chamber. The gas inlet 203 is located on the compartment 205a. The incoming gas leads to a first positive pressure of pressure P1 (relative to atmospheric pressure) in the compartment 205a, whereby a second positive pressure of pressure P2 (relative to atmospheric pressure) is established in the second compartment 205b. According to the embodiment shown in FIG. 5, P1 is higher than P2. The pressure P1 can be 3000 hPa. The pressure P2 can be 1500 hPa. By these compartments, a pressure gradient is set up in the pressure chamber. The maximum cross-sectional portion 207a of the clear width of the internal space shown in FIG. 9 is larger than the maximum cross-sectional portion 207 of the clear width of the internal space.

[0095] Figures 8 and 9 show an embodiment in which the cone shape joining above the inlet 201 has an opening angle α. Furthermore, Figures 8 and 9 show an embodiment in which the cone shape joining above the outlet 202 has an opening angle β. According to the embodiment depicted in Figures 8 and 9, α is greater than β.

[0096] FIG. 10 shows a schematic diagram of yet another embodiment of a pressure chamber 200 in which the interior space 205 has several enlarged and reduced cross-sectional areas, which form several conical sections in the pressure chamber. These conical sections form three compartments 205a, 205b, and 205c in the interior space of the pressure chamber 200, and the hollow fiber membrane 104 is passed through the inlet 201 and the outlet 202 into the pressure chamber 200. The inner conical sections of the pressure chamber are arranged symmetrically with respect to the gas inlet 203. The gas inlet 203 is located on the compartment 205a. The inlet gas provides a first positive pressure of pressure P1 (relative to atmospheric pressure) in the compartment 205a, which establishes a second positive pressure of pressure P2 (relative to atmospheric pressure) in the second compartment 205b, and provides a third positive pressure of pressure P3 (relative to atmospheric pressure) in the third compartment 205c. According to the embodiment shown in Fig. 6, P1 is higher than P2. Pressure P1 may be 3000 hPa and is higher than pressure P2. Pressure P2 is higher than pressure P3, which may be 1500 hPa. According to Fig. 10, at least one gas inlet 203 of the pressure chamber 200 is arranged at a position where the cross section of the clear width of the internal space of the pressure chamber has a maximum part 207, which gas inlet is centrally located between the inlet 201 and the outlet 202 of the pressure chamber. The cross-sectional maximum parts 207, 207a and 207b of the clear width of the internal space of the pressure chamber shown in Fig. 10 are of different sizes. In particular, the cross-sectional maximum part 207 is smaller than the cross-sectional maximum parts 207b and 207a.

[0097] Fig. 10 shows an embodiment in which the cone shape joining above the inlet 201 has an opening angle α. Furthermore, Fig. 10 shows an embodiment in which the cone shape joining above the cross-sectional maximum 207b or 207a and pointing towards the centrally located gas inlet 203 has an opening angle γ. In this embodiment, α is smaller than γ. This has the advantage that the separated water can be particularly well removed. This can make it possible to limit the total length of the pressure chamber 200 in the extension direction of the hollow fiber membrane 104 guided through the pressure chamber to less than 50 cm, preferably less than 20 cm, preferably less than 12 cm.

[0098] Figure 11 shows a schematic diagram of yet another embodiment of the pressure chamber 200. This embodiment essentially corresponds to the embodiment shown in Figure 10, but in contrast to the embodiment shown in Figure 10, the cross-sectional maximums 207, 207a and 207b are of equal size, respective outlets 208, 208a and 208b for liquids, in particular water, are arranged in each of the cross-sectional maximums 207, 207a and 207b, the water being separated from the hollow fiber membranes 104 in the pressure chamber 200, and the gas inlet 203 is additionally arranged in the cross-sectional maximum 207.

[0099] Figure 12 shows a schematic diagram of yet another embodiment of the pressure chamber 200. This embodiment essentially corresponds to the embodiment shown in Figure 6, but in contrast to the embodiment shown in Figure 6, the outlets 208, 208a, and 208b for the water separated from the hollow fiber membranes 104 in the pressure chamber 200 are arranged on the sections 205a, 205b, and 205c, respectively.

[0100] FIG. 13 shows a schematic view of an embodiment of the pressure chamber 20 corresponding to the embodiment shown in FIG. 10. FIG. 13 shows further details of the embodiment according to FIG. 10. FIG. 13 is a schematic view illustrating the parts of the illustrated pressure chamber in a semi-transparent manner. According to the illustrated embodiment, the pressure chamber is constructed in a tubular manner. Furthermore, the pressure chamber is constructed in a rotationally symmetric manner with respect to the longitudinal extension axis, except for the gas inlet 200. The longitudinal extension axis of the pressure chamber corresponds to the axis on which the hollow fiber membrane 104 is guided through the pressure chamber. In the illustrated schematic view, the hollow fiber membrane referenced 104 is located on the longitudinal extension axis. In FIG. 13, the peripheral tubular wall 212 of the pressure chamber as well as the structural parts of the gas inlet 203 are illustrated in a semi-transparent manner. In the central area 217a of the pressure chamber, the wall 217 has a diameter larger than the diameter in the area of ​​the ends 217b, 217c. The interior space 205 of the pressure chamber 200 is subdivided into conical sections, with the conical sections 211, 212, 213, 214, 215, and 216 joining each other. The first conical section 211 extends from the inlet 201 for the hollow fiber membrane to the first cross-sectional maximum of the interior space 205 of the pressure chamber 200. The second conical section 212 then extends from the first cross-sectional maximum 217b to the cross-sectional minimum 210a. The third conical section 213 then extends from the first cross-sectional minimum 210a to the second cross-sectional maximum 207. The fourth conical section 214 then extends from the second cross-sectional maximum 207 to the second cross-sectional minimum 210b. A fifth conical section 215 then extends from the second cross-sectional minimum 210b to the third cross-sectional maximum 207a. A sixth conical section 216 then extends from the third cross-sectional maximum to the outlet 202 for the hollow fiber membrane 104. The gas flowing through the gas inlet creates a positive pressure (compared to atmospheric pressure) in the inner space 205 of the pressure chamber, which extends from the inlet 201 for the hollow fiber membrane to the outlet 202 for the hollow fiber membrane. Funnel-shaped openings 201a and 202a join the inlet 201 and the outlet 202. This protects the hollow fiber membrane or group of hollow fiber membranes as they enter and leave the pressure chamber.In particular, all edges in the internal space 205 of the pressure chamber are rounded to avoid damage to one or more hollow fiber membranes. The opening angles α and β of the conical sections are determined by the arrangement of the inner surface of the conical section relative to the longitudinal extension line of the pressure chamber. In the first and sixth conical sections 211, 216, the opening angle is designated as α. In the second and fifth conical sections, the opening angle is designated as β. Preferably, α is smaller than β, as shown in FIG. 10. The adjacent conical sections 211, 212, 213, 214, 215, 216 of the internal space 205 of the pressure chamber 200 form three compartments 205a, 205b, and 205c such that when gas flows into the internal space 205, the pressure gradient described with respect to the embodiment shown in FIG. 10 is established in the region from the gas inlet to the inlet 201 for the hollow fiber membranes and to the outlet 202 for the hollow fiber membranes. Comparative Example 1

[0101] Sixteen hollow fiber membranes were produced simultaneously according to one of the embodiments disclosed in DE 10 2016 224 627. The following specifications were used for the production of the hollow fiber membranes: 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 stirred, heated to 60° C. and processed with degassing into a homogeneous spinning mass. The spinning mass was co-extruded through an annular gap nozzle with a central bore through which a coalescing medium passes to form a spinning thread. A coalescing medium consisting of 35% DMAC and 65% water was guided inside the hollow spinning thread. The temperature of the annular gap nozzle was 70° C. The extruded spinning thread was passed through a deposition gap with an atmosphere having a relative humidity of 100%. The height of the deposition gap was 200 mm and a residence time in the deposition gap of 0.4 s was set. The withdrawal speed of the spinning thread was therefore 650 mm / s. The residence time of the spinning thread in the deposition gap depends on the withdrawal speed and can be varied in alternative comparative examples. The spinning thread was introduced into a deposition bath consisting of water regulated at 80° C., whereby the spinning thread was deposited into a hollow fiber membrane. The hollow fiber membrane was then passed into a washing bath regulated at a temperature between 75° C. and 90° C. Thereafter, the hollow fiber membrane was passed into the tempering chamber of a drying unit at a temperature between 100° C. and 150° C., whereby it was dried. The conveying speed of the hollow fiber membrane was adapted to the withdrawal speed.

[0102] Afterwards, 16 hollow fiber membranes were wound on a reel and combined. The wound hollow fiber membranes were analyzed for any possible fiber defects. Some cases of flattened fibers or fiber breakage were detected in the reeled hollow fiber membranes. Comparative Example 2

[0103] The conditions for producing hollow fiber membranes were selected according to Comparative Example 1. The spinning thread and hollow fiber membrane withdrawal speed were reduced to 450 mm / s. The hollow fiber membrane conveying speed was adapted to the withdrawal speed. The obtained hollow fiber membrane had no fiber flattening and no fiber breakage. EXAMPLES

[0104] In contrast to Comparative Example 1, in Example 1, a group of 16 hollow fiber membranes was guided through a pressure chamber according to the embodiment described in FIG. 10 after passing through a washing tank and before being introduced into a tempering chamber. Air was introduced through the gas inlet of the pressure chamber so as to generate a pressure of 3000 hPa in the central conical cavity of the pressure chamber, a pressure of 1500 hPa in the second conical cavity of the pressure chamber, and a pressure of 1300 hPa in the third conical cavity of the pressure chamber. The dried hollow fiber membrane was rolled up and inspected for any possible defects. The production of hollow fiber membranes according to Example 1 was carried out using various withdrawal speeds. According to this implementation, no fiber damage was found at a withdrawal speed of 650 mm / s. The term withdrawal speed is intended to mean the speed at which the hollow fiber membrane passes through the device for producing hollow fiber membranes.

[0105] Thus, according to Example 1, the withdrawal speed can be increased so as to result in a higher production rate when compared to the comparative example and thus the prior art, which results in an energy saving per km of hollow fiber. Alternatively, the distance of the tempering section can also be shortened thereby, so that the device for producing hollow fiber membranes can be operated with low construction costs. [Explanation of symbols]

[0106] 100 Apparatus for manufacturing hollow fiber membranes 101 Annular gap nozzle 104 Hollow fiber membrane 300 Tempering Chamber 350 Drying Unit

Claims

1. a spinning unit comprising at least one annular gap nozzle (101) fluidly connected to a source of the spinning mass and to a source of the agglomeration medium for extruding at least one hollow spun thread (102) from the spinning mass, the cavity of the hollow spun thread being filled with the agglomeration medium; a precipitation tank (103) for precipitation of said at least one spinning thread (102) to form at least one hollow fiber membrane (104); At least one drying unit (350) for drying at least one hollow fiber membrane (104), comprising: the at least one drying unit includes a pressure section, the pressure section being configured such that a positive pressure can be established in the pressure section relative to atmospheric pressure; the pressure section of the drying unit comprises a pressure chamber (200), the pressure chamber (200) comprising 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), the at least one gas inlet (203) being in fluid communication with a gas source, the pressure section being further configured to be capable of generating a positive pressure in the interior space (205) of the pressure chamber (200) through the gas source; The clear width of the internal space (205) has at least one enlarged cross-sectional portion and at least one reduced cross-sectional portion in a cross section parallel to the traveling direction of the at least one hollow fiber membrane (104), the cross-sectional expansion and the cross-sectional contraction result in a conical shape of an inner surface of the pressure chamber; the pressure chamber (200) has one or more outlets (208, 208a, 208b) for discharging liquid, the outlets being located at a position where the cross section of the clear width of the internal space of the pressure chamber (200) has a maximum portion; 1. An apparatus (100).

2. at least one washing unit (106) for washing the at least one hollow fiber membrane (104); The apparatus (100) of claim 1.

3. a receiving unit (400) for receiving the at least one hollow fiber membrane (104) on a support; 2. The apparatus of claim 1.

4. The pressure in the pressure section of the drying unit is configured to be between 1100 hPa and 10,000 hPa.

4. Apparatus according to any one of claims 1 to 3.

5. a cross-sectional area of ​​the inlet (201) for introducing the at least one hollow fiber membrane (104) into the internal space of the pressure chamber (200) and a cross-sectional area of ​​the outlet (202) for discharging the at least one hollow fiber membrane (104) from the pressure chamber (200) are less than 30 times and at least 1.1 times or more than the cross-sectional area of ​​the hollow fiber membrane (104) or the sum of the cross-sectional areas of a plurality of the hollow fiber membranes; 5. Apparatus according to any one of claims 1 to 4.

6. The drying unit (350) further comprises a tempering section having a heating device arranged so that a temperature of 50 to 230° C. can be set in the tempering section. The apparatus (100) according to any one of the preceding claims.

7. the tempering section of the drying unit comprises a tempering chamber (300) having 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); 7. The apparatus of claim 6.

8. The pressure chamber (200) and the tempering chamber (300) are separate chambers; the apparatus is further configured such that the at least one hollow fiber membrane or several hollow fiber membranes obtained from the precipitation bath are passed first through the pressure chamber (200) and then through the tempering chamber (300), 8. The apparatus (100) of claim 7.

9. The pressure chamber (200) of the pressure section is divided into several compartments (205a), (205b), (205c), 9. Apparatus according to any one of claims 1 to 8.

10. The at least one gas inlet (203) of the pressure chamber (200) is arranged at a position in the center between the inlet (201) for introducing the at least one hollow fiber membrane (104) into the pressure chamber (200) and the outlet (202) for discharging the at least one hollow fiber membrane (104) from the pressure chamber (200), where the cross section of the clear width of the internal space of the pressure chamber (200) has a maximum part (207).

10. Apparatus according to any one of claims 1 to 9.

11. Providing a source of spun mass; providing a source of coalescence medium; co-extruding the spun mass and the agglomeration medium through at least one annular gap nozzle (101) into at least one hollow spun thread (102), the cavity of the hollow spun thread (102) being filled with the agglomeration medium; introducing said at least one spinning thread (102) into a precipitation tank (103) containing a precipitation agent and precipitating said at least one spinning thread (102) into at least one hollow fiber membrane (104); introducing at least one hollow fiber membrane (104) obtained from the precipitation tank (103) into a drying unit (350); A method for producing at least one hollow fiber membrane (104) comprising: The at least one hollow fiber membrane (104) passes through a pressure section in the drying unit, in which a positive pressure is generated compared to atmospheric pressure by introducing a gas into the pressure section, and at least a portion of the precipitant or cleaning agent contained in the at least one hollow fiber membrane (104) is separated from the at least one hollow fiber membrane; The pressure section of the drying unit includes a pressure chamber (200), the pressure chamber (200) having an interior space (205) and an inlet (201); The at least one hollow fiber membrane (104) is introduced into the internal space (205) of the pressure chamber (200) through the inlet (201) and discharged from an outlet (202) for discharging the at least one hollow fiber membrane (104) from the internal space (205) of the pressure chamber; The clear width of the internal space (205) of the pressure chamber (200) has at least one cross-sectional enlarged portion and at least one cross-sectional reduced portion in a cross section parallel to the traveling direction of the at least one hollow fiber membrane (104); the cross-sectional expansion and the cross-sectional contraction result in a conical shape of an inner surface of the pressure chamber; the pressure chamber has one or more outlets (208, 208a, 208b) for discharging liquid, the outlets being located at a position where the cross section of the clear width of the interior space of the pressure chamber (200) has a maximum; A method comprising:

12. After introducing the at least one spinning thread (102) into a precipitation bath (103), the at least one hollow fiber membrane (104) is introduced into a washing unit (106) containing a washing agent, The method of claim 11.

13. The method further comprises introducing the at least one hollow fiber membrane obtained from the washing unit (106) into a drying unit (250). The method of claim 12.

14. The gas is selected from the group consisting of air, nitrogen, argon, carbon dioxide, water vapor, or a mixture thereof; 14. The method according to any one of claims 11 to 13.

15. The positive pressure in the pressure section compared to atmospheric pressure is set to a pressure of 1100 hPa to 10,000 hPa; 15. The method according to any one of claims 11 to 14.

16. The pressure section is adjusted to 30 to 125° C.

16. The method according to any one of claims 11 to 15.

17. The conveying speed of the spinning thread is from 550 mm / s to 1000 mm / s; 17. The method according to any one of claims 11 to 16.

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