In-progress drying of hollow fiber membranes

Abstract

The present disclosure relates to an apparatus for the ongoing drying of permselective hollow fiber membranes. The present disclosure also relates to a continuous method for the ongoing drying of permselective hollow fiber membranes using said apparatus.

Description

[Technical Field]

[0001] The present disclosure relates to an apparatus for the ongoing drying of permselective hollow fiber membranes. The present disclosure also relates to a continuous method for the ongoing drying of permselective hollow fiber membranes using said apparatus. [Background technology]

[0002] The manufacturing method of permselective hollow fiber membranes usually includes a step of drying the membrane before it can be transferred to a housing to produce a filter. Drying can be performed discontinuously, for example, by preparing membrane strands or bundles and subsequently drying them in a drying chamber or oven, or continuously, i.e., on-going. Most on-going drying methods known in the prior art involve drying hollow fiber membranes with hot air, for example, in a convection oven.

[0003] U.S. Patent No. 4,346,006 discloses a method for fabricating multiple flat, monolayer arrays of substantially parallel capillary membrane tubes, including forming a pair of flat, substantially two-dimensional monolayer arrays of capillary tubes from a spool and placing the individual capillary tubes in close proximity to one another. After the array passes through guide rollers, it passes through a comb member that reciprocates back and forth in a direction parallel to the plane of the flat array, forming a serpentine pattern within the array. An adhesive material is applied to the fiber array, and the individual capillary tubes of the array are bonded to one another at their intersections with an adhesive. Following this, the bonded portions of the array pass through roller members, one or more of which are heated rollers that allow the adhesive to cure.

[0004] Chinese Patent Publication No. 104562239 relates to a fiber drawing method in the production of ultra-high molecular weight polyethylene fibers, which can reduce the deviation in fiber fineness.

[0005] The method comprises the steps of preparing a jelly thread, pre-stretching a bundle, extracting, drying and hot stretching.

[0006] The bundle pull-out device is composed of a parallel-arranged reciprocating rod, a godet roller, an active bundle pulling roller set, and a motor. The active bundle pulling roller set is composed of at least one drive roller and is driven by the motor via a gear. The bundle pull-out device can simultaneously pull out multiple jelly fibers during the fiber pulling process, and multiple bundle pull-out devices can be connected in series. A plurality of equally spaced U-shaped dividing teeth are arranged above the reciprocating rod, and the reciprocating rod reciprocates parallel to its axial direction to prevent the jelly fibers from adhering to the roller.

[0007] German Patent Application No. 3734226 discloses a method for producing short-cut carbon fibers for the reinforcement of thermoplastics. A multifilament yarn having at least 100,000 filaments is fanned and divided by a comb inclined in the direction of yarn movement. The comb oscillates in a direction perpendicular to the direction of yarn movement.

[0008] WO 2016 / 102442 discloses an apparatus for continuously drying and tempering hollow fiber membranes, which includes a plurality of independently heatable rollers. The roller axes are parallel and lie in a common plane. This apparatus allows for a two-stage drying and tempering process of the hollow fiber membranes.

[0009] The aim of the present disclosure is to further improve the apparatus and methods disclosed in WO 2016 / 102442. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 4,346,006 [Patent Document 2] Chinese Patent Application Publication No. 104562239 [Patent Document 3] DE 3734226 A1 [Patent Document 4] International Publication No. 2016 / 102442 [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a longitudinal cross-sectional view of one embodiment of a device of the present disclosure. [Figure 2] 2 is a partial perspective view of the device of FIG. 1 including a laterally movable comb. Summary of the Invention

[0012] The present disclosure relates to an apparatus for the ongoing drying of permselective hollow fiber membranes, capable of performing a two-stage drying and tempering process for the hollow fiber membranes. The apparatus includes a plurality of rollers having a high-temperature surface. A laterally movable comb, which guides the plurality of hollow fiber membranes into the ongoing dryer, is positioned at the entrance of the ongoing dryer and oscillates continuously and periodically about a zero position to continuously change the trajectory of the hollow fiber membranes on the surface of the heated rollers.

[0013] The present disclosure also relates to a continuous method for making permselective hollow fiber membranes, comprising a two-stage drying and tempering process of the hollow fiber membranes in the apparatus of the present disclosure, which results in a narrow pore size distribution and high selectivity in the final membrane. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present disclosure provides an apparatus capable of performing a continuous two-stage drying and tempering process on a plurality of permselective hollow fiber membranes.

[0015] An apparatus for continuously drying and tempering a plurality of hollow fiber membranes 4 includes a plurality of rollers 5 disposed within a housing 1. The housing 1 has an inlet 2 and an outlet 3 for the plurality of hollow fiber membranes 4 and an exhaust port 7. A laterally movable comb 10, which guides the plurality of hollow fiber membranes 4 into the apparatus, is located outside the housing 1 at the inlet 2 of the apparatus. The comb 10 is configured to continuously and periodically oscillate about a zero position in a direction parallel to the axes of the plurality of rollers 5, thereby continuously changing the trajectory of the plurality of hollow fiber membranes 4 on the surface of the heated roller 5. In some embodiments, the comb 10 is configured to continuously oscillate about the zero position with an amplitude ranging from 1 mm to 20 mm, e.g., from 3 mm to 5 mm, or from 12 mm to 18 mm. In the context of the present disclosure, the term "amplitude" refers to the maximum deviation from the zero position. In some embodiments, the comb 10 is configured to oscillate at a speed ranging from 10 mm / min to 100 mm / min, e.g., from 30 mm / min to 40 mm / min.

[0016] In some embodiments, the frequency of vibration is in the range of 1 / min to 5 / min, such as 2 / min to 3 / min, for example 2.5 / min.

[0017] The rollers 5 are configured to heat the plurality of hollow fiber membranes 4. The plurality of hollow fiber membranes 4 pass over the outer surfaces of the rollers 5 and come into contact with the high-temperature surface, and are heated during processing. The outer surface of each roller 5 of the plurality of rollers 5 is independently heatable. In some embodiments, the outer surface of each roller 5 is configured to be heatable to a temperature in the range of 150°C to 300°C. The temperature of each roller 5 is independently controlled. Heating can be performed in various ways. For example, the outer surface of the rollers 5 can be heated electrically, i.e., by resistance heating or induction heating, or by radiative heating from either the inside of the roller 5, the outside of the roller 5, or both.

[0018] Each roller 5 is individually driven by a drive device 6. The drive device 6 is typically a motor. The speed of each roller 5 is individually adjusted. In one embodiment, each roller 5 is configured to rotate at a peripheral speed in the range of 30 to 100 m / min, for example, 45 to 75 m / min.

[0019] The rollers 5 are arranged in the housing 1 such that the axes of all the rollers 5 are parallel and all lie in a single common plane. In one embodiment, the number of rollers 5 is 2 to 20, such as 5 to 10, for example 8 to 10. In one embodiment, the gap a between the first two rollers 5 downstream of the inlet 2 is in the range of 0.2 to 8 mm, for example 1 to 7 mm, for example 3 to 5 mm. In one embodiment, all the rollers 5 in the device have the same diameter D. In one embodiment of the device, the diameter D is in the range of 200 to 300 mm.

[0020] On their way through the device from inlet 2 to outlet 3, the plurality of hollow fiber membranes 4 pass over the heated surfaces of rollers 5, as shown in Figure 1. For devices with equal-sized rollers, the length of each individual hollow fiber membrane of the plurality of hollow fiber membranes 4 that contacts the heated surface of roller 5 (the "contact length") is approximately (N-1)*π*D, where N is the number of rollers 5 in the device and D is the diameter of roller 5. In one embodiment of the device, the contact length is at least 1 m. In another embodiment, the contact length is at least 2 m. In yet another embodiment, the contact length is at least 6 m.

[0021] In one embodiment of the device, every other roller 5 of the plurality of rollers 5 is configured to be movable to a position such that its axis is outside the plane formed by the axes of two adjacent rollers 5 .

[0022] The housing 1 features an exhaust port 7 connected to a fan 9. During operation of the device, the fan 9 removes water vapor generated by evaporating water from the hollow fiber membranes 4 from the housing 1, thereby assisting in the drying process. The throughput of the fan 9 is controlled by a controller 8. In one embodiment, the fan 9 is configured to blow air at a rate of 200-400 m / hour. 3The present invention is configured to have a throughput of a range of gases.

[0023] In one embodiment of the device, the housing 1 is configured to be separated into two sections, each section containing a portion of the total number of rollers 5. In one illustrative example of the device, the total number of rollers is 10, with the first section downstream of the inlet 2 comprising four rollers 5 and the second section comprising six rollers 5.

[0024] An exemplary embodiment of an apparatus having five rollers 5 is shown in FIG. 1. The apparatus comprises a housing 1 having an inlet 2 and an outlet 3 for hollow fiber membranes 4. The five rollers 5 are disposed within the housing 1. Each roller 5 is individually driven by a motor 6. FIG. 1 shows the apparatus during processing of a plurality of hollow fiber membranes 4 ("working position"). The rollers 5 are positioned within the housing 1 so that their centers are aligned. The minimum distance a between the first two rollers 5 is also shown. As shown in FIG. 1, the plurality of hollow fiber membranes 4 enter the apparatus through the inlet 2, pass over the surfaces of the rollers 5, and exit the apparatus through the outlet 3. The housing 1 features an exhaust port 7 connected to a fan 9. The throughput of the fan 9 is controlled by a controller 8. In one embodiment of the apparatus, the fan is configured to blow air from the housing 1 at a rate of 200 m / h. 3 ~400m / h 3 is configured to remove a gas volume in the range of

[0025] As shown in Figures 1 and 2, the hollow fiber membranes 4 are guided into the inlet 2 of the apparatus through the gaps of a laterally movable comb 10. The lateral vibration of the comb 10 causes the trajectory of the hollow fiber membranes 4 on the heated roller 5 to move continuously over time, thereby improving heat transfer from the heated roller to the hollow fiber membranes 4 being dried by the apparatus.

[0026] In the device disclosed in WO 2016 / 102442, the trajectory of the hollow fiber membranes 4 on the heated roller 5 is fixed, and the hollow fiber membranes 4 always contact the same area of ​​the heated roller 5. This contact area cools, reducing heat transfer. In addition, an insulating layer of polymer deposited from the hollow fiber membranes accumulates on the surface of the heated roller 5 over time, which also reduces heat transfer from the heated roller 5 to the hollow fiber membranes 4. This effect must be compensated for by increasing the temperature of the heated roller 5. Oscillatory displacement of the trajectory of the hollow fiber membranes 4 on the heated roller 5 by the motor-driven comb 10 improves utilization of the entire surface of the heated roller 5, so that heat transfer remains constant over time. As a result, the overall temperature level of the heated roller 5 is lower, and heating power can be reduced, resulting in less collapse of the hollow fibers and saving heating energy. The formation of a heat insulating layer on the surface of the heated roller 5 is delayed and the removal of deposits from the surface of the heated roller 5, for example by grinding, is required less frequently, so less maintenance of the device is required.

[0027] A laterally movable comb 10 is disposed outside the device housing 1 near the inlet 2, and the orientation of the comb, i.e., its longitudinal axis, is parallel to the axes of the rollers 5, so that the hollow fiber membranes 4 to be dried pass through the gaps, i.e., between the teeth, of the comb 10. As the comb 10 moves laterally, the teeth of the comb 10 also move the hollow fiber membranes 4 in the same direction.

[0028] The laterally movable comb 10 includes a movement unit that continuously and periodically oscillates the comb 10 about a zero position in the laterally movable direction, i.e., perpendicular to the direction of movement of the hollow fiber membranes 4 through the apparatus and thus parallel to the axis of the heated roller 5 within the apparatus. The movement unit is typically driven by a motor. A linear actuator, such as a rack and pinion, may be used to generate the oscillating movement.

[0029] The movement unit allows for adjustment of the amplitude and speed of vibration, so that the amplitude of vibration of comb 10 and its movement speed can be adjusted as needed. In some embodiments, the movement unit is configured to oscillate the comb laterally about a zero position with an amplitude ranging from 1 mm to 20 mm, e.g., from 3 mm to 5 mm, or from 12 mm to 18 mm. In some embodiments, the movement unit is configured to move comb 10 at a speed ranging from 10 mm / min to 100 mm / min, e.g., from 30 mm / min to 40 mm / min.

[0030] The present disclosure also provides a continuous method for making permselective hollow fiber membranes, which method comprises subjecting a plurality of hollow fiber membranes 4 to a two-stage drying and tempering process in an apparatus of the present disclosure.

[0031] In some embodiments of the method, the two-stage drying and tempering process comprises drying the plurality of hollow fiber membranes 4 by applying a temperature in the range of 210 to 280°C, e.g., 220 to 260°C, to the outer surface of the plurality of hollow fiber membranes for a time period in the range of 1 to 4 seconds, e.g., 2 to 3 seconds, and subsequently tempering the plurality of hollow fiber membranes 4 by applying a temperature in the range of 180 to 200°C to the outer surface of the plurality of hollow fiber membranes for a time period in the range of 2 to 5 seconds, e.g., 3 to 4 seconds.

[0032] The two-stage drying and tempering process provides sufficient evaporation of water and clear shrinkage of the pores. In one embodiment of this method, the drying and tempering are carried out by contacting the hollow fiber membrane with a high-temperature surface (e.g., a heated roller) having a temperature in the range of 180 to 280°C.

[0033] In some embodiments of the method, comb 10 guides the hollow fiber membranes 4 into inlet 2 of the apparatus and oscillates about a zero position in a direction perpendicular to the direction of movement of the hollow fiber membranes 4 through the apparatus, thereby continuously and periodically varying the trajectory of the hollow fiber membranes 4 on the outer surfaces of rollers 5. The oscillation of comb 10 has an amplitude ranging from 1 mm to 20 mm, e.g., from 3 mm to 5 mm, or from 12 mm to 18 mm. In some embodiments of the method, comb 10 moves at a speed ranging from 10 mm / min to 100 mm / min, e.g., from 30 mm / min to 40 mm / min.

[0034] In some embodiments, the methods of the present disclosure comprise the following steps in sequence:

[0035] a) i. at least one polysulfone, polyethersulfone (PES), or polyarylethersulfone (PAES), optionally in combination with polyamide (PA); ii. at least one polyvinylpyrrolidone (PVP), and iii. at least one solvent; extruding the polymer solution containing b) forcing the central fluid through the inner opening of the nozzle; c) washing the obtained hollow fiber membrane; d) In the device of the present disclosure, the hollow fiber membrane is subjected to a two-stage drying and tempering treatment.

[0036] The polymer solution ("spinning solution") used in step a) comprises at least one polysulfone, polyethersulfone (PES), or polyarylethersulfone (PAES), optionally in combination with polyamide (PA), and at least one polyvinylpyrrolidone (PVP). In one embodiment, polyvinylpyrrolidone consisting of a low molecular weight component having a molecular weight less than 100 kDa and a high molecular weight component having a molecular weight equal to or greater than 100 kDa is used to make the membrane.

[0037] Examples of suitable polyethersulfones have the general formula -[O-Ph-SO2-Ph-] n - a polymer having a weight average molecular weight of about 60,000 to 65,000 Da, preferably 63,000 to 65,000 Da, and an Mw / Mn of about 1.5 to 1.8.

[0038] In one embodiment of this method, the polymer solution comprises 12-16 wt% polyethersulfone and 3-12 wt%, e.g., 5-8 wt%, PVP, based on the total weight of the solution, with the PVP comprising 3-8 wt%, e.g., 4-6 wt%, low molecular weight (<100 kDa) PVP components and 0-4 wt%, e.g., 1-3 wt%, high molecular weight (≥100 kDa) PVP components, based on the total weight of the solution. In one embodiment, the total PVP in the spinning solution comprises 22-34 wt%, e.g., 25-30 wt%, high molecular weight (≥100 kDa) components and 66-78 wt%, e.g., 70-75 wt%, low molecular weight (<100 kDa) components. Examples of high and low molecular weight PVPs include PVP K85 / K90 and PVP K30, respectively.

[0039] In certain embodiments, the polymer solution further comprises 66-81 wt% of a solvent, based on the total weight of the solution, and 0-10 wt%, e.g., 0-5 wt%, of a suitable additive, based on the total weight of the solution. Suitable additives are, for example, selected from the group consisting of water, glycerol, and other alcohols. In one embodiment, water is present in the spinning solution in an amount of 0-8 wt%, e.g., 2-6 wt%, based on the total weight of the solution.

[0040] In one embodiment, the solvent used in the method is selected from the group consisting of N-methyl-pyrrolidone (NMP), N-ethylpyrrolidone, N-octylpyrrolidone, dimethylacetamide (DMAC), dimethylsulfoxide (DMSO), dimethylformamide (DMF), butyrolactone, and mixtures of the aforementioned solvents. In a particular embodiment, NMP is used as the solvent.

[0041] The kinematic viscosity of the polymer solution, measured according to DIN EN ISO 1628-1 at 22° C., is typically in the range of 3,000 to 15,000 mPa·s, for example 4,000 to 9,000 mPa·s, or even 4,900 to 5,900 mPa·s.

[0042] The center fluid or bore liquid used in step b) of the disclosed method comprises at least one of the solvents mentioned above and a precipitation medium selected from the group of water, glycerol and other alcohols.

[0043] In certain embodiments, the center fluid further comprises an additional additive for modifying the surface of the membrane to further enhance membrane performance. In one embodiment of the present invention, the amount of additive in the center fluid is 0.02-2 wt %, e.g., 0.05-0.5 wt %, or 0.05-0.25 wt %, based on the total weight of the center fluid.

[0044] Examples of suitable additives include hyaluronic acid and zwitterionic polymers, as well as copolymers of a vinyl polymerizable monomer having a zwitterion in the molecule with another vinyl polymerizable monomer. Examples of zwitterionic (co)polymers include phosphobetaines, sulfobetaines, and carboxybetaines.

[0045] The center fluid generally comprises 40-100 wt% precipitation medium and 0-60 wt% solvent. In one embodiment of the method, the center fluid comprises 44-69 wt% precipitation medium and 31-56 wt% solvent. In a particular embodiment, the center fluid comprises 49-63 wt% water and 37-51 wt% NMP. In another embodiment, the center fluid comprises 53-56 wt% water and 44-47 wt% NMP.

[0046] In one embodiment of the method, the polymer solution exiting through the outer slit opening of the spinneret is directed through a spinning shaft in a controlled atmosphere. In one embodiment of the method, the spinning shaft is maintained at a temperature in the range of 2 to 90°C, for example, 25 to 70°C, or 30 to 60°C.

[0047] In one embodiment, the hollow fibers to be precipitated are exposed to a wet steam / air mixture containing a solvent content of 0-10 wt %, e.g., 0-5 wt %, or 0-3 wt %, based on the water content. The temperature of the wet steam / air mixture is at least 15°C, preferably at least 30°C, and up to 75°C, e.g., 62°C or less. Furthermore, the relative humidity of the wet steam / air mixture is 60-100%.

[0048] The effect of the solvent in the temperature-controlled steam atmosphere is to control the precipitation rate of the fibers. If less solvent is used, the outer surface will have a denser surface, and if more solvent is used, the outer surface will have a more porous structure. By controlling the amount of solvent in the temperature-controlled steam atmosphere surrounding the precipitated membrane, the amount and size of pores on the outer surface of the membrane can be varied and controlled.

[0049] In one embodiment of the disclosed method, the temperature of the spinneret is 50-70°C, e.g., 55-61°C, and the temperature of the spinning shaft is 25-65°C, e.g., 50-60°C. The distance between the nozzle opening and the precipitation tank is 30-110 cm, e.g., 45-55 cm. The precipitation tank has a temperature of 10-80°C, e.g., 20-40°C. In one embodiment, the spinning speed is in the range of 15-100 m / min, e.g., 25-55 m / min.

[0050] In one embodiment of the invention, the precipitation tank contains 85-100 wt% water and 0-15 wt% solvent, such as NMP, while in another embodiment, the precipitation tank contains 90-100 wt% water and 0-10 wt% NMP.

[0051] The hollow fiber membranes obtained in steps a) and b) are then washed to remove unwanted components (step c). In one embodiment of this method, the hollow fiber membranes are passed through at least one water bath at a temperature ranging from 70 to 90°C. In another embodiment, the membranes are passed through two water baths. In yet another embodiment, the membranes are passed through five water baths. In certain embodiments of this method, the individual water baths have different temperatures. For example, each water bath may have a higher temperature than the preceding water bath.

[0052] The membrane is then subjected to a two-stage drying and tempering treatment (step d) comprising drying said membrane by applying a temperature in the range of 210-280°C, for example 220-260°C, to the outer surface of the membrane for a time in the range of 1-4 seconds, for example 2-3 seconds, and subsequently tempering said membrane by applying a temperature in the range of 180-200°C to the outer surface of the membrane for a time in the range of 2-5 seconds, for example 3-4 seconds.

[0053] The hollow fiber membranes are optionally sterilized after dyeing. Suitable sterilization methods include treatment with steam, ethylene oxide, or radiation. In one embodiment of this method, the hollow fiber membranes are steam sterilized at a temperature of at least 121° C. for at least 21 minutes.

[0054] In one embodiment, the membrane obtained by the method of the present disclosure comprises 80-99 wt % polysulfone, polyethersulfone (PES), or polyarylethersulfone (PAES), optionally in combination with polyamide (PA), and 1-20 wt % polyvinylpyrrolidone (PVP).

[0055] In one embodiment, the PVP contained in the selectively permeable hollow fiber membrane consists of a high molecular weight component (≧100 kDa) and a low molecular weight component (<100 kDa), and contains 10 to 45 wt% of the high molecular weight component based on the total weight of the PVP in the membrane, and 55 to 90 wt% of the low molecular weight component based on the total weight of the PVP in the membrane.

[0056] In one embodiment, the hollow fiber membrane obtained by the method of the present disclosure has an inner diameter of 180 to 250 μm. In another embodiment, the inner diameter is 185 to 195 μm. In yet another embodiment, the inner diameter is 210 to 220 μm.

[0057] The wall thickness of the hollow fiber membrane is typically in the range of 20 to 55 μm. In one embodiment, the wall thickness is 33 to 37 μm. In another embodiment, the wall thickness is 38 to 42 μm. In yet another embodiment, the wall thickness is 43 to 47 μm. In yet another embodiment, the wall thickness is 48 to 52 μm.

[0058] The hollow fiber membrane obtained by the method of the present disclosure can have a symmetric wall structure or an asymmetric wall structure. In one embodiment, the membrane wall has a symmetric sponge structure. In another embodiment, the membrane wall has an asymmetric sponge structure. In yet another embodiment of the method, the membrane wall has an asymmetric wall structure and comprises a layer having a finger structure, i.e., characterized by macrovoids having a size of more than 5 μm.

[0059] It will be understood that the features mentioned above and those described below may be used not only in the combinations specified but also in other combinations or alone without departing from the scope of the invention.

[0060] The present invention will be described in more detail in the following examples, which are not intended to limit the scope of the invention but are merely illustrative of particular embodiments of the invention.

[0061] Example A polymer solution was prepared by dissolving polyethersulfone (Ultrason® 6020, BASF Aktiengesellschaft) and polyvinylpyrrolidone (K30 and K85, BASF Aktiengesellschaft) and distilled water in N-methylpyrrolidone (NMP). The weight fractions of the different components in the polymer spinning solution were PES:PVP K85:PVP K30:HO:NMP = 13.6:2.6:5:75.6. The kinematic viscosity of the polymer solution was 4,600 mPa·s. The kinematic viscosity η of the polymer solution was measured at 22 °C using a capillary viscometer (ViscoSystem® AVS 370, Schott-Gerate GmbH, Mainz, Germany) according to DIN ISO 1628-1.

[0062] To prepare the solution, NMP and water were first charged into a 30 L container equipped with a finger paddle stirrer. PVP was added to the NMP and stirred at 50°C until a homogeneous, clear solution was obtained. Finally, polyethersulfone was added. The mixture was stirred at 50°C until a clear, highly viscous solution was obtained. The warm solution was cooled to 20°C and degassed at 50 mmHg for 1-2 hours. The highly viscous polymer solution was transferred to a stainless steel container.

[0063] The bore fluid was prepared by mixing distilled water and N-methylpyrrolidone (NMP). The weight fractions of the two components in the center fluid were HO:NMP = 53 wt%:47 wt%.

[0064] The bore liquid was prepared as follows.

[0065] → A stainless steel container was filled with distilled water, NMP was added, and the mixture was stirred for approximately 1 minute.

[0066] The clear mixture was filtered into a second stainless steel container and degassed at 50 mmHg.

[0067] The polymer solution was heated to 50°C, and hollow fiber membranes were formed by passing the solution and bore liquid through a spinning die. The die temperature was 54°C, and the spinning shaft temperature was 52°C. Hollow fiber membranes were formed at a spinning speed of 50 m / min. The liquid capillary emerging from the die was passed through a water bath (ambient temperature). The distance between the die and the precipitation bath was 100 cm. The formed hollow fiber membranes were guided through five different water baths.

[0068] After exiting the fifth water tank, the hollow fiber membranes were fed into an ongoing dryer having two sections equipped with heated rollers, the first section equipped with four heated rollers and the second section equipped with six heated rollers.

[0069] The hollow fiber membranes were dried in the first compartment at temperatures ranging from 220 to 280°C (roller 2, 245°C; roller 3, 230°C) and tempered in the second compartment at temperatures ranging from 180 to 190°C (roller 6, 190°C; roller 7, 180°C). The residence time in the first compartment was 2.4 seconds, and the residence time in the second compartment was 3.2 seconds.

[0070] The dry hollow fiber membranes had an inner diameter of 215 μm, a wall thickness of 50 μm, and a completely asymmetric membrane structure. The active separation layer of the hollow fiber membrane was on the inside. The active separation layer is defined as the layer with the smallest pores.

[0071] Example 1 The hollow fiber membrane was guided through a laterally vibrating comb into the inlet of the dryer, with an amplitude of vibration of ±3.5 mm and a speed of comb movement of 35 mm / min, resulting in a frequency of vibration of 2.5 / min.

[0072] The temperature of the individual rollers and the heating power supplied to each roller were continuously monitored over a 10 day period.

[0073] During the first four days, the heating power supplied to roller 2 decreased by 2.8% and then remained within a certain range. During the 10-day period, no overall decrease in the heating power supplied to roller 3 was observed.

[0074] It is speculated that the formation of a heat insulating layer on the roller surface reduces the heat flow from the roller surface to the hollow fiber membrane. Because less heat is released from the roller, less heating power is required to maintain the roller at a constant temperature.

[0075] During the first 6 days, the heating power supplied to roller 6 increased by 7% and then remained within a certain range. The heating power supplied to roller 7 increased by 7.9% during the first 6 days and then remained within a certain range.

[0076] If less heat is transferred from the rollers in the first section of the on-going dryer to the hollow fiber membranes, more water will remain on the hollow fiber membranes exiting the first section, which must be evaporated by the rollers in the second section of the on-going dryer. This requires a larger amount of heat to be transferred from the rollers in the second section to the hollow fiber membranes, necessitating increased heating power.

[0077] Comparative Example 1 Example 1 was repeated using a fixed comb, i.e. without lateral comb oscillation. The temperature of the individual rollers and the heating power supplied to each roller were monitored continuously over a period of 5 days.

[0078] During the first day, the heating power supplied to roller 2 decreased by 2.7% and then remained within a constant range. The heating power supplied to roller 3 decreased by 2.6% during the first day and then remained within a constant range.

[0079] During the first day, the heating power supplied to roller 6 increased by 7.1% and then remained within a constant range. The heating power supplied to roller 7 increased by 8.6% during the first day and then remained within a constant range.

[0080] Comparison of the data shows that the efficiency of the two-stage drying and tempering process is substantially increased by the vibrating comb. The formation of insulating deposits on the surface of the roller in the first section is significantly reduced (by a factor of 4-6), resulting in more efficient heat transfer in the first stage of the process and saving heating energy in the tempering stage.

Claims

1. An apparatus for continuously drying and tempering a plurality of hollow fiber membranes (4), the apparatus comprising a plurality of rollers (5) arranged in a housing (1), the housing (1) having an inlet (2) and an outlet (3) for the hollow fiber membranes (4) and an exhaust port (7), the rollers (5) configured to heat the hollow fiber membranes (4), the outer surface of each roller (5) of the plurality of rollers (5) being individually heatable, each roller (5) being individually driven by a drive device (6), and the rollers (5) all The rollers (5) are positioned in a housing (1) such that the axes of all the rollers (5) are parallel and lie in a single common plane, and the device comprises a comb (10) arranged outside the housing (1) at an inlet (2) of the device, the comb (10) being configured to guide the plurality of hollow fiber membranes (4) into the device and to oscillate continuously and periodically around a zero position in a direction parallel to the axes of the plurality of rollers (5) to continuously change the trajectory of the plurality of hollow fiber membranes (4) on the outer surfaces of the plurality of rollers (5).

2. 2. The device of claim 1, wherein the comb (10) is configured to oscillate about a zero position with an amplitude in the range of 1 mm to 20 mm.

3. 3. The device according to claim 1 or 2, wherein the comb (10) is configured to oscillate at a speed in the range of 10 mm / min to 100 mm / min.

4. 4. The device according to any one of claims 1 to 3, wherein the comb (10) comprises a movement unit configured to periodically oscillate the comb (10) about a zero position in a direction parallel to the axes of the rollers (5) in the housing (1).

5. 5. The apparatus of claim 4, wherein the movement unit allows for adjusting the maximum deflection (amplitude) and speed from the zero position of the vibration.

6. An apparatus according to any one of the preceding claims, wherein the surface of each roller (5) is adapted to be heatable to a temperature in the range of 150°C to 300°C.

7. An apparatus according to any one of the preceding claims, wherein each roller (5) is arranged to rotate at a peripheral speed in the range of 30 to 100 m / min.

8. 8. Apparatus according to any one of the preceding claims, wherein the width of the gap (a) between the first two rollers (5) downstream of the inlet (2) is in the range of 0.2 to 8 mm.

9. An apparatus according to any one of the preceding claims, wherein the number of rollers (5) is between 2 and 20.

10. The exhaust port (7) is 200 to 400 m per hour from the housing (1). ３ 10. The device according to any one of claims 1 to 9, connected to a fan (9) configured to remove a gas volume of.

11. 11. The device according to any one of claims 1 to 10, wherein the number of rollers is at least three and every other roller (5) of the plurality of rollers (5) is configured to be movable to a position where its axis is outside the plane formed by the axes of two adjacent rollers (5).

12. 12. A continuous method for producing permselective hollow fiber membranes, comprising subjecting a plurality of hollow fiber membranes (4) to a two-stage drying and tempering treatment in an apparatus according to any one of claims 1 to 11.

13. 13. The method according to claim 12, wherein the two-stage drying and tempering treatment comprises drying the plurality of hollow fiber membranes (4) by applying a temperature in the range of 210 to 280°C to the outer surfaces of the plurality of hollow fiber membranes (4) for a time in the range of 1 to 4 seconds, and subsequently tempering the plurality of hollow fiber membranes (4) by applying a temperature in the range of 180 to 200°C to the outer surfaces of the plurality of hollow fiber membranes (4) for a time in the range of 2 to 5 seconds.

14. 14. The method according to claim 12 or 13, wherein a comb (10) guides the plurality of hollow fiber membranes (4) into the inlet (2) of the device and oscillates about a zero position in a direction perpendicular to the direction of movement of the plurality of hollow fiber membranes (4) through the device, thereby periodically varying the trajectory of the plurality of hollow fiber membranes (4) on the outer surfaces of the plurality of rollers (5), and the oscillation of the comb (10) has a maximum deflection (amplitude) from the zero position in the range of 1 mm to 20 mm.

15. The method according to claim 14, wherein the comb (10) moves at a speed ranging from 10 mm / min to 100 mm / min.

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