Hollow fiber membrane and method for sealing said hollow fiber membrane

Abstract

A method is disclosed for sealing one side of a hollow fiber membrane (40), the hollow fiber membrane (40) having an inner space (41) and a wall (42) radially surrounding the inner space (41), the wall (42) having an inner textile layer (43), wherein a portion (45) of a low viscosity resin (46) flows at least partially through an end face (48) of the hollow fiber membrane (40) into an end region (44) of the hollow fiber membrane (40), sealing the end region (44) with an outer free surface (49), and is cured by UV light. Further disclosed is a hollow fiber membrane (40) having an inner space (41) and a wall (42) with an inner textile layer (43) surrounding the inner space (41), the end regions (44) of the hollow fiber membrane (40) being sealed by a UV-light-cured portion (45) of a resin (46) that has a low viscosity before curing and has an outer free surface (49). In order to reduce the tendency of blocking between the end regions (44) of the hollow fiber membrane (40) during filtration operation, it is proposed that the portion (45) is delivered completely into the end region (44) through the end face (48) by means of overpressure, is cured after a maximum of 5 seconds, and is located only inside the hollow fiber membrane after curing.

Description

[Technical field]

[0001] The present invention relates first to a method for sealing one side of a hollow fiber membrane, the hollow fiber membrane having an inner space and a wall radially surrounding the inner space, the wall having an inner textile layer, and a portion of a low viscosity resin flows at least partially through an end face of the hollow fiber membrane into an end region of the hollow fiber membrane, sealing the end region with an outer free surface and curing by UV light.

[0002] The invention also relates to a hollow fiber membrane having an inner space and a wall with an inner textile layer surrounding the inner space, the end regions of the hollow fiber membrane being sealed at their outer free surface by a UV-cured portion of a low viscosity resin before curing.

[0003] Such a method and a membrane filter with hollow fiber membranes are known from US Patent Application Publication No. 2013 / 0240436 and US Patent Application Publication No. 20090039012.

[0004] In a known method, the free end of a hollow fiber membrane is inserted vertically into a low-viscosity photocurable resin (adhesive), and a portion of the low-viscosity resin flows partially through the end face of the hollow fiber membrane into the end region of the hollow fiber membrane, sealing the end region with the outer free surface and curing with UV light.

[0005] In a first known method, the hollow fiber is removed from the resin before curing, leaving a droplet at the free end, which is allowed to harden. In this case, the droplet also forms an outer free surface facing outwards. In a second known method, the hollow fiber membrane is inserted into a mold containing the resin and remains in this mold until curing. The mold is then removed and the sealed end also has an outer free surface with the contour of the mold.

[0006] In either case, one part of the part fills the inner space of the end region of the hollow fiber membrane, another part surrounds the outer surface of the membrane in the end region, and another part extends beyond the end face of the hollow fiber membrane and seals it, thereby ensuring that not only the inner space but also the textile layer and the membrane layer applied thereto, i.e. the entire hollow fiber membrane including the wall, are sealed.

[0007] The resin layer of the droplets on the outer surface of the hollow fiber membrane simultaneously leads to a thickening of the end region of the hollow fiber membrane. The maximum diameter of the droplets in the first known method is 0.1-1.6 mm larger than the outer diameter of the hollow fiber membrane. Moreover, the droplets protrude significantly beyond the end cross section of the membrane in the longitudinal direction of the membrane. The same ratio applies to the second known method.

[0008] The disadvantage of using such membranes in single-header membrane filters is that the thickening of the membrane ends reduces the flow cross-section, which prevents hair and fibrous compounds in the membrane filter from being removed from the bundle of hollow fiber membranes (especially if the bundle is integrated into a housing, e.g. a tube). Furthermore, the outer thickening and the application of material behind the end faces of the hollow fiber membranes require a relatively large amount of resin for sealing.

[0009] By way of background to the invention, JP 11-319505 A describes a method for simultaneously sealing a number of hollow fiber membranes whose walls are not reinforced with an inner textile layer. The ends of the hollow fiber membranes are first positioned in a row at intervals from one another, for example by fixing them with an adhesive tape. The free fiber ends of the hollow fiber membranes are then inserted perpendicular to the length of the membrane into a low-viscosity resin. In this case, the resin rises in the inner space of the hollow fiber membranes only by capillary action, and even to a level significantly higher than the surface of the resin reservoir into which the membrane ends are inserted.

[0010] After the hollow fiber membranes are removed from the resin reservoir, the resin is cured by irradiation with UV light. The pre-spacing of the hollow fiber membranes prevents the resin from rising outward between the membranes by capillary action to the same height as the capillary action of the inner space of the membrane. That is, the resin level in the inner space of the hollow fiber membrane is much higher than the outside of the hollow fiber membrane. After curing, the inserted ends of the hollow fiber membranes have a resin layer on the outside of the membrane surface. There is a risk that some membranes will stick at their ends. To ensure that there is no possible membrane sticking and outer thickening due to the resin cured on the membrane surface, the ends of the membranes are cut after the resin has cured, so that a part of the resin still remains in the inner space of the membrane to seal the end of the hollow fiber membrane and no resin remains on the outside of the hollow fiber membrane. This part of the resin remaining in the fiber where the cutting is completed was introduced into the end region purely by capillary action through the end face of the hollow fiber membrane. After cutting the end at the inner space, the section has a smooth cut surface towards the end face of the membrane.

[0011] In the background, a prerequisite for using this method is a sufficiently high capillary effect in the inner space of the hollow fiber membrane, which causes the resin in the inner space to rise significantly higher than the resin level on the outside when inserted. Such a high capillary effect generally only occurs in hollow fiber membranes without a textile layer, where the diameter of the inner space is very small. As an example, an inner space diameter of about 0.35 mm is shown in the background of this method. As the diameter of the inner space increases, the capillary effect decreases and at a certain point the resin does not rise to a sufficient height in the inner space, making it impossible to use this method.

[0012] Similarly, for hollow fiber membranes without an inner textile layer, CN110960988 suggests thinning the epoxy or polyurethane resin with a solvent, introducing it under pressure into the membrane bundle so that the resin particles penetrate into the pores of the fiber layer, drying the solvent with a gas stream, and curing the resin at room temperature for several hours or in a microwave for at least several minutes. Over such a long time, the thin resin will be completely absorbed from the inner space of the membrane by the capillary action of the inner textile layer, thereby reopening the inner space.

[0013] By way of further background to the invention, WO 2012 / 147932 describes a method for repairing hollow fiber membranes of membrane filters, in which the membrane is fixed at the top and bottom in a header. The defective area of ​​the membrane is cut out, resulting in two free ends of the cut hollow fiber membrane, which must be sealed. In this case, the sealing is performed manually with a hot glue gun. The end of the hollow fiber membrane is first inserted in a short length into the tip of the hot glue gun. To easily perform this insertion, the tip of the hot glue gun is made larger than the outer diameter of the membrane. Subsequently, a section of hot glue is extruded under pressure from the hot glue gun, only part of which reaches the inner space of the hollow fiber membrane through the end face. Subsequently, the hot glue gun is removed from the membrane end, after which the section hardens by cooling and seals the fiber end. The maximum diameter of the hardened section is significantly larger than the outer diameter of the hollow fiber membrane and further protrudes significantly beyond the end face of the hollow fiber membrane. These two points are important in the case of this method to ensure a reliable sealing of the free end. This is because the hot glue has a very high viscosity even at high temperatures and therefore does not penetrate the membrane wall to seal it. Therefore, sealing of the fiber end can only be achieved if the hot glue forms an outer layer in addition to a plug in the inner space of the membrane outside the outer diameter of the hollow fiber membrane and even protrudes beyond the end face of the hollow fiber membrane in the longitudinal direction of the hollow fiber membrane. In the above-mentioned publication, a value of 1 to 2 times the outer diameter of the hollow fiber membrane is given for the thickening of the membrane end, and a value of 0.1 to 0.5 times the outer diameter of the hollow fiber membrane is given for the length of the resin layer behind the end cross section in the longitudinal direction of the hollow fiber membrane.

[0014] assignment It is an object of the present invention to reduce the tendency for blocking between the end regions of hollow fiber membranes.

[0015] solution Starting from known methods, it is proposed according to the invention that the aforementioned part is delivered completely through the end face into the end region by overpressure and cured after a maximum of 5 seconds, and after curing is located only inside the hollow fiber membrane.

[0016] This has the advantage that the outer region of the hollow fiber membrane is not thickened by the resin and that no resin accumulates behind the end face of the hollow fiber membrane, for example in the form of resin droplets. As a result, only a small amount of resin is required to seal the hollow fiber membrane, which makes the method according to the invention less material-intensive and therefore more cost-effective. Furthermore, due to the overpressure injection and the short waiting time until curing, the time required to seal the hollow fiber membrane can be controlled and therefore kept very short, making the process easier to automate and therefore more economical.

[0017] Starting from the known hollow fiber membranes, it is proposed that said part is located completely inside the hollow fiber membrane.

[0018] As a result, the membrane has no resin thickening at its sealed ends to which hair and fibrous compounds can adhere, and as a result, the membrane according to the invention has a reduced tendency to block.

[0019] Even in the membrane according to JP 11-319505, known from the background of the invention, said part is located completely inside the hollow fiber membrane after curing. However, this membrane does not have a wall with an inner textile layer. The method described in JP 11-319505 works only with hollow fiber membranes with high capillary action in the inner space. Due to the capillary action, the resin in the inner space must rise higher than the outside of the membrane so that the end of the membrane thickened with resin after curing can be cut off. Only then does the part of the resin remaining at the membrane end go completely inside the hollow fiber membrane. This method does not work in the case of hollow fiber membranes with walls with an inner textile layer, since the capillary action in the inner space of such a hollow fiber membrane is not sufficient. The reason is that the suction effect of the textile layer on the low-viscosity resin is so high that, as a result, the capillary effect in the inner space is almost completely erased. When the free membrane end of the textile-reinforced hollow fiber membrane is inserted into a resin with low viscosity, the resin that has entered the inner space is immediately absorbed into the textile layer. The resin level in the inner space therefore does not rise, and may even remain below the resin surface where the hollow fiber membrane is inserted. This is also demonstrated in the membrane known from EP 2 825 296 A1. From Fig. 2, Fig. 2A and Fig. 3 B1 of this known document, it can be seen that the resin level in the inner space hardens even below the resin surface where the membrane end is inserted. That is, the capillary effect in the inner space is almost nonexistent. The method of JP 11-319505 A1, which is the background art, therefore does not work with such textile-reinforced membranes.

[0020] The advantage of the method according to the present invention is that the resin portion is located completely inside the hollow fiber membrane, without cutting the membrane ends as in the method of the background art. As a result, a method step is omitted, and the material yield in the manufacturing process is higher, i.e., more membrane material is included in the final product. Therefore, the method according to the present invention is more cost-effective and simpler.

[0021] In the membrane according to the invention, a polymer layer is generally applied on the outside of the textile layer, which determines the separation properties of the membrane. The membrane preferably belongs to the field of microfiltration or ultrafiltration, but may also come from the field of nanofiltration or low pressure reverse osmosis membranes. The textile layer gives the membrane high mechanical strength, which is advantageous, for example, when operating a membrane bioreactor (MBR) for wastewater treatment. Here, microfiltration or ultrafiltration membranes with pore sizes in the range of 0.02-0.4 μm are generally used. The outer diameter of the commonly used one-sidedly clamped hollow fiber membranes is 1.5-3.0 mm, the inner diameter is in the range of 0.7-1.8 mm.

[0022] The textile layer of the hollow fiber membrane according to the invention gives the membrane high mechanical strength, which is particularly advantageous in the harsh operating conditions in membrane bioreactors (MBRs) for wastewater treatment. It is within the scope of the invention that the inner textile layer is, for example, a woven, warp-knitted or fiber cloth tube, a weft-knitted tube or a fleece or felt tube. However, it may also be any other textile material suitable for reinforcing hollow fiber membranes, for example a strip made of yarn, twine or rope.

[0023] A particularly important task when sealing such hollow fiber membranes on one side with a textile layer is to seal not only the inner space of the membrane, but also the wall, in particular the textile layer therein. In an alternative sealing method, the sealing of the fiber-reinforced wall is always achieved by the cured resin surrounding a continuous area outside the surface of the hollow fiber membrane and behind the end face of the hollow fiber membrane, so that the wall of the hollow fiber membrane is completely embedded in the end region and is also sealed via this embedment.

[0024] In the method according to the invention, where the sealed membrane does not have such a continuous area between the outside of the membrane and the rear of the end face, the resin has to soak into the wall of the end region including the textile layer, in order to achieve this the resin before curing has to have a low viscosity, since a high viscosity medium penetrates the textile layer poorly (see also the method of WO 2012 / 147932 A1 for further background).

[0025] It is within the scope of the present invention that the outer free surface of the part of the hardened resin in the inner space is formed concavely. This is achieved if the viscosity of the resin is very low, because in this case the resin penetrates from the inner space into the textile layer quickly and is also sucked away from the end face of the hollow fiber membrane. The inwardly concave formation of the free surface has the advantage that all the resin part at the outer end of the membrane is sucked inward before the resin hardens, so that the membrane end is very clean and free of irregularities caused by hardened resin residues. This is optimal for removing hair and fibrous compounds in the filtration operation of the hollow fiber membrane.

[0026] To achieve good and rapid penetration of the textile layer, a resin viscosity in the range of 200 to 900 mPas (cP) is advantageous.

[0027] It is also within the scope of the present invention that this method seals with other UV curable adhesives or other media with similar viscosities, all of which are summarized herein within the framework of the present invention under the term "resin".

[0028] It is also within the scope of the method according to the invention that there is a time for the low viscosity resin to penetrate and soak into the textile layer. On the other hand, this time should not be too long, otherwise the resin may penetrate into the textile layer from the inner space, which may reopen and no longer be sealed by the resin. Thus, the challenge is to allow the resin to penetrate and soak into the textile layer for a sufficient time, and then quickly cure the resin using UV light while the inner space is still sealed with the resin. Thus, the curing must take place within a limited time window.

[0029] The delivery of the resin portion is also time-critical: if it is too slow, the entire resin will penetrate directly into the textile layer and the inner space of the hollow fiber membrane will not be filled with resin, i.e. the free end will not be functionally sealed. Therefore, the delivery must be fast enough to fill the inner space with resin in the first place. To achieve this, the delivery is carried out using overpressure.

[0030] The overpressure for delivering the resin can be generated by a pump or the resin can be placed in a reservoir with an overpressure setting. The resin can also be delivered to the end region of the membrane via an injection needle or a piston. Portions of the resin can be pre-separated, for example by using a syringe or a pump, by defining a pump volume, or can be delivered continuously from a reservoir, for example via a pump.

[0031] In order to achieve a functional sealing of the membrane ends, i.e. the time timing of the sealing process is of utmost importance. It is therefore advantageous in the method according to the invention that the delivery takes place within the range of 0.5-2.5 seconds, the inner space in the end region is filled with resin first, and between the end of the delivery and the start of the UV irradiation there is a waiting time of at least 1 second during which the resin penetrates from the inner space to the wall up to the membrane surface in the end region and therewith soaks into the wall, during which the inner space remains sealed by the resin.

[0032] Furthermore, in the method according to the present invention, the longitudinal axis of the hollow fiber membrane is in a horizontal position during sealing, which is advantageous for an automated process, since the risk of the resin flowing out of the inner space due to gravity is reduced, resulting in a cleaner process and simpler automation.

[0033] As part of a possible automation of the method, the hollow fiber membranes are held by grippers in front of the end regions during sealing, while being continuously and automatically a hopper opening into the tube section is pushed over the end region until the tube section closely surrounds the membrane surface; delivering said portion from a free end of the pipe section through an end face into an end region; The hopper is again pushed away from the end area, Positioning a UV curing unit above the edge region and directing UV light to the edge region by the UV curing unit, thereby curing the portion.

[0034] The aforementioned process steps are advantageously carried out within the time window previously described in order to obtain an optimal sealing result. The waiting time therefore consists of the time to push the hopper out and the time to position the UV curing unit above the end region of the hollow fiber membrane before starting the UV light curing process.

[0035] It is within the scope of the invention that the hollow fiber membranes to be sealed are taken directly from the membrane production plant in an automated process and gripped by grippers, which grip the membranes in their end regions, i.e. the free membrane ends that are not yet sealed protrude beyond the grippers, in which case the membrane ends may be bent in one direction or another.

[0036] The hopper serves to "catch" the free end of the hollow fiber membrane behind a sealed gripper and center it in the axis of the hopper or tube section, thus threading the membrane through the hopper when it is fitted. A hopper angle of 45° has proven advantageous. When the membrane is threaded through the hopper, it is in a defined position in the hopper axis. Resin is then delivered from the free end of the tube section through the end face of the hollow fiber membrane to its end region via a resin feeder using overpressure.

[0037] After delivery, the remainder of the liquid resin may initially protrude from the inner space as a convex bulge behind the end face. During the waiting time, the suction effect of the textile layer draws the resin from this bulge into the fibers. This suction further causes the hardened resin plug in the inner space of the hollow fiber membrane to have an inner free surface concave towards the inner space and an outer free surface concave towards the end face. After the resin has hardened, the gripper releases the membrane before gripping and sealing the next membrane.

[0038] Furthermore, it is within the scope of the method according to the invention for the inner diameter of the tube section to be 0.05-0.2 mm larger than the outer diameter of the hollow fiber membrane. On the one hand, this results in an inner diameter that is large enough to allow the hollow fiber membrane to slide easily and reliably into the hopper when the latter is fitted over. On the other hand, the inner diameter is small enough to prevent as little resin as possible from entering the gap between the membrane surface and the inner wall of the tube section.

[0039] In technical processes, depending on the ellipticity and the nature of the membrane surface, it may be unavoidable that very small amounts of resin will find their way into the gaps at some points. In order to keep the amount of resin that finds its way into the gaps to a minimum in such cases, it is advantageous for the part of the tube section that closely surrounds the membrane surface to be as long as possible. A length of at least 7 mm has proven to be advantageous here.

[0040] In the method according to the invention, the liquid resin is only delivered to the end region through the end face of the hollow fiber membrane, so the UV light does not have easy access to the resin part from the outside. Nevertheless, to achieve an effective and fast curing time, the light output of the UV curing unit reaching the membrane surface must be relatively high. For a conventional hollow fiber membrane with a textile layer, this is 5-40 W / cm 2 should be in the range.

[0041] The time for curing the resin part with UV light is preferably 0.5 to 2.5 seconds. If the light output is low, i.e. the curing is too slow, the resin may penetrate further from the inner space into the wall, which may cause the inner space to open again. If the light output is too high, the membrane may be damaged or substances such as, for example, glycerin may evaporate uncontrollably from the membrane material, damaging the UV lamp.

[0042] Furthermore, it has proven advantageous if the hopper is temperature controlled during the method according to the invention in order to maintain the temperature of the resin during encapsulation and, as well as the viscosity, in a defined range, so that constant flow properties of the resin are guaranteed as a condition of the defined time of each method step during the encapsulation process, which is also advantageous for controlling the process as part of the process automation.

[0043] The scope of the invention also includes membrane filters for filtering liquids, comprising hollow fiber membranes each having an inner space and a wall with an inner textile layer surrounding the inner space, the hollow fiber membranes being fixed at their lower part to a base element and each having individually sealed ends at their upper part, which are free floating in the liquid, the base element having a permeate collecting chamber to which the inner spaces of the hollow fiber membranes are connected for collecting filtrate from the inner spaces. According to the invention, the ends of the hollow fiber membranes of such membrane filters are sealed according to one of the methods according to the invention.

[0044] Such a membrane filter is generally called a single-header membrane filter. Such a membrane filter according to the present invention is suitable for example for submerged operation in a membrane bioreactor (MBR) for treating wastewater. The advantage here is that hair and fibrous compounds from the MBR sludge are freely removed upwards during operation of the membrane filter and do not stick in the membrane filter.

[0045] The scope of the invention further includes a hollow fiber membrane having an inner space and a wall with an inner textile layer radially surrounding the inner space, the end region of the hollow fiber membrane being sealed by a UV-cured portion of a resin having a low viscosity before curing, the portion having an outer free surface, said portion being located completely inside the hollow fiber membrane.

[0046] It is advantageous if the outer free surface of said portion of the inner space is formed concavely, since in that case the outer edge of the membrane is free of irregularities due to outwardly facing resin parts and therefore the membrane edge is very smooth and neat.

[0047] Further included within the scope of the present invention is a membrane filter for filtering liquids, comprising hollow fiber membranes fixed at their lower part to a base element and each having at their upper part individually sealed ends floating freely in the liquid, the base element having a permeate collecting chamber connected to the inner space of the hollow fiber membranes for collecting filtrate from the inner space, characterized in that in the membrane filter the hollow fiber membranes are formed according to one of the two preceding paragraphs.

[0048] Moreover, in the membrane filter according to the invention, it is advantageous if the hollow fiber membranes of the basic element are surrounded by tubes. As a result, for example, when the membrane filter is operated in a membrane bioreactor (MBR), the air introduced for cleaning the membranes is retained in the membrane bundle and is more effectively utilized. In particular, when using such tubes, it is advantageous for the membranes to have no resin thickenings at the end cross sections. Such thickenings would lead to an unfavorable reduction in the flow cross section, which would impede the flow of the liquid to be filtered and would impede the removal of hair and fibrous compounds from the hollow fiber membranes.

[0049] The present invention will now be described with reference to examples. [Brief description of the drawings]

[0050] [Figure 1a] 1A-1D illustrate process steps of a first method according to the invention in cross section; [Figure 1b] 1A-1D illustrate process steps of a first method according to the invention in cross section; [Figure 1c] 1A-1D illustrate process steps of a first method according to the invention in cross section; [Figure 1d] 1A-1D illustrate process steps of a first method according to the invention in cross section; [Figure 1e] 1A-1D illustrate process steps of a first method according to the invention in cross section; [Figure 1f] 1A-1D illustrate process steps of a first method according to the invention in cross section; [Figure 2a]3 shows further details in cross section for carrying out a first method according to the invention; FIG. [Figure 2b] 3 shows further details in cross section for carrying out a first method according to the invention; FIG. [Figure 2c] 3 shows further details in cross section for carrying out a first method according to the invention; FIG. [Figure 2d] 3 shows further details in cross section for carrying out a first method according to the invention; FIG. [Figure 2e] 3 shows further details in cross section for carrying out a first method according to the invention; FIG. [Figure 2f] 3 shows further details in cross section for carrying out a first method according to the invention; FIG. [Figure 2g] 3 shows further details in cross section for carrying out a first method according to the invention; FIG. [Figure 3a] 3A-3D show process steps of a second method according to the invention in cross section. [Figure 3b] 3A-3D show process steps of a second method according to the invention in cross section. [Figure 3c] 3A-3D show process steps of a second method according to the invention in cross section. [Figure 3d] 3A-3D show process steps of a second method according to the invention in cross section. [Figure 4a] FIG. 1 shows cross sections of two different hollow fiber membranes according to the present invention. [Figure 4b] FIG. 1 shows cross sections of two different hollow fiber membranes according to the present invention. [Diagram 5] FIG. 1 is a diagram showing a cross section of a first membrane filter having a hollow fiber membrane according to the present invention. [Figure 6] FIG. 2 is a diagram showing a cross section of a second membrane filter having a hollow fiber membrane according to the present invention.

[0051] Working Example The drawings shown in the figures are not to scale. All details of the method, hollow fiber membrane or membrane filter according to the invention described below that are not shown are identical to the previously described embodiments of the method, hollow fiber membrane or membrane filter according to the invention.

[0052] Figures 1a to 1f show in cross section the process steps of a first method according to the invention for sealing one side of a braided reinforced hollow fiber membrane 1 with a portion 2 of a low-viscosity resin 3 curable by UV light (Figure 1a). The volume of the portion is 50 μl. The viscosity of the resin 3 is 300 mPas (cP).

[0053] The hollow fiber membrane 1 has a longitudinal axis 4, which is in a horizontal position when sealed. The hollow fiber membrane 1 further has an inner space 5 and a wall 6 radially surrounding the inner space 5. The wall 6 has an inner textile layer 7 for reinforcing the hollow fiber membrane 1, the outer diameter 8 of the wall 6 is 2.6 mm, and the diameter 9 of the inner space is 1.4 mm.

[0054] The part 2 is delivered completely under overpressure through the end face 10 of the hollow fiber membrane 1 into the end region 11 of the hollow fiber membrane 1. In this case, the resin 3 first fills the inner space 5 and as soon as the part 2 starts to be delivered, the resin 3 starts to soak into the wall 6 and the textile layer 7 (FIG. 1b). At the end of the delivery, the part 2 is only present inside the hollow fiber membrane 1 and initially has a convex bulge 12 of the resin 3 that remains liquid behind the outside of the end face 10 (FIG. 1c). The delivery time is 1 s.

[0055] During the waiting time that begins after the resin 3 is delivered to the end region 11, the resin 3 penetrates from the inner space 5 into the wall 6, including into the textile layer 7. In this case, the resin 3 withdraws from the convex bulge 12 into the inner space 5 of the hollow fiber membrane 1 (FIG. 1d).

[0056] With further waiting time, the resin 3 is further drawn into the inner space 5, and as it permeates from the inner space 5 to the wall 6, the outer free surface 13 of the part 2 forms a concave shape in the inner space 5 (FIG. 1e). At the same time, the resin permeates down the wall to the outer membrane surface 14 of the hollow fiber membrane 1.

[0057] The waiting period is ended by a final irradiation with UV light 15, which hardens the resin 3, thereby fixing the current distribution of the portions 2 in the edge region 11. The waiting period is 2 seconds in total, with hardening taking a further 1.4 seconds.

[0058] After curing, the portion 2 of the resin 3 is located only inside the hollow fiber membrane 1, and the resin plug 16 formed in the inner space 5 has a concave outer free surface 13. In this way, the portion 2 seals the inner space 5 and the wall 6 of the hollow fiber membrane 1, including the textile layer 7, without the membrane surface 14 of the hollow fiber membrane 1 having an outer layer of resin 3 that would thicken the hollow fiber membrane 1 in the end region 11, and without the presence of cured resin 3 outside behind the end face 10 of the hollow fiber membrane 1.

[0059] 2a to 2g show further details in cross section for carrying out a first method according to the invention.

[0060] The hollow fiber membrane 1 is removed from the manufacturing process for its continuous production and is held by a gripper 17 in front of the end region 11. The gripper 17 holds the hollow fiber membrane 1 throughout the entire sealing process. The end region 11 of the hollow fiber membrane 1 can bend slightly in one direction or another relative to the longitudinal axis 4 during the gripping process. To "catch" and center the end region 11, a hopper 18 opening into a tube section 19 is pushed over the end region 11 until the tube section 19 closely surrounds the membrane surface 14 (Figures 2a-2b). The part of the tube section 19 closely surrounding the membrane surface is about 8 mm.

[0061] The tube section 19 has an internal diameter 20, i.e. 2.7 mm, which is 0.1 mm larger than the external diameter 8 of the hollow fiber membrane 1. The portion 2 is then delivered from the free end 21 of the tube section 20 through the end face 10 into the end region 11. This delivery is performed by a micro-metering pump designed as a diaphragm pump with an extremely small stroke of 5 μl. The portion 2 of 50 μl of resin 3 thus corresponds to a total of 10 strokes of the micro-metering pump, which are performed during a total time of 1 second required to deliver the resin 3.

[0062] Depending on the ovality of the hollow fiber membrane, a small amount of resin 3 may get into the gap between the inner diameter 20 of the tube section 19 and the outer diameter 8 of the hollow fiber membrane 1. This may amount to a maximum of 0.1% of the part 2, causing a thickening of the wall 6 of less than 0.05 mm.

[0063] Subsequently, a waiting period begins, during which the hopper 18 is again pushed away from the end region 11 and a UV curing unit 22 is positioned above the end region 11 by being pushed over the end region 11 in place of the hopper 18. After positioning the UV curing unit 22, the end region is irradiated with UV light 15 to cure the portion 2. The UV curing unit 22 has an installed power of 100 W and the total light output of the UV radiation irradiated on the film surface 14 is 24 W / cm. 2 The curing time of the portion 2 of the resin 3 by the UV light 15 is 1.4 seconds.

[0064] After curing, the curing unit 22 is pushed away again from the end region 11 and the gripper 17 releases the hollow fiber membrane 1 again, thereby completing the automated sealing process of the hollow fiber membrane 1.

[0065] Figures 3a-3d show process steps of a second method according to the invention in cross section: A hollow fibre membrane 24 reinforced with a textile layer 23 is held in an end region 25 by a gripper 26 such that the longitudinal axis 27 of the hollow fibre membrane 24 is aligned with an injection needle 28 (Figure 3a).

[0066] Subsequently, the injection needle 28 is inserted into the inner space 29 of the hollow fiber membrane 24. The injection needle 28 has an outer needle diameter 30 that is 0.1 mm smaller than the diameter 31 of the inner space (FIG. 3b).

[0067] Thereafter, a portion 32 of the resin 33 is delivered through the injection needle 28 and thus through the end face 34 of the hollow fiber membrane 24 into the inner space 29 of the hollow fiber membrane 24, so that the portion first expands in the inner space 29 and seals it. Then, a waiting period begins, during which the resin 33 penetrates from the inner space 29 into the wall 35 of the hollow fiber membrane 24 and soaks into the textile layer 23 and the entire wall 35.

[0068] During the waiting time, the injection needle 28 is again withdrawn from the inner space 29. The waiting time ends when the resin 33 has penetrated through the wall 35 to the membrane surface 36. The part is then cured by UV light 37 before the gripper 26 releases the hollow fiber membrane again, completing the sealing process.

[0069] The cured portion 32 of the resin 33 has an outer free surface 38 in the inner space, which is concavely shaped. An inner free surface 39 of the cured portion 32 of the inner space 29, which faces the inner space 29, is also concavely shaped.

[0070] FIG. 4a shows a cross-sectional view of a first hollow fiber membrane 40 according to the invention, produced by a first method according to the invention, with an inner space 41 and a wall 42, the wall 42 having an inner textile layer 43. The end region 44 of the hollow fiber membrane 40 is sealed with a portion 45 of resin 46 cured by UV light, which penetrates the wall 42 including the textile layer 43 and forms a plug 47 in the inner space 41 with an outer free surface 49 concavely formed towards the end face 48 of the hollow fiber membrane 40. The inner free surface 50 facing inwardly of the inner space 41 is also concavely formed. This portion 45 is located only in the interior of the hollow fiber membrane 40, starting from the end face 47 of the hollow fiber membrane 40. A very small proportion of the portion 45 of resin 46, less than 0.1%, may also cure outside the membrane surface 51 of the hollow fiber membrane 40. This results in a maximum thickness of the wall 42 of less than 0.05 mm.

[0071] FIG. 4b shows a cross-sectional view of a second hollow fiber membrane 52 according to the invention, produced by a second method according to the invention, which has an inner space 53 and a wall 54, the wall 54 having an inner textile layer 55. The end region 56 of the hollow fiber membrane 52 is sealed with a portion 57 of a resin 58 cured by UV light, which penetrates (seeps) into the wall 54 including the textile layer 54 and forms a resin plug 59 in the inner space 53, which has an outer free surface 61 concavely formed towards the end face 60 of the hollow fiber membrane 52. The inner free surface 62 facing inwards towards the inner space 53 is also concavely formed. The portion 58 is located only inside the hollow fiber membrane 52, starting from the end face 60 at a distance 63.

[0072] FIG. 5 shows a cross-sectional view of a first membrane filter 64 for filtering liquids with hollow fiber membranes 65 according to the invention, each having an inner space 66 and a wall 67 surrounding the inner space 66, the hollow fiber membranes 65 being fixed at the bottom to a base element 68 and each having individually sealed ends at the top that float freely in the liquid, the base element 68 having a permeate collecting chamber 70 to which the inner space 66 of the hollow fiber membranes 65 is connected for collecting filtrate from the inner space 66, the ends 69 being sealed by one of the methods according to the invention.

[0073] 6 shows a cross-sectional view of a second membrane filter 71 for filtering liquids with hollow fiber membranes 72 according to the invention, which is attached at the bottom to a base element 73 and at the top to an individually sealed membrane filter 71 floating freely in the liquid. The membrane filter 71 has almost the same structure as the first membrane filter 64. Moreover, the hollow fiber membranes 72 of the base element 73 are surrounded by a tube 74. As a result, the air introduced into the membrane filter 71 for flushing the hollow fiber membranes 72 is better retained in the bundle of hollow fiber membranes 72 and is thereby better utilized for flushing purposes. [Explanation of symbols]

[0074] 1. Hollow fiber membrane 2 parts 3. Resin 4 Longitudinal axis 5. Inner Space 6. Wall 7 Textile Layer 8 Outer diameter 9. Diameter of inner space 10 End face 11 Edge area 12 Swelling 13 Outer free surface 14 Membrane surface 15 UV light 16 Resin plug 17 Gripper 18 Hopper 19 Pipe Section 20 Inner diameter 21 Free end 22 UV curing unit 23 Textile layer 24 Hollow fiber membrane 25 Edge area 26 Gripper 27 Longitudinal axis 28 Injection needle 29 Inner Space 30 Needle outer diameter 31 Diameter of inner space 32 parts 33 Resin 34 End face 35 Wall 36 Membrane surface 37 UV light 38 outer free surface 39 Inner free surface 40 Hollow fiber membrane 41 Inner Space 42 Wall 43 Textile layer 44 Edge area 45 portions 46 Resin 47 Plug 48 End face 49 Outer free surface 50 inner free surface 51 Membrane surface 52 Hollow fiber membrane 53 Inner Space 54 Wall 55 Textile Layer 56 Edge area 57 parts 58 Resin 59 Resin plug 60 End face 61 outer free surface 62 Inner free surface 63 distance 64 Membrane Filter 65 Hollow fiber membrane 66 Inner Space 67 Wall 68 Basic Elements 69 End 70 Permeate collection chamber 71 Membrane Filter 72 Hollow fiber membrane 73 Basic Elements 74 tube

Claims

1. A method for sealing one side of a hollow fiber membrane (1, 24, 40, 52, 65, 72), the hollow fiber membrane (1, 24, 40, 52, 65, 72) having an inner space (5, 29, 41, 53, 66) and a wall (6, 35, 42, 54, 67) radially surrounding the inner space (5, 29, 41, 53, 66), the wall (6, 35, 42, 54, 67) having an inner textile layer (7, 23, 43, 55), the wall (6, 35, 42, 54, 67) being made of a resin having a viscosity in the range of 200 to 900 mPas (cP). a portion (2, 32, 45, 57) of the grease (3, 33, 46, 58) flows at least partially through the end faces (10, 34, 48, 60) of the hollow fiber membranes (1, 24, 40, 52, 65, 72) into the end regions (11, 25, 44, 56) of the hollow fiber membranes (1, 24, 40, 52, 65, 72), seals said end regions (11, 25, 44, 56) with their outer free surfaces (13, 38, 49, 61) and is cured by UV light (15, 37), The portion (2, 32, 45, 57) of the resin (3, 33, 46, 58) - hardened after a maximum of 5 seconds after being completely delivered through said end faces (10, 34, 48, 60) into said end regions (11, 25, 44, 56) using overpressure; located only inside the hollow fiber membrane (1, 24, 40, 52, 65, 72) after the curing; method.

2. 2. The method according to claim 1, characterized in that the outer free surface (13, 38, 49, 61) of the inner space (5, 29, 41, 53, 66) is concavely shaped.

3. The delivery is performed within a range of 0.5 to 2.5 seconds, the inner space (5, 29, 41, 53, 66) of the end region (11, 25, 44, 56) is initially filled with the resin (3, 33, 46, 58), and between the end of the delivery and the start of the UV irradiation, the resin (3, 33, 46, 58) is removed from the inner space (5, 29, 41, 53, 66) to the walls (6, 35, 42, 54, 3. The method according to claim 1, wherein the resin (3, 33, 46, 58) penetrates to the membrane surface (14, 36, 51) of the end region (11, 25, 44, 56) and thereby soaks into the wall (6, 35, 42, 54, 67), during which the inner space (5, 29, 41, 53, 66) remains sealed by the resin (3, 33, 46, 58).

4. 3. The method according to claim 1 or 2, characterized in that the longitudinal axes (4, 27) of the hollow fiber membranes (1, 24, 40, 52, 65, 72) are in a horizontal position during the sealing.

5. The hollow fiber membranes (1, 24, 40, 52, 65, 72) are held by grippers (17, 26) in front of the end regions (11, 25, 44, 56) during the sealing, while the - a hopper (18) opening into a tube section (19) is pushed over said end region (11, 25, 44, 56) until said tube section (19) closely surrounds the membrane surface (14, 36, 51); - delivering said portion (2, 32, 45, 57) of said resin (3, 33, 46, 58) from a free end (21) of said pipe section (19) through said pipe section (19) into said end region (11, 25, 44, 56); - pushing the hopper (18) away from the end regions (11, 25, 44, 56) again, positioning a UV curing unit (22) on said end region (11, 25, 44, 56) and irradiating said end region (11, 25, 44, 56) with UV light (15, 37) by said UV curing unit (22), thereby curing said portion (2, 32, 45, 57) of said resin (3, 33, 46, 58); 3. The method according to claim 1 or 2, characterized in that

6. A method for manufacturing a membrane filter (64, 71) for filtering liquids, the membrane filter (64, 71) comprising a plurality of hollow fiber membranes (1, 24, 40, 52, 65, 72) each having an inner space (5, 29, 41, 53, 66) and a wall (6, 35, 42, 54, 67) with an inner textile layer (7, 23, 43, 55) surrounding the inner space (5, 29, 41, 53, 66), the plurality of hollow fiber membranes (1, 24, 40, 52, 65, 72) being subjected to a process for producing the membrane filter (64, 71) for filtering liquids. , 40, 52, 65, 72) are fixed at their lower parts to a base element (68, 73) and each have at its upper part an individually sealed end part (69) floating freely in the liquid, said base element (68, 73) having a permeate collecting chamber (70) to which the inner spaces (5, 29, 41, 53, 66) of said plurality of hollow fiber membranes (1, 24, 40, 52, 65, 72) are connected for collecting filtrate from said inner spaces (5, 29, 41, 53, 66); A method for producing a membrane filter (64, 71), characterized in that the ends (69) are sealed according to the method of claim 1 or 2.

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