Hollow fiber membrane and method for sealing hollow fiber membrane

Abstract

A method for one-sidedly sealing a hollow fiber membrane (40) is disclosed, the hollow fiber membrane having a cavity (41) and a wall (42) radially surrounding the cavity (41), wherein the wall (42) has a textile layer (43) located on the inside, wherein a portion (45) of a low-viscosity resin (46) flows at least partially through the end side (48) of the hollow fiber membrane (40) into the end region (44) of the hollow fiber membrane (40), the end region is sealed via an outer free surface (49) and cured by ultraviolet light. A hollow fiber membrane (40) is also disclosed, the hollow fiber membrane having a cavity (41) and a wall (42) surrounding the cavity (41), wherein the wall has a textile layer (43) located on the inside, wherein the end region (44) of the hollow fiber membrane (40) is sealed via an outer free surface (49) by a portion (45) of the low-viscosity resin (46) cured by ultraviolet light before curing. In order to reduce the tendency of clogging between the end regions (44) of the hollow fiber membranes (40) during filtration operation, it is proposed that the portion (45) is introduced completely into the end region (44) through the end side (48) by overpressure and solidifies after a maximum of 5 seconds and is located only within the hollow fiber membranes (40) after solidification.

Description

Technical Field

[0001] The invention firstly relates to a method for one-sided sealing of a hollow fiber membrane, which has a cavity and a wall radially surrounding the cavity, wherein the wall has a textile layer located on the inside, wherein a portion of a low-viscosity resin flows at least partially through the end side of the hollow fiber membrane into the end region of the hollow fiber membrane, the end region is sealed via the outer free surface and cured by UV light.

[0002] The invention also relates to a hollow fiber membrane having a cavity and a wall surrounding the cavity, the wall having an inner textile layer, wherein the end regions of the hollow fiber membrane are closed by UV-cured portions of a low-viscosity resin prior to curing via the outer free surface. Background Art

[0003] Such a method and a membrane filter having such a hollow fiber membrane are known from the documents US 2013 / 0240436 A1 and US 20090039012 A1.

[0004] In the known method, the free ends of the hollow fiber membranes are dipped vertically into a low-viscosity, photocurable resin (adhesive), wherein a portion of the low-viscosity resin flows partially through the end sides of the hollow fiber membranes into the end region of the hollow fiber membranes and seals the hollow fiber membranes with the outer free surface and is cured by UV light.

[0005] In a first known method, the hollow fiber is removed from the resin before curing and a drop of resin remains at the free end, which is cured. It then forms an external free surface to the outside. In a second known method, the hollow fiber membrane is immersed in a mold with resin and remains in the mold until curing. The mold is then removed and the closed end also has an external free surface, which has the contour of the mold.

[0006] In both methods, one part of the section fills the cavity in the end region of the hollow fiber membrane, another part surrounds the membrane surface on the outside in the end region, and another part extends beyond the end side of the hollow fiber membrane and closes it. This achieves a safe closure not only of the cavity but also of the textile layer and the membrane layer applied thereto, i.e. a safe closure of the entire hollow fiber membrane including the wall.

[0007] The resin layer of the drops on the outside on the hollow fiber membrane surface simultaneously causes a thickening of the hollow fiber membrane in the end region. In the first known method, the maximum diameter of the drops is between 0.1 and 1.6 mm, which is greater than the outer diameter of the hollow fiber membrane. In addition, the drops clearly exceed the end cross section of the membrane in the longitudinal direction of the membrane. A similar situation also applies to the second known method.

[0008] A disadvantage when using such membranes in single-head membrane filters (German: Single-Header-Membranfilter) is that the thickening of the membrane ends results in a reduction in the flow cross section, which impedes the removal of hair and fiber connections from the hollow fiber membrane bundle in the membrane filter, especially when the membrane bundle is integrated in a housing, such as a tube. In addition, due to the outer thickening and the application of material behind the end sides of the hollow fiber membranes, a relatively large amount of resin is required for sealing.

[0009] In the background of the invention, document JP-H11 319505 describes a method for simultaneously closing a plurality of hollow fiber membranes, the walls of which are not reinforced by a textile layer located inside. The ends of the hollow fiber membranes are first positioned to be spaced in rows from each other, for example by fixing with adhesive tape. The free fiber ends of the hollow fiber membranes are then immersed in a low-viscosity resin vertically along the longitudinal direction of the membrane. In this resin only rises into the cavity of the hollow fiber membrane by capillary action, more precisely above the surface of the resin reservoir into which the membrane ends are immersed.

[0010] After the hollow fiber membrane is pulled out from the resin storage tank, the resin is cured by irradiating with ultraviolet light. The previous interval of the hollow fiber membrane prevents the resin from acting between the membranes by capillary rise, and it rises like in the cavity of the membrane by capillary action. That is, the resin level in the cavity of the hollow fiber membrane is significantly higher than that outside the hollow fiber membrane. After curing, the immersed end of the hollow fiber membrane has a resin layer on the membrane surface outside. The risk generated here is that some membranes are bonded to each other with their ends. In order to safely overcome possible mutual bonding and the thickening of the outside of the membrane caused by the resin cured on the membrane surface, the end of the membrane is cut like this after the resin is cured, so that a part of resin is still retained in the cavity of the membrane, the end of the resin-sealed hollow fiber membrane, and the outside of the hollow fiber membrane does not have resin. This part of the resin left in the cut fiber is only added to the end region by capillary action through the end side of the hollow fiber membrane. It has a smooth surface after cutting in the cavity to the end side direction of the membrane after the end is cut.

[0011] The condition for the application of this method in the background is a sufficiently high capillary effect in the cavity of the hollow fiber membrane, whereby the resin in the cavity rises significantly above the resin level on the outer side during immersion. This high capillary effect usually only occurs in hollow fiber membranes without a textile layer and with a very small cavity diameter. As an example, the cavity diameter in the method in the background is about 0.35 mm. As the cavity diameter increases, the capillary effect decreases and the resin no longer rises high enough in the cavity at a certain point to be able to use this method.

[0012] Likewise, for hollow fiber membranes without an inner textile layer, patent document CN 110960988A suggests diluting epoxy resin or polyurethane resin with solvent and introducing it into the membrane bundle under pressure, allowing the resin particles to enter the pores of the fiber layer, drying the solvent by air flow and curing the resin at room temperature for several hours or by microwave curing for at least several minutes. Over such a long period of time, the diluted resin will be completely sucked out of the cavity of the membrane by the capillary action of the inner textile layer, and the cavity will reopen as a result.

[0013] In another context of the present invention, document WO 2012 / 147932 A1 describes a method for repairing hollow fiber membranes in membrane filters, wherein the membrane is fixed in a head component (German: Header) at the top and bottom. Here, the defective position of the membrane is cut out, thereby producing two free ends of the cut hollow fiber membrane, which need to be closed. In this case, the closing is performed manually with the help of a hot glue gun. The end of the hollow fiber membrane is first inserted into the tip of the hot glue gun with a shorter length. In order to facilitate this insertion, the tip of the hot glue gun is larger than the outer diameter of the membrane. Then a portion of the hot adhesive is squeezed out from the hot glue gun under pressure, of which only a portion reaches the cavity of the hollow fiber membrane through the end side. The hot glue gun is then removed from the membrane end, after which this portion solidifies and closes the fiber end by cooling. The solidified portion has the largest diameter here, which is significantly larger than the outer diameter of the hollow fiber membrane and significantly protrudes from the end side of the hollow fiber membrane. In this method, both points are important for ensuring reliable closure of the free ends, because the hot adhesive has a high viscosity even in the hot state and therefore does not penetrate into the membrane wall in order to close it. Therefore, the fiber ends can only be closed when, in addition to the plug in the cavity of the membrane, the hot adhesive forms an outer layer outside the outer diameter of the hollow fiber membrane and protrudes from its end side in the longitudinal direction of the hollow fiber membrane. In the above-mentioned document, for the thickening of the membrane end, a value of 1-2 times the outer diameter of the hollow fiber membrane is given, and for the length of the resin layer behind the end cross section in the longitudinal direction of the hollow fiber membrane, a value of 0.1-0.5 times the outer diameter of the hollow fiber membrane is given. Summary of the invention

[0014] The technical problem to be solved by the present invention is to reduce the tendency of hollow fiber membranes to become blocked between their end regions.

[0015] Based on the known method, it is proposed according to the invention that the portion is introduced completely through the end side into the end region by overpressure and solidifies after a maximum of 5 seconds and is located exclusively within the hollow fiber membranes after solidification.

[0016] This has the advantage that the outer region of the hollow fiber membranes has no thickening caused by the resin and there is no resin accumulation, for example in the form of resin drops, behind the end sides of the hollow fiber membranes. As a result, the amount of resin used to seal the hollow fiber membranes is very small, which leads to a small amount of material used according to the method of the invention and thus low costs. In addition, by means of overpressure input and a short waiting time to solidification, the time for sealing the hollow fiber membranes is controllable and can therefore be kept very short, so that the process is easier to automate and is therefore more economical.

[0017] Based on the known hollow fiber membrane proposals, the section is located completely within the hollow fiber membrane.

[0018] As a result, the membrane has no resin thickenings at its closed ends, to which hair and fiber connections can adhere. As a result, the membrane according to the invention has a low tendency to clog.

[0019] In the membrane according to document JP-H11319505 known in the background of the present invention, the part is also completely located in the hollow fiber membrane after solidification. But this membrane does not have a wall with a textile layer located inside. The method described in document JP-H11319505 only works for hollow fiber membranes with higher capillary action in the cavity. Due to the capillary effect, the resin in the cavity rises higher than on the outside of the membrane, so the end of the membrane thickened by the resin can be cut off after solidification. The resin part remaining in the membrane end can be completely located in the hollow fiber membrane. This method does not work for hollow fiber membranes with walls with a textile layer located inside, because this hollow fiber membrane does not have enough capillary effect in the cavity. The reason is that the textile layer has a very large suction effect on low-viscosity resins, which almost completely blocks the capillary effect in the cavity. When the free membrane end of the hollow fiber membrane reinforced by textile is immersed in the low-viscosity resin, the resin entering the cavity is immediately absorbed by the textile layer. Therefore, the resin level in the cavity does not rise, but on the contrary even remains below the resin surface immersed in the hollow fiber membrane. The same is true for the membrane known from document EP2825296. As can be seen from Figures 2, 2A and 3B1 of the known document, the resin level in the cavity is even cured below the resin surface in which the membrane ends are immersed. That is to say, the capillary effect of the cavity is almost non-existent. Therefore, the method in the background document JP-H11319505 does not work for such textile-reinforced membranes.

[0020] The advantage of the method according to the invention is that the part of the resin is completely located in the hollow fiber membrane, and it is not necessary to cut the membrane ends as in the method described above. This saves a method step and the material utilization rate in the production process is higher, i.e. more membrane material goes into the final product. The method according to the invention is therefore more cost-effective and simpler.

[0021] In the membrane according to the invention, a polymer layer is usually applied to the textile layer on the outside, which determines the separation properties of the membrane. Such membranes preferably belong to the field of microfiltration or ultrafiltration, but can also come from the field of nanofiltration or low-pressure reverse osmosis membranes. The textile layer makes the mechanical strength of the membrane higher, which is advantageous, for example, when operating a membrane bioreactor (MBR) for wastewater treatment. Microfiltration or ultrafiltration membranes with pore sizes in the range of 0.02-0.4 μm are usually used here. The outer diameter of the hollow fiber membranes usually used here, which are clamped on one side, is in the range of 1.5-3.0 mm, and the cavity diameter is 0.7-1.8 mm.

[0022] The textile layer of the hollow fiber membrane according to the invention gives the membrane a high mechanical strength, which is advantageous precisely under the harsh operating conditions in the membrane bioreactor (MBR) for wastewater treatment. The scope of the invention includes that the textile layer located inside is, for example, a braided tube (Gewebe-Schlauch), a knitted tube (Gewirk--Schlauch) or a braided tube (Geflecht-Schlauch), a crocheted tube (Strickschlauch) or a nonwoven tube (Vlies-Schlauch) or a felt tube (Filz-Schlauch). But it can also be any other textile material suitable for strengthening the hollow fiber membrane, such as a winding of thread, rope or cable.

[0023] The particular challenge in the one-sided sealing of such hollow fiber membranes with a textile layer in the wall is to seal not only the cavity of the membrane, but also the membrane wall and in particular the textile layer located in the membrane. In alternative methods for sealing, the sealing of the textile-reinforced wall is always achieved in that the cured resin surrounds a continuous area on the outside on the hollow fiber membrane surface and behind the hollow fiber membrane end side, and the wall of the hollow fiber membrane is thus completely embedded in the end region and sealed by this embedding.

[0024] In the method according to the invention, the closed membrane has no such continuous region on the outside on the membrane and behind its end faces and must be impregnated with resin (German: ) The wall in the end region together with the textile layer. To achieve this purpose, the resin must be low-viscosity before curing, because high-viscosity media are difficult to penetrate into the textile layer (see the method in other background document WO2012 / 147932A1).

[0025] The scope of the invention includes that the outer free surface of the part of the resin that solidifies in the cavity is configured to be concave. This can be achieved when the viscosity of the resin is very low, because the resin quickly seeps out of the cavity into the textile layer, so that it is also sucked away from the end side of the hollow fiber membrane. The inwardly concave configuration of the free surface formed here has the advantage that before the resin solidifies, all resin components on the outer end of the membrane are sucked inwardly, and the membrane end is therefore very clean and not uneven due to the residual solidified resin. This is very suitable for scraping off hair and fiber connections during the filtration operation of the hollow fiber membrane.

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

[0027] The scope of the invention includes that the method can also be closed by other UV-curable adhesives or other media with similar viscosities, which are hereby included under the term "resin" within the scope of the invention.

[0028] It is also within the scope of the method according to the invention that the low-viscosity resin has time to penetrate into the textile layer in order to impregnate the textile layer. On the other hand, this time must not be too long, because otherwise there is a risk that the resin will penetrate too far from the cavity into the textile layer, so that the cavity is opened again and is no longer closed by the resin. The challenge is therefore to allow the resin to penetrate the textile layer long enough to impregnate the textile layer and then to cure the resin quickly by UV light, during which time the cavity is still closed by the resin. The curing must therefore be carried out within a limited time window.

[0029] The time of feeding the said part of the resin is also critical. If it is carried out too slowly, the entire resin penetrates directly into the textile layer, wherein the cavity of the hollow fiber membrane is not filled with resin, i.e. the free end is not functionally closed. Therefore, the feeding must be carried out quickly enough to first fill the cavity with resin. To achieve this purpose, the feeding is carried out by overpressure.

[0030] The overpressure during the resin feed can be generated by a pump or by placing the resin in a storage container under overpressure. The resin can also be delivered to the end region of the membrane by means of an injection needle or a piston. In this case, the resin portions can be separated beforehand, for example when using a syringe or a pump with a defined pump volume, or can be continuously discharged from the reservoir, for example by means of a pump.

[0031] Therefore, in order to achieve effective sealing of the membrane ends, the time sequence of the sealing process is important. Therefore, in the method according to the invention, the feeding is advantageously carried out within 0.5-2.5 seconds, and the cavity is first filled with resin in the end region, and there is a waiting time of at least one second between the end of the feeding and the start of the UV irradiation, during which the resin penetrates from the cavity into the wall as far as the membrane surface in the end region and impregnates the wall, while the cavity remains sealed by the resin.

[0032] The method according to the invention also comprises that the longitudinal axis of the hollow fiber membrane is also in a horizontal position during the closing. This is advantageous for the automated process, since the risk of the resin flowing out of the cavity due to gravity is reduced. The process thus runs cleaner and is also easier to automate.

[0033] In the context of a possible automation of the method, it is advantageous if the hollow fiber membranes are held in front of the end region during closing by means of a clamp, during which the

[0034] Push the funnel into the pipe section onto the end area until the pipe section tightly surrounds the membrane surface,

[0035] The part is introduced from the free end of the pipe section through the end side into the end region,

[0036] · Move the funnel away from the end area, and

[0037] Positioning a UV curing unit over the end region, the UV curing unit irradiating the end region with UV light and thereby curing the portion.

[0038] Advantageously, the above process steps are carried out within the time window described above in order to achieve an optimal sealing result. The waiting time is thus composed of the time for pushing out the funnel plus the time for positioning the UV curing unit on the end region of the hollow fiber membrane until the curing process by UV light begins.

[0039] The invention includes the fact that the hollow fiber membranes to be sealed are removed directly from the membrane production plant in an automated process and clamped by a clamp. The clamp clamps the membrane in front of the membrane end region, i.e. the free and not yet sealed membrane ends protrude beyond the clamp. The membrane ends can be bent in one direction or the other.

[0040] The funnel here serves to "catch" the free end of the hollow fiber membrane behind the closed clamp and to center it on the axis of the funnel or the pipe section so that the membrane can be inserted into the funnel when the funnel is pushed on. A funnel angle of 45° has proven to be advantageous here. Once the membrane has penetrated the funnel, it is in a position determined axially by the funnel. The resin is then fed into the end region of the hollow fiber membrane from the free end of the pipe section through the end side by the resin feed device by means of overpressure.

[0041] After the introduction, the residues of the liquid resin can first protrude from the cavity behind the end side as a convex curvature. During the waiting time, the resin is sucked from this curvature into the fibers due to the suction effect of the textile layer. This suction also causes the solidified resin plug in the cavity of the hollow fiber membrane to have a concave inner free surface towards the cavity and a concave outer free surface towards the end side. After the resin solidifies, the clamp releases the membrane before the next membrane is clamped and closed.

[0042] The method according to the invention also includes the pipe section having an inner diameter which is 0.05-0.2 mm larger than the outer diameter of the hollow fiber membrane. This ensures, on the one hand, that the inner diameter is large enough so that the hollow fiber membrane can slide easily and reliably into the funnel when it is pushed onto the funnel. On the other hand, the inner diameter is small enough to ensure that as little resin as possible enters the gap between the membrane surface and the inner wall of the pipe section.

[0043] In the technical process, it is sometimes inevitable that, depending on the ovality and properties of the membrane surface, a very small amount of resin will penetrate into the gap at individual locations. In order to keep the amount of resin that penetrates into the gap to a minimum in this case, it is advantageous to design the part of the pipe section that closely surrounds the membrane surface as long as possible. A length of at least 7 mm has proven to be advantageous.

[0044] Since in the method according to the invention the liquid resin is fed only into the end region via the end sides of the hollow fiber membranes, said part of the resin is not easily accessible from the outside for UV light. Nevertheless, in order to achieve an effective and rapid curing time, the light power of the UV curing unit on the membrane surface must be relatively high. In conventional hollow fiber membranes with a textile layer, this light power should be between 5 and 40 W / cm 2 In range.

[0045] The curing time of the resin section by UV light should be between 0.5 and 2.5 seconds. At low light powers, i.e. too slow curing, there is the risk that the resin will penetrate further from the cavity into the wall and the cavity will open again. At excessive light powers, damage to the membrane can occur or the UV emitter can be damaged by materials, such as glycerol, evaporating uncontrollably from the membrane material.

[0046] It has also proven to be advantageous to temperature-control the hopper during the method according to the invention in order to keep the temperature and, via the temperature, the viscosity of the resin within a predetermined range during the closing process. This ensures constant flow properties of the resin as a condition for defined times of the individual method steps during the closing process. This in turn facilitates the control of the process within the scope of process automation.

[0047] The scope of the invention also includes a membrane filter for filtering liquids, which has hollow fiber membranes, each of which has a cavity and a wall surrounding the cavity, the wall having a textile layer located on the inside, wherein the hollow fiber membranes are fixed in a base element at the bottom and each have a separately closed end at the top, which ends float freely in the liquid, wherein the base element has a permeate collecting space, the cavity of the hollow fiber membrane is connected to the permeate collecting space, and the permeate collecting space is used to collect filtrate from the cavity. According to the invention, the ends of the hollow fiber membranes in this membrane filter are closed according to the method according to the invention.

[0048] Such membrane filters are generally referred to as single-head membrane filters. Such membrane filters according to the invention are suitable, for example, for submerged operation in a membrane bioreactor (MBR) for treating wastewater. Advantageously, hair and fiber connections from the membrane bioreactor sludge are scraped off freely upwards during operation of the membrane filter without getting stuck in the membrane filter.

[0049] The scope of the present invention also includes a hollow fiber membrane having a cavity and a wall radially surrounding the cavity, the wall having a textile layer located on the inside, wherein the end area of ​​the hollow fiber membrane is closed by a UV-cured portion of a low-viscosity resin before curing via the external free surface and wherein the portion is completely located inside the hollow fiber membrane.

[0050] It is advantageous here if the outer free surface of the part in the cavity is designed to be concave, since the film end is then very smooth and clean, since it is not uneven due to outwardly directed resin portions at the outer end of the film.

[0051] The scope of the invention also includes a membrane filter for filtering liquids, the membrane filter having hollow fiber membranes, which are fixed in a base element at the bottom and have a separate closed end at the top, which ends float freely in the liquid, wherein the base element has a permeate collecting space, and the cavity of the hollow fiber membrane is connected to the permeate collecting space in order to collect filtrate from the cavity, characterized in that the hollow fiber membrane is formed according to one of the last two paragraphs mentioned above.

[0052] It is also advantageous that in the membrane filter according to the invention the hollow fiber membranes of the base element are surrounded by a tube. As a result, when operating the membrane filter, for example in a membrane bioreactor (MBR), the air entering for flushing the membranes is retained in the membrane bundle and utilized more efficiently. In particular, when using such a tube, it is advantageous that the membranes do not have resin thickenings in the end cross section. Such thickenings would lead to an unfavorable reduction in the flow cross section, thereby hindering the flow of the liquid to be filtered and scraping hair and fiber attachments from the hollow fiber membranes.

[0053] The present invention is explained below based on embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figures 1a to 1f The process steps of a first method according to the invention are shown in cross section,

[0055] Figure 2a to Figure 2g Further details are shown in cross section for carrying out the first method according to the invention,

[0056] Figure 3a to Figure 3d The process steps of a second method according to the invention are shown in cross section,

[0057] Figure 4a and 4b Shown are cross sections obtained by cutting two different hollow fiber membranes according to the present invention,

[0058] Figure 5 and Figure 6 The figure shows a cross section obtained by cutting through the first and second membrane filters having the hollow fiber membranes according to the present invention.

[0059] The figures shown in the drawings are not to scale. All details not given of the method, hollow fiber membrane or membrane filter according to the invention described below are identical to the description of the method, hollow fiber membrane or membrane filter according to the invention described above. DETAILED DESCRIPTION

[0060] Figures 1a to 1f The process steps of a first method according to the invention for one-sidedly enclosing braided reinforcement of hollow fiber membranes 1 ( Figure 1a ). This portion has a volume of 50 μl. Resin 3 has a viscosity of 300 mPas (cP).

[0061] The hollow fiber membrane 1 has a longitudinal axis 4 which is in a horizontal position during closing. The hollow fiber membrane 1 also has a cavity 5 and a wall 6 radially surrounding the cavity 5. The wall 6 has a textile layer 7 located on the inside for reinforcing the hollow fiber membrane 1, which has an outer diameter 8 of 2.6 mm and a cavity diameter 9 of 1.4 mm.

[0062] The portion 2 is introduced completely through the end side 10 of the hollow fiber membrane 1 into the end region 11 of the hollow fiber membrane 1 by overpressure. In this process, the resin 3 first fills the cavity 5. At the beginning of the introduction of the portion 2, the resin 3 begins to penetrate into the wall 6 and the textile layer 7 ( Figure 1b At the end of the feed, the section 2 is only inside the hollow fiber membrane 1 and outside behind the end side 10 initially has a convex curvature 12 of the still liquid resin 3 ( Figure 1c ). The time used for input is one second.

[0063] During the waiting time starting after the resin 3 has been introduced into the end region 11, the resin 3 seeps out of the cavity 5 into the wall 6 and impregnates the wall 6 together with the textile layer 7. In this case, the resin 3 also returns from the convex curvature 12 into the cavity 5 of the hollow fiber membrane 1 ( Figure 1d ).

[0064] In the subsequent course of the waiting time, the outer free surface 13 of the portion 2 in the cavity 5 is concave, by the resin 3 returning further into the cavity 5 and penetrating from the cavity 5 into the wall 6 ( Figure 1e ). At the same time, the resin penetrates through the wall to the outer membrane surface 14 of the hollow fiber membrane 1.

[0065] After the last irradiation with UV light 15, the waiting time ends and the resin 3 is cured by UV light 15. The current distribution of the parts 2 in the end region 11 is fixed. The waiting time lasts a total of 2 seconds, and the curing lasts a further 1.4 seconds.

[0066] 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 cavity 5 has a concave free outer surface 13. The portion 2 thus closes the cavity 5 and the wall 6 of the hollow fiber membrane 1 together with the textile layer 7, while the membrane surface 14 of the hollow fiber membrane 1 is free on the outside from a layer of resin 3 thickening the hollow fiber membrane 1 in the end region 11 and no cured resin 3 is present outside behind the end side 10 of the hollow fiber membrane 1.

[0067] Figure 2a to Figure 2g Further details for carrying out the first method according to the invention are shown in cross section.

[0068] The hollow fiber membrane 1 is taken out of the production process for its continuous production and is held by a clamp 17 in front of the end region 11. The clamp 17 holds the hollow fiber membrane 1 during the entire closing process. During the clamping process, the end region 11 of the hollow fiber membrane 1 can be slightly bent in one or another direction transverse to the longitudinal axis 4. In order to "catch" and center the end region 11, a funnel 18 leading into a pipe section 19 is pushed onto the end region 11 until the pipe section 19 tightly surrounds the membrane surface 16 ( Figure 2a-2b ). The portion of the tube section 19 that closely surrounds the membrane surface is approximately 8 mm.

[0069] The pipe section 19 has an inner diameter 20 which is 0.1 mm greater than the outer diameter 8 of the hollow fiber membrane 1, i.e. 2.7 mm. The portion 2 is then fed from the free end 21 of the pipe section 20 through the end side 10 into the end region 11. This feeding is carried out by means of a micrometering pump which is designed as a diaphragm pump with a very small stroke of 5 μl. Thus, a portion 2 of 50 μl of resin 3 corresponds to 10 strokes of the micrometering pump, which are carried out in total within one second for feeding the resin 3.

[0070] Depending on the ovality of the hollow fiber membranes, a small portion of the resin 3 enters the gap between the inner diameter 20 of the tube section 19 and the outer diameter 8 of the hollow fiber membrane 1. This portion is at most 0.1% of the portion 2 and results in a thickening of the wall 6 of less than 0.05 mm.

[0071] Then a waiting time begins, during which the funnel 18 is pushed out of the end region 11 again and the UV curing unit 22 is positioned on the end region 11 by pushing it onto the end region 11 instead of the funnel 18. After the UV curing unit 22 is positioned, the end region is irradiated with UV light 15 to cure the portion 2. The UV curing unit 22 has an installed electrical power of 100 W, wherein the total optical power of the UV radiation incident on the film surface 14 is 24 W / cm 2 The curing time of the portion 2 of the resin 3 by the ultraviolet light 15 is 1.4 seconds.

[0072] After curing, the curing unit 22 is pushed out from the end region 11 again, and the clamp 17 releases the hollow fiber membrane 1. The automated closing process of the hollow fiber membrane 1 is thus completed.

[0073] Figure 3a to Figure 3d The process steps of the second method according to the invention are shown in cross section. Here, the hollow fiber membrane 24 reinforced by the textile layer 23 is held by the clamp 26 in the end region 25 so that the longitudinal axis 27 of the hollow fiber membrane 24 is aligned with the injection needle 28 ( Figure 3a ).

[0074] Then, an injection needle 28 is inserted into the lumen 29 of the hollow fiber membrane 24, wherein the injection needle 28 has a needle outer diameter 30 which is 0.1 mm smaller than the lumen diameter 31 ( Figure 3b ).

[0075] A portion 32 of the resin 33 is then introduced into the cavity 29 of the hollow fiber membrane 24 via the injection needle 28 and thus also via the end side 34 of the hollow fiber membrane 24, wherein this portion first diffuses in the cavity 29 and seals it. A waiting time then begins, during which the resin 33 seeps out of the cavity 29 into the wall 35 of the hollow fiber membrane 24 and impregnates the textile layer 23 and the entire wall 35.

[0076] During the waiting time, the injection needle 28 is again withdrawn from the cavity 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, and the clamp 26 then releases the hollow fiber membrane again and the sealing process is thus ended.

[0077] The cured portion 32 of the resin 33 has an outer free surface 38 of concave configuration within the cavity. The inner free surface 39 of the cured portion 32 facing the cavity 29 is also of concave configuration in the cavity 29 .

[0078] Figure 4aA section through a first hollow fiber membrane 40 according to the invention is shown, which membrane is produced according to a first method according to the invention and has a cavity 41 and a wall 42, wherein the wall 42 has a textile layer 43 located on the inside. The end region 44 of the hollow fiber membrane 40 is closed by a portion 45 of a resin 46 cured by UV light, which penetrates (impregnates) the wall 42 together with the textile layer 43 and forms a plug 47 in the cavity 41, which plug has a concavely configured outer free surface 49 toward the end side 48 of the hollow fiber membrane 40. The inner free surface 50 facing inwardly toward the cavity 41 is also concavely configured. The portion 45 is located only inside the hollow fiber membrane 40, starting at the end side 47. A very small portion of the resin 46, less than 0.1% of the portion 45, can also cure on the outside on the membrane surface 51 of the hollow fiber membrane 40. This results in a maximum thickening of the wall 42 of less than 0.05 mm.

[0079] Figure 4b A second hollow fiber membrane 52 according to the invention is shown in section, which membrane is produced according to a second method according to the invention and has a cavity 53 and a wall 54, wherein the wall 54 has a textile layer 55 located on the inside. The end region 56 of the hollow fiber membrane 52 is closed by a portion 57 of a resin 58 cured by UV light, which penetrates (impregnates) the wall 54 together with the textile layer 54 and forms a resin plug 59 in the cavity 53, which has a concavely configured outer free surface 61 toward the end side 60 of the hollow fiber membrane 52. The inner free surface 62 facing inwardly toward the cavity 53 is also of concave configuration. The portion 58 is located only inside the hollow fiber membrane 52 and begins at a distance 63 from the end side 60.

[0080] Figure 5 A cross section is shown of a first membrane filter 64 for filtering liquids, the membrane filter having hollow fiber membranes 65 according to the invention, the hollow fiber membranes each having a cavity 66 and a wall 67 surrounding the cavity 66, wherein the hollow fiber membranes 65 are fixed at the bottom in a base element 68 and each have a separately closed end 69 at the top, which ends float freely in the liquid, wherein the base element 68 has a permeate collecting space 70, to which the cavity 66 of the hollow fiber membranes 65 is connected in order to collect filtrate from the cavity 66, wherein the end 69 is closed according to one of the methods according to the invention.

[0081] Figure 6A cross section of a second membrane filter 71 for filtering a liquid is shown, which has hollow fiber membranes 72 according to the invention, which are fixed in a base element 73 at the bottom and float freely in the liquid in an individually closed manner at the top. The membrane filter 71 is constructed essentially the same as the first membrane filter 64. In addition, 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 can be better retained in the cluster of hollow fiber membranes 72 and thus better used for flushing purposes.

[0082] List of reference numerals:

[0083] 1Hollow fiber membrane

[0084] Part 2

[0085] 3. Resin

[0086] 4 Vertical axis

[0087] 5 chambers

[0088] 6 walls

[0089] 7 textile layers

[0090] 8 outer diameter

[0091] 9 cavity diameter

[0092] 10. Terminal side

[0093] 11 End area

[0094] 12 Arch Department

[0095] 13 External free surface

[0096] 14 Membrane surface

[0097] 15. Ultraviolet light

[0098] 16 Resin plug

[0099] 17 Clamp

[0100] 18 Funnel

[0101] 19 pipe sections

[0102] 20 inner diameter

[0103] 21 Free end

[0104] 22 UV curing units

[0105] 23 textile layers

[0106] 24Hollow fiber membrane

[0107] 25 End area

[0108] 26 Clamps

[0109] 27 Vertical Axis

[0110] 28 Injection Needles

[0111] 29 chambers

[0112] 30 needle outer diameter

[0113] 31 cavity diameter

[0114] 32 parts

[0115] 33 Resin

[0116] 34 end side

[0117] 35 walls

[0118] 36 membrane surface

[0119] 37 UV light

[0120] 38 External free surface

[0121] 39 Internal free surface

[0122] 40 hollow fiber membrane

[0123] 41 chambers

[0124] 42 walls

[0125] 43 textile layers

[0126] 44 End area

[0127] Part 45

[0128] 46 resin

[0129] 47 plug

[0130] 48 side

[0131] 49 External free surface

[0132] 50 Internal free surface

[0133] 51 membrane surface

[0134] 52 Hollow fiber membrane

[0135] 53 chambers

[0136] 54 walls

[0137] 55 textile layers

[0138] 56 End area

[0139] Part 57

[0140] 58 resin

[0141] 59 resin plug

[0142] 60 side

[0143] 61 External free surface

[0144] 62 Internal free surface

[0145] 63Distance

[0146] 64 membrane filters

[0147] 65 hollow fiber membrane

[0148] 66 chambers

[0149] 67 walls

[0150] 68 base element

[0151] 69 end

[0152] 70 permeate collection space

[0153] 71 membrane filter

[0154] 72 Hollow fiber membrane

[0155] 73 base element

[0156] 74 pipe

Claims

1. A method for one-sidedly closing a hollow fiber membrane having a cavity and a wall radially surrounding the cavity, wherein: The wall has an inner textile layer, wherein a portion of the low-viscosity resin flows at least partially through the end side of the hollow fiber membrane into the end region of the hollow fiber membrane, the end region is closed by the outer free surface and cured by UV light, characterized in that the portion is completely introduced into the end region through the end side by means of an overpressure and is cured after a maximum of 5 seconds and is located only in the hollow fiber membrane after curing, wherein the overpressure is generated by a pump and the power range of the UV light used for curing is 5-40 W / cm 2 .

2. The method according to claim 1, characterized in that The outer free surface within the cavity is configured to be concave.

3. The method according to claim 1, characterized in that The input takes place within 0.5-2.5 seconds, and during this the cavity is first filled with the resin in the end region, and there is a waiting time of at least one second between the end of the input and the start of the UV irradiation, during which the resin penetrates from the cavity into the wall as far as the membrane surface in the end region and impregnates the wall, while the cavity remains closed by the resin.

4. The method according to claim 1, characterized in that The longitudinal axes of the hollow fiber membranes are in a horizontal position during closing.

5. The method according to any one of claims 1 to 4, characterized in that When the hollow fiber membrane is closed, it is held by a clamp in front of the end area, during which the funnel introduced into the tube section is automatically pushed onto the end area until the tube section tightly surrounds the membrane surface, the part is input into the end area from the free end of the tube section through the tube section, the funnel is then removed from the end area, and a UV curing unit is positioned above the end area, which irradiates the end area with UV light and thereby cures the part.

6. A membrane filter for filtering liquids, the membrane filter having hollow fiber membranes, the hollow fiber membranes each having a cavity and a wall surrounding the cavity, the wall having a textile layer located inside, wherein the hollow fiber membranes are fixed at the bottom in a base element and each have a separately closed end at the top, which ends float freely in the liquid, wherein: The base element has a permeate collecting space to which the lumens of the hollow fiber membranes are connected in order to collect filtrate from the lumens, characterized in that the end portions are closed according to the method of any one of claims 1 to 5.

7. A hollow fiber membrane produced by the method according to any one of claims 1 to 5, the hollow fiber membrane having a cavity and a wall radially surrounding the cavity, the wall having a textile layer located on the inside, wherein: The end regions of the hollow fiber membranes are closed by means of the outer free surface by means of UV-cured portions of a low-viscosity resin prior to curing, wherein said portions are completely located inside the hollow fiber membranes.

8. The hollow fiber membrane according to claim 7, characterized in that An outer free surface of the portion in the cavity is concave in configuration.

9. A membrane filter for filtering liquids, the membrane filter having hollow fiber membranes which are fixed at the bottom in a base element and have individually closed ends at the top, which ends float freely in the liquid, wherein: The base element has a permeate collecting space to which the lumen of the hollow fiber membranes is connected in order to collect filtrate from the lumen, characterized in that the hollow fiber membranes are constructed according to claim 7 or 8.

10. The membrane filter according to claim 9, characterized in that The hollow fiber membranes of the base element are surrounded by tubes.

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