Method for potting a hollow-fibre membrane bundle in a filter housing

Abstract

The present invention relates to a method for potting the ends of a hollow fibre membrane bundle in a filter housing with a potting compound, by placing a potting cap having a projection on at least one end region of the filter housing, wherein a curable potting compound is injected into the projection of the potting cap and the curable potting compound flows over a terminating edge of the filter housing and pots the ends of the hollow fibre membranes on the end face formed by the hollow fibre bundle.

Description

Method for encapsulating a hollow fiber membrane bundle in a filter housing

[0001] The present application relates to a method for potting the ends of a hollow fiber membrane bundle in a filter housing with a potting compound, a device for carrying out the method, a special potting cap also for carrying out the method, a method for producing a hollow fiber membrane filter, and a hollow fiber membrane filter.

[0002] Hollow-fiber membrane filters are used in extracorporeal blood treatment of patients, water treatment, or biopharmaceutical processes. In the manufacture of hollow-fiber membrane filters, a bundle of hollow-fiber membranes, previously produced using a spinning and bundling process, is inserted into a filter housing of a hollow-fiber membrane filter. Cylindrical filter housings are typically used. The ends of the hollow-fiber membranes are potted in the end regions of the filter housing with a curable potting compound, usually polyurethane, and thus fixed in the housing. The end faces of the potting compounds are then partially removed to expose the open ends of the hollow-fiber membranes. Filter caps are then placed on the end regions of the filter housing. This creates two flow chambers in the hollow-fiber membrane filter.Two fluids can flow through the respective flow chambers and are in a mass transfer relationship with each other via the membrane wall of the hollow fiber membranes. The respective fluids are flowed through the respective flow chambers via one fluid connection on the filter cap and two fluid connections on the filter housing, or two fluid connections on the filter caps. In extracorporeal blood treatment, a first fluid, e.g., patient blood, flows through the fiber interior, and a second fluid, e.g., dialysis fluid, flows through the interior surrounding the hollow fiber membranes.

[0003] A crucial step in the manufacturing process of hollow fiber membrane filters is the casting of the ends of the hollow fiber membrane bundles in the filter housing. This process step is crucial for the productivity of the hollow fiber membrane filter production. This production step requires many individual steps, such as clamping the filter housings in a casting machine, injecting the curable The casting compound is then poured into the end region of the filter housing and the curing of the casting compound is carried out. It is therefore important that these process steps can be largely automated so that the production of hollow fiber membrane filters can be carried out efficiently on the required large scale.

[0004] In addition, the encapsulation of the hollow-fiber membrane bundles in the filter housings also causes significant costs in the production of hollow-fiber membrane filters. Typically, a potting compound that flows at room temperature is used to encapsulate the ends of the hollow-fiber membranes. Such potting compounds generally consist of a composition of several components, particularly prepolymer components, which are designed to cure into a resin within a certain time after mixing and undergoing a chemical reaction. Such curable potting compounds, which are suitable for the production of hollow-fiber membrane filters, are relatively expensive. Therefore, there are ongoing efforts to improve the industrial manufacturing process for hollow-fiber membrane filters so that less potting compound is required to ensure reliable encapsulation of the hollow-fiber membranes in the hollow-fiber membrane filter.

[0005] Furthermore, hollow-fiber membrane filters undergo thermal treatment, e.g., steam sterilization at 121 °C, and material stresses also occur because the materials of the potting compound, the filter housing, and the hollow-fiber membranes have different thermal expansion coefficients. Such material stresses can lead to defective products, which must be identified and eliminated through appropriate quality controls in the industrial manufacturing process. It is therefore desirable to reduce such material stresses by using less potting compound, thus reducing the contact between materials with different thermal expansion coefficients in the hollow-fiber membrane filter.

[0006] In common industrial processes, the curable potting compound is injected into the end areas of the filter housing, whereby the filter housing is rotated around an axis perpendicular to the longitudinal axis of the filter housing and the curable potting compound is evenly distributed in the end area of ​​the filter housing between the hollow fiber membranes by centrifugal forces. The amount of curable potting compound required to securely seal a hollow fiber membrane bundle in the end area of ​​a Potting a hollow fiber membrane filter depends on several factors. Basically, during the rotation and distribution process, the curable potting compound forms a meniscus in the end region of the filter housing. This means that the potting compound takes on a concave surface on the side facing the axis of rotation. In the center of the hollow fiber membrane bundle, the potting height is therefore lower than in the side areas of the hollow fiber membrane bundle that border the filter housing. Depending on the filter type, the meniscus can be more or less pronounced. For filters with a large number of hollow fiber membranes, it may be necessary under certain process conditions to introduce a larger amount of curable potting compound into the end region of the filter housing so that all of the fibers in the center of the hollow fiber membrane bundle can be securely embedded in the potting compound.The formation of the meniscus of the potting compound during rotation can also depend on other process conditions, such as the rotation speed, the diameter, and the length of the filter housing. However, it has been shown that these process conditions cannot be optimized arbitrarily without adequately ensuring the distribution of the curable potting compound between the hollow fiber membranes and thus secure embedding of the hollow fiber membranes in the potting compound. Particularly when the packing density is increased to increase the filtration area, secure embedding becomes more difficult due to the resulting smaller available filling volume between the hollow fibers.

[0007] The patent specification EP 2 024 067 B1 describes a method for introducing a potting compound into a filter device with two flow spaces, of which a first space is formed by the tube passages of the fibers of a hollow fiber membrane bundle and a second space is formed by a housing enclosing the hollow fiber membrane bundle, wherein the end regions of the fibers are cast in a potting compound after casting, and potting caps are placed on top for the introduction of the potting compound. The potting compound is distributed from a potting chamber via the potting caps to the ends of the filter device and the potting chamber and the filter device are set in rotation. The potting compound is injected via the resulting centrifugal forces, so that the potting compound, starting from the potting chamber, overcomes a gap between the potting chamber and the potting cap into a rotationally symmetrical, freely projecting projection of the respective potting cap.

[0008] The principle of the process described in EP 2 024 067 B1 is based on filter devices with tabs at the ends of the housing. In this process, the injected curable potting compound flows between the tabs into the end region of the hollow fiber membranes and is distributed among the hollow fiber membranes, embedding them in the potting compound. Although the process described in EP 2 024 067 B1 is ideally suited for the large-scale industrial production of hollow fiber membrane filters, this process is not suitable for reducing the required amount of curable potting compound. OBJECT OF THE INVENTION

[0009] Based on the disadvantages prevailing in the state of the art, there was a need to optimize the casting of hollow fiber membranes in a filter housing and thus also the production of hollow fiber membrane filters in terms of cost efficiency and mechanical-thermal resilience. SUMMARY OF THE INVENTION

[0010] In a first aspect of the invention, the object is achieved by a method for casting the ends of a hollow fiber membrane bundle in a filter housing according to claim 1.

[0011] In a second aspect of the invention, the object is achieved by a device for casting a hollow fiber membrane bundle in a filter housing according to claim 10.

[0012] In a third aspect of the invention, the object is achieved by a potting cap according to claim 12.

[0013] In a fourth aspect of the invention, the object is achieved by a method for producing a hollow fiber membrane filter according to claim 13.

[0014] In a fifth aspect of the invention, the object is achieved by a Hollow fiber membrane filter according to claim 14. DESCRIPTION OF THE INVENTION

[0015] In a first aspect, the invention relates to a method for potting the ends of a hollow fiber membrane bundle in a filter housing with a potting compound comprising the steps of Inserting a hollow fiber membrane bundle into a filter housing open at two ends with a longitudinal axis, in particular a tubular or cylindrical filter housing with a longitudinal axis, the filter housing having an inner side and an outer side, wherein the filter housing has an end region at each of the two open ends, wherein each end region has a closing edge to the open end of the filter housing, wherein the hollow fiber membranes are inserted into the filter housing in such a way that the hollow fiber membrane bundle forms an end face at the closing edge of the filter housing, Placing a potting cap on at least one end region of the filter housing, the potting cap having at least one first receiving region for receiving the end face of the hollow fiber membrane bundle and the at least one end region of the filter housing, and having a projection which projects beyond the at least one end region on the outside of the filter housing, Injecting a curable casting compound into the projection of the casting cap, so that the curable casting compound flows between the outside of at least one end region of the filter housing and the casting cap, Flowing the curable casting compound over the final edge of the first filter housing so that the curable casting compound flows onto the end face of the hollow fiber membrane bundle formed by the hollow fiber bundle, Casting the ends of the hollow fiber membranes of the hollow fiber membrane bundle in the filter housing and Allowing the casting compound to harden, characterized in that the filter housing with the hollow fiber membrane bundle is rotated about a rotation axis which is perpendicular to the longitudinal axis of the filter housing, so that the overflow of the closing edge of the filter housing with the casting compound and the inflow of the casting compound onto the front side of the hollow fiber membrane bundle is carried out by the centrifugal forces resulting from the rotation of the filter housing.

[0016] The method of the aforementioned type has the advantage that the potting process can be automated. This is made possible in particular by the projection of the potting cap, which allows the curable potting compound to be injected into the potting cap without having to adhere to strict assembly tolerances, which are particularly difficult to achieve during rotation of the filter housing. Furthermore, the curable potting compound penetrates between the fibers from the direction of the end face of the hollow-fiber membrane bundle. The penetration of the curable potting compound between the hollow-fiber membranes thus occurs against the direction of the centrifugal forces acting due to the rotation of the filter housing with the hollow-fiber membrane bundle arranged therein.The curable potting compound on the front side of the ends of the hollow fiber membranes is pressed and distributed between the hollow fiber membranes by the subsequently flowing curable potting compound. The penetration of the curable potting compound from the front side of the ends of the hollow fiber membranes against the prevailing centrifugal forces causes the meniscus depth of the curable potting compound in the end region of the filter housing to decrease. The "meniscus depth" is the difference between the potting height adjacent to the filter housing and the potting height in the center of the hollow fiber membrane bundle. Ultimately, the process distributes the potting compound more evenly in the end region of the filter housing, which allows the potting height and thus also the amount of curable potting compound to be reduced without losing the secure embedding of the hollow fiber membranes in the potting compound.

[0017] For the purposes of this application, the term "hollow fiber membrane bundle" refers to a plurality of hollow fiber membranes arranged largely parallel to one another. The ends of the individual hollow fiber membranes are located adjacent to one another within the hollow fiber membrane bundle.

[0018] According to the present application, the filter housing has an elongated extension and is in particular tubular or cylindrical in shape.

[0019] The term “elongated extension” in the context of the present application means that an object has a larger dimension in one direction than in another direction perpendicular to it.

[0020] In the context of the present application, the term "end region of a filter housing" refers to an end section on the filter housing that extends longitudinally from the end of the filter housing to the center of the filter housing. The term "end region" indicates that this is a region on the filter housing that occupies only a small portion compared to the longitudinal extent of the filter housing. In particular, each of these end regions occupies less than one-fifth, or less than one-eighth, or less than one-tenth, or less than one-fifteenth of the total length of the filter housing.

[0021] As a “final edge 1 is understood as a circumferential edge at the end of the filter housing

[0022] In the context of the present application, the "end face" of the hollow fiber membrane bundle is understood to mean an end face of the hollow fiber membrane bundle in which the ends of the hollow fiber membranes are essentially adjacent to one another. Such an end face can be created, for example, by cutting the hollow fiber membrane bundle perpendicular to its longitudinal extent.

[0023] In the context of the present application, a "potting cap" is understood to mean a cap that can be placed on the end region of the filter housing and covers the end face of the hollow fiber membrane bundle. The potting cap is designed such that the end region or part of the end region of the filter housing and the end face of the hollow fiber membrane bundle are accommodated in a receiving area of ​​the potting cap.

[0024] During the casting step, the curable casting compound flows evenly from the end face between the hollow fiber membranes so that each hollow fiber membrane is enclosed by the casting compound at its respective end. The curable casting compound is a prepolymer mixture that is self-curing, i.e., it reacts to form a cured polymer within a period of time, the so-called pot life. The pot life of the curable casting compound is adjusted so that the curable casting compound is flowable and, in the sense of casting the hollow fiber membranes, can be processed in the liquid state. During the casting process, the ends of the hollow fiber membranes are embedded in the casting compound so that they are fixed to the end areas of the filter housing. The casting compound seals the The potting compound is largely plate-shaped and is arranged in the end area of ​​the filter housing perpendicular to the longitudinal axis of the cylindrical housing.

[0025] In contrast to the method described in the prior art, the potting compound is not directed through lateral openings at the end of the filter housing onto the inside of the filter housing and between the fibers of the hollow fiber membrane bundle. It is preferred that the potting compound be directed exclusively from the end face of the hollow fiber membrane bundle between the ends of the hollow fiber membranes in order to achieve a uniform distribution of the potting compound between the hollow fiber membranes with only a minimal meniscus of the potting compound.

[0026] In a further embodiment of the first aspect, the projection of the potting cap is a partially circumferential projection that partially projects circumferentially beyond the outer side of the end region of the filter housing. The projection of the potting compound ensures that the curable potting compound can be completely introduced into the potting zone at the end region of the filter housing. In particular, the projection eliminates the need to introduce the curable potting compound into the potting zone via a liquid connection. If the projection on the potting cap is partially circumferential, it is also not necessary to specifically align the filter housing. The placement of the potting caps on the end region of the filter housing can therefore advantageously be carried out in an automated manner.

[0027] In a further embodiment of the first aspect, the closure cap sits positively on the end region of the filter housing, and the curable potting compound is flowed through through openings between the potting cap and the outside of the end region of the filter housing onto the end face of the ends of the hollow fiber membrane bundle. The potting cap can thus be placed positively on the end region of the filter housing, but at the same time, a continuous flow of potting compound onto the end face of the hollow fiber membrane bundle is enabled, so that the curable potting compound can penetrate from the end face between the hollow fiber membranes against the direction of the centrifugal forces. In order to create the through openings when the closure cap is in place, slot-shaped recesses are provided on the inside of the closure cap.

[0028] In a further embodiment of the first aspect, the potting cap has a second receiving area, wherein the second receiving area receives the end face of a second hollow fiber membrane bundle, which is introduced into a second filter housing, and the end region of the second filter housing, wherein a transfer channel is arranged between the first and the second receiving area of ​​the potting cap, through which the curable potting compound flows from the first receiving area into the second receiving area onto the end face of the second hollow fiber membrane bundle and the ends of the hollow fiber membranes of the second hollow fiber membrane bundle are potted in the second filter housing.

[0029] According to this embodiment, it is possible to simultaneously cast two hollow-fiber membrane bundles in two filter housings using the method. Furthermore, a casting cap can also be configured to have first, second, and third or first, second, third, and fourth receiving regions for the end regions of the filter housing, so that three hollow-fiber membrane bundles or four hollow-fiber membrane bundles in the respective filter housings can be simultaneously cast with a curable casting compound according to the method according to the invention. In this way, several filter housings can be cast simultaneously in one device, which ultimately reduces the equipment required for casting the hollow-fiber membrane bundles in the filter housings.

[0030] According to a further embodiment of the first aspect, the potting compound is simultaneously injected into the projections of two potting caps, each of which is arranged on two filter housings that are preferably arranged crossed one above the other. Potting caps having one, two, three, four, or more receiving areas can be used, for example, with transfer channels arranged between the respective receiving areas so that the curable potting compound is transferred from the first receiving area to the second, third, and fourth, or to further receiving areas. For example, two filter housings, each with a potting cap having two receiving areas, can be arranged crossed one above the other.Analogously, three or four filter housings connected to potting caps with three or four receiving areas can be arranged crosswise with another three or four filter housings connected to potting caps with three or four receiving areas, one above the other. These arrangements serve to minimize the equipment structure of the potting device.

[0031] In a further embodiment according to the first aspect, the curable potting compound is provided in a potting chamber, and the potting chamber is rotated synchronously with the rotation of one or more filter housings. The curable potting compound is guided via potting channels, each in a radial direction to the axis of rotation of the filter housings in the direction of the projection of the potting cap. The potting chamber is arranged centrally between two potting caps, which are each attached to the opposite end regions of one or more filter housings. According to this embodiment, the curable potting compound is discharged via the potting channels by the centrifugal forces generated during rotation. The potting channels are arranged such that the potting compound is guided in a radial direction to the axis of rotation in the direction of the potting caps.The discharge of the curable casting compound from the casting chamber can thus be caused solely by the resulting centrifugal forces. The rotation of the filter housing and the casting chamber can be synchronized electronically or mechanically.

[0032] In a further embodiment according to the first aspect, the curable potting compound, when injected into the projection of the potting cap, jumps over an air gap due to centrifugal forces and is captured by the projection of the potting compound. In particular, in a further embodiment, the potting compound is discharged from the potting chamber by centrifugal forces and flows radially to the rotation axis through the potting channels and is injected through an opening at the end of the potting channels. This arrangement eliminates the need for the potting chamber and the potting cap to be connected by specially provided fluid-connecting channels.

[0033] In a further embodiment according to the first aspect, the filter housing and the casting chamber are arranged on an assembly table, and the assembly table is rotated about the rotation axis (R). In this arrangement, it can be provided that the filter housing is fastened to the assembly table by a holding device, and the casting chamber is also installed on the assembly table by fastening means. In this case, the rotation of the casting chamber and that of the filter housing are mechanically coupled. It is therefore no longer necessary to synchronize the rotation of the casting chamber and that of the filter housing. In an alternative embodiment, it can be provided that the casting chamber and assembly table are mounted separately, and the synchronization of the rotations of the casting chamber and the filter housing takes place electronically. This can This can be particularly the case if several, e.g. 2, 4, 6, 8, 10 filter housings are arranged on an assembly table.

[0034] A further embodiment of the first aspect is characterized in that at least one further filter housing (200), e.g., a second (200), third (300), and fourth (400) filter housing, each with a hollow fiber membrane bundle incorporated therein, is arranged on the assembly table. The arrangement of multiple filter housings on an assembly table enables economical process control, particularly when multiple filter housings are connected to one another by sealing caps with multiple receiving areas.

[0035] According to this embodiment, it is advantageous that the respective end faces of the ends of the first and of the at least one further hollow fiber membrane bundle, e.g. the end faces of the ends of the second, third and fourth hollow fiber membrane bundle and the respective end regions of the first and of the at least one further filter housing, e.g. the respective end regions of the second, third and fourth filter housing are each received in the first and second and e.g. further receiving regions of a potting cap, and the ends of the first and of the at least one further, e.g. second, third and fourth hollow fiber membrane bundle are potted simultaneously in the respective first and at least one further, e.g. second, third and fourth filter housings.

[0036] In a second aspect, the invention relates to a device for potting a hollow fiber membrane bundle in a filter housing for carrying out a method according to an embodiment of the first aspect of the invention, wherein the device has an arrangement with an assembly table with at least one holding device for at least one filter housing with a hollow fiber membrane bundle arranged therein with an elongated extension, in particular a tubular elongated extension, along a longitudinal axis of extent, and potting caps which are placed on the respective end regions of the filter housing, and having a potting chamber, wherein the assembly table is mounted so as to be rotatable about an axis of rotation which runs perpendicular to the longitudinal axis of extent of the filter housing.

[0037] The device is particularly characterized in one embodiment in that the casting chamber is fixedly mounted on the assembly table and thus performs the same rotation as the assembly table and the filter housings installed in the holding device. According to this arrangement, the curable casting compound can be introduced via casting channels into radially to the rotation axis (R) in the direction of the potting cap and are injected through terminal openings on the potting channels via an air gap into the projection of the potting cap. The potting chamber and filter housing are advantageously arranged on the assembly table such that the rotation of the assembly table around the rotation axis passes through the centers of gravity of the potting chamber and the one or more filter housings.

[0038] In an alternative embodiment according to the second aspect, the assembly table of the encapsulation device has holding devices for an even number of filter housings, in particular 2, 4, 6, 8 filter housings. It is particularly advantageous if the assembly table has holding devices for filter housings that are connected in pairs, optionally three or four times, to respective encapsulation caps with two receiving areas, optionally three or four receiving areas.

[0039] In a third aspect, the invention relates to a potting cap for potting at least two hollow fiber membrane bundles with a curable potting compound, which are each arranged in a first and a second filter housing, wherein the potting cap has a first receiving area for receiving an end area of ​​the first filter housing and the first hollow fiber membrane bundle introduced therein and at least one second receiving area for receiving an end area of ​​the second filter housing and the second hollow fiber membrane bundle introduced therein, wherein the first receiving area and the second receiving area are connected to a transfer channel with which the curable potting compound can flow from the first receiving area into the second receiving area and wherein the potting cap has at least partially a circumferential projection,with which a curable casting compound injected through an air gap can be collected and flowed into the first receiving area.

[0040] With the aid of such a potting cap, two filter housings can be potted simultaneously according to the method according to the invention. In an alternative embodiment, such a potting cap can also have a third and a fourth receiving area and a transfer channel between the second receiving area and the third receiving area and between the third and fourth receiving areas. The potting cap is designed in such a way that it can simultaneously fit positively onto the end areas of a first filter housing and a second The potting compound is flowed to the end faces of the hollow-fiber membrane bundles via through-holes located in the closure cap at the form-fitting seat between the potting cap and the end area of ​​a filter housing.

[0041] In a fourth aspect, the invention relates to a method for producing a hollow fiber membrane filter comprising the method steps according to an embodiment of the first aspect of the invention, and further comprising the steps of exposing the lumens of the hollow fiber membranes by removing a layer of the potting compound on the end face of the potted ends of the hollow fiber membranes, sealingly attaching filter caps to the respective end regions of the filter housing so that two flow spaces are formed, wherein the first flow space comprises the inner volume of the hollow fiber membranes and the second flow space comprises the volume between the hollow fiber membranes and the filter housing.

[0042] According to the method, hollow fiber membrane filters with a low potting height can be produced, since only a weakly pronounced meniscus depth is formed during the potting of the hollow fiber membranes in the filter housing according to the method of the first aspect.

[0043] In a fifth aspect, the invention relates to a hollow fiber membrane filter comprising a filter housing, the filter housing comprising two end regions, each with two closing edges, a hollow fiber membrane bundle arranged in the filter housing, wherein the hollow fiber membrane bundle is embedded in a potting compound at the ends of the hollow fiber membranes with the filter housing in the end region of the filter housing, filter caps are each sealingly attached to the end regions of the filter housing, wherein the hollow fiber membrane filter has two flow spaces, wherein the first flow space comprises the inner volume of the hollow fiber membranes and the second flow space comprises the volume between the hollow fiber membranes and the filter housing, characterized in that the potting height of the potting compound is 3 to 7 mm, in particular 4 to 6 mm, or 4.5 to 5.5 mm.The potting height is lower in the center of the hollow fiber membrane bundle than at the edge of the hollow fiber membrane bundle adjacent to the filter housing. The potting height is the smallest thickness of the potting.

[0044] In a further embodiment of the fifth aspect, the meniscus depth of the The thickness of the cured potting cap is preferably less than 3 mm, 2 mm, or 1 mm. Meniscus depth is defined as the difference in the thickness of the potting compound between the point of minimum thickness and the thickness of the potting compound at the edge of the hollow fiber bundle.

[0045] The inner diameter of the filter housing of a hollow fiber membrane filter according to the invention is, in one embodiment, 25 to 45 mm, preferably 30 to 40 mm. In particular, 6000 to 15000, preferably 9000 to 15000 hollow fiber membranes can be arranged in the filter housing of the hollow fiber membrane filter, so that the hollow fiber membrane filter has a membrane surface of 1.2 to 2.5 m2 The filter housing of the hollow-fiber membrane filter is preferably tubular, in particular cylindrical. The "membrane surface area" is calculated from the product of the inner surface area of ​​the hollow-fiber membranes and the number of hollow-fiber membranes arranged in the cylindrical housing of the hollow-fiber membrane filter. The inner surface area of ​​the hollow-fiber membranes is calculated from the product of the inner diameter of a hollow-fiber membrane, the circular constant TT, and the effective effective length.

[0046] In alternative embodiments, the membrane surface of the hollow fiber membrane filter according to the invention is 1.3 to 1.9 m 2 or 1.3 to 1.8 m 2 , or 1.4 to 1.7 m 2 .

[0047] In certain embodiments, the hollow fiber membrane filters of the present invention have an aspect ratio of 8.0 to 10.0 with a membrane surface area of ​​1.6 to 2.0 m 2In alternative embodiments, the hollow fiber membrane filters have an aspect ratio of 8.5 to 9.5 with a membrane surface area of ​​1.3 to 1.6 m 2 In the context of the present application, the "aspect ratio" is understood to be the quotient of the effective effective length of the hollow fiber membranes and the inner diameter of the cylindrical housing of the hollow fiber membrane filter.

[0048] In the context of the present application, the "effective effective length" of the hollow fiber membrane filter is understood to be the distance between the potting compounds at the point of the smallest thickness of the potting compound, at which effective mass transfer can occur via the hollow fiber membranes. In certain embodiments, the hollow fiber membrane filter according to the present invention has an aspect ratio of 8 to 12, 8.5 to 11, 8.5 to 10, or 9 to 10.

[0049] The effective effective length of the hollow fiber membranes in these embodiments is 270 to 320 mm. In an advantageous embodiment According to the invention, the hollow fiber membrane filter is characterized in that the effective effective length of the hollow fiber membranes is 280 to 320 mm, in particular 285 to 310 mm or 290 to 310 mm. The selection of the aspect ratio, the membrane surface area, and the effective effective length within the previously described ranges enables, in particular, effective removal of middle molecules in extracorporeal blood purification therapies, such as hemodialysis or hemofiltration. In this context, middle molecules are referred to as blood serum proteins with a molecular weight of 10,000 Daltons to 50,000 Daltons. At the same time, however, an excessive pressure drop across the length of the lumen of the hollow fiber membranes is avoided, which thus prevents the problem of excessive hemolysis or membrane clogging.

[0050] The effective effective length of the hollow fiber membranes is increased by the low potting height of the cured potting compound. Therefore, with the same length of the filter housing, higher performance parameters of the hollow fiber membrane filter can be achieved with the reduced potting height according to the first, fourth or fifth aspect of the invention.

[0051] The inner diameter of the cylindrical housing can be reduced to 25 to 35 mm, or 25 to 33 mm or 28 to 33 mm within the aspect ratio defined according to the invention, so that an improved flow to the hollow fiber membranes in the second flow space can take place.

[0052] Hollow fiber membranes made of polysulfone and polyvinylpyrrolidone are preferably used to construct a hollow fiber membrane filter according to the invention.

[0053] The potting compounds with which the hollow fiber membranes are embedded and sealed at the respective end areas of the cylindrical housing are preferably made of polyurethane.

[0054] The filter housing and filter caps are preferably made of polypropylene. A polypropylene housing is advantageous for reliably accommodating long fiber bundles during production.

[0055] In an advantageous embodiment of the invention, the hollow fiber membrane filter is characterized in that the packing density of the hollow fiber membranes is greater than 50%, preferably greater than 57%, more particularly greater than 60%, particularly preferably greater than 62%. In certain embodiments, the packing density is not greater than 70%. In the context of the present application, "packing density" is defined as the proportion in the interior of the cylindrical housing, which is occupied by the hollow fiber membranes. The packing density is calculated from the percentage ratio of the sum of the cross-sectional areas of the hollow fiber membranes, measured at the outer fiber diameter, to the cross-sectional area of ​​the cylindrical housing of the hollow fiber membrane filter, whereby the cross-sectional area of ​​the cylindrical housing is understood only to be the cross-sectional area determined by the inner diameter, measured at the narrowest point of the housing. Hollow fiber membrane filters are particularly difficult to cast during production if the packing density is particularly high. In contrast, the separation properties, measured as clearance for low-molecular-weight substances, are particularly high if the packing density is high and, if applicable, the aspect ratio is also high. For such hollow fiber membrane filters, the teaching of the invention has been shown to be particularly advantageous.The manufacturing process is simplified, costs are reduced and material consumption, especially the consumption of potting material, is reduced. DESCRIPTION OF THE INVENTION WITH RESPECT TO THE FIGURES

[0056] The invention is further explained below with reference to the figures. Fig. 1 is a schematic representation of a filter housing with a potting cap attached and the schematically represented flow path of a curable potting compound, Fig. 2 is a schematic representation of a potting cap with two receiving areas and two filter housings arranged therein and the schematically represented flow path of a curable potting compound. Fig. 3 is a schematic representation of a cylindrical filter housing in which a casting compound is located at the respective end areas. Fig. 4 is a schematic representation of a part of a filter housing in which a casting compound is located at one end area. Fig. 5 is a construction drawing of an assembly table of a device according to the invention with four filter housings held therein.

[0057] Fig.1 shows a part of a cylindrical filter housing 100 in a side view with an end region 105 and a closing edge 107, which forms an open end 103 of the Filter housing 100. Furthermore, Fig. 1 shows a cross-section of a potting cap 109 which sits positively on the end region 105 and covers an end face 108 of a hollow fiber membrane bundle, which is not shown in Fig. 1. Reference 110 designates the receiving area of ​​the potting cap, which excludes the end face 108 of the hollow fiber membrane bundle and part of the end region 105 of the filter housing. The potting cap 109 has a projection 111 which projects beyond the end region 105 and part of the filter housing 100. Furthermore, the path 112 of an inflow of a curable potting compound is shown schematically by arrows. In the embodiment shown in Fig. 1, a filter housing 100 is shown which has lateral openings 101.These openings are provided to allow an inflow or outflow of liquid into the second flow region of the hollow fiber membrane filter during its functional use. Advantageously, these openings 101 are arranged laterally on the filter housing 100, i.e., in the illustration shown, they are directed towards the viewer. The openings are not relevant in connection with the method according to the first aspect of the invention. Furthermore, Fig. 1 shows a casting channel 511 through which a curable casting compound can be discharged via the opening 512. Between the opening 512 and the projection 111 there is an air gap over which the curable casting compound jumps during the casting process. The discharged curable casting compound is then captured by the projection 111 of the casting cap 109 and further guided through the casting compound. As in Fig.1, the curable potting compound flows between an outer region of the end region 105 of the filter housing 100 and the wall of the potting cap, overflowing the final edge 107 and the potting compound flowing onto the end face 108. Along the arrows shown in Fig. 1, the potting compound flows from the end face into the end of the hollow fiber membrane bundle and is distributed between the hollow fiber membranes not shown in Fig. 1. The discharge of the curable potting compound through the potting channel 511 and through the opening 512 as well as the flowing through the potting cap with the curable potting cap is caused by the rotational movement that is carried out around the rotation axis R.

[0058] Fig. 2 shows a schematic cross-sectional view of another embodiment for encapsulating hollow fiber membrane bundles in a filter housing. The encapsulation cap 209 shown in Fig. 2 has two receiving areas 210a and 210b. and is positively mounted on the end regions 105, 205 of two filter housings 100 and 200. Symmetrically arranged, the potting cap 209 has two projections 211a and 211b. According to the flow path of the curable potting cap shown by the arrows in Fig. 2, however, in the embodiment shown, only the projection 211a is used to introduce the curable potting compound into the potting cap. The potting cap 209 sits positively on the end regions 105 and 205 of the filter housings 100 and 200 and covers the respective end faces of the hollow fiber membrane bundles, which are not shown in Fig. 2 or are not visible in the cross-sectional drawing. References 214a and 214b in Fig. 2 indicate one of several through-openings through which the curable potting compound can flow between the potting cap and the outside of the end region of the filter housing onto the front side of the ends of the hollow fiber membranes.According to the arrows shown, the discharged curable potting compound is captured via the projection 211a and flows between the wall of the potting cap and the outer region of the end region 105 of the filter housing 100, over the closing edge 107 onto the end face of the hollow fiber membrane bundle of the first filter housing 100, where it is distributed between the hollow fiber membranes. The curable potting compound flows via the openings 214a onto the end face of the hollow fiber membrane bundle. The potting compound flows through the first receiving region 210a and is flowed via the transfer channel 213 into the second receiving region 210b through the openings 214b onto the end face of the hollow fiber membrane bundle of the second filter housing 200. According to the embodiment shown in Fig. 2, two hollow fiber membrane bundles can be potted simultaneously in a first and a second filter housing, respectively. Analogous to the embodiment shown in Fig.1, the discharge of the curable casting compound through the casting channel and through the opening as well as the flow through the casting cap with the curable casting compound is caused by the rotational movement which is carried out around the rotation axis R.

[0059] Fig. 3 shows an embodiment of a filter housing 100 in a side view, as it is used in the method according to the invention and is rotated about the rotation axis R. The filter housing has a cylindrical shape along a longitudinal axis L. In the embodiment shown, the filter housing 100 has openings 101a and 101b at the respective end regions 105 and 106. The Openings in the assembled hollow fiber membrane filter serve to allow liquid, e.g. dialysate, if the hollow fiber membrane filter is a dialyzer for extracorporeal blood treatment, to flow into the second flow chamber of the hollow fiber membrane filter, which comprises the space between the hollow fiber membranes inside the filter housing. Furthermore, in Fig. 3, a casting compound 113a and 113b is shown schematically on the inside of the end regions 105 and 106 at the respective ends 103 and 104 of the filter housing. The casting compound is plate-shaped and embeds the hollow fiber membrane bundle (not shown in Fig. 3) in a sealing manner at the respective end regions 105, 106 of the filter housing 100. The surface of the casting compound is concavely curved in the direction of the rotation axis R and forms the typical meniscus.3 also shows the terminating edges 107a and 107b of the filter housing at the respective end regions 105 and 106. As previously described, according to the method according to the invention, the terminating edges on the outside of the end regions are flowed over, such that the curable potting compound reaches the end faces 108a and 108b shown in Fig. 3 and from there flows between the hollow fiber membranes on the inside of the end regions 105 and 106. In the method according to the invention, care is taken to ensure that the openings 101a and 101b are not covered by the curable potting compound. Based on the method according to the invention, the potting height and the meniscus depth of the potting compound in the end regions 105 and 106 can be kept so low that the openings 101a and 101b shown are not covered.

[0060] The characteristics of the potting height and meniscus depth achieved by the method according to the invention are further illustrated in Fig. 4. Fig. 4 shows an enlargement of the upper part of the filter housing 100 from Fig. 3. According to Fig. 4, it is shown that the potting height of the potting compound 113a laterally adjacent to the end region 105 of the filter housing 100 is 6.0 mm. In the center of the potting compound, the potting height is 5.0 mm. The meniscus depth is thus 1 mm. The meniscus depth is calculated from the value of the highest potting height minus the value of the lowest potting height.

[0061] Fig. 5 shows an embodiment of an assembly table 501 of a device according to the invention for receiving four filter housings 100, 200, 300, 400 and encapsulating hollow fiber membrane bundles in the respective filter housings. In the embodiment shown, the filter housings are connected in pairs via closure caps 209, each with two receiving areas placed on the end areas of the filter housings. The closure caps are designed in detail as shown in Fig. 2. Of the four closure caps in Fig. 5, two of the four closure caps shown are referenced. The filter housing pairs are fastened crosswise in the assembly table via holding devices 502A, 502B, 502C, 502D. The assembly table is rotatably mounted so that the assembly table can rotate about the rotation axis R. The bearing for the rotational movement is not shown in Fig. 5. In the arrangement shown in Fig. 5, the rotation axis R is perpendicular to the longitudinal extension axes L of the filter housings, which in Fig. 5 is shown only for the filter housing 200. According to the arrangement shown in Fig. 5, the rotation axis is also perpendicular to the longitudinal extension axes (not shown) of the other filter housings 100, 300, 400.The assembly table 501 is designed and the arrangement of the filter housings is selected such that rotation occurs around the center of gravity of each filter housing. Reference 510 in Fig. 5 shows a potting chamber. During potting, the curable potting compound for potting the hollow fiber membrane bundles in the filter housings is located in the potting chamber. The hollow fiber membrane bundles are not shown in Fig. 5. Potting channels 511A, 511B, 511C, 511D extend from the potting chamber 501, the orientation of the potting channels being selected such that the potting compound is discharged in the radial direction to the rotation axis by rotation of the potting chamber around the rotation axis R. At the end of the casting channels 511A, 511B, 511C, 511D there are openings 512A, 512B, 512C, 512D so that the casting compound can exit through the openings while rotating and be injected into the projection 211a of the casting cap 209. According to the diagram shown in Fig.In the arrangement shown in Figure 5, the potting compound jumps over an air gap when the assembly table 501 rotates and is captured by a respective projection of the potting caps 209. The potting chamber 510 is connected to the assembly table via one or more fastening means 513. The position of the potting chamber on the assembly table is selected such that the axis of rotation runs through the center of gravity of the potting chamber. In the illustration shown, the potting chamber is arranged above the crosswise arranged filter housing pairs. The assembly table, filter housing, and potting chamber therefore perform an identical rotational movement during the rotational movement.

Claims

CLAIMS 1. A method for potting the ends of a hollow fiber membrane bundle in a filter housing (100) with a potting compound comprising the steps Inserting a hollow fiber membrane bundle into a filter housing (100) open at two ends (103, 104) with a longitudinal axis (L), in particular a tubular or cylindrical filter housing with a longitudinal axis (L), the filter housing having an inner side and an outer side, wherein the filter housing has an end region (105, 106) at each of the two open ends (103, 104), wherein each end region (105, 106) has a closing edge (107, 107a, 107b) to the open end (103, 104) of the filter housing, wherein the hollow fiber membranes are inserted into the filter housing in such a way that the hollow fiber membrane bundle (101) forms an end face (108) at the closing edge (101) of the filter housing (100), Placing a potting cap (109, 209) on at least one end region (105) of the filter housing (100), the potting cap (109, 209) having at least one first receiving region (110, 210a) for receiving the end face (108) of the hollow fiber membrane bundle and the at least one end region (105) of the filter housing (100), and having a projection (111, 211a) which projects beyond the at least one end region (105) on the outside of the filter housing (100), Injecting a curable casting compound into the projection (111, 211) of the casting cap (109, 209) so that the curable casting compound flows between the outer side of the at least one end region (105) of the filter housing (100) and the casting cap (109, 209), Flowing over the final edge (107, 107a, 107b) of the first filter housing (100) with the curable casting compound, so that the curable casting compound flows onto the end face (108) of the hollow fiber membrane bundle formed by the hollow fiber bundle (101), Casting the ends of the hollow fiber membranes of the hollow fiber membrane bundle in the Filter housing (100) and Allowing the casting compound to harden, characterized in that the filter housing (100) with the hollow fiber membrane bundle is rotated about a rotation axis (R) which is perpendicular to the longitudinal axis (L) of the filter housing, such that the casting compound flows over the final edge (107, 107a) of the filter housing (100) and the casting compound flows into the end face (108) of the hollow fiber membrane bundle due to the centrifugal forces resulting from the rotation of the filter housing (100).

2. Method according to claim 1, characterized in that the projection (111, 211a) of the casting cap (109, 209) is a partially circumferential projection which partially projects circumferentially beyond the outer side of the at least one end region (105) of the filter housing (100).

3. Method according to one of the preceding claims, characterized in that the closure cap (109, 209) sits positively on the end region (105) of the filter housing (100) and the curable potting compound flows via through openings between the potting cap and the outside of the end region (105) of the filter housing onto (into?) the end face (108) of the hollow fiber membrane bundle.

4. Method according to one of the preceding claims, characterized in that the potting cap (209) has a second receiving area (210b), wherein the second receiving area (210b) receives the end face of a second hollow fiber membrane bundle, which is introduced into a second filter housing (200), and the end area (205) of the second filter housing, wherein between the first and the second receiving area (210b) of the potting cap (209) a transfer channel (213) is arranged through which the curable potting compound flows from the first receiving area (210a) into the second receiving area (210b) onto the end face of the second hollow fiber membrane bundle and the ends of the hollow fiber membranes of the second hollow fiber membrane bundle in the second Filter housings are cast.

5. Method according to claim one of the preceding claims, characterized in that the curable potting compound is provided in a potting chamber (510) and the potting chamber is rotated synchronously with the rotation of the filter housing (100) and is guided via at least one potting channel (511A, 511B, 511C, 511D) radially to the axis of rotation (R) of the filter housing in the direction of the projection (111) of the potting cap (109).

6. The method according to claim 5, characterized in that the curable potting compound, starting from an opening of the at least one potting channel (512A, 512B, 512C, 512D), jumps over an air gap when injected into the projection (111) of the potting cap (109) and is captured by the projection (111) of the potting compound.

7. The method according to claim 5 or 6, characterized in that the at least one filter housing (100) and the casting chamber (510) are arranged on an assembly table (301) and the assembly table (501) is rotated about a rotation axis (R).

8. The method according to claim 7, characterized in that at least one further filter housing (200), e.g. a second (200), third (300) and a fourth (400) filter housing, each with a hollow fiber membrane bundle introduced therein, is arranged on the assembly table.

9. The method according to claim 8, characterized in that the respective end faces of the ends of the first and of the at least one further hollow fiber membrane bundle, e.g. the end faces of the ends of the second, third and fourth hollow fiber membrane bundle and the respective end regions (105, 204) of the first and of the at least one further filter housing (100, 200), e.g. the respective end regions of the second (200), third (300) and fourth filter housing (400) are each received in the first (110) and second (210) receiving regions of a potting cap according to claim 4, and the ends of the first and of the at least one further e.g. second, third and fourth hollow fiber membrane bundle in the respective first (100) and at least one further, e.g. second (200), third (300) and fourth (400) filter housings are cast simultaneously.

10. Device for potting a hollow fiber membrane bundle in a filter housing (100) for carrying out a method according to one of claims 1 to 9, comprising an arrangement with an assembly table (501) with a holding device (502) for at least one filter housing (100) with a hollow fiber membrane bundle arranged therein and an elongated extension, in particular a tubular elongated extension, along a longitudinal axis (L), and potting caps (109) which are placed on the respective end regions (105) of the filter housing (100), and comprising a potting chamber (510), wherein the assembly table (501) is mounted so as to be rotatable about an axis of rotation (R) which runs perpendicular to the longitudinal axis (L) of the filter housing.

11. Device according to claim 10, characterized in that the assembly table (501) has holding devices (502) for an even number of filter housings, in particular 2, 4, 6, 8, 10 filter housings.

12. Potting cap (213) for potting at least two hollow fiber membrane bundles with a curable potting compound (112), which are each arranged in a first (100) and a second (200) filter housing, wherein the potting cap (209) has a first receiving area (210a) for receiving an end area (105) of the first filter housing (100) and the first hollow fiber membrane bundle introduced therein and at least one second receiving area (210b) for receiving an end area (205) of the second filter housing (200) and the second hollow fiber membrane bundle introduced therein, wherein the first receiving area (210a) and the second receiving area (210b) are connected to a transfer channel (213) with which the curable potting compound can flow from the first receiving area (210a) into the second receiving area (210b), and wherein the potting cap (209) has at least partially a cantilever (211) with which a curable casting compound injected via an air gap can be collected and flowed into the first receiving area (210a).

13. A method for producing a hollow fiber membrane filter comprising the method steps according to claims 1 to 9, and further comprising the steps Exposing the lumina of the hollow fiber membranes by removing a layer of the potting compound on the front side of the potted ends of the hollow fiber membranes, sealingly attaching filter caps to the respective end regions of the filter housing so that two flow spaces are formed, wherein the first flow space comprises the inner volume of the hollow fiber membranes and the second flow space comprises the volume between the hollow fiber membranes and the filter housing.

14. Hollow fiber membrane filter comprising a filter housing, the filter housing comprising: two end regions (105, 106) each with two closing edges (107a, 107b), a hollow fiber membrane bundle arranged in the filter housing, wherein the hollow fiber membrane bundle is embedded in a potting compound at the ends of the hollow fiber membranes with the filter housing in the end region of the filter housing, filter caps sealingly attached to the end regions of the filter housing, wherein the hollow fiber membrane filter has two flow spaces, wherein the first flow space comprises the inner volume of the hollow fiber membranes and the second flow space comprises the volume between the hollow fiber membranes and the filter housing, characterized in that the potting height of the potting compound is 3 to 7 mm, in particular 4 to 6 mm, or 4.5 to 5.5 mm.

15. Hollow fiber membrane filter according to claim 16, characterized in that the meniscus depth is less than or equal to 3 mm, preferably less than or equal to 2 mm, more preferably less than or equal to 1 mm.

16. Hollow fiber membrane filter according to claim 14 or 15, characterized in that the aspect ratio of the effective effective length of the hollow fiber membranes and the inner diameter of the cylindrical housing is 8 to 12.

17. Hollow fiber membrane filter according to claim 14 to 16, characterized in that the Packing density of the hollow fibers in the filter housing is greater than 57%, in particular greater than 60%, further in particular greater than 62%.

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