EP4337372A1

EP4337372A1 - Hollow-fibre membrane filter having improved separation properties

Info

Publication number: EP4337372A1
Application number: EP22728503.8A
Authority: EP
Inventors: Paul Gastauer; Franz Kugelmann; Michael Paul; Andreas Ruffing; Tobias VEIT
Original assignee: Fresenius Medical Care Deutschland GmbH
Current assignee: Fresenius Medical Care Deutschland GmbH
Priority date: 2021-05-11
Filing date: 2022-05-10
Publication date: 2024-03-20
Also published as: CA3219396A1; WO2022238373A1; BR112023023424A2; CN117412802A; DE102021112314A1; AU2022272646A1; KR20240006567A

Abstract

The invention relates to a hollow-fibre membrane filter for purifying liquids, said membrane filter having improved separation properties and comprising: a cylindrical housing; first inflow or outflow chambers and second inflow or outflow chambers surrounding a first and a second end portion, respectively, of the cylindrical housing, the hollow-fibre membrane filter having an aspect ratio of the effective length of the hollow-fibre membranes and the inner diameter of the cylindrical housing so as to improve the inflow of a liquid to the hollow-fibre membranes inside the cylindrical housing.

Description

Hollow fiber membrane filter with improved separation properties

The present invention relates to a hollow-fiber membrane filter for purifying liquids, in particular for purifying blood.

BACKGROUND

[0002] Hollow fiber membrane filters are used in the purification of liquids. In particular, hollow-fiber membrane filters are used in medical technology for the treatment and decontamination of water and in the therapy of patients with kidney damage in extracorporeal blood treatment as dialyzers or haemofilters. The hollow-fiber membrane filters generally consist of a cylindrical housing and a plurality of hollow-fiber membranes arranged therein, which are cast at the ends in the housing with a casting compound in a casting zone and are connected to the housing in a sealing manner. As is known, such hollow-fiber membrane filters are designed in such a way that they are operated in the so-called dead-end process, in the "cross-flow" process or in the countercurrent process of two liquids, so that a material exchange can take place via the membrane wall of the hollow-fiber membranes and a desired purification of the liquid or a of the liquids takes place. For this purpose, the hollow-fiber membrane filters are structurally designed in such a way that the lumina of the hollow-fiber membranes form a first flow space and a first liquid flows through them, and the spaces between the hollow-fiber membranes in the housing of the hollow-fiber membrane filter form a second flow space through which a second liquid can flow. Inflow or outflow chambers are located at one or both end regions of the hollow-fiber membrane filter, which have liquid accesses in order to introduce and discharge the first and the second liquid into the respective flow spaces of the hollow-fiber membrane filter.

There are a large number of hollow-fiber membrane filters on the market, which are designed differently, particularly with regard to the structural design of the end regions and their inflow or outflow chambers adjoining the ends. With regard to the development of hollow-fiber membrane filters for extracorporeal blood treatment (dialyzers and hemofilters), there are ongoing attempts to design to change and improve the hollow fiber membrane filter. On the one hand, emphasis is placed on the geometry of the inflow and outflow chambers of a hollow-fiber membrane filter, through which blood flows, enabling the gentlest possible flow through the chambers, so that turbulent flow or stagnant flows, which can damage blood cells, can be avoided . As is common practice in extracorporeal blood purification, the hollow-fiber membrane filters are constructed in such a way that the patient's blood is conducted through the first flow space, ie through the lumina of the hollow-fiber membranes.

[0004] In addition, there are a number of design proposals for commercially available hollow-fiber membrane filters for extracorporeal blood treatment that are intended to improve the inflow of the hollow-fiber membranes in the second flow space. In the therapeutic use of hollow-fiber membrane filters for extracorporeal blood treatment, an aqueous, physiologically compatible liquid (dialysis liquid) usually flows through the second flow space. The removal of harmful metabolites from the patient's blood then takes place through the transmembrane mass transfer. Among other things, the inflow of the hollow-fiber membranes in the second flow space is decisive for an improved separation of the metabolites.

[0005] Kunikata et al. (Kunikata; ASAIO Journal; 55(3), p. 231-235 (2009) evaluate the performance data of various commercially available dialyzers with regard to their different designs in the inflow area of the dialysis fluid. This publication shows various design models that ensure favorable flow behavior of the Dialysis liquid entering the dialyzer and thus enabling improved performance properties of the hollow fiber membrane filter.

EP 3 238 758 A1 discloses hemodia filters, which are characterized by a specific selection of the design parameters, the packing density of the hollow-fiber membranes, the total length of the hollow-fiber membranes, the effective membrane surface area, and the area ratios of the inner surface of the hollow-fiber membranes and the frontal area of the casting compound. According to EP 3 238 758 A1, the selection this parameter avoids an excessive pressure loss on the blood side and the dialysate side when using the hemofilter, so that the risk of damage to the hollow fiber membranes should be reduced. EP 3 238 758 A1 refers in particular to the integrity of the hollow fiber membranes in the therapeutic use of hemodiafiltration. EP 3 238 758 A1 discloses the use of hollow-fiber membranes with a diameter of 195 to 205 μm.

In terms of improved performance properties of hollow-fiber membrane filters in the application of hemodialysis, it is particularly preferred to use hollow-fiber membranes with a diameter of 190 μm or less in combination with a wall thickness of 38 μm and less in order to be able to achieve the high performance characteristics desired for hemodialysis. In addition, however, there is still a need to improve the design of hollow-fiber membrane filters in such a way that the flow against the hollow-fiber membranes in the second flow space is further improved and the performance properties of the hollow-fiber membrane filter can be further improved.

[0008] Compared to the designs examined in Kunikata, there was therefore a need to develop an alternative design. In addition, there is a continuous search for possibilities to be able to carry out the production of hollow fiber membrane filters in a cost-effective manner.

OBJECT OF THE INVENTION

The object was therefore to provide a hollow-fiber membrane filter which has an improved inflow onto the hollow-fiber membranes and, associated therewith, improved performance data.

SUMMARY OF THE INVENTION

The task is solved by a hollow fiber membrane filter with the features of claim 1. Claims 2 to 14 relate to preferred embodiments. DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a hollow-fiber membrane filter having a cylindrical housing, which extends longitudinally along a central axis, with a housing interior, a first end region with a first end and a second end region with a second end, a plurality of hollow-fiber membranes, having an inner diameter from 150 to 190 pm and a wall thickness of 25 to 38 gm, the hollow-fiber membranes being arranged in the cylindrical housing and being embedded in a sealing compound in the first end area and in the second end area of the cylindrical housing in each case in a sealing compound with the housing in a respective potting zone, wherein the Ends of the hollow-fiber membranes are open, so that the lumens of the hollow-fiber membranes form a first flow space and the interior of the housing surrounding the hollow-fiber membranes forms a second flow space, first inflow or outflow chambers, each on the face side at the first and at the second end of the cylindrical housing it and the casting zone, which are in fluid connection with the first flow space of the hollow-fiber membrane filter and each have first fluid inlets in order to feed or drain fluid into/out of the first inflow or outflow chambers, second inflow or outflow chambers surrounding the first and second end areas of the cylindrical housing, which are in fluid communication with the second flow region and each have second fluid accesses to supply or drain fluid into/from the second inflow or outflow chambers, each has a seal that separates the first inflow or outflow chambers from the second in - Separating or outflow chambers, passage openings in the end regions of the cylindrical housing, which form a liquid connection between the second inflow and/or outflow chambers and the second flow space, characterized in that the aspect ratio of the hollow-fiber membrane filter is 8 to 12.

The hollow-fiber membrane filter of the aforementioned type has high performance parameters with regard to the purification of liquids. Furthermore, the hollow-fiber membrane filter has an improved inflow of the hollow-fiber membranes in the second flow space, since the inner diameter is smaller over the defined aspect ratio with the membrane surface remaining the same. As a result, the liquid entering the second flow space can flow around the multiplicity of hollow-fiber membranes more quickly and effectively. In particular, for the Hollow fiber membrane filter according to the invention measured an improved separation performance of the test solutes urea and vitamin B12. A measure of the separation performance is the clearance, which is determined according to the DIN/EN/ISO 8637:2014 standard.

In one embodiment, the hollow-fiber membrane filter can be configured as a dialyzer. In the context of the present application, the term “dialyzer ^M ” is used to represent blood filter devices that are based on the structure of a hollow-fiber membrane filter, eg a dialysis filter or a hemofilter. In other applications, the hollow fiber membrane filter according to the invention can also be used as a filter for water treatment.

In the context of the present application, the term “end region of the cylindrical housing” is to be understood as meaning a section on the cylindrical housing which extends in the longitudinal direction from the end of the housing towards the middle of the cylindrical housing. The term "end area" indicates that it is an area on the cylindrical housing that only takes up a small part compared to the longitudinal extent of the cylindrical 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 overall length of the cylindrical housing.

The casting zone is located in a part of the end region of the cylindrical housing. In the context of the present application, the “potting zone” refers to the area in which the hollow-fiber membranes of the hollow-fiber membrane filter are embedded in a potting compound. The hollow-fiber membranes are embedded in the casting compound in such a way that they are fixed to the end areas of the cylindrical housing. The potting compound seals with the end portion of the cylindrical housing. In particular, it is provided that the casting zone takes up less than three quarters, or less than two thirds, or less than half of the width of the end area. The potting compound is plate-shaped and is arranged in the cylindrical housing perpendicularly to the central axis of the cylindrical housing. The “central axis” is to be understood as meaning a central longitudinal axis which runs centrally in the cylindrical housing of the hollow-fiber membrane filter. In the context of the present application, the term “central axis” is used for the geometric description of the hollow-fiber membrane filter. [0016] First inflow or outflow chambers are located at the ends of the cast zones at the respective ends of the cylindrical housing. In the context of the present application, the term "first inflow or outflow chamber" is understood to mean a volume area in the hollow-fiber membrane filter into which liquid can enter, either before it enters the first flow space of the hollow-fiber membrane filter or after it has exited the first flow space of the hollow-fiber membrane filter . The first inflow and outflow chambers connect to the cast zone and/or at the end of the end region of the cylindrical housing in a sealing manner via a wall of the end caps. In the current design, the first inflow or outflow chambers can be designed as end caps. The end caps are located at the ends of the cylindrical housing and are connected to the cylindrical housing of the hollow-fiber membrane filter via a wall of the end caps in a liquid-tight and form-fitting manner. The first inflow or outflow chambers each have a first liquid access in order to direct liquid into or out of the first inflow or outflow chambers. The ends of the hollow fiber membranes in the potting compound are open. The first inflow or outflow chambers are therefore in fluid connection with the first flow space of the hollow-fiber membrane filter, which is formed by the lumina of the hollow-fiber membranes. In the context of the present application, “lumina” or “lumen” is understood to be the cavity of the hollow-fiber membranes.

According to the first aspect, the hollow fiber membrane filter further has second inflow or outflow chambers surrounding the respective end portions of the cylindrical housing. In the context of the present application, the term "second inflow or outflow chambers" is understood to mean a limited volume area in the hollow-fiber membrane filter, into which liquid can enter, either before it enters the second flow space of the hollow-fiber membrane filter, or after it has exited the second flow space of the hollow-fiber membrane filter is. The second inflow or outflow chambers are each formed by casings which enclose the end regions of the cylindrical housing. A wall of the sheathing adjoins the cast zone and/or the end of the end region of the cylindrical housing in a sealing manner. The shrouds may be part of and attached to the cylindrical housing, with the shroud then sealingly enclosing the second inflow or outflow chambers. Alternatively, the casing can also be formed by separate sleeves or as part of end caps, which also enclose the first inflow or outflow chambers. The end caps are then designed in such a way that they are seated in a form-fitting manner on the ends of the cylindrical housing, close off the housing in a liquid-tight manner and at the same time also form the casing of the second inflow or outflow chambers. The second inflow or outflow chambers each have a second liquid access in order to direct liquid into or out of the second inflow or outflow chambers. The second inflow or outflow chambers are in fluid connection with the second flow space of the hollow-fiber membrane filter, which is formed by the housing interior of the hollow-fiber membrane filter surrounding the hollow-fiber membranes.

The first and second inflow or outflow chambers sealingly at the potting zone and / or at the end of the end portion of the cylindrical housing. The first and second inflow or outflow chambers are therefore separated from one another at this point in a liquid-tight manner. O-rings, welding zones or bonding zones, for example, can be used as sealing means, which are arranged between the ends of the end area of the cylindrical housing or the casting compound and the wall of the first and second inflow or outflow chambers.

A liquid connection between the second inflow or outflow chambers and the second flow chamber is formed via the passage openings in the end region of the cylindrical housing. Liquid can thus enter the second flow space or be discharged from the second flow space. The number of passage openings in an end region of the cylindrical housing can be at least 5, or 10, or 15, or 20, or 30, or 40, or 60. The number of passage openings is at most 350, or 300, or 250, or 200, or 180, or 150. The number of passage openings in an end region of the cylindrical housing is preferably between 10 and 350, or between 10 and 40 or between 15 and 300, or between 20 and 250, or between 30 and 200, or between 40 and 180, or between 60 and 180.

In the context of the present application, “aspect ratio” is understood to be the quotient of the effective effective length of the hollow-fiber membranes and the inside diameter of the cylindrical housing of the hollow-fiber membrane filter. As “effective "Effective length" of the hollow-fiber membrane filter is understood in the context of the present application as the distance between the casting compounds in which an effective material exchange can take place via the hollow-fiber membranes. The aspect ratio defined according to the present invention leads to improved performance characteristics, particularly in the case of hollow-fiber membrane filters with a large membrane area. In certain embodiments, the hollow fiber membrane filter of the present invention has an aspect ratio of 8.5-11, or 8.5-10, or 9-10.

In an advantageous embodiment of the invention, the hollow-fiber membrane filter is characterized in that the membrane surface area of the hollow-fiber membrane filter is 1.2 to 2 m ² . In alternative embodiments, the membrane surface area 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 The inside diameter of the cylindrical housing can be within the aspect ratio defined according to the invention be reduced to 25 to 35 mm, or 25 to 33 mm or 28 to 33 mm, so that an improved inflow of the hollow fiber membranes can take place in the second flow space.

An additional advantage of reducing the diameter of the cylindrical housing due to the aspect ratio defined according to the invention can be seen in the fact that a smaller number of hollow-fiber membranes is required to produce the same membrane surface area as with a commercially available hollow-fiber membrane filter with an aspect ratio of less than 8. As a result, the amount of casting compound that is necessary to fix the hollow-fiber membranes in the cylindrical housing can also be effectively reduced. On the one hand, this offers cost advantages and, on the other hand, it also shortens the process step of casting the hollow-fiber membrane in the cylindrical housing during the production of the hollow-fiber membrane filter.

In certain embodiments, the hollow fiber membrane filters of the present invention have an aspect ratio of 8.0 to 10 with a membrane surface area of 1.6 to 2.0 m ² . In 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 . The effective effective length of the hollow-fiber membranes in these embodiments is correspondingly 270 to 320 mm. In an advantageous embodiment of 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 effective working lengths in the ranges described above enables in particular an effective removal of middle molecules in therapies of extracorporeal blood purification, such as hemodialysis or hemofiltration. In this context, middle molecules are proteins of the blood serum that have a molecular weight of 10,000 daltons to 50,000 daltons. At the same time, however, it is also avoided that an excessively high pressure drop occurs on the lumen side over the length of the lumens of the hollow-fiber membranes and thus the problem of excessive hemolysis or membrane clogging occurs.

In a further embodiment of the invention, the hollow-fiber membrane filter is characterized in that the ratio of the effective working length of the hollow-fiber membranes to the average distance between the second liquid inlets of the second inflow or outflow chambers is 1 to 1.1 or 1 to 1.05 or 1.0 to 1.03. The mean distance between the second liquid access points of the second inflow or outflow chambers is preferably 270 to 320 mm, or 245 to 290 mm, or 257 to 305 mm, or 262 to 310 mm. The distance between the central axes of the liquid accesses is understood as the “mean distance of the second liquid accesses”.

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 50 to 70%, preferably 56 to 63%, more particularly between 57 and 63%. In the context of the present application, “packing density” is understood to mean the proportion in the housing interior of the cylindrical housing that 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 to the cross-sectional area of the cylindrical housing of the hollow-fiber membrane filter, with the cross-sectional area of the cylindrical housing only being understood as the cross-sectional area predetermined by the inside diameter. For a given fiber length, the packing density has an influence on the transmembrane pressure difference. Fiber length and packing density are advantageously coordinated in such a way that in therapy applications of extracorporeal blood purification, an effective back-filtration of a substitute can be ensured due to ultrafiltrate previously removed by convective action.

In a further embodiment of the invention, the hollow-fiber membrane filter is characterized in that the hollow-fiber membranes have a wavy shape, in particular the amplitude of the wavy shape of the hollow-fiber membranes is 0.1 to 0.5 mm and the wavelength of the wavy shape of the hollow-fiber membranes is 5 is up to 10 mm. The wavy shape of the hollow-fiber membranes causes the multiplicity of hollow-fiber membranes arranged in the cylindrical housing to be stiffened. This is particularly advantageous when processing hollow-fiber membrane bundles in the production of hollow-fiber membrane filters according to the invention with a high effective working length and an aspect ratio defined according to the invention. In certain embodiments, the amplitude of the undulation of the hollow fiber membranes is 0.35 to 0.45 mm or 0.38 to 0.43 mm. In alternative embodiments, the wavelength of the wave form of the hollow fiber membrane is 6 to 9 mm or 7 to 8 mm. In certain embodiments, the amplitude of the waveform of the hollow fiber membrane is 0.35 to 0.45 mm and the wavelength of the waveform of the hollow fiber membrane is 6 to 9 mm. In another embodiment, the amplitude of the wave form of the hollow fiber membrane is 0.38 to 0.43 mm, and the wavelength of the wave form of the hollow fiber membrane is 7 to 8 mm.

In a further advantageous embodiment of the invention, the hollow-fiber membrane filter is characterized in that in the end regions of the cylindrical housing the ratio of the sum of the flow cross sections of all passage openings to the flow cross section of the at least one second inflow or outflow chamber is in the range from 0.5: 1 to 7:1, or 0.75:1 to 5:1 or 1:1 to 3:1.

According to the above definition of the flow cross-sections, in the end region of the hollow-fiber membrane filter, the hollow-fiber membranes are flowed better by a liquid that flows through the one second connection in the second inflow or outflow chamber and through the passage openings in the end region of the cylindrical housing into the second flow chamber.

[0030] The sum of the areas of all individual through-openings in an end region of the cylindrical housing is understood as the “sum of the flow cross-sections of the through-openings”.

In the context of the present application, the “flow cross section of a second inflow or outflow chamber ^M ” means the cross-sectional area of the second inflow or outflow chamber that is created by forming a cross section through the hollow-fiber membrane filter and through the central axis of the cylindrical housing. The cross section is placed in such a way that the second liquid access points at the second inflow and outflow chambers are not touched. If in said cross-sectional consideration two cross-sectional areas of the second input or

Outflow chamber are mapped, e.g. with a rotationally symmetrical geometry of the second inflow or outflow chambers, is used to determine the

Flow cross section used only one of these cross-sectional areas.

In an advantageous embodiment of the invention is the

Hollow fiber membrane filter, characterized in that at the end areas of the cylindrical housing, the inflow or outflow chambers form a rotationally symmetrical circumferential space, in particular an annular gap, starting from the second liquid access to the central axis of the cylindrical housing. Due to the rotationally symmetrical geometry of the second inflow or outflow chambers, the components for the hollow-fiber membrane filter can be produced in a process-optimized manner, in particular by injection molding techniques.

In a further advantageous embodiment of the invention is the

Hollow fiber membrane filter, characterized in that the passage openings are circular, oval or slit-shaped. Depending on the different inside diameters of the cylindrical housing, which are provided for different applications, the number and shape of the passage openings in the end area of the cylindrical housing can vary. This also depends on the manufacturing capabilities of the cylindrical housing, which is preferably made by injection molding. The arrangement of a large number of passage openings on is therefore advantageous End portion of the cylindrical housing, which have a circular, oval or slit-like shape.

In a further advantageous embodiment of the invention, the hollow-fiber membrane filter is characterized in that the passage openings are arranged on separate and/or opposite sections or evenly around the end area of the cylindrical housing.

In a further embodiment, the hollow-fiber membrane filter is characterized in that the at least one end area and optionally the second end area is divided into a proximal end area, a distal end area and a transition area arranged between the proximal and distal end areas, with one end of the distal end portion is the end of the cylindrical housing, and the distal end portion has an inner diameter that is at least 2% larger than the inner diameter of the proximal end portion. In the sense of this embodiment, the proximal end area is arranged proximally to the center of gravity of the cylindrical housing. The distal end area is correspondingly arranged distally to this center of gravity of the cylindrical housing and is thus located at the ends of the cylindrical housing. The packing density of the hollow-fiber membranes arranged in the cylindrical housing of the hollow-fiber membrane filter is advantageously reduced in the distal end region due to the larger inner diameter of the cylindrical housing in this part of the end region. This offers the advantage that fewer defects occur when casting the hollow-fiber membrane in the cylindrical housing during manufacture of the hollow-fiber membrane filter. Furthermore, the hollow-fiber membranes in this distal end area can be flowed more easily by dialysis fluid due to the lower packing density.

In the transition area of the end area, the inside diameter of the cylindrical housing increases by more than 2%. Preferably, the inner diameter of the cylindrical housing in the transition area increases by more than 3%, or more than 4%, or more than 5% and at most 10%, or at most 8%, or at most 7%, or at most 6%, in particular by 2 to 10%, or 3 to 8%, or 4 to 7%. The transition area takes at least 1/10, or at least 1/12, or at least 1/14, or at least 1/15, or at least 1/17, or at least 1/18, or at least 1/20 and at most 1/40, or at most 1/35, or at most 1/30 or at most 1/25, particularly 1/10 to 1/40, or 1/12 to 1/35, or 1/14 to 1/30, or 1/15 to 1/25 of the total length of the cylindrical body.

In a further development of the aforementioned embodiment, the hollow-fiber membrane filter is characterized in that the passage openings are arranged at the distal end area. The dialysis liquid entering the second flow chamber can thus be conducted directly via the through-openings into the part of the hollow-fiber membranes that have a lower packing density. This results in an advantageous circumferentially uniform flow of the hollow-fiber membranes in the distal end area, which can also penetrate the arrangement of hollow-fiber membranes better due to the lower packing density in this part of the end area, before the flow of dialysis liquid enters the part of the hollow-fiber membranes with a higher packing density.

In a further advantageous embodiment of the invention, the hollow-fiber membrane filter is characterized in that the sum of the flow cross sections of all passage openings is 10 to 350 mm ² , or 15 to 200 mm ² , or 15 to 150 mm ² , or 20 to 110 mm ² . The intended sum of the throughflow cross sections of all passage openings depends on the inner diameter of the cylindrical housing of the hollow-fiber membrane filter and is therefore linked to the number of hollow-fiber membranes. Hollow-fiber membrane filters with a larger membrane area and a higher number of hollow-fiber membranes require a correspondingly high inflow volume in the second flow space of the hollow-fiber membrane filter in order to achieve adequate filtration performance. In one example, with an arrangement of approximately 10,000 hollow-fiber membranes in the second flow space of the hollow-fiber membrane filter, the sum of all flow cross sections of the through-openings is in the range of approximately 90 to 150 mm ² . The inner diameter of the cylindrical housing can be between 28 and 33 mm. Adjusting the sum of all flow cross sections of the passage openings to the inner diameter of the cylindrical housing serves to regulate a defined inflow of liquid into the second flow space and thus to achieve improved flow against the hollow-fiber membranes in the second flow space. In a further advantageous embodiment of the invention, the hollow-fiber membrane filter is characterized in that the flow cross section of the one or both second inflow or outflow chambers is 20 to 50 mm ² , 20 to 40 mm ² or 25 mm ² . Here, too, the flow cross section of the inflow or outflow chambers can be adapted to the inside diameter of the cylindrical housing of the hollow-fiber membrane filter and thus also assume different values depending on the number of hollow-fiber membrane filters. In one example, with an arrangement of approximately 10,000 hollow-fiber membranes in the second flow space of the hollow-fiber membrane filter, the flow cross section of the inflow or outflow chambers is 20 to 30 mm ² . The adaptation of the flow cross section of the inflow or outflow chambers to the inner diameter of the cylindrical housing causes an efficient distribution of the liquid flowing into the second inflow or outflow chamber, so that when the liquid enters the second flow space, a uniform flow onto the hollow-fiber membranes can be achieved.

In one embodiment, the inner diameter of a hollow-fiber membrane filter according to the invention is 25 to 35 mm. In particular, 6000 to 12000 hollow-fiber membranes can be arranged in the cylindrical housing of the hollow-fiber membrane filter, so that the hollow-fiber membrane filter can have a membrane surface of 1.2 to 2.0 m ² . The "membrane surface area" is calculated as 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 of the hollow-fiber membranes is calculated from the product of the inner diameter of a hollow-fiber membrane, the circular constant p and the effective effective length.

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

The casting compounds with which the hollow-fiber membranes are embedded and sealed at the respective end regions of the cylindrical housing are preferably made of polyurethane. The cylindrical body and end caps are preferably made of a polypropylene material. A housing made of polypropylene is advantageously suitable for accommodating long fiber bundles in a production-safe manner.

In a further advantageous embodiment of the invention, the hollow-fiber membrane filter is characterized in that the first and the second inflow or outflow chambers in the first end area of the cylindrical housing and the first and the second inflow or outflow chambers in the second end area of the cylindrical housing a first and a second end cap are respectively enclosed. Advantageously, the end caps are designed in one piece. The end caps are designed in such a way that one wall of the end cap encloses the respective first inflow or outflow chamber and a further wall in each case forms a casing which encloses the respective second inflow or outflow chamber. The end caps are geometrically shaped in such a way that they are positively seated on the end regions of the cylindrical housing and are liquid-tight due to seals. The end caps are advantageously made by injection molding. The production of a hollow-fiber membrane filter using the end caps defined here contributes to a process-optimized production of the hollow-fiber membrane filter. First and second fluid ports are located on the end caps.

In a further advantageous embodiment of the invention is the

Hollow-fiber membrane filter, characterized in that the first end cap connects positively, in particular in a liquid-tight manner, to an annular, outer-circumferential projection on the first end region of the cylindrical housing. In particular, the second end cap is also connected to an annular, outer-circumferential projection on the second end region of the cylindrical housing in a form-fitting manner, in particular in a liquid-tight manner. End caps and cylindrical housing are thus connected in a liquid-tight manner along the outer peripheral projection. Sealing can be done by welding or gluing.

In a further advantageous embodiment of the invention is the

Hollow-fiber membrane filter, characterized in that the first end cap connects to the first end of the cylindrical housing along an inner circumferential circular line in a form-fitting manner, in particular in a liquid-tight manner. In particular, the second end cap along an inner circumferential circular line in a form-fitting manner, in particular in a liquid-tight manner, on the second end of the cylindrical housing. The inner peripheral circular line may be formed, for example, as a circular ridge or protrusion on the inside of the end caps. Alternatively, however, the inside of the wall of the end caps can be connected directly to the end of the cylindrical housing. The connection of the circular line of end caps to the ends of the cylindrical housing creates a fluid seal between the first inflow and outflow chambers and the second inflow and outflow chambers, respectively, via welding, bonding or O-rings.

In a further advantageous embodiment of the invention is the

Hollow fiber membrane filter, characterized in that the capacity of one or both of the second inflow or outflow chambers is between 1.5 and 5 cm ³ . A limited volume area of the second inflow and/or outflow chambers can in particular ensure that, depending on the inside diameter of the cylindrical housing, the liquid entering the second inflow and/or outflow chambers can be evenly distributed. This also prevents flows from stagnating in areas of the at least one second inflow or outflow chamber and inhomogeneous flow onto the hollow-fiber membranes in the second flow area.

In a further advantageous embodiment of the invention is the

Hollow fiber membrane filter, characterized in that the cylindrical housing and the end caps are made of a thermoplastic material, in particular polypropylene. The cylindrical housing and the end caps can thus advantageously be produced in a process-optimized injection molding process. Furthermore, the selection of the materials also results in the advantage that the cylindrical housing and the end caps can be connected to one another in a form-fitting and sealing manner in a welding process.

DESCRIPTION OF THE INVENTION USING THE FIGURES

1a shows a cross section of a hollow fiber membrane filter according to the invention through the center axis A of the cylindrical housing. Fig. 1b shows a further cross section of a hollow fiber membrane filter according to the invention, which runs both through the central axis A of the cylindrical housing and the central axis B of the second liquid access.

Figure 2a shows a side view of a cylindrical housing of a hollow fiber membrane filter according to the invention, showing the end area of the cylindrical housing.

Figure 2b shows a side view of another embodiment of a cylindrical housing of a hollow fiber membrane filter according to the invention, showing the end region of the cylindrical housing. The representation according to FIG. 2b is provided with dimensions. The values specified for the dimensions refer to the unit millimeters (mm).

shows a schematic representation of a cross section of a commercially available FX60 hollow fiber membrane filter from Fresenius Medical Care Germany GmbH, which runs both through the central axis A of the cylindrical housing and the central axis B of the second liquid access.

Fig. 4 shows a side view of a cylindrical housing of a commercially available FX60 hollow fiber membrane filter from Fresenius Medical Care.

5a shows a schematic representation of a lateral cross-sectional representation of a commercially available FX 60 hollow-fiber membrane filter.

5b shows a schematic representation of a hollow-fiber membrane filter according to the invention.

Fig. 1a shows a cross section of a hollow-fiber membrane filter 100 according to the invention along the central axis A of the cylindrical housing 101. Only part of the hollow-fiber membrane filter is shown in Fig. 1a, which depicts a first end 104 on the cylindrical housing 101 with a first end region 103 . Part of the end area 103 is occupied by a potting zone 106, in which a potting compound 105 is arranged on the front side to the longitudinal alignment, i.e. perpendicular to the central axis A of the cylindrical housing, which contains the hollow-fiber membranes, not shown in Fig. 1a, in the housing interior 102 in the first end area 103 and in the second end region, not shown, of the cylindrical housing 101 is embedded in a sealing compound 105 with the housing 101 in each case. Also shown is an end cap 111 with a wall 114 which encloses the first inflow or outflow chamber 107 and a casing area 115 which encloses the second inflow or outflow chamber 109 . The area of \u200b\u200bthe flow cross-section of the second Inflow or outflow chamber 109 is marked with parallel lines in FIG. 1a. A fluid access port 108 is also shown. The liquid access 108 shows the typical details of a blood connection of a dialyzer in the illustration. The liquid access 108 forms a liquid access to the first inflow or outflow chamber 107. The end cap 111 shown in FIG. 1 is designed in one piece, so that the wall 114 and the casing 115 are part of the end cap. According to the arrangement shown in FIG. The first inflow or outflow chamber is sealed off at the end 104 of the cylindrical housing 101 by a peripheral seal 110 . An inner circular periphery 110a of the end cap 111, which is only shown in cross-section in FIG. 1, serves for this purpose. In the embodiment shown in FIG. 1, the inner circumference 110a of the end cap 111 sits on the end 104 of the cylindrical housing 101 in a form-fitting manner, so that the seal 110 between the end 104 of the cylindrical housing and the end cap 111 is formed. Fluid passing through the fluid access

108 flows into the first inflow or outflow chamber 107, it flows exclusively via the open ends of the hollow-fiber membranes in the casting compound 105 (not shown in Fig. 1a) into the lumina of the hollow-fiber membranes and thus into the first flow space (not in Fig. 1a shown). A further peripheral liquid seal 112 is created by the annular outer peripheral projection 112a on the cylindrical housing 101, which is connected to the casing 115 of the end cap 111 in a form-fitting and liquid-tight manner.

Fig. 1b shows another cross section of a hollow fiber membrane filter 100 according to the invention, which runs both through the central axis A of the cylindrical housing and the central axis B of the second liquid access. The central axis B runs centrally in the second liquid access 116, which connects to the second inflow or outflow chamber 109. The designations 100 to 111 and 114 and 115 in FIG. 1b are identical to the designations from FIG. 1a. Also, as shown in FIG. 1a, is the flow cross-section of the second inflow or outflow chamber

109 in Fig. 1b marked with parallel lines. In addition, the passage openings 113 can be seen on opposite sides of the end region 103 of the cylindrical hollow-fiber membrane filter in this cross-sectional illustration. From this figure it can be seen that the second liquid access 116 is in liquid connection with the second inflow or outflow chamber 109 and via the passage openings 113 there is also a liquid connection to the second Flow space in the housing interior 102 of the hollow fiber membrane filter 100 is. In an embodiment shown in FIG. 1b, a large number of passage openings are arranged opposite one another on the end region 103 of the cylindrical hollow-fiber membrane filter, of which only two are visible in the cross-sectional representation of FIG. 1b.

2a shows a schematic representation of part of a cylindrical housing 101 of a hollow-fiber membrane filter according to the invention in a side view. In the representation of FIG. 2a, the part with the first end 104 of the cylindrical housing 101 is shown. FIG. 2a also shows the ring-shaped, outer-circumferential projection 112a on the cylindrical housing 101, which is intended to produce a seal 112 on a casing 115 of an end cap 111. Reference 103 designates the end region of the cylindrical housing 101. Reference 106 designates the casting zone in the end region, with a casting compound 105 per se not being shown in FIG. 2a. The central axis A indicates the longitudinal orientation of the cylindrical housing; however, in the side view shown, it lies below the plane of the drawing of the illustrated surface of the cylindrical housing. In the side view, a large number of passage openings 113 are shown, which form the connection between the second inflow or outflow chamber 109 and the second flow space in the hollow-fiber membrane filter (neither of which is shown in FIG. 2a). In the illustration shown, the passage openings are shown as circular, but they can also be designed in an oval, slot-shaped or U-shaped manner. The flow cross sections of the passage openings 113 result from the sum of the flow cross sections of all individual passage openings 113. The embodiment shown in FIG. 2a has 22 passage openings 113 in the end region 103 of the cylindrical housing 101, of which only half, i.e. 11, are visible in FIG. 2a are. 11 further passage openings are located on the opposite side of the end area 103 of the cylindrical housing 101.

2b shows a schematic representation of an embodiment of part of a cylindrical housing 101 of a hollow-fiber membrane filter according to the invention in a side view. In the representation of FIG. 2b the part with the first end 104 of the cylindrical housing 101 is shown. Also shown in FIG. 2b is the annular, outer peripheral projection 112a on the cylindrical housing 101, which is intended to produce a seal 112 on a casing 115 of an end cap 111 (not shown in FIG. 2b). Also shown in Figure 2b: 103 - der End area of the cylindrical housing 101, the central axis A, 113 - circular passage openings.

The distance from the center of the passage openings 113 to the end 104 of the cylindrical housing 101 is 10 mm in the embodiment shown. At the end 104 of the cylindrical body, the diameter of the opening of the cylindrical body is 34 mm. In the illustration shown, the end area 103 of the cylindrical housing is divided into a proximal end area 103a and a distal end area 103b. In the illustration shown, the proximal end area 103a is arranged adjacent to the ring-shaped, outer-circumferential projection 112a and is therefore, in the sense of the embodiment shown in FIG. 2b, proximal to a center of gravity of the cylindrical housing. In the embodiment shown in Figure 2b, the inner diameter of the distal end portion 103b of the cylindrical housing is larger than that of the proximal end portion 103a. The proximal and distal end areas connect to one another by a transition area 103c. In the transition area 103c of the end area 103, the inner diameter of the cylindrical housing increases by more than 3%. In particular, according to the embodiment according to FIG. 2b, the diameter of the distal end region 103b at the end of the cylindrical housing is 34 mm, whereas the inner diameter of the distal end region 103b is 33.5 mm subsequent to the transition region 103c. The inner diameter of the cylindrical housing 101 at the proximal end area is 31.9 mm in the embodiment shown in FIG. 2b. The increase in the inner diameter from the proximal 103a to the distal 103b end area is therefore 1.6 mm in the embodiment shown. The inner diameter of the cylindrical housing 101 is 31.4 mm in a central area. From the dimensions shown in FIG. 2b it can be seen that the inner diameter in the individual regions of the distal 103b and the proximal end region 103a tapers further towards the central region of the cylindrical housing. The conical shape of the inner diameter of the individual areas of the cylindrical housing 101 illustrated in FIG. 2b results from the need to be able to demould the cylindrical housing as an injection-molded part from an injection-molding system. Such required geometries of injection molded parts are known in injection molding technology. The inner diameter change at the transition area 103c is to be distinguished from these necessary conical changes in the inner diameter. The transition region 103c occupies an area of less than 2 mm in the direction in which the central axis A extends in the illustration shown in FIG Inner diameter of the proximal end area of 31.9 mm to the inner diameter of the distal end area of 33.5 mm increases. Measured against the total length of the cylindrical housing, the transition area takes up approximately only 1/15.

In one embodiment of a hollow-fiber membrane filter according to the invention, which is worked according to the details shown in FIGS. 1a, 1b and 2, the sum of the flow cross-sections of all passage openings can be 17 mm ² , for example. Furthermore, in this embodiment, the flow cross section of the second inflow or outflow chamber can then be approximately 26 mm ² . The ratio of the sum of the flow cross sections of all passage openings to the flow cross section of the at least one second inflow or outflow chamber is 0.65: 1.

Fig. 3 shows a schematic representation of part of a cross section of a commercially available FX hollow fiber membrane filter from Fresenius Medical Care, the cross section running both through the central axis A of the cylindrical housing and the central axis B of the second liquid access. Analogously to the previous figures, Fig. 3 shows:

300 a hollow fiber membrane filter

301 a cylindrical case

302 a housing interior of the cylindrical housing for accommodating a multiplicity of hollow fiber membranes (not shown in FIG. 3)

303 an end portion of the cylindrical housing

304 a first end of the cylindrical housing

305 a potting compound,

306 a potting zone,

307 a first inflow or outflow chamber,

308 a first liquid access to the first inflow or outflow chamber,

309 a second inflow or outflow chamber,

310 a peripheral seal, designed as an O-ring,

310a an inner circumference in the end cap,

311 an end cap,

312a, an annular outer peripheral projection,

314 a wall of the end cap,

315 a shroud of the end portion of the cylindrical housing at the end cap,

316 a second liquid access. As can be seen from FIG. 3, the hollow-fiber membrane filters shown in FIGS. 1a, 1b and FIG. 3 differ structurally in the construction of the second inflow and outflow chamber. The passage openings that connect the second inflow or outflow chambers to the second flow area of the hollow-fiber membrane filter (not shown) cannot be seen in FIG. 3 .

4 shows a schematic representation of a side view of a cylindrical housing 401 of a commercially available FX hollow-fiber membrane filter from Fresenius Medical Care, which carries a casting compound 405 in a casting zone 406 . Figure 4 shows an annular outer peripheral projection 412a. Furthermore, the through openings 413 are shown in the side view, which are arranged circumferentially on the end area 403 of the housing 401 . The FX60 hollow-fiber membrane filter illustrated according to FIGS. 3 and 4 has a flow cross section of the second inflow or outflow chamber of 26 mm ² . In the same embodiment of the FX hollow-fiber membrane filter, the sum of the flow cross-sections of all through-openings is 392 mm ² . The ratio of the sum of the flow cross sections of all passage openings to the flow cross section of the at least one second inflow or outflow chamber is 15:1.

5a shows a schematic representation of a lateral cross-sectional representation of a commercially available FX 60 hollow-fiber membrane filter 300 from Fresenius Medical Care. Structural details of the hollow-fiber membrane filter represented in FIG. 5a correspond to FIG. FIG. 5a shows second liquid inlets 316a and 316b, the casting compounds 305a and 305b, and a cylindrical housing 301. The total length of a hollow-fiber membrane filter shown in FIG. 5a is 292 mm. The mean distance of the second liquid accesses is 248 mm. The effective working length of the hollow fiber membranes is 228 mm. The inner diameter of the cylindrical case is 34 mm. The aspect ratio of the hollow fiber membrane filter shown is 6.71. The ratio of the effective working length of the hollow-fiber membranes to the average distance between the second liquid inlets 316a and 316b is 0.92.

5b shows a schematic representation of a hollow-fiber membrane filter 100 according to the invention. Structural details of the hollow-fiber membrane filter shown in FIG. 5b correspond to FIG. Fig. 5b shows second Liquid inlets 116a and 116b, the casting compounds 105a and 105b, and a cylindrical housing 101. The overall length of a hollow-fiber membrane filter shown in FIG. 5b is 333 mm. The mean distance of the second liquid accesses is 285 mm. The effective effective length is 280 mm. The inner diameter of the cylindrical case is 31 mm. The aspect ratio of the hollow fiber membrane filter shown is 9.1. The ratio of the effective working length of the hollow-fiber membranes to the mean distance between the second liquid inlets 116a and 116b is 1.018.

EXAMPLES

Determination of Clearance

The clearance is determined according to the standard DIN/EN/ISO 8637:2014, with a blood flow of 300 ml/min and a dialysate flow of 500 ml/min being set in the examples. Aqueous solutions of 16.7 mmol/l urea (Merck) and 36.7 pmol/l vitamin B12 (BCD Chemie, Biesterfeld) on the blood side and distilled water on the dialysate side are used as test solutions. The concentration of vitamin B12 is determined photometrically at 361 nm. The Cobas Integra 400 plus device with the UREAL test (Roche Diagnostics, Germany) is used to determine urea.

Example 1: Hollow fiber membrane filter according to the invention

A hollow-fiber membrane filter with the structural details according to FIGS. 1a, 1b and 5b and the parameters shown in Table 1 was produced. Corrugated polysulfone/polyvinylpyrrolidone hollow fiber membranes were used, which are installed in particular in the FX60 filter from Fresenius Medical Care. The hollow fiber membrane filter was manufactured using methods known in the prior art.

The hollow-fiber membrane filter according to the invention was sterilized by a steam sterilization method known in the prior art, which is described in published application DE 10 2016 224 627 A1. Clearance and sieving coefficients were examined on both the sterile and non-sterile versions. The results are compiled in Table 2.

Comparative Example 1: FX60 hollow fiber membrane filter A FX60 hollow fiber membrane filter from Fresenius Medical Care was used as a comparative embodiment. The structural details of the FX 60 hollow fiber membrane filter are shown schematically in Figures 3, 4 and 5a. The technical characteristics of the FX60 filter are shown in Table 1.

The FX60 hollow fiber membrane filter was sterilized using the same steam sterilization method used for the hollow fiber membrane filter of the present invention. The clearance determined with the hollow-fiber membrane filter was examined on both the sterile and non-sterile versions. The results are compiled in Table 2.

Table 1 For the hollow-fiber membrane filter according to the invention according to Example 1 and for the FX 60 hollow-fiber membrane filter according to Comparative Example 1, hollow-fiber membranes were used which originate from the same production. These hollow-fiber membranes have the same dimensions in terms of diameter, wall thickness, pore structure and material composition. The number of hollow-fiber membranes in Example 1 and Comparative Example 1 was adjusted so that the respective hollow-fiber membrane filters each had the same membrane surface area of 1.4 m ² . Table 2

The results from Table 2 show that the clearance of sterile and non-sterile hollow-fiber membrane filters according to Example 1 for urea and vitamin B12 is higher than for the FX60 hollow-fiber membrane filter of Comparative Example 1. In addition, the example according to the invention shows only a slight drop in urea clearance after sterilization on.

Claims

Claims Hollow-fiber membrane filter (100) having a cylindrical (101) housing that extends longitudinally along a central axis (A) with a housing interior (102), a first end region (103) with a first end (104) and a second end region with a second end, a plurality of hollow fiber membranes having an inner diameter of 150 to 190 gm and a wall thickness of 25 to 38 gm, the hollow fiber membranes being arranged in the cylindrical housing (101) and in the first end region (103) and in the second end region of the cylindrical housing are each embedded in a sealing compound (105) in a sealing manner with the housing in a respective potting zone (106), the ends of the hollow-fiber membranes being open, so that the lumens of the hollow-fiber membranes form a first flow space and the interior of the housing (102) surrounding the hollow-fiber membranes forms one forms the second flow chamber, first inflow or outflow chambers (107), each on the end face of e first (104) and then at the second end of the cylindrical housing (101) and the casting zone (106), which are in fluid communication with the first flow space of the hollow fiber membrane filter and each have first fluid inlets (108) to pump fluid into/from the first inlet - or outflow chambers (107) to or from, second inflow or outflow chambers (109) surrounding the first and the second end area (103) of the cylindrical housing (101), which are in fluid communication with the second flow area and each have second fluid inlets (116) each have a seal (110), which separates the first inflow or outflow chambers (107) from the second inflow or outflow chambers (109), in order to feed or drain liquid into/from the second inflow or outflow chambers (109),

Through openings (113) in the end areas (103) of the cylindrical housing (101), which form a liquid connection between the second inflow and/or outflow chambers (109) and the second flow space, characterized in that the aspect ratio of the effective working length of the hollow fiber membranes and the inner diameter of the cylindrical housing is 8 to 12.

2. Hollow-fiber membrane filter (100) according to claim 1, characterized in that the membrane surface area of the hollow-fiber membrane filter is 1.2 to 2 m ² .

3. Hollow fiber membrane filter (100) according to claim 1 or 2, characterized in that the effective length of the hollow fiber membranes is 270 to 320 mm.

4. Hollow fiber membrane filter (100) according to at least one of the preceding

Claims, characterized in that the inner diameter of the cylindrical housing (101) is 25 to 35 mm.

5. Hollow fiber membrane filter (100) according to at least one of the preceding

Claims, characterized in that the packing density of the hollow-fiber membranes is 50 to 70%.

6. Hollow fiber membrane filter (100) according to at least one of the preceding

Claims, characterized in that the hollow-fiber membranes have a wavy shape, in particular the amplitude of the wavy shape of the hollow-fiber membranes is 0.1 to 0.5 mm and the wavelength of the wavy shape of the hollow-fiber membranes is 5 to 10 mm.

7. Hollow-fiber membrane filter according to at least one of the preceding claims, characterized in that in the end regions of the cylindrical housing the ratio of the sum of the flow cross sections of all through openings (113) to the flow cross section of the at least one second inflow or outflow chamber (109) is in the range of 0.5 : 1 to 7:1, or 0.75: 1 to 5:1 or 1:1 to 3:1.

8. hollow fiber membrane filter (100) according to claim 7, characterized in that at the end regions (103) of the cylindrical housing (101), the inflow or outflow chambers (109) starting from the second liquid access to Central axis (A) of the cylindrical housing (101) form a rotationally symmetrical circumferential space, in particular an annular gap. Hollow fiber membrane filter (100) according to at least one of the preceding claims, characterized in that the passage openings (113) are arranged on isolated and/or opposite sections or circumferentially on the end area (103) of the cylindrical housing (101). Hollow fiber membrane filter according to one of the preceding claims, characterized in that the at least one end area (103), and optionally the second end area, is divided into a proximal end area (103a), a distal end area (103b) and one arranged between the proximal and distal end area Transition region (103c), wherein one end of the distal end region (103b) of the first and/or second end region (103) corresponds to the respective end of the cylindrical housing (104), and the distal end region has an inner diameter which is at least 2% larger , than the inner diameter of the proximal end portion. Hollow fiber membrane filter (100) according to at least one of the preceding

Claims, characterized in that the sum of the flow cross sections of all passage openings (113) is 10 to 350 mm ² , or 15 to 200 mm ² , or 15 to 150 mm ² , or 20 to 110 mm ² . Hollow fiber membrane filter (100) according to at least one of the preceding

Claims, characterized in that the flow cross section of the second inflow or outflow chambers is 20 to 50 mm ² , 20 to 40 mm ² or 20 to 25 mm ² . Hollow fiber membrane filter (100) according to at least one of the preceding

Claims, characterized in that in each case the first (107) and the second inflow or outflow chamber (109) on the first end area (103) of the cylindrical housing (101) and the first and the second inflow or outflow chamber on the second end area of the cylindrical housing are enclosed by a respective first and second end cap (111). Hollow-fiber membrane filter (100) according to claim 8, characterized in that the first and the second end cap (111) on an annular outer peripheral projection (112a) each connect to the first (103) and the second end region of the cylindrical housing (101) in a form-fitting manner, in particular in a liquid-tight manner . Hollow-fiber membrane filter (100) according to claim 8 or 9, characterized in that the first and the second end cap (111) along an inner peripheral circular line (110a) in a form-fitting manner, in particular in a liquid-tight manner, respectively at the first end (104) and at the second end of the cylindrical housing ( 101) connect.