Dialyzer

Abstract

The invention relates to a filtration device for substance exchange, comprising a tube-section-shaped housing with a center of gravity and two ends, in which a bundle of hollow fibers formed by semipermeable membranes is arranged, further comprising a lid with a first and a second opening, wherein the housing and the lid form a first sealing surface that hermetically connects them, and wherein the first sealing surface is separated from the center of gravity of the housing more than the opening, and wherein a first fluid chamber is formed between the first sealing surface and the first opening of the lid, through which the first opening is connected to the first flow chamber, wherein the housing and the lid form a second sealing surface, wherein the first and second sealing surfaces are not formed by a sealant.

Description

Dialyzer Technical area The present invention relates to a filtration device for substance exchange, in particular for hemodialysis, comprising a tubular housing with a center of gravity and two housing ends, in which a bundle of hollow fibers made of semipermeable membranes is disposed, the fiber cavities of which form a first flow chamber and the interior of the housing surrounding the bundle of hollow fibers forms a second flow chamber, wherein the flow chambers at the ends of the housing are separated from each other by at least one flow chamber seal, wherein the housing has at least one opening at at least one of its ends, and the at least one opening is disposed closer to the center of gravity of the housing than the flow chamber seal, further comprising at least one end cap having a first and a second opening.The present invention also relates to a method for manufacturing said filtering device. Basis of the present invention Filtration devices for substance exchange, particularly for hemodialysis, are known in the state of the art. In filtration technology, and especially in hemodialysis, the use of semipermeable hollow fiber membranes as a separation medium has proven advantageous because they are easy to manufacture and exhibit excellent separation characteristics. In hemodialysis, the use of polysulfone-based materials in combination with the addition of polyvinylpyrrolidone for hollow fiber membranes has become dominant in the market. One such membrane is described in application EP0168783A1. These membranes are bundled into hollow fibers and inserted into a filtration housing. The two flow chambers are then sealed. In the case of hemodialysis, the seal is made between the blood side and the dialysate side of the hemodialyzer.Therefore, fluid inlets and outlets are necessary to supply unprocessed fluids to the filter and to discharge processed fluids. In hemodialysis, the two fluids, separated by the semipermeable membrane or hollow fiber membrane bundle, flow in countercurrent, requiring a total of four fluid inlets per dialyzer. In the case of blind-end filtration, two fluid inlets may be sufficient. This type of dialysis filter housing is described in application EP2326410A1. It specifies that the corresponding dialysate inlets and outlets are located in the tubular housing, while the corresponding blood inlets are located in separate components, the end caps. The end caps are sealed against the filter housing by an independent elastomeric gasket. All components are manufactured from thermoplastics using injection molding. Applications DE10147907 and US4724900 describe a simplified design that provides one fluid inlet and one fluid outlet per end cap. This arrangement significantly simplifies production by reducing the tooling required to manufacture the tubular housings. This allows for the elimination, at least partially, of complex components such as slides, which would otherwise be large. These components can then be more easily incorporated into a smaller end cap tooling. This also avoids the need for excessively large injection molding machines. In application DE10147907, the respective fluid chambers are also connected, at least partially, by elastomeric sealing components. However, the use of elastomeric sealing components unfortunately leads to the formation of dead volumes, which hinders the efficiency of substance exchange. Dead volumes are particularly disadvantageous in the blood compartment, as blood that does not flow out of the body or flows at too slow a rate tends to cause platelet aggregation and can therefore lead to dialyzer obstruction. Furthermore, the need for additional components is a disadvantage. Elastomeric components are also often disadvantageous because these materials can have low compatibility with blood. When these elastomeric components are made of EPDM, for example, plasticizers can be released into the bloodstream. The same generally applies to filtration technology, as the transfer of substances to the filtrate is also a disadvantage in these applications. In addition to using elastomeric components as sealants, adhesives can also be used. The use of adhesives is very complex from a production standpoint and, depending on the adhesive's reaction kinetics, is also time-consuming. Moreover, harmful components of the adhesive can be transferred to the filtrate or bloodstream. Object of the present invention Therefore, an object of the invention is to provide a filtration device for substance exchange, particularly for hemodialysis, that prevents or at least minimizes the disadvantages of the prior art. In particular, the object of the present invention is to provide a filtration device for substance exchange, particularly for dialysis, that is particularly simple to manufacture and that, at the same time, reduces adverse effects on the filtrate. In the case of a dialyzer, the object is to reduce any adverse effects on the blood being purified. Summary of the invention According to the present invention, the object is a filtration device for substance exchange, particularly for hemodialysis, comprising a tubular housing with a center of gravity and two housing ends, in which a bundle of hollow fibers made of semipermeable membranes is disposed, the fiber cavities of which form a first flow chamber and the interior of the housing surrounding the bundle of hollow fibers forms a second flow chamber, wherein the flow chambers at the ends of the housing are separated from each other by at least one flow chamber seal, wherein the housing has at least one opening at at least one of its ends, and the at least one opening is disposed closer to the center of gravity of the housing than the flow chamber seal, further comprising at least one end cap having a first and a second opening, wherein the housing and the at least oneend caps form a first sealing surface that seals the housing and the end cap, wherein the first sealing surface is located farther from the center of gravity of the housing than the at least one opening, and wherein a first fluid chamber is formed between the first sealing surface and the first opening of the end cap, through which the first opening is connected by a fluid connection to the first flow chamber, wherein the housing and the at least one end cap form a second sealing surface that seals the housing and the end cap, and the second sealing surface is arranged closer to the center of gravity of the housing than the seal of the flow chamber and at least one opening.and wherein a second fluid chamber is formed between the first and second sealing surfaces and the second end cap opening, through which the second end cap opening is fluidly connected to the second flow chamber by means of at least one opening, wherein the first and second sealing surfaces are not formed by a sealant. A particularly easy-to-manufacture filtering device is proposed, which does not require the use of sealing elements such as elastomeric components or adhesives. This prevents or reduces dead volumes. When the filtering device is used for hemodialysis, adverse effects on the blood are reduced. In particular, the tendency for obstruction due to platelet aggregation is reduced. According to the invention, a filtering device is proposed characterized in that the molecules of the housing are intertwined with the molecules of the end cap at the first and second sealing surfaces. This molecular intertwining ensures a particularly secure and stable long-term connection between the end cap and the housing. The intertwining of the housing molecules with the end cap molecules at the first and second sealing surfaces is achieved by ensuring that, during the joining of the housing with the end cap, the respective surfaces fuse together. The fused surfaces are then brought into contact with each other, thus ensuring the intertwining of the molecules. It has been shown to be particularly advantageous for the melting or glass transition points of the housing and end cap materials to differ by less than 10 °C, preferably less than 5 °C, and most preferably less than 3 °C. This allows for especially secure connections which, in turn, minimize adverse effects on the filtrate or blood. In one embodiment, the first sealing surface can be located further from the center of gravity of the housing than the at least one opening and the seal of the flow chamber. This arrangement is even more compact and is characterized, above all, by a reduced dead volume. Furthermore, in one particular embodiment, the tubular housing and the end cap can be made from the same material group. When both components are made from the same material group, the sealing process is considerably simplified. In particular, the interlocking of the molecules of the end cap and the housing is facilitated when the same material group is used for both components. A material group could be understood, for example, as identical materials of different colors. Different copolymer compositions can also be grouped within the same material group. According to the invention, the housing and end cap materials comprise polypropylene or polypropylene copolymers or polycarbonate, in particular, polypropylene or polypropylene copolymers. Both materials exhibit sufficiently high transparency and, as thermoplastic materials, are suitable for ensuring the interlocking of the housing molecules with those of the end cap. Polypropylene, in particular, is especially suitable because it is a particularly lightweight material and allows for the manufacture of housings with especially thin walls, less than 2 mm thick. Accordingly, one embodiment of the invention is characterized in that the wall thickness of the housing is less than 2 mm. In another embodiment, the wall thickness of the end cap is also less than 2 mm, in particular, less than 1.5 mm.Therefore, in a particular embodiment, the wall thickness of the end cap may be less than that of the housing, in which case a polypropylene-based material is preferred for both components. According to another specific embodiment, the first sealing surface is intended to be equal to or greater than, in particular greater than, the cross-sectional area of ​​the tubular casing at its end. When the sealing surface is equal to the cross-sectional area of ​​the tubular casing at its end, a particularly effective seal is ensured by making optimal use of the available sealing surface. In a preferred embodiment, the sealing surface may also be larger than the cross-sectional area of ​​the tubular casing at its end. This can be achieved by designing the fusion process so that a greater quantity of material is melted and compression is applied during the subsequent joining process. This component features a flanged sealing surface, which improves the sealing effectiveness.Furthermore, the flange can contribute to a further reduction in dead volume, which is particularly desirable in hemodialysis. In a preferred embodiment of the filter device, two end caps are provided at opposite ends of the tubular housing. The housing is equipped with flow chamber openings and seals at both ends, with the openings positioned closer to the housing's center of gravity than the flow chamber seals. The use of two end caps is particularly advantageous for hemodialysis, as it allows the blood and dialysate to flow in countercurrent flow. This results in especially efficient blood purification. Furthermore, the housing may be provided with a plurality of openings at at least one end. In the case of hemodialysis, this ensures a particularly uniform dialysate flow. This further improves the efficiency of uremic toxin removal. At the same time, the hydraulic pressure in the dialysate is reduced, and consequently, the mechanical stress on the sealing surfaces. This also allows for a higher dialysate flow rate, which in turn positively influences the separation efficiency of the filtration device. Alternatively, the housing may be provided with a plurality of openings at each end. One particular embodiment is characterized by a dialyzer in the filtering device, with the first openings in the end caps allowing blood to enter and exit, and the second openings allowing dialysate to enter and exit. According to another refinement of the invention, the tubular housing has no dialysate inlet or outlet. This housing is particularly cost-effective and can be manufactured using a simplified tooling. Furthermore, this significantly simplifies the design of a multi-cavity tooling for the housing, resulting in cost and energy savings. In a preferred embodiment, the flow chamber seal material comprises either epoxy resin or polyurethane resin as the sealing material. Polyurethane is particularly preferred because it provides an especially optimal seal when using hollow fibers with an outer diameter of less than 300 µm. Even with hollow fiber bundle packing densities exceeding 60%, polyurethane remains advantageous due to its flow properties. In another embodiment, at least one energy direction sensor is arranged in the tubular section of the housing and / or in the end cap. This arrangement is preferable when the end cap and the housing are joined by ultrasonic welding. Such an energy direction sensor significantly increases the sealing effect of the joint and speeds up and simplifies the joining process. Preferably, the semipermeable membrane material comprises polysulfone, polyethersulfone, polyvinylpyrrolidone, polymethyl methacrylate, polyamide, polyester, cellulose, or polyacrylonitrile. A material composed predominantly of a mixture of polysulfone or polyethersulfone and polyvinylpyrrolidone is particularly preferred. This means that the material contains more than 50% by weight of this mixture. This mixture is particularly compatible with blood and thus further improves the properties of the filtration device, especially the dialyzer. According to a second aspect of the invention, the problem is solved by a process for manufacturing a filter device according to the first aspect of the invention, characterized in that the first and second sealing surfaces are produced by melting and recooling the areas of the housing and end cap that face the sealing surfaces so that they are tightly connected, and in that an interlacing of molecules of the housing with molecules of the end cap is carried out. In a refinement of the process, the sealing surfaces are produced by welding, specifically contact welding, laser welding, rotary welding, or ultrasonic welding. These processes ensure reliable fusion and bonding of the components. In particular, they guarantee the desired bonding surface, especially a flanged bonding surface and optimal sealing. Preferably, to manufacture a filter device by contact welding or mirror welding, the following steps are followed: a) Provide the end cap b) Provide the cross-section of the tubular casing c) Provide the mirror welding tool between the end cap and the housing section, wherein the mirror welding tool exhibits a temperature at least on the intended contact surfaces that is above the melting point or glass transition point of the respective joining material d) Bring the mirror welding tool into contact with the contact surfaces to be welded on the end cap and the housing section e) Melt the contact surfaces f) Remove the mirror welding tool g) Weld the end cap and the housing by compressing the molten contact surfaces h) Cool the molten contact surfaces below the melting point or glass transition point of the corresponding material. According to a third aspect of the application, a mirror welding tool is intended to be suitable for providing a procedure according to the second aspect of the invention or for use in a procedure according to the second aspect of the invention. Therefore, said mirror welding tool has 4 contact surfaces on which, during the procedure according to the second aspect of the invention, local contact and fusion of the end cap material and the tubular housing section occur simultaneously. In a preferred embodiment, the contact surface between the housing section to be melted and the mirror welding tool is designed such that the contact surfaces of the housing section or end cap meet the tool at angles other than 0° and 90° in the (imaginary) longitudinal direction of the housing section. Angles between 20° and 70° are preferred, more preferably between 30° and 60°, and even more preferably between 40° and 50°. According to another form of execution, these contact surfaces are designed to be concave. Brief description of the drawings Other details and advantages of the present invention are explained in detail according to an exemplary embodiment shown in the drawings. The figures show: Figure 1: a schematic representation of a tubular-shaped casing. Figure 2: A schematic representation of an end cap. Figure 3: A schematic representation of a filtering device consisting of a tubular housing and an end cap. Figure 3a: an enlarged representation of figure 3 in the area of ​​the first sealing surface. Figure 4: A schematic representation of an arrangement consisting of a tubular housing, an end cap, and a mirror welding tool during the heating phase of a mirror welding process. Figure 5a: A schematic representation of a section of a heating element or mirror welding tool with its corresponding housing section, representing a particular embodiment. Figure 5b: A schematic representation of a section of a heating element or mirror welding tool with its corresponding end cap section, representing a particular embodiment. Figure 6a: A schematic representation of a section of a heating element or mirror welding tool, depicting a particular embodiment. Detailed description of an execution example Figure 1 shows the tubular housing 2 of a filtration device 1, which contains a bundle of hollow fibers 3 formed by semipermeable membranes 4. At its ends, the tubular housing 2 has a flow chamber seal 8, shown here as concave towards the center of gravity S. The flow chamber seal 8 is made of polyurethane; an arrangement made of epoxy resin or ceramic material is also possible. When the filtration device 1 is used for dialysis, polyurethane is preferred. The outer surface of the flow chamber seal 8 is designed so that the hollow fiber membranes 4 are open, forming a first flow chamber 6 that surrounds the interior of these hollow fiber membranes. The second flow chamber 7 is located in the housing 2, outside the hollow fiber membranes 4.Figure 1 also shows the openings 9 in the housing 2, which are located closer to the center of gravity S of the housing 2 than the flow chamber seal 8. When the filtering device 1 is a dialyzer, the dialysate can be introduced into or extracted from the outer surface of the hollow fiber membrane 4 through the openings 9, allowing the exchange of substances between the blood side of the dialyzer, represented by the first flow chamber 6, and the dialysate, represented by the second flow chamber 7. In another embodiment, it is also possible for the blood to flow through the second flow chamber 7 and the dialysate through the first flow chamber 6. The housing 2 also features a housing projection 2a, which is located closer to the center of gravity S of the housing 2 than the flow chamber seal 8 and the openings 9. Figure 2 shows an end cap 10 with a first opening 11 and a second opening 12. On the outside sides of these openings 11 and 12 are threads 18 or devices for connecting fluid lines that are not shown here. Figure 3 shows the assembly of the end cap 10 with the tubular housing 2. Both components are designed to have a first sealing surface 13 and a second sealing surface 14. Through the first opening 11, the fluid can now enter or exit the first flow chamber 6; the first sealing surface 13 prevents the fluid from undesirably passing into the second flow chamber 7. Through the second opening 12, the fluid can now enter or exit the second flow chamber 7; the first 13 and second 14 sealing surfaces prevent the fluid from undesirably passing into the first flow chamber 6. The projection 2a on the tubular housing 2 is shown, which in this embodiment, together with the end cap 10, forms the second sealing surface 14. Figure 3a shows an enlargement of the first sealing surface 13, in which a first sealing surface 13 is formed that is larger than the cross-sectional area of ​​the tubular housing 2 at the end of the housing. A flange 15 is formed. In this embodiment, this flange was formed by a mirror welding process, where the parts to be joined were pressed together with such pressure that an increase in the sealing surface 13 was produced. Figure 4 schematically illustrates the joining process for constructing the filter device 1 by joining the end cap 10 and the tubular section of the housing 2, both made of polypropylene. Other materials, particularly polycarbonate, can also be used. Figure 4 shows the end cap 10, the tubular section of the housing 2, and a cross-section of a mirror welding tool 16. The tool provides a contact surface with the surfaces of the end cap 10 and the housing 2 that are to be joined to form the sealing surfaces 13 and 14. The illustration also shows a tool heating system 17, which ensures that the contact surfaces of the parts to be joined are heated above the melting point or glass transition point of the material.After the heating process, the parts to be joined can be separated, allowing the mirror welding tool 16 to be removed. The parts are then joined, forming the first 13 and second 14 sealing surfaces. In this example, the molecules of the end cap 10 interlock intimately with the molecules of the tubular section of the housing 2. This creates the first 13 and second 14 sealing surfaces, which exhibit a particularly high degree of sealing. Alternatively, the first 13 and second 14 sealing surfaces can be formed by rotary welding or laser welding. Rotary welding is possible and preferable when the first 13 and second 14 sealing surfaces are arranged symmetrically. Ultrasonic welding is also possible; in which case, it is recommended to install at least one energy direction transmitter in the tubular section of the housing 2 and / or in the end cap 10. Figure 5a shows another preferred embodiment of the joining process for manufacturing the filtering device 1 by joining the end cap 10 and the tubular housing section 2, where the tubular housing section and the mirror welding tool 16 are shown in the foreground. In this embodiment, the contact surface between the housing section 2 to be fused and the mirror welding tool 16 is designed such that the contact surface of the housing section 2 rests on the tool at an angle other than 0° and 90° in the longitudinal direction of the housing section. An angle between 20° and 70° is preferred, more preferably between 30° and 60°, and even more preferably between 40° and 50°. In the example embodiment, an angle of 45° is specified.This method offers the advantage of precise control over the joint point, resulting in a particularly reliable connection with minimal waste. Furthermore, in this design, the weld bead is particularly small, reducing potential fluid flow restrictions during the separation process. In the case of a dialyzer, this is especially relevant on the dialysate side. Figure 5b shows another preferred embodiment of the joining process for forming the filtering device 1 by joining the end cap 10 and the tubular housing section 2, with the end cap and mirror welding tool 16 shown in a magnified section. In this embodiment, the contact surface between the portion of the end cap 10 to be fused and the mirror welding tool 16 is designed such that the contact surface of the end cap 10 meets the tool 16 at an angle other than 0° and 90° in the (imaginary) longitudinal direction. An angle between 20° and 70° is preferred, more preferably between 30° and 60°, and even more preferably between 40° and 50°. An angle of 45° is shown in the example embodiment.This method of implementation offers the advantage of precise control over the joining point, resulting in a particularly reliable joint with minimal waste. Furthermore, in this design, the weld bead is particularly small, reducing potential fluid flow restrictions during the separation process. In the case of a dialyzer, this is especially relevant for the blood side. The weld bead is shaped to minimize, or even eliminate, the dead volume in the blood space. Dead volume on the blood side can lead to excessive blood clotting, resulting in progressive dialyzer obstruction. Figure 6a shows another embodiment, representing an improved modification of the embodiment shown in Figure 5a. In this embodiment, the contact surface between the housing section 2 to be melted and the mirror welding tool 16 is designed such that the contact surface of the housing section 2 rests on the tool at an angle other than 0° and 90° in the longitudinal direction of the housing section, where the surface is concave. The concave curvature means that the curve extends into the welding tool. The radius of curvature must be adapted to the dimensions of the housing. For a filtering device the size of a dialyzer, preferred radii of curvature are between 1 mm and 10 mm, particularly between 2 and 8 mm, and more specifically between 3 and 6 mm. A radius of 4.5 mm is specified in the embodiment.The concave curvature facilitates the precise fitting of the parts to be joined, even with tight tolerances, resulting in greater product safety and improved weld quality. Increased tolerances are particularly effective when using a polyolefin as the housing material, especially a polypropylene-based material. Figure 6b applies to the joint of end cap 2. List of reference symbols: 1 Filtering device 2 Tubular casing 2a Housing protrusion 3 Bundle of hollow fibers 4 Semipermeable membrane 5 Inside the casing 6 First flow chamber 7 Second flow chamber 8 Flow chamber seal 9 Openings 10 End cap 11 First opening 12 Second opening 13 First sealing surface 14 Second sealing surface 15 Bulging 16 Mirror welding tool 17 Tool Warm-up 18 Thread S Center of gravity K Contact surfaces

Claims

1. A filtering device (1) for substance exchange, in particular for hemodialysis, comprising: • a tubular housing (2) with a center of gravity (S) and two housing ends, in which a bundle of hollow fibers (3) made of semipermeable membranes (4) is disposed, the fiber cavities of which form a first flow chamber (6) and the interior of the housing surrounding the bundle of hollow fibers (3) forms a second flow chamber (7), • wherein the flow chambers at the ends of the housing are separated from each other by at least one flow chamber seal (8), • wherein the housing (2) has at least one opening (9) at at least one of its ends, and the at least one opening (9) is disposed closer to the center of gravity (S) of the housing than the flow chamber seal (8), • further comprising at least one end cap (10) having a first (11) and a second opening (12), wherein the casing (2) and the, at least one,end cap (10) forms a first sealing surface (13) that seals the housing (2) and the end cap (10), wherein the first sealing surface (13) is located further from the center of gravity (S) of the housing (2) than the at least one opening (9), and wherein a first fluid chamber is formed between the first sealing surface (13) and the first opening (11) of the end cap (10), through which the first opening (11) is fluid-connected to the first flow chamber (6), wherein the housing (2) and at least one end cap (10) form a second sealing surface (14) that seals the housing (2) and the end cap (10),and the second sealing surface (14) is arranged closer to the center of gravity (S) of the housing (2) than the flow chamber seal (8) and at least one opening (9). • and wherein a second fluid chamber is formed between the first (13) and the second sealing surface (14) and the second opening (12) of the end cap, through which the second opening (12) of the end cap (10) is fluidically connected to the second flow chamber by means of at least one opening (9), • wherein the first (13) and the second sealing surface (14) are not formed by a sealant, • characterized in that the material of the housing (2) and the end cap (10) comprises polypropylene or copolymers of polypropylene or polycarbonate, in particular, polypropylene or copolymers of polypropylene,and on the first (13) and second sealing surfaces (14), the molecules of the housing interlock with the molecules of the end cap.

2. Filtering device (1) according to claim 1, characterized in that the first sealing surface (13) is farther from the center of gravity (S) of the housing (2) than the at least one opening (9) and the seal of the flow chamber (8).

3. Filtering device (1) according to any one of the preceding claims, characterized in that the tubular housing (2) and the end cap (10) are made of the same group of materials.

4. Filtering device (1) according to any one of the preceding claims,characterized in that two end caps (10) are provided at opposite ends of the tubular housing (2), and the housing (2) is provided at both ends with openings (9) and flow chamber seals (8), and the openings (9) are arranged closer to the center of gravity (S) of the housing (2) than the flow chamber seals (8).

5. Filtering device (1) according to any one of the preceding claims, characterized in that the housing (2) has a plurality of openings (9) at at least one end.

6. Filtering device (1) according to claim 4, characterized in that the filtering device (1) consists of a dialyzer, and in that the first openings (11) of the end caps allow the inlet and outlet of blood, and in that the second openings (12) of the end caps allow the inlet and outlet of the dialysate.

7. Filtering device (1) according to claim 6,characterized in that the tubular housing (2) has no dialysate inlet or outlet.

8. Filtration device (1) according to any of the preceding claims, characterized in that the material of the semipermeable membranes (4) comprises polysulfone, polyvinylpyrrolidone, polymethyl methacrylate, polyamide, polyester, cellulose, or polyacrylonitrile.

9. Method for manufacturing a filtration device (1) according to any of the preceding claims, characterized in that the first (13) and second sealing surfaces (14) are produced respectively by melting and subsequent cooling of the areas of the housing (2) and the end cap (10) that face the sealing surfaces (13, 14) so ​​that they are connected by sealing, and in that an intertwining of molecules of the housing (2) with molecules of the end cap (10) is produced, wherein the sealing surfaces (13, 14) are manufactured respectively by hot surface welding.

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