EP3528934A1

EP3528934A1 - Method for determining a permeation property of hollow fibre membranes

Info

Publication number: EP3528934A1
Application number: EP17797250.2A
Authority: EP
Inventors: Elmar Grausam; Ingo Fehr
Original assignee: Fresenius Medical Care Deutschland GmbH
Current assignee: Fresenius Medical Care Deutschland GmbH
Priority date: 2016-10-24
Filing date: 2017-10-23
Publication date: 2019-08-28
Also published as: JP7167016B2; CN109862957B; WO2018077782A1; US11007486B2; CN109862957A; US20190247798A1; JP2019532809A; DE102016012730A1

Abstract

The invention relates to a method for determining a permeation property of hollow fibre membranes, where the permeation property of the hollow fibre membrane is determined on a hollow fibre membrane bundle which is introduced into a housing and comprises, at a first end of said hollow fibre membrane bundle, hollow fibre membranes that are open at the ends and, at a second end of said hollow fibre membrane bundle, hollow fibre membranes that are closed at the ends. In particular, the invention relates to a method for determining clearance, particularly diffusive clearance of hollow fibre membranes.

Description

Method for determining a permeation property of

Hollow fiber membranes

Theme of the invention

The invention relates to a method for determining a permeation property of hollow fiber membranes. In particular, the invention relates to a method with which the "clearance", in particular the "diffusive clearance" of hollow-fiber membranes, can be determined from a determined permeation property.

Moreover, the invention relates to an apparatus for carrying out a method for determining the permeation properties of hollow fiber membranes in a hollow fiber membrane bundle, and their use.

Furthermore, the invention relates to a method for producing hollow fiber membrane bundles of hollow fiber membranes having predetermined permeation properties.

Background of the Invention Hollow fiber membranes are widely used in the purification of liquids. In particular, hollow fiber membranes are used in medical technology for water treatment and blood purification, especially in the dialysis of kidney patients. Corresponding hollow-fiber membranes are installed in hollow-fiber membrane bundles in filter modules. The production of such filter modules for blood purification is now carried out in mass production scale.

The construction of hollow fiber membrane filter modules and the preparation of hollow fiber membranes for dialysis is known in the art (Uhlenbusch Körwer, Bonnie-Schorn, Grassmann, Vienken, "Understanding Membranes and Dialysers" Publisher: Pabst Science Publishers, 2004).

The hollow fiber membranes used for the purification of blood often consist of polysulfone (PSU) and polyvinylpyrrolidone (PVP) and are usually prepared by a so-called dry-wet spinning process. In such processes, a spinning solution containing the polymers PSU and PVP and a solvent is extruded through an annular die into a hollow spun yarn. The filament is first guided vertically through an air space, the so-called precipitation gap. In the lumen of the spun yarn, a coagulation medium is extruded simultaneously with the extrusion to the spun yarn, which starts a coagulation process in the dope of the spun yarn. During coagulation, phase inversion occurs, so that so-called sol and gel phases form within the strand. The spun yarn is introduced after passing through the precipitating gap in a precipitation bath, in which the thread is completely brought to precipitation and forms the solid hollow fiber membrane structure. Subsequently, the obtained hollow fiber membrane passes through several rinsing baths and drying zones. Depending on the preset spinning conditions, hollow fiber membranes having a different pore structure are obtained. The term "PSU" is understood in the context of this application as a generic term for all polymers containing sulfonic groups such as polyethersulfone and polyphenylsulfone and copolymers comprising these polymers.

In general, a plurality of hollow fiber membranes is extruded simultaneously and in parallel in a production plant, so that the obtained after passing through the production plant hollow fiber membrane fibers can be combined as a group of threads or fiber bundles and are taken up by a reel.

The manufacturing process of hollow fiber membranes is a continuous process that is operated in the production facilities in three-shift operation. It is therefore continually necessary to monitor the quality of the fibers produced in order to avoid larger production errors. Therefore, it is constantly checked if the properties of produced hollow fiber membrane are in the specified range and the production process proceeds according to the preset conditions.

Depending on the process conditions different hollow fiber membranes with different permeation properties, for example, so-called "high flux" or "low flux" hollow fiber membranes can be obtained. Corresponding hollow-fiber membranes differ in their separation behavior and are therefore suitable, e.g. in the dialysis of kidney patients, for different therapeutic procedures. In order to determine the permeation properties of hollow-fiber membranes, it has hitherto been necessary to construct filter modules from the hollow-fiber membrane bundles produced, which are then first subjected to the separation properties of the membrane according to a test method, e.g. according to DIN / EN / ISO 8637: 2014.

For the construction of filter modules, the hollow fiber membrane bundles must be formed in a filter housing and encapsulated end. The casting of the hollow-fiber membrane bundle at the fiber ends takes place with the aid of curable resin compositions, in particular with polyurethane. The casting itself and the curing are time-consuming process steps. The construction of filter modules and the following analyzes on the filters in the production laboratories can take up to several hours. During this time, the production of hollow fiber membranes continues. If in doubt, it may happen that the analysis results after a few hours show that the specifications of the manufactured hollow fiber membrane are no longer complied with, so that the production result of several hours must be discarded.

On the other hand, if the results of the analysis indicate that the hollow fiber membranes produced meet the specifications, then the corresponding production result of hollow fiber membranes can be further processed into corresponding filter modules.

As mentioned above, such hollow fiber membrane filter modules are used for the blood purification of kidney patients. The blood purification of kidney patients is based on the principle of transmembrane mass transfer. It will Blood in along the inner cavity of the hollow-fiber membranes, also called lumen, out, while on the outside of a corresponding dialysis fluid is flowed. The flow direction of the liquids is opposite, so that a filtration using the countercurrent principle.

According to the filtration conditions in the blood treatment of kidney patients, undesirable metabolites such as urea, creatinine, β-2-microglobulin, interleukin-6, phosphate are removed from the blood by permeating them through the membrane wall and being taken up by the dialysis fluid. Likewise, dissolved constituents of the dialysis fluid can also permeate through the membrane wall onto the blood side. The dialysis fluid is provided as an aqueous physiological solution containing electrolytes (for example, Na ^+, K ^+, Mg ^2+, Ca ^2+, Cl ^"), glucose, and a buffer (such as NaHC0 ₃₎ included. [0014] In principle, the transmembrane mass transfer in the described principle of blood purification done in two ways, convective and diffusive.

In convective mass transfer, liquid and substances therein permeate through the membrane according to a transmembrane pressure gradient. In the diffusive mass transport, the permeation of substances through the membrane occurs due to the molecular intrinsic motion of the solutes and a concentration gradient that exists across the membrane wall.

Depending on the nature of the hollow-fiber membrane, or the pore size of the hollow-fiber membrane and the set flow rate of blood and dialysate, the filtration process can be carried out according to one or the other type. If e.g. For the blood treatment in a hemofiltration or hemodiafiltration process, hollow-fiber membranes with relatively large pores are used and / or high flow rates of the two fluid streams, blood and dialysate, are preset, so that part of the filtration is convective.

If the blood treatment, however, in the context of a simple dialysis, so membranes are used with smaller pores and the transport of energy diffusive. Under these conditions, especially low-molecular substances such as urea, electrolytes, creatinine and phosphate permeate.

The separation of harmful plasma proteins in the blood of kidney patients, however, can only be achieved in therapeutic methods in which a convective mass transfer is possible. Such plasma proteins are in the so-called middle molecular weight range. Known proteins in the middle molecular range are β-2 microglobulin and interleukin-6. The separation efficiency with which harmful metabolites are removed during the purification of blood by hollow-fiber membranes is referred to as clearance. Methods for determining the clearance of hollow fiber membranes are known in the art. For example, the standard DIN / EN / ISO 8637: 2014 describes a standardized method for determining clearance.

In the production of hollow fiber membranes, the specification, in particular the specification for clearance, in particular the specification of the diffusive clearance of a hollow fiber membrane is important in order to be able to monitor the production process.

The method described in WO 2013/03461 1 for determining a permeation property of hollow-fiber membranes is known from the prior art. On page 18 of WO 2013/03461 A1, a method for determining the hydraulic permeability on a hollow fiber membrane bundle is described.

Object of the invention

It has been shown that existing methods for quality monitoring in the production of hollow fiber membranes are in need of improvement. It was therefore an object of the present invention to provide a simplified method for determining a Permeationseigenschaft, in particular the clearance, further in particular the diffusive clearance of hollow fiber membranes provide.

Another object of the invention was to provide a device under the use of hollow fiber membrane bundles can be examined and the diffusive clearance of the hollow fiber membranes can be determined.

A further object of the invention was also to provide a production process of hollow fiber membranes, which makes it possible to produce hollow fiber membranes within a production process so that before production for the hollow fiber membranes defined range of at least one Permeationseigenschaft, especially the clearance, more particularly the diffusive Clearance, can be met.

Definitions and Summary of the Invention

In a first aspect of the invention, it has surprisingly been found that the stated problems for determining a permeation property can be achieved by providing a method according to claim 1. The claims 2 to 12 represent preferred embodiments of the invention according to the first aspect there.

Furthermore, it has been found in a second aspect of the invention that the described problems can be solved by a device according to claim 13.

In a further aspect, the invention relates to a method for producing hollow fiber membrane filter modules according to claims 15 to 17 using a method according to claims 1 to 12.

In the context of the present invention, the term "permeation property" of a membrane designates the characteristic of a transmembrane mass transfer, which is characterized by a permeation of a substance through a membrane Membrane wall is related. A permeation property of a membrane provides information about the pore structure of the membrane and is understood as a measure with which a membrane can be characterized in terms of its porous structure. Permeation observed through the transmembrane mass transfer is generally considered in relation to other quantities. In particular, for the purposes of the present invention, the term also means how much of a substance per unit of time can be separated from a liquid by permeation. Based on the initial concentration of the substance, this permeation value indicates the "clearance." In this sense, the clearance is understood as a permeation property describing the membrane.

For the production of hollow fiber membrane filter modules hollow fiber membrane bundles are formed in a housing of a filter module and encapsulated end with a casting resin in the housing by methods of the prior art. The end space between the fibers is filled with the casting resin, so that no fluid can penetrate the interspace between the fibers. First, the lumens of the hollow fiber membranes are closed at the ends. The lumens of the hollow fiber membranes are exposed again by the end part of the grout is separated. For the determination of a permeation property, in particular of the ultrafiltration coefficient, it is possible according to the method of the invention to dispense with an end-side encapsulation of the hollow-fiber membrane bundle and the construction of the hollow-fiber membrane filter module. Within the scope of the invention, the hollow-fiber membranes only have to be closed at the end on one side and placed in a housing in order to be measured. The embedding of the hollow fiber membranes in a Harzverguss, however, is superfluous by the novel process.

For the purposes of the invention, the term "molding in" is understood to mean a process in which a hollow-fiber membrane bundle is introduced into a housing A hollow-fiber membrane bundle is deformable and can be introduced under compression into the housing so that the bundle is inside the housing is under tension and exerts a force on the inner surface of the housings, Accordingly, the term "introduction" thus also a process to be understood, in which a compressed hollow fiber membrane bundle is inserted into a housing such that the hollow fiber membrane bundle strives to expand according to its tension, thereby completely filling the inner space of the housing with hollow fiber membranes. For the purposes of the present application, the introduction of a hollow fiber membrane bundle into a housing under compressive stress of the hollow fiber membrane bundle so that the hollow fiber membranes largely fill the space of the housing is also referred to as a "molding in" of the hollow fiber membrane bundle into the housing to a hollow fiber membrane bundle results in a packing of hollow fiber membranes in which the hollow fiber membranes abut each other in a density predetermined by the packing.) Hollow fiber membrane bundles form a resistive force in such a packing as a hollow fiber membrane bundle, meaning that a hollow fiber membrane bundle is compressible and builds up a restoring force upon compression Compressed hollow-fiber membrane bundles endeavor to return to a relaxed state The restoring force is in particular also associated with a corrugation of the hollow-fiber membranes, which used in the production of hollow fiber membranes. Corresponding methods for producing hollow-fiber membranes and hollow-fiber membrane bundles are known from the prior art, for example from DE 100 07 327 A1.

For the purposes of the present application, the term "test liquid" is to be understood as meaning a liquid with which a membrane can be examined with regard to a permeation property Such test liquids may be, for example, aqueous solutions or pure water, but in particular also blood plasma or blood The term "membrane-like" in the context of the present application means that the test liquid, or part of the test liquid, is from the lumen of the hollow-fiber membrane permeate through the membrane wall into the outer environment of the hollow fiber membrane. For the purposes of the application, the term "test substance" is understood as meaning a substance which is a constituent of a test fluid .In particular, test substances may represent dissolved constituents of a test fluid, for example salts or water-soluble compounds.

Detailed description of the invention

Surprisingly, it has been found according to a first aspect of the invention that the above-mentioned object can be achieved by a new method for determining a permeation property of hollow-fiber membranes.

The method according to the invention for determining at least one permeation property, in particular the clearance of hollow-fiber membranes, comprises the following steps:

(a) providing a hollow fiber membrane bundle comprising a plurality of

Hollow fiber membranes having a first end and a second end, wherein the lumens of the hollow fiber membranes at the first end of the

Hollow-fiber membrane bundle open at the end, in particular liquid-permeable and at the end of the second end of the hollow-fiber membrane bundle

closed, in particular designed liquid-tight

(b) providing a housing for receiving the hollow fiber membrane bundle

comprising a first end and a second end, the first end having at least one liquid inlet (c) introducing the hollow fiber bundle into the housing, wherein the first end of the

Hollow fiber bundle is aligned with the end open lumen of the hollow fiber membranes to the at least one liquid inlet at the first end of the housing

(d) determining a permeation property of the hollow fiber membranes It has been found that it is possible with the aid of the specified method steps to determine permeation properties of hollow fiber membranes without having to previously produce hollow-fiber membrane filter modules from the hollow-fiber membrane bundles. It thus eliminates the effort that has to be made available for the production of the test filter modules. The determination of the permeation property of the hollow fiber membrane is carried out without previously potting the hollow fiber membrane bundle.

In one embodiment, the method according to the invention comprises the following steps:

Providing a hollow fiber membrane bundle comprising a plurality of hollow fiber membranes having a first end and a second end, the openings of the lumens of the hollow fiber membranes open at the first end of the hollow fiber membrane bundle, in particular liquid-tight, and end-closed at the second end of the hollow fiber membrane bundle, in particular liquid-tight, are,

Providing a housing for receiving the hollow-fiber membrane bundle, having a first end and a second end, the first end of the housing having at least one liquid inlet and the second end of the housing having at least one liquid outlet,

(C) introducing the hollow fiber membrane bundle into the housing, wherein the first end of the hollow fiber membrane bundle with the open end lumens of

Hollow fiber membranes is aligned for at least one liquid inlet and the second end of the hollow fiber membrane bundle is directed with the end closed lumen of the hollow fiber membranes to at least one liquid outlet,

(d) providing a first test liquid and a second test liquid, wherein at least the first test liquid or the second test liquid comprises at least one test substance and the second test liquid from the first test liquid is different, in particular at least in the concentration of the at least one test substance is different from the first test liquid, (e) filling the housing and / or the hollow fiber membrane bundle

Supplying the first test liquid through the at least one liquid inlet at the first end of the housing into the interior of the housing and / or the hollow-fiber membrane bundle, (f) inflowing a second test liquid through at least one

Liquid inlet at the first end of the housing in the interior of the housing and / or the hollow fiber membrane, or the hollow fiber membranes, (g) measuring the concentration of the at least one test substance, at least one liquid outlet of the housing, while the second test liquid through at least one liquid inlet into the housing and or the hollow fiber membrane bundle flows. The method according to the invention has the advantage that the clearance, in particular the diffusive clearance, of the hollow-fiber membranes can be determined quickly and reliably. This has the advantage, in particular in processes for producing hollow-fiber membranes, of being able to promptly control the production process on the basis of the clearance values obtained. As a result, larger production errors can be avoided.

In another embodiment, the method of the invention consists of the following steps: (a) providing a hollow fiber membrane bundle comprising a plurality of

Hollow fiber membranes having a first end and a second end, wherein the openings of the lumens of the hollow fiber membranes at the first end of the hollow fiber membrane bundle open end, in particular liquid permeable, and at the second end of the hollow fiber membrane bundle closed at the end, in particular liquid-tight, are

(b) providing a housing for receiving the hollow fiber membrane bundle, having a first end and a second end, the first end of the housing having at least one liquid inlet and the second end of the housing having at least one liquid outlet,

(c) introducing the hollow fiber membrane bundle into the housing, the first end of the hollow fiber membrane bundle being aligned with the end open lumens of the hollow fiber membranes for at least one liquid inlet and the second end of the hollow fiber membrane bundle with the end closed lumens of the hollow fiber membranes is directed to at least one liquid outlet,

(d) providing a first test liquid and a second test liquid, wherein at least the first test liquid or the second test liquid having a test substance and the second test liquid is different from the first test liquid, in particular at least in the concentration of the at least one test substance is different from the first test liquid .

(e) filling the housing and / or the hollow-fiber membrane bundle by feeding the first test liquid through the at least one liquid inlet at the first end of the housing into the interior of the housing and / or the hollow-fiber membrane bundle or hollow-fiber membranes,

(f) flowing a second test liquid through at least one liquid inlet at the first end of the housing in the interior of the housing and / or the hollow-fiber membrane bundle, (g) measuring the concentration of the at least one test substance at at least one liquid outlet of the housing while the second test liquid flows through at least one liquid inlet into the housing and or the hollow fiber membrane bundle.

In a first step of the method according to the invention, a hollow fiber membrane bundle is provided, comprising a plurality of hollow fiber membranes having a first end and a second end, the openings of the lumens of the hollow fiber membranes at the first end of the hollow fiber membrane bundle open end, in particular liquid permeable, and at the second end of the hollow fiber membrane bundle closed end, in particular liquid-tight configuration.

For the purposes of the present application, the term "hollow-fiber membrane bundle" is to be understood as meaning a bundle of a multiplicity of hollow-fiber membranes. In particular, the hollow-fiber membrane is a membrane in the form of hollow filaments consisting of a porous material and having a substantially circular diameter, the wall thicknesses of such hollow-fiber membranes intended for dialysis, 10 to 100 μηι, depending on the membrane material, with luminal diameters of such hollow-fiber membranes lying between 150μηι to 250μηι, in particular between 180μηι and 220μηι, the fiber length is in the range of 150μηι to 300mm, in particular between 250mm and 300mm The cavity of hollow fiber membranes can thereby of liquids In particular, provision is made for material to be separated on hollow-fiber membranes which, by utilizing a permeation of substances through a transmembrane mass transfer, from the outside to the inner cavity, or from the inner cavity to the outside of the hollow-fiber membrane Such hollow fiber membranes are typically used in therapeutic blood treatment

The material of the hollow-fiber membranes can be selected from polymers, preferably from polysulfone, polyethersulfone, polyvinylpyrollidone, polypropylene, polyacrylonitrile, polyamide, polyvinylpyrrolidone, polyethylene ether, cellulose, Cellulose regenerate, cellulose acetate or mixtures thereof. Particular preference is given to hollow-fiber membranes which have a hydrophobic polymer material, for example polysulfone or polyethersulfone, and a hydrophilic polymer material, for example polyvinylpyrrolidone, in particular consisting thereof. The hollow fiber membrane has a plurality of pores, which serve to allow a mass transfer between the interior of the hollow fiber membrane and surrounding the hollow fiber membrane environment. The hollow interior of the hollow-fiber membrane is called "lumen." The hollow-fiber membrane bundle which is used for the purposes of the present invention is not cast, ie, the ends of the hollow-fiber membrane bundle are not embedded in a plastic matrix.

For the purposes of the present application, the term "lumen" is understood to mean a coherent cavity extending lengthwise inside the hollow-fiber membrane The lumen of hollow-fiber membranes is surrounded by the porous membrane wall, so that liquids which flow through the membrane The openings of the lumens at the fiber ends thereby form accesses to allow fluids, in particular liquids, to flow through the interior of the fiber Heat action are closed at the end, in particular, the lumens can be closed so that a respective end of the hollow fiber membrane is fluid, in particular liquid-tight.

When a plurality of hollow-fiber membranes are combined to form a hollow-fiber membrane bundle, intermediate spaces are created between the individual hollow-fiber membranes, through which liquids and / or gases can likewise be passed. A hollow fiber membrane bundle preferably has at least 50 to 20,000 hollow fiber membranes. Typical diameters of hollow fiber membrane bundles are in the range of 15 mm to 50 mm. The hollow-fiber membrane bundle which is used in the method according to the invention is not cast, ie the ends of the hollow-fiber membrane bundle are not cast in a casting resin. The hollow fiber membrane bundle has a first end and a second end, wherein the first end is different from the second end. The first end of the hollow fiber membrane bundle has open hollow fiber membranes. In particular, the openings of the lumens of the hollow fiber membranes at the first end of the hollow fiber membrane bundle are open at the ends. This allows fluids and / or gas to escape from the lumen into the environment or enter the lumen from the environment.

In determining a permeation property according to the method of the invention, the starting point is a hollow-fiber membrane bundle which consists of a large number of hollow-fiber membranes whose permeation properties, in particular the clearance, are to be determined. Hollow fiber membrane bundles are obtained from the prior art production processes and used for the production of hollow fiber membrane filter modules. In a first step of the method, the openings of the lumens of the hollow fiber membranes in the hollow fiber membrane bundle are closed at one end. Methods for sealing the hollow fiber membranes at one end of the hollow fiber membrane bundle are known in the art. The hollow fibers can be closed by the action of heat, for example by heat radiation or thermal contact, by filling with waxes or plastics, or by laser radiation. In the present case, a thermal contact method on an aluminum foil is preferred. In this context, closed means that the fiber ends are liquid-tight, so that no liquid can enter or exit the lumen of the fiber via the fiber end. Subsequently, the hollow-fiber membrane bundle is formed with the hollow-fiber membranes end-closed at the second end and hollow-fiber membranes open at the first end in an elongate, preferably vertically positioned housing. For the purposes of the present application, the term "housing" is to be understood as meaning a hollow body which is intended to receive a plurality of hollow-fiber membranes If a hollow-fiber membrane bundle consisting of a multiplicity of hollow-fiber membranes is introduced into a housing, a space in the housing remains the hollow fiber membranes and between the inside of the housing and the outside of the hollow fiber membranes, of liquids can be flowed through. Suitable housings can have an elongate extent, so that an extension axis of a housing is longer than a second and third extension axis and can thus be referred to as the longitudinal axis of the housing. According to the longitudinal extent of a proposed housing, this can be used in preferred orientations, vertical and horizontal.

In a preferred form, a corresponding housing is cylindrical, e.g. designed as a sleeve. Corresponding sleeve-shaped housings may be open to at least one of the ends, so that a hollow-fiber membrane bundle can be introduced into the sleeve. Then the housing can be closed or combined with appropriate end caps or fittings. Corresponding sleeves, which serve as casings for hollow-fiber membrane bundles, are known from the construction of dialyzers in the prior art. Corresponding housings are preferably made of a rigid plastic material, e.g. Polycarbonate, polypropylene or polyoxymethylene, or of metals, e.g. Stainless steel or aluminum.

The packing density of the hollow fiber membrane bundle formed in the housing is preferably 20 to 80%, preferably 50 to less than 65%. The elongate housing has a first end and a second end, the housing further having a fluid inlet at the first end and a fluid outlet at the second end. The arrangement of the hollow-fiber membrane bundle in the housing is such that the end-face open hollow fiber membranes are aligned for liquid inlet, and the end closed hollow fiber membranes are aligned to the liquid outlet.

In a further step, a first and a second test liquid are provided, wherein at least the first test liquid contains a test substance. The housing is filled with the first test liquid. The filling takes place so that existing air is displaced from the pores of the hollow-fiber membrane, the space between the hollow-fiber membranes and the lumen of the hollow-fiber membrane and is flushed out of the housing. The hollow fiber membrane bundle is completely flushed during the filling of the first test liquid, so that the hollow fiber membrane bundle is completely surrounded by the first test liquid. As a result of the filling of the housing, it is provided to allow an excess of the first test liquid to flow over the liquid outlet of the housing. Preferably, the volume rate of the incoming test liquid is adjusted so that the volume of the housing with the hollow fiber membrane bundle therein is exchanged once between 30 seconds and 5 minutes. In particular, it is provided to allow the test liquid to flow at a volume rate of 20 to 150 ml / min. Subsequently, the influx of the first test liquid is stopped and a second test liquid is added. The second test liquid is different from the first test liquid in at least the concentration of the test substance from the first test liquid. Preferably, the second test liquid is distilled water. During the inflow of the second test liquid, the concentration of the test substance is measured at the liquid outlet of the housing by suitable measuring means. The measuring means may be detectors which provide a concentration-dependent signal with respect to the test substance. Such detectors may be, for example, conductivity detectors or photometric detectors. Other detectors are well known in the art.

Since the second test liquid does not contain the test substance or in a different concentration, a concentration of the test substance which is generally different from the concentration of the test substance in the first test liquid is measured in the outflowing liquid at the liquid outlet of the housing. Preferably, the concentration of the test substance in the second test liquid is present in a lower concentration than in the first test liquid, or not present, so that the observable concentration at the liquid outlet of the housing indicates a lower concentration with increasing inflow time of the second liquid time.

In the latter case, an observable decreasing concentration of the test substance at the liquid outlet, because on the one hand, the interspace volume of the hollow fiber membranes by the inflow more liquid from the test liquid is rinsed free. This results in a concentration gradient of the test substance between the Holfaserzwischenraum on the one hand and the pore space and the lumen side of the hollow fiber membranes on the other side. In the further course, the test substance permeates through the membrane wall in accordance with the concentration gradient in order to compensate for the concentration gradient and is flushed by the stream of the second test liquid to the liquid outlet.

It has been found that the concentration determined by the measuring means, in particular the determined concentration profile of the test substance at the liquid outlet, is characteristic of the permeation behavior of the examined hollow-fiber membrane in the hollow-fiber membrane bundle. Therefore, e.g. By changing the permeation properties of hollow fiber membranes during a production process of the hollow fiber membranes, conclusions about the quality of the production process or the resulting hollow fiber membranes are made.

For the inventive method, it is not necessary, as hitherto customary, to make individual test filter modules from the hollow-fiber membrane bundles of the hollow-fiber membrane production in order to determine the permeation behavior of the membrane. It thus eliminates the effort to be provided for the production of the test filter modules. According to the invention, the hollow-fiber membrane bundle to be examined only has to be closed on one side and all further steps for producing a ready-to-use test filter module are dispensed with.

In this context, a test filter module is understood to be a filter module which is similar to the structure of dialyzers but is used exclusively for determining the permeation properties of the hollow fiber membrane bundles produced and is subsequently disposed of. To prepare the test filter modules, the usual manufacturing steps of the filter construction must be run through. That is, the hollow fiber membrane bundles are molded into the housing of the test filter modules and are end-sealed with a molding resin in the housing, which is disadvantageous. Furthermore, an effect of the invention according to the first aspect is to be seen in that the hollow fiber membranes can be examined in a short time, ie within a few minutes after their preparation in terms of their permeation property. Investigations according to previous methods, which require the construction of complete Prüfffiltermodule take at least a period of 3 hours to complete. During this period, it may already come to a large waste production, which can be avoided with the inventive method. According to one embodiment of the first aspect of the invention, it has been found that the clearance, in particular the diffusive clearance, can be determined on the basis of a test substance by suitable evaluation of the measurement results obtained. Clearance, especially diffusive clearance, is considered to be a characteristic permeation property of a hollow fiber membrane. In the production of hollow-fiber membranes, the determined clearance and the determined diffusive clearance thus also serve as a measure of whether the production process proceeds according to predetermined process parameters, or whether the production process deviates unnoticed from the specification of the process parameters. To determine the clearance, in particular the diffusive clearance, as previously described, the concentration of the test substance is measured repeatedly or continuously on at least one liquid outlet of the housing during the inflow of the second test liquid into the housing, as a function of time. From the measured values obtained or the course of the measured values, a concentration profile of the test substance is recorded at the liquid outlet. Preferably, the second test liquid either has no test substance or the test substance is present in the second test liquid in a lower concentration than in the first test liquid, so that the recorded concentration curve represents a decreasing concentration of the test substance with time. Surprisingly, it was found that the clearance, in particular the diffusive clearance can be determined by a characteristic curve parameter of the recorded concentration curve. In order to determine the characteristic curve parameter, in one step a mathematical function is approximated to at least one section of the curve of the determined concentration curve. For example, known fit functions can serve as mathematical functions.

In the simplest case, a straight line can be adapted to a nearly linear section of the determined concentration curve. Other suitable fit functions may be exponential or sigmoidal functions. In a further step, at least one characteristic parameter of the approximated mathematical function is determined. This can e.g. be the slope in a considered section of the concentration curve of the mathematical function.

Furthermore, according to an embodiment of the first aspect of the invention, it has been found that the determined characteristic parameter can serve to determine a second parameter which directly reflects the permeation property or the clearance, in particular the diffusive clearance.

For this purpose, the determined characteristic curve parameter value was assigned to a specific value for the clearance, in particular the diffusive clearance, on the basis of previously determined calibration values. The previously determined calibration values can be in the form of tables and the clearance, in particular the diffusive clearance, can be determined from the characteristic parameter of the approximated mathematical function. The previously determined calibration values may e.g. serve a calibration function, or to create a calibration curve, so that an assignment of a first parameter that describes the mathematical approximation function with the clearance, in particular the diffusive clearance, is possible.

The calibration curve is preferably created with the aid of hollow-fiber membranes whose clearance value was determined by known methods. The clearance can be determined, for example, on test filter modules which contain cast hollow-fiber membrane bundles of the hollow-fiber membrane to be examined, in accordance with the method specified in DIN / EN / ISO Standard 8637: 2014. Subsequently, identical Measure hollow fiber membrane bundle according to the method of the invention. From the determined concentration curve of the test substance, eg a characteristic slope value is determined, which is correlated with the already known clearance value of the test filter modules. Several such evaluations and correlations are performed on hollow fiber bundles with different pore nature of the hollow fiber membranes. From several of these correlations, a calibration curve is then created. It was found that a unique correlating curve can be established between the known clearance values and the evaluated curve parameter values.

In a further embodiment of the invention according to the first aspect has been found that the evaluation and thus the accuracy of the inventively determined clearance, in particular the diffusive clearance can be improved if corresponding curve fit functions as a mathematical function of the determined decreasing concentration curve of the test substances.

In cases in which the decreasing concentration profile of a test substance in sections is largely linear, equation 1 offers itself as a mathematical function for rapid evaluation.

Y = A ₁ - A ₂ - t GL 1

A-i concerns the position of a straight line according to equation 1

A ₂ concerns the slope of the line

In an alternative application, it may be advantageous to approximate the decreasing concentration curve of a test substance according to the method according to the invention by a mathematical exponential function according to equation 2:

Y = B ₁ - e ~ ^{B2 't} Eq. 2 In a further alternative application, it may be advantageous to approximate the decreasing concentration curve of a test substance by the method according to the invention by a mathematical sigmoidal function according to Equation 3: l + _e C ₃ - (tC ₂ )

Ci refers to the starting point of the curve

C ₂ indicates the X-axis section to the inflection point

C ₃ determines the slope at the point of inflection

For the evaluation of the concentration profile of the method according to the invention according to one of the equations 1 to 3, the corresponding calibration curves must also be made according to the same evaluation according to one of the equations 1 to 3. The characteristic curve parameter used for evaluating a hollow-fiber membrane bundle with an unknown clearance value is the same as that used to determine the corresponding calibration curve.

In a further embodiment of the first aspect of the invention, it has been found that, for the determination of the clearance value, in particular the slope in a point of a mathematical function, e.g. the inflection point of a sigmoidal mathematical function, which was approximated to the descending concentration curve of the test substance, is advantageous for the evaluation.

The test substance of the test liquid is advantageously a substance whose concentration in the outflowing liquid is easily detectable and which can representatively reflect the examined permeation properties. In particular, sodium, creatinine, phosphate or vitamin B12 proves advantageous to determine the diffusive clearance of hollow fiber membrane. These substances are particularly preferred, since they are low molecular weight and therefore representative of the intrinsic molecular motion for the diffusive mass transport. In a further embodiment according to the first aspect of the invention, the concentration of the test substances in the test liquid is chosen so that a good detectability is given. In a further embodiment according to the first aspect of the invention, NaCl is to be used as the test substance in concentrations of 30 to 100 g / l, more preferably 70 to 90 g / l in order to be able to determine reproducible measurement results by measuring the conductivity at the liquid outlet of the housing of the measuring device , Furthermore, it has been shown that vitamin B12 is very well suited as a test substance, since vitamin B12 can be very well detected photometrically. Due to the higher molecular weight in comparison to NaCl, information about the pore size distribution of the hollow fiber membranes tested can additionally be obtained. In a further embodiment according to the first aspect of the invention, therefore, vitamin B12 is used as the test substance in concentrations of 100 to 3000 mg / l, preferably 200 to 2000 mg / l, preferably 400 to 600 mg / l.

Depending on the type of hollow-fiber membranes, the volume rate of the incoming second test liquid may be of importance for the process according to the invention.

Depending on the pore nature of the hollow-fiber membranes, it is advantageous for the determination of the diffusive clearance to keep the convective mass transport through the membrane as low as possible. In a further embodiment according to the first aspect of the invention it has therefore been found that the accuracy of the measurement is ensured if at the liquid outlet of the test device, a volume rate of 10 to 120 ml / min, preferably 40 to 100 ml / min, preferably 60 to 80 ml / min is present.

Furthermore, the packing density of the hollow-fiber membranes in the housing of the measuring device also influences the transmembrane pressure difference under flow conditions. According to a further embodiment according to the first aspect of the invention, hollow fiber membrane bundles having a number of hollow fiber membranes of from 50 to 20,000 hollow fiber membrane can be successfully tested, provided that a packing density of 20 to 80% in the housing of the test device is present. Below the packing density of 80%, it was found that no significant transmembrane pressure difference occurs in the flow state of the test method. This also avoids or reduces the convective mass transport across the membrane wall, which is particularly important for the determination of diffusive clearance.

In a second aspect, the invention relates to an apparatus with which the method according to at least one embodiment of the first aspect of the invention is executable. Accordingly, the device consists of at least one reservoir for receiving at least one liquid, in particular the first test liquid and / or the second test liquid, a measuring device comprising a housing having a first end and a second end for receiving a hollow fiber membrane bundle, wherein the first end the housing has at least one liquid inlet and the second end of the housing has at least one liquid outlet,

at least one connection device, in particular pump means and fluid connections, for allowing at least one first test fluid and / or at least one second test fluid to flow from the at least one reservoir into the housing through the at least one fluid inlet at the first end of the housing,

a detector for detecting the concentration of the at least one test substance, at least one liquid outlet at the second end of the housing.

In a third aspect, the invention relates to the use of a device according to the second aspect of the invention for carrying out a method according to the first aspect of the invention.

In a fourth aspect, the invention relates to the production of hollow fiber membrane filter modules, wherein the inventive method according to the First aspect of the invention is used to produce hollow fiber membrane having a predetermined permeation property.

The method comprises the following steps:

(a) determining at least one range of values for at least one or more permeation properties of hollow fiber membranes intended for the manufacture of hollow fiber membrane filter modules, (b) selecting one or more manufacturing parameters

Producing hollow-fiber membranes having the value range specified in step (a) having at least one or more permeation properties, (c) producing hollow-fiber membranes by a spinning process according to the one or more production parameters selected in step (b),

(d) bundling the obtained hollow fiber membranes into hollow fiber membrane bundles, (e) performing a method for determining one or more

Permeation properties, in particular the clearance of the hollow fiber membranes according to an embodiment of the first aspect of the invention, (f) Use of the hollow fiber membrane bundles for the construction of filter modules if it is determined that the one or more permeation properties lie in the at least one range of values defined in step (a) , According to the manufacturing method, in a first step, a range of values for a permeation property provided for the production of hollow fiber membranes is set. Such ranges of values may be, for example, a specific range for the clearance of a particular test substance, eg NaCl. Of the Range of values is determined in advance in order to produce specific hollow-fiber membranes, which are suitable, for example, by their diffusive NaCl clearance for certain therapeutic procedures in dialysis. In a further step, on the basis of the value range of the permeation property to be achieved, at least one production parameter, but in particular a plurality of production parameters, is determined in order to be able to produce corresponding hollow-fiber membranes. The production parameters relate to those parameters which have an influence on the spinning process for producing the hollow-fiber membrane. The production parameters include, for example, the composition of the spinning solution, the composition of the internal coagulant, the temperature of the annular die through which the spinning solution is extruded, the extrusion rate, or the height of the precipitating gap. The variety of manufacturing parameters that affect the permeability property of hollow fiber membranes are described in the prior art. The hollow fiber membranes produced subsequently in accordance with the given manufacturing parameters and according to a spinning process are then bundled and provided in the form of hollow-fiber membrane bundles for the further production of the hollow-fiber membrane filter modules. Next, a representative number of these hollow fiber membrane bundles are examined by the method of the present invention for determining one or more permeation properties according to an embodiment of the first aspect of the invention. It can thus be determined whether the one or more of the permeation properties lies within the predetermined range of values. In particular, it can thus be ascertained whether or not the hollow fiber membranes of the respective hollow-fiber membrane bundles are or are not in terms of, for example, clearance in the predetermined range of values.

Since with the method according to the invention according to the first aspect of the invention, a permeability property of the hollow fiber membranes produced can be investigated in a short time, the manufacturing process can be controlled in a timely manner with the aid of the method according to the invention. In particular, it can be checked whether the hollow fiber membranes produced, for example, the predetermined Clearance range and whether the hollow-fiber membranes for the construction of hollow fiber membrane filter modules can be released.

In the event that it is determined that the properties of the hollow fiber membranes produced the predetermined range of values not adhered to by the manufacturing process or only just met, appropriate conclusions can be made with respect to the manufacturing parameters. The production parameters can be subsequently adjusted so that the properties of the resulting hollow fiber membranes correspond to the specified value ranges. The thus regulated manufacturing process again passes through steps (a) to (d) until it can be decided for the manufactured hollow fiber membranes to use them for the construction of the hollow fiber membrane filter modules.

The above manufacturing method is particularly suitable for the production of hollow fiber membranes, which are prepared based on the membrane materials polysulfone and polyvinylpyrrolidone. The spinning solution used to make such hollow fiber membranes contains polysulfone (PSU) and polyvinylpyrrolidone (PVP), typically dissolved in polar aprotic solvents. Suitable solvents are, for example, N-methyl-pyrrolidone, dimethyl sulfoxide or di-methyl-acetamide. It has been found that mixtures of polysulfone / polyvinylpyrrolidone spinning solutions are particularly difficult to exactly observe the permeation properties, in particular the diffusive clearance, of the hollow-fiber membranes produced, since they are very sensitive to fluctuations in the production parameters. The present production process according to the invention has proven to be particularly advantageous for the production of PSU / PVP hollow-fiber membranes, since it offers the possibility of detecting the deviations caused by the change in the production parameters in the shortest possible time and adapting the production process accordingly. Description of the invention with reference to the examples

Example 1 - Device for Determining Permeation Properties of Hollow Fiber Membranes

FIG. 1 shows an apparatus for determining a permeation property of hollow-fiber membranes on a hollow-fiber membrane bundle.

The device shown consists of a reservoir with distilled water (1), which is controlled by a thermostat to a temperature of 25 ° C. In the water bath is another container (2), with a first Prüfflüssigkeit. The test fluid is an aqueous solution of the test substances NaCl at a concentration of 90 g / l and vitamin B12 at a concentration of 500 mg / l. With the help of a pump (3) either the water or the first test liquid can be transported. The flow leads to a closure which is sealed with an O-ring and which is attached to the lower end of a sleeve-shaped housing (4). The housing (4) in this case has the form of a sleeve, in which the hollow fiber membrane bundle (5) is introduced. The cap has a 4mm center hole through which the fluid enters the sleeve and serves as a fluid inlet (6).

According to the method of the invention, a hollow fiber membrane bundle is molded into the sleeve. The total length of the sleeve is 330 mm in the present embodiment and is open at the top. According to the present embodiment of Figure 1, this upper end with an inner diameter of 54 mm is slightly wider than the rest of the sleeve, which has an inner diameter of 34 mm. The hollow fiber membrane bundle itself is located in this narrower area and ends at its upper edge. An approximately 1 mm wide and 10 mm high annular gap (7) was milled out of the sleeve in the present embodiment, to obtain a flow for the test liquid. About 2 mm above is the liquid outlet (8) for sampling. Example 2 - Method for Determining Permeation Property of Hollow Fiber Membranes

For the first test liquid 90 g of sodium chloride and 500 mg of vitamin B12 are dissolved in about 500 ml of distilled water with constant stirring and made up to 1 liter with distilled water and heated to a temperature of 25 ° C in a water bath.

The hollow fiber membrane bundle to be examined is melted with the aid of an aluminum foil on a hot plate at about 300 ° C. on one side (5b). After cooling the bundle, the aluminum foil is peeled off and the bundle is molded into the sleeve-shaped housing (4) as shown in FIG. The peristaltic pump is set to a flow rate of 70 ml / min and the housing (4) is first filled with the first test liquid. The open end (5a) of the hollow fiber membrane bundle (5) is adjacent to the bore (6).

Because of the air permeability of the still-dry membrane, it is ensured that not only the interspace of the hollow-fiber membranes, but also the lumen side and the pore volume of the hollow-fiber membranes are filled completely and without air bubbles with the first test liquid.

As soon as the concentrate has completely covered the closed side of the fiber bundle (5b), the delivery of the first test liquid to the delivery of the second test liquid is converted by means of the hose pump (3). The second test liquid is distilled water. As a result, distilled water now flows through the fluid inlet into the housing. At the outlet nozzle, a sample of 10 ml is taken every minute with the beginning of the inflow of the second test liquid. Alternatively, the measurement of the concentration can also take place continuously. The vitamin B12 concentration is determined in each sample by means of a photometer. The concentration of NaCl in the respective samples can be done by conductivity measurement. Example 3 - Evaluation of Permeation Properties

The substance concentrations of the respective samples determined from Example 2 are plotted against the time according to FIG. According to the present example, the concentration profile of the test substances NaCl and vitamin B12 at the liquid outlet, by a sigmoid function according to equation 3:

l + _e C ₃ - (tC ₂ ) approximated.

C- _\ relates to the starting point of the curve

C ₂ gives the X-intercept to the inflection point

C ₃ determines the slope at the point of inflection

The sigmoid function is mathematically approximated to the measured values by means of a software program, eg the program "Scilab", or the software program "Excel 2010". In the software program "Excel 2010", for example, the parameters Ci to C _{3 can} be optimized with the help of an "add-in" with the designation "Solver" in such a way that the least possible deviation square is created the solution approach "GRG nonlinear" leads to good results. The value obtained for C ₃ from Equation 3 is preferably used for the determination of diffusive clearance. Example 4 - Comparison with Conventional Clearance Measurement Using the Example of Vitamin B12 Clearance

The following clearance values for vitamin B12 were determined on commercially available dialyzers by methods as described in the prior art and in particular in the standard DIN / EN ISO 8637:

Tab. 1

The dialyzers studied were dialyzers made by Fresenius Medical Care.

In addition, the hollow-fiber membrane bundles of the dialyzers with the name listed in Tab. 1 were investigated by the method according to the invention. As fit function, Equation 3 was approximated to the determined measurement curve. The C ₃ values obtained from the approximation of Equation 3 gave:

Tab. 2

The plot of the clearance values against the determined C ₃ values is shown in FIG. 3. The plot shows a good correlation of the clearance values for vitamin B12 measured on the dialyzers and the C ₃ values determined by the method according to the invention. The correlation can in turn by a suitable mathematical function and are used as a calibration curve or calibration function for further investigations.

Example 5 - Other options for evaluation

As described in Examples 1 to 4, the traces of four hollow fiber membrane bundles F1 to F4 for vitamin B12 and sodium chloride are recorded. The clearance values of the hollow fiber membranes were previously determined on corresponding dialyzers with identical hollow fiber membranes by known methods, e.g. determined according to the method of the standard DIN EN ISO 8637 2014:

Tab. 3

The curve of the concentration curve over time can now be approximated with different functions. Different parameters are determined by regression or least-square adjustments, for example, using the Excel 2010 program. It has been shown that a linear regression can be sufficient:

Y = A ₁ - A ₂ - t GL 1

In the example, the readings between two and six minutes were used to do a regression. Alternatively, other measurement points can be selected. It is important that the same procedure is used between the creation of the calibration curve and the measurement for an unknown bundle.

Alternatively, an exponential function of the formula according to Equation 2: Y = B - e ^{~ B} ^ Eq. 2 are used. The formulas of Equation 1 and 2 have the advantage that the coefficients A _2, B _\ and _B2 simply "Excel 2010" can be determined by adding the appropriate trend line in the respective software program, for example.

Subsequently, a calibration function can be created for these hollow-fiber membrane bundles with the aid of the previously determined clearance values which were determined on the dialyzer. It has been shown that the use of the parameters "A ₂ " or "B ₂ " is particularly useful.

For the evaluation of larger time periods, it may prove useful to use sigmoidal functions. A sigmoidal function describes an "S" curve and can typically be represented by Equation 3 as shown in Example 4.

At hollow-fiber membrane bundles according to the dialyzers F1 to F4, the following calibration parameters according to formulas 1 to 3 were determined. FIGS. 4 to 6 show the concentration course recorded on the hollow-fiber membrane F1 and the approximate mathematical functions from which the parameters A2, B2, and C3 are determined. Overall, the parameters listed in Table 4 were determined for the hollow-fiber membrane bundles F1 to F4:

Tab. 4

By combining the clearance values from Tab. 3 and Tab. 4 with the determined calibration parameters, the corresponding calibration functions can be displayed. These can be used while maintaining the experimental and evaluation conditions to determine the clearance values of unknown hollow-fiber membranes. It has been shown in the examined hollow-fiber membrane bundles F1 to F4 that in particular the mathematical approximation of the measured concentration profile by a sigmoid function according to FIG. 6 is suitable for generating a calibration function. FIG. 7 shows a calibration line which was generated on the basis of the determined C3 values of the hollow-fiber membrane bundles F1 to F4.

LIST OF REFERENCE NUMBERS

(1) Reservoir with distilled water

(2) Container with test liquid

(3) pump

(4) housing

(5) Hollow fiber membrane bundle

(5a) open end of the fiber bundle

(5b) closed end of the fiber bundle

(6) liquid inlet

(7) Annular gap

(8) liquid outlet

Claims

claims

Method for determining at least one permeation property of hollow-fiber membranes, comprising the steps:

(a) providing a hollow fiber membrane bundle (5) comprising a plurality of hollow fiber membranes having a first end and a second end, the lumens of the hollow fiber membranes open at the first end of the hollow fiber membrane bundle (5a), in particular liquid permeable, and at the second end of the hollow fiber membrane bundle (5b) closed at the end, in particular designed to be liquid-tight,

(b) providing a housing (4) for receiving the hollow fiber membrane bundle having a first end and a second end, the first end having at least one liquid inlet (6),

(c) inserting the hollow fiber bundle (5) into the housing (4) wherein the first end of the hollow fiber bundle is aligned with the end open lumen of the hollow fiber membranes to the at least one liquid inlet (6) at the first end of the housing,

(d) determining a permeation property of the hollow fiber membranes.

Method for determining at least one permeation property, in particular the clearance, of hollow-fiber membranes according to claim 1, characterized in that in step

(b) providing a housing (4) for receiving the hollow fiber membrane bundle (5) having a first end and a second end, the first end of the housing having at least one liquid inlet (6) and the second end of the housing having at least one liquid outlet ( 8), and in step

(c) a hollow-fiber membrane bundle (5) is introduced into the housing (4) such that the first end of the hollow-fiber membrane bundle (5a) is aligned with the end-open lumens of the hollow fiber membranes to the at least one liquid inlet (6) and the second end of the hollow fiber membrane bundle (5a). 5b) is aligned with the end-closed lumens of the hollow-fiber membranes to at least one liquid outlet (8), the method further comprising the steps:

(d) providing a first test liquid and a second test liquid, wherein at least the first or the second test liquid having at least one test substance and the second test liquid is different from the first test liquid, in particular at least in the concentration of the at least one test substance is different from the first test liquid .

(e) filling the housing (4) and / or the hollow-fiber membrane bundle by feeding the first test liquid through the at least one liquid inlet (6) at the first end of the housing into the interior of the housing and / or the hollow-fiber membrane bundle or hollow-fiber membranes

(f) inflow of a second test liquid through at least one liquid inlet (6) at the first end of the housing (4) in the interior of the housing and / or the hollow-fiber membrane bundle (5),

(g) measuring the concentration of the at least one test substance, at least one liquid outlet (8) of the housing, while the second Test liquid through at least one liquid inlet (6) into the housing and or the hollow fiber membrane bundle (5) flows.

Method according to claim 2, characterized in that the method further comprises the steps of:

(h) measuring the concentration of the test substance repeatedly or continuously on at least one liquid outlet (8) of the housing (4) during the flow of the second test liquid into the housing (4) and / or the hollow-fiber membrane bundle (5) or hollow-fiber membranes, respectively a liquid inlet (6) and receiving a time-dependent concentration curve, at least one test substance at at least one liquid outlet (8),

(i) approximating a mathematical function to at least a portion of the concentration profile of the at least one test substance recorded in step (h),

(j) determining a first parameter that characterizes the mathematical function in the at least one portion of the concentration profile that characterizes at least one test substance.

A method according to claim 3, characterized in that the method further comprises the step of:

(k) determining a second parameter, which is characteristic of the permeation property of the hollow-fiber membrane, based on the mathematical function characterizing the first parameter.

A method according to claim 4, characterized in that the second parameter, which is characteristic of the permeation property of the hollow-fiber membrane, is the clearance determined on the basis of calibration values from the first parameter characterizing the mathematical function. Method according to at least one of claims 3 to 5, characterized in that the mathematical function is a linear regression according to equation 1:

Y = A ₁ - A ₂ - t GL 1 or that the mathematical function is an exponential function according to Equation 2:

Y = B ₁ - e ^{~ B2't} GL 2 or that the mathematical function is a sigmoidal function according to Equation 3:

Method according to at least one of claims 3 to 6, characterized in that the curve slope of the approximated mathematical function in the selected section of the concentration curve is used for the evaluation and determination of the permeation property, in particular the clearance.

8. The method according to at least one of the preceding claims, characterized in that the hollow fiber membrane bundle (5) is not shed. 9. The method according to at least one of the preceding claims, characterized in that the at least one test substance is selected from salts, in particular NaCl; Vitamins, in particular vitamin B12; uremic metabolites, in particular urea, creatinine, phosphate, or proteins, in particular β2-microglobulin or interleukin-6.

10. The method according to at least one of the preceding claims, characterized in that the flow velocity at the at least one Liquid outlet 10 ml / min to 120 ml / min, preferably 40 ml / min to 100 ml / min, preferably 60 ml / min to 80 ml / min.

Method according to at least one of the preceding claims, characterized in that the hollow fiber membrane bundle (5) in the housing (4) has a packing density of at least 20% to less than 80%, preferably from at least 50% to less than 65%.

Method according to at least one of the preceding claims, characterized in that the concentration of the at least one test substance by electrochemical methods, such as conductivity measurement, or by amperometric, photometric, chromatographic or biochemical method is determined.

Apparatus for performing a method according to any one of claims 1 to 12 comprising:

(a) at least one reservoir (1) for receiving at least one liquid, in particular the first test liquid and / or the second test liquid,

(B) a measuring chamber comprising a housing (4) having a first end and a second end for receiving a hollow fiber membrane bundle (5), wherein the first end of the housing at least one liquid inlet (6) and the second end of the housing at least one liquid outlet (8 ) having,

(c) at least one connecting device, in particular pumping means (3) and fluid connections, for at least one first test fluid and / or at least one second test fluid from the at least one reservoir (1) into the housing (4) through the at least one fluid inlet (6) on the flow first end of the housing (4), (d) at least one detector for detecting the concentration of the at least one test substance at which at least one liquid outlet (8) at the second end of the housing (4).

Use of a device according to claim 13 for carrying out a method according to claims 1 to 12.

A process for producing hollow fiber membrane filter modules comprising the steps

(a) defining at least one range of values for at least one or more permeation properties of hollow fiber membranes intended for the manufacture of hollow fiber membrane filter modules,

(b) selecting one or more manufacturing parameters to produce hollow fiber membranes having the at least one or more permeation properties of the range of values defined in step (a),

(c) preparing hollow fiber membranes by a spinning process according to the one or more manufacturing parameters selected in step (b),

(d) bundling the obtained hollow fiber membranes into hollow fiber membrane bundles,

(e) carrying out a method for determining one or more permeation properties, in particular the clearance, more particularly of the diffusive clearance, of the hollow-fiber membranes according to one of claims 1 to 12,

(f) using the hollow fiber membrane bundles for the construction of filter modules when it is determined that the one or more permeation properties are in the at least one range of values defined in step (a). A method for producing hollow fiber membrane filter modules according to claim 15, characterized by the adaptation of the at least one or more selected manufacturing parameters from step (b), if it is determined that the one or more permeation properties of the produced hollow fiber membranes not in that in step (a) lie at least one range of values, so that the permeation properties of produced hollow fiber membranes are again in the specified in step (a) at least one range of values.

A process for producing hollow fiber membrane filter modules according to at least one of claims 15 or 16, characterized in that the spinning process comprises the production of hollow fiber membranes consisting of a material comprising at least polysulfone and polyvinylpyrrolidone.