DE102010055731A1 - Membrane used for e.g. reverse osmosis, comprises at least two layers which are at least partly covalently and delamination free bonded to each other, where each layer comprises layer-forming material(s) comprising polymer(s) - Google Patents

Abstract

A membrane comprises at least two layers, where each layer comprises layer-forming material(s) comprising polymer(s). At least two layers differ from each other with respect to the layer-forming material. At least two layers are at least partly covalently and delamination free bonded to each other. An independent claim is included for production of membrane.

Description

FIELD OF THE INVENTION

The present invention relates to a membrane, in particular a hollow-fiber membrane, preferably delamination-free and urea permeable, as well as their preparation and use, preferably for methods for blood purification, in particular for hemodialysis and peritoneal dialysis.

STATE OF THE ART

Membranes, particularly hollow fiber membranes, can be used in hemodialysis and peritoneal dialysis to allow deposition of harmful metabolites, such as urea from the blood, to clean it. The membrane serves as a semi-permeable barrier between the blood to be purified on one side, and the so-called dialysate on the other side. By diffusion and convection, a mass transfer between blood and dialysate takes place, whereby the purification of the blood is achieved.

Furthermore, membranes, in particular also hollow-fiber membranes, are used in the dialysate preparation, which can also take place during the dialysis process. In particular, urea is selectively removed from spent dialysate, for which purpose a so-called urea-selective hollow-fiber membrane is used. The urea is transported across the membrane, and then degraded by urease. At the same time, other electrolytes important to the organism, in particular mono- and divalent cations such as Na ⁺ , K ⁺ , Ca ²⁺ or Mg ^{2+, are} retained in the dialysate. It is known from the prior art that such urea-selective membranes have a two-layer structure consisting of selective layer and support or carrier layer. Two-layer and multi-layer membranes for hemodialysis are known from the prior art, and are described, for example, in the documents US 4,276,172 . CA 2 707 818 A1 . US 4,164,437 described.

Two- or multi-layered membranes are known in the art as composite membranes. The production of such two-layered or multi-layered membranes, which are usually designed as flat membranes, takes place via the consecutive application of the layers to an already existing solid support membrane, and is for example made US 5,156,740 . EP 0 286 091 B1 or EP 0 359 834 B1 known.

Hollow fiber membranes are produced by means of so-called hollow fiber nozzles, which have one or more concentric annular channels around a central bore. Over the outer concentric rings, dissolved polymers or suitable polymer blends are extruded. The lumen of the hollow fiber is created by an agent that is forced through the central bore of the nozzle. The nozzle design used in each case is to be tuned with the geometry of the fiber and the properties of the polymers used, called spinning dope in this stage, so that symmetrical fibers with a uniform wall thickness are formed. Such a spinneret is for example off US 7,393,195 known. A distinction is made between various spinning processes, such as the phase inversion process, the dry-wet spinning process or the melt spinning process, which are known to the person skilled in the art ( M. Mulder, Basic Principals of Membrane Technology, Second Edition, Kluwer, 1996, pages 71 to 91 ).

In the case of composite membranes, in particular composite hollow fiber membranes which have been produced by coextrusion, it is possible for the layer to delaminate, ie for the separation or detachment of the layers and thus for the loss of function of the membrane. A layer delamination occurs mainly in composite membranes; their layers of different polymers are made up, since between the adjacent layers only very weak interactions can take place. As a result, no effective adhesion of the layers to each other can be ensured. This problem can be solved by using identical polymers and similar polymer concentrations. Since the maximum achievable mass transfer of such a membrane also depends on the material of the support layer, it is particularly advantageous in terms of performance optimization to be able to independently select the polymers of the support layer and the selection layer. A particular feature of composite membranes consisting of identical polymers is the lack of a visible interface between the layers, which can be visualized by electron microscopy. This distinguishes composite membranes consisting of identical polymers, of membranes whose layers are composed of different polymers. The latter have a clearly visible boundary between the layers in electron micrographs. From this it can be concluded that few to no interactions take place between the layers

Functional loss delamination may occur with multilayered hollow fiber membranes depending on the choice of material, days or weeks after storage of the fibers in the aqueous medium. Thus, delamination is a major problem, especially in hemodialysis and peritoneal dialysis.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a membrane, in particular a hollow-fiber membrane, whose at least two layers are different from one another with respect to the layer-forming material and which are connected to one another without delamination.

SUMMARY OF THE INVENTION

This is achieved according to the invention by the teaching of the independent claims. Further developments of the invention are the subject of the dependent claims.

The object is achieved by a membrane which has at least two layers, wherein the at least two layers each have at least one polymer and are different from one another with regard to the material-forming material. The at least two layers are at least partially covalently bonded to one another without delamination.

The invention thus relates to a membrane having at least two layers, wherein the at least two layers each have at least one polymer and are different from each other with respect to the material-forming material
characterized in that
the at least two layers are at least partially covalently bonded together delamination-free.

In one embodiment, the at least two layers with a differential pressure ≤ 3 bar, preferably ≤ 5 bar, preferably ≤ 7 bar are not separable.

In a further embodiment, the membrane without an annealing step has a selectivity of urea to sodium of from 5 to 40, more preferably from 10 to 30, in particular from 5 to 20 and more preferably from 5 to 10. The selectivity of the membrane of urea to sodium may increase to 200 and more after application of an annealing step.

In a further embodiment, the at least two layers are coextruded layers.

In a further embodiment, at least one layer is formed as a selection layer.

In a further embodiment, the selection layer comprises at least one polymer which is selected from cellulose acetate, preferably a cellulose acetate having an acylation degree of 0.5 to 3, cellulose esters, and mixed esters thereof.

In a further embodiment, the selection layer has at least one further additive.

In a further embodiment, the additive is formed as an adhesion-promoting additive, which preferably has reactive groups, more preferably is amino-functional.

In a further embodiment, the additive is selected from polyethyleneimine or polyamine or mixtures thereof.

In a further embodiment, the selection layer in the dry state has a layer thickness between 30 nm and 50 μm, preferably between 30 nm and 200 nm.

In a further embodiment, the at least one layer is formed as a support layer.

• (a) Polyimin, Polysulfon, Polyethersulfon, Polyimid, Polyetherimid, Polyethylenimin, Polyvinylpyrrolidon, Polymethylmethacrylimid oder Mischungen daraus; oder
• (b) sulfoniertes Polysulfon, sulfoniertes Polyethersulfon, sulfoniertes Polyetherimid, sulfoniertes Polymethylmethacrylimid oder Mischungen daraus; oder
• (c) Polyimin, Polysulfon, Polyethersulfon, Polyimid, Polyetherimid, Polyethylenimin, Polyvinylpyrrolidon, Polymethylmethacrylimid und sulfoniertes Polysulfon, sulfoniertes Polyethersulfon, sulfoniertes Polyetherimid, sulfoniertes Polymethylmethacrylimid oder Mischungen daraus

In a further embodiment, the support layer comprises at least one polymer which is selected from

• (a) polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide or mixtures thereof; or
• (b) sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherimide, sulfonated polymethylmethacrylimide, or mixtures thereof; or
• (c) polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide and sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherimide, sulfonated polymethylmethacrylimide, or mixtures thereof

In a further embodiment, the support layer in the dry state has a layer thickness of 1 .mu.m to 500 .mu.m, preferably of 35 .mu.m.

In a further embodiment, the membrane is formed as a hollow fiber membrane.

In a further embodiment, the hollow-fiber membrane has an average diameter of the lumen of 20 μm to 500 μm, preferably of 200 μm.

In a further embodiment, the hollow-fiber membrane has at least one layer which is configured as a selection layer comprising cellulose diacetate and polyethyleneimine.

In a further embodiment, the hollow-fiber membrane has at least one layer which is designed as a support layer which comprises polyetherimide.

In a further embodiment, the hollow-fiber membrane has at least one layer which is designed as a support layer which comprises polyethersulfone and polymethylmethacrylimide.

In a further embodiment, the hollow-fiber membrane has at least one layer which is configured as a support layer which comprises polyethersulfone and sulfonated polyethersulfone.

In a further embodiment, the hollow-fiber membrane has at least one layer, which is configured as a support layer which comprises polyetherimide and polyvinylpyrrolidone.

In another embodiment, the membrane has three coextruded layers.

In a further embodiment, the at least one layer in the dry state has a layer thickness of 30 nm to 50 μm, preferably from 30 nm to 200 nm, at least one second layer in the dry state has a layer thickness of 30 nm to 50 μm, preferably 30 nm to 200 nm, and at least one third layer in the dry state, a layer thickness of 1 .mu.m to 500 .mu.m, preferably 35 .mu.m.

In a further embodiment, the membrane has at least one layer of cellulose diacetate.

In a further embodiment, the membrane has at least one second layer of cellulose diacetate and polyethyleneimine.

In a further embodiment, the membrane has at least one third layer of polyetherimide.

• • Bereitstellung mindestens einer ersten klaren Spinmasse, aufweisend ein Material für die mindestens erste Schicht
• • Bereitstellung mindestens einer zweiten klaren Spinnmasse, welche von der ersten klaren Spinnmasse verschieden ist, und ein Material für die mindestens zweite Schicht aufweist
• • Koextrusion der mindestens zwei Spinmassen durch eine Spinndüse, aufweisend eine Anzahl an konzentrischen Ringen entsprechend der Anzahl bereitgestellter Spinnmassen, wobei mindestens ein erster Ring zur Aufnahme und/oder Extrusion mindestens einer ersten Spinnmasse, und mindestens ein zweiter Ring zur Aufnahme und/oder Extrusion mindestens einer zweiten Spinnmasse, welche von der ersten Spinnmasse verschieden ist, befähigt sind, wobei die mindestens zwei konzentrischen Ring um einen zentralen Rundkanal angeordnet sind, welcher zur Aufnahme oder Extrusion oder Aufnahme und Extrusion eines Agens, bevorzugt eines Fällungsagens, bevorzugt Wasser befähigt ist,

dadurch gekennzeichnet, dass die klaren Spinnmassen mindestens ein Polymer oder zu einer Reaktion befähigtes Material oder mindestens ein Polymer und zu einer Reaktion befähigtes Material, insbesondere zur chemischen Quervernetzung befähigtes Material aufweist.Process for the preparation of a membrane comprising the following steps:

• Providing at least a first clear spin mass comprising a material for the at least first layer
• Providing at least one second clear dope which is different from the first clear dope and has a material for the at least second layer
• Coextrusion of the at least two spin masses through a spinneret, comprising a number of concentric rings corresponding to the number of spunbonds provided, at least one first ring for receiving and / or extruding at least one first dope, and at least one second ring for receiving and / or extruding at least a second spinning dope which is different from the first dope, the at least two concentric rings being arranged around a central circular duct which is capable of receiving or extruding or receiving and extruding an agent, preferably a precipitating agent, preferably water,

characterized in that the clear spinning masses comprises at least one polymer or material capable of reacting or at least one polymer and material capable of reacting, in particular material capable of chemical crosslinking.

In one embodiment, the process for producing a membrane comprises at least one first dope comprising at least one polymer selected from the group consisting of cellulose acetate, in particular a cellulose acetate having an acylation degree of from 0.5 to 3, cellulose esters or mixed esters thereof or at least one Polymer which is selected from the group cellulose acetate, in particular a cellulose acetate having a degree of acylation of 0.5 to 3, cellulose ester, or mixed esters thereof and at least one further additive, preferably an adhesion-promoting amino-functional additive which is selected from the group polyethylenimine or a polyamine or polyethyleneimine and a polyamine.

• • Polyimin, Polysulfon, Polyethersulfon, Polyimid, Polyetherimid, Polyethylenimin, Polyvinylpyrrolidon, Polymethylmethacrylimid oder Mischungen daraus; oder
• • sulfoniertes Polysulfon, sulfoniertes Polyethersulfon, sulfoniertes Polyetherimid, sulfoniertes Polymethylmethacrylimid oder Mischungen daraus; oder
• • Polyimin, Polysulfon, Polyethersulfon, Polyimid, Polyetherimid, Polyethylenimin, Polyvinylpyrrolidon, Polymethylmethacrylimid und sulfoniertes Polysulfon, sulfoniertes Polyethersulfon, sulfoniertes Polyvinylpyrrolidon, sulfoniertes Polymethylmethacrylimid oder Mischungen daraus.

In one embodiment, the method for producing a membrane comprises at least one second dope comprising at least one polymer selected from

• Polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide or mixtures thereof; or
• Sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherimide, sulfonated polymethylmethacrylimide or mixtures thereof; or
• Polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide and sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyvinylpyrrolidone, sulfonated polymethylmethacrylimide or mixtures thereof.

Use of the membrane according to the invention in peritoneal dialysis, in particular for the regeneration of the dialysate, blood purification, in particular for hemodialysis, reverse osmosis, power generation in osmotic power plants, gas separation, pervaporation, nano-, ultra-, micro- or particle filtration.

DETAILED DESCRIPTION OF THE INVENTION

To achieve this object, as described in detail below, a membrane is provided, in particular a hollow-fiber membrane comprising at least two layers, wherein the at least two layers each have at least one polymer and are different from each other with respect to the material-forming material. The at least two layers are at least partially covalently bonded to one another without delamination.

The term covalent is to be understood as meaning a covalent bond or interaction, ie a bond or interaction in which the groups and / or elements capable of binding or interaction are bonded via an atomic bond, homopolar bond, σ-σ interaction, σ- π-interaction, two-electron two-site bonding, single bond, double bond, triple bond, as well as combinations of these interactions or bonds are interconnected. The interactions or bonds mentioned can be polar or polarized or nonpolar or not polarized.

The term "at least partially covalent" means that in addition to covalent bonds or interactions, other, non-covalent interactions or bonds may also be present.

The term non-covalent means that the groups and / or elements capable of binding or interacting preferably via zone pairs, via hydrogen bonds, via dipole-dipole interactions, via charge-transfer interactions, via π-π electrons Interactions, via cation-π-electron interactions, van der Waals interactions and disperse interactions, via hydrophobic (lipophilic) interactions, via complex formation, preferably complex formation of transition metal cations, as well as the combination of these interactions or bonds may combine ,

In one embodiment, up to 50% of the interactions or bonds are covalent.

In another embodiment, up to 70% of the interactions or bonds are covalent.

In a preferred embodiment, up to 100% of the interactions or bonds are covalent.

The term membrane is to be understood as a separating layer.

In one embodiment, the membrane is formed as a hollow fiber membrane.

The membrane according to the invention has at least two layers.

In one embodiment, the membrane has between 2 to 10 layers.

In a further embodiment, the membrane has 2, 3, 4 or 5 layers.

According to the invention, the membrane has layers, wherein the layers each have at least one polymer and are different from one another with regard to their layer-forming material. In one embodiment, the layers are obtained independently starting from different spinning masses.

In one embodiment, the membrane is formed as a separating layer between liquids.

In another embodiment, the membrane is designed as a separating layer between gases.

In another embodiment, the membrane is formed as a separating layer between liquids and gases.

The term layer (s) is to be understood as meaning that this layer (s) have a three-dimensional propagation, the propagation in one dimension being at least 50%, preferably at least 75%, preferably at least 90%, smaller than the propagation into the others two dimensions. Layer (s) can be formed from any layer-forming material.

By "layer-forming material" is meant all materials, such as polymers, that comprise the layer.

In one embodiment, the layers comprise synthetic or natural polymers.

In one embodiment, the layers comprise polymers that are soluble in organic solvents, which are preferably at least partially miscible with water.

The term "soluble" is to be understood as meaning obtaining a clear, undiluted, optically transparent solution in the visible wavelength range of the light, which preferably has at least one macroscopic phase. In other words, no Tyndal effect can be detected in the visible range of the light. Macroscopically, this means that the solution forms a phase and is free of undissolved constituents, such. B. Polymer gel particles.

This definition is also applicable with respect to the term "clear spinning solution" used later.

In one embodiment, the layers each have at least one polymer which is soluble in dimethylacetamide, pyrrolidone, N-methylpyrrolidone, dimethylsulfoxide, formamide, N-methylformamide, primary alcohols, secondary alcohols, tertiary alcohols, dioxane, tetrahydrofuran or mixtures thereof.

In one embodiment, in addition to the polymers, the layers preferably have up to 10% by weight, preferably up to 5% by weight, preferably up to 2% by weight of oligomers, which preferably correspond to the polymers used, or preferably are different from the polymers used. Typically, the oligomers have a degree of polymerization of 2 to 10.

A first layer may be distinguished from a second layer by different chemical (eg permeability or material) and / or physical (eg average pore size distribution) properties.

In one embodiment, at least one layer is formed as a selection layer.

The term selection layer is to be understood as meaning that this layer is permeable to at least one selected substance, preferably urea or water, from a substance mixture, preferably a liquid substance mixture, preferably blood or dialysate, or blood and dialysate.

The term selection layer also means that this layer simultaneously for other substances, preferably for mono- and divalent cations, preferably for mono- and divalent cations of the first and second main group of the periodic table of chemical elements, such as sodium in the form of Na ⁺ , potassium in Form of K ⁺ , magnesium in the form of Mg ²⁺ , or calcium in the form of Ca ²⁺ , as well as their present in aqueous environments such as in blood or dialysate water complexes, has a reduced, preferably minimized permeability, preferably impermeable.

In one embodiment, the selection layer comprises at least one polymer.

In one embodiment, the selection layer comprises at least one polymer which is selected from cellulose acetate, in particular a cellulose acetate having an acylation degree of from 0.5 to 3, that is, for example, a cellulose diacetate, or a cellulose triacetate; Cellulose ester, cellulose diacetate or mixed esters thereof.

The term "degree of acylation" means the average number of acyl groups per structural unit. In one embodiment, an acylation level in the range of 2.5 to 3, e.g. B. 2.7 used.

In a further embodiment, the selection layer comprises a polyamide, which may also be a crosslinked polyamide. It is conceivable to spin an uncrosslinked precursor and then to crosslink the spun material.

In one embodiment, the selection layer is preferably arranged on the lumen side, that is to say in the interior, that is to say the inner layer forming the membrane, which in this embodiment is designed as a hollow-fiber membrane.

In a further embodiment, the selection layer is outside, or the outer layer of the membrane forming, which is formed in this embodiment as a hollow fiber membrane arranged.

In one embodiment, at least one layer is formed as a carrier layer.

• a) Polyimin, Polysulfon, Polyethersulfon, Polyimid, Polyetherimid, Polyethylenimin, Polyvinylpyrrolidon, Polymethylmethacrylimid oder Mischungen daraus; oder
• b) sulfoniertes Polysulfon, sulfoniertes Polyethersulfon, sulfoniertes Polyetherimid, sulfoniertes Polymethylmethacrylimid oder Mischungen daraus; oder
• c) Polyimin, Polysulfon, Polyethersulfon, Polyetherimid, Polyethylenimin, Polyvinylpyrrolidon, Polymethylmethacrylimid und sulfoniertes Polyimin, sulfoniertes Polysulfon, sulfoniertes Polyethersulfon, sulfoniertes Polymethylmethacrylimid oder Mischungen daraus.

The term support layer is to be used synonymously with the term carrier layer. The term support layer is to be understood as meaning a layer which has a high porosity and a high mechanical stability, preferably a high mechanical stability in the sense of buckling and tensile strength. The support layer has at least one polymer, which is preferably selected from:

• a) polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethyleneimine, polyvinylpyrrolidone, polymethylmethacrylimide or mixtures thereof; or
• b) sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherimide, sulfonated polymethylmethacrylimide or mixtures thereof; or
• c) polyimine, polysulfone, polyethersulfone, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide and sulfonated polyimine, sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polymethylmethacrylimide or mixtures thereof.

Possible useful polyimides are known under the trade name Ultem 1000, Matrimid, or Pleximid.

In one embodiment, the carrier layer is preferably directed outwards, thus forming the outer layer of the membrane, which in this embodiment is designed as a hollow-fiber membrane.

In a further embodiment, the carrier layer is directed on the lumen side or inwards, thus forming the inner layer of the membrane, which in this embodiment is designed as a hollow-fiber membrane.

In one embodiment, a layer, preferably the selection layer, has a layer thickness, which was preferably determined in the dry state, between 30 nm and 50 μm, preferably between 30 nm and 200 nm.

In one embodiment, a layer, preferably the support layer, has a layer thickness, which was preferably determined in the dry state, of preferably 1 .mu.m to 500 .mu.m, preferably of 35 .mu.m.

The drying of the fibers to determine the layer thickness takes place in one embodiment in two successive drying chambers at temperatures of 120 ° C ± 5 ° C.

The layer thickness is determined in one embodiment in an electron microscope under high vacuum after completion of the drying.

In this case, it is essential according to the invention that the layers to be connected without delamination are formed during the production process in such a way that they can react with one another. If an adhesion-promoting additive is used, it can accordingly be present in a mixture for producing the support layer or the mixture for producing the selection layer, or in an adhesion-promoting layer which can be arranged between the selection layer and the support layer.

The term "delamination-free" is to be understood as meaning that the at least two layers are bonded to one another in a material-locking manner, ie by atomic and / or molecular forces, and not destructively detachable from one another, so that delamination of the layers is reduced, preferably minimized, and more preferably prevented. This is done by covalent and / or non-covalent interactions and / or bonds between the at least two layers

This is achieved in one embodiment by at least one layer, preferably the layer which is formed as a selection layer, comprising at least one polymer and additionally at least one additive.

In a further embodiment, at least one layer, preferably the selection layer, comprises at least one polymer which is selected from cellulose acetate, in particular a cellulose acetate having an acylation degree between 0.5 and 3, for example also cellulose diacetate or cellulose triacetate, cellulose ester, cellulose diacetate and / or mixed esters thereof, and at least one additive.

In one embodiment, the additive is configured as an adhesion-promoting additive.

In one embodiment, the adhesion promoting additive is amino functional.

In one embodiment, the additive comprises a material having reactive groups.

In one embodiment, the additive comprises at least one polymer having reactive groups selected from polyethyleneimine, polyamine, amine-containing copolymers, polyvinylamine, poly-L-lysine, or mixtures thereof.

Possible useful polyamines are known under the trade names Epomin or Polyment (Nippon Shokubai), Lupasol (BASF) or Jeffamine (Huntsmann). Polyvinylamine can be purchased, for example, from BASF.

In one embodiment, low molecular weight polymers having reactive groups may also be included in the additive, such as oligoamines.

In one embodiment, the additive comprises at least one polymer which is soluble in organic solvents.

In one embodiment, the additive comprises at least one polymer that is soluble in organic solvents, which are preferably at least partially miscible with water, which are preferably selected from dimethylacetamide, pyrrolidone, N-methylpyrrolidone, dimethylsulfoxide, formamide, N-methylformamide, dimethylformamide, primary alcohols, secondary alcohols, tertiary alcohols, dioxane, tetrahydrofuran or mixtures thereof.

The term reactive groups includes all functional groups and / or elements which are capable of other reactive groups or elements of the same material, but preferably with reactive groups and / or elements of an at least second material, preferably at least one second polymer, covalent or non-covalent or covalent and non-covalent bonds or interactions.

In one embodiment, the additive is selected such that preferably covalent bonds or interactions between the at least two layers can be formed.

In principle, all reactions known to the person skilled in the art are used to form such bonds or interactions.

In one embodiment, these are condensation reactions, in particular esterifications and amide formation reactions

The term hollow fiber membrane is synonymous synonymous to understand a hollow fiber capillary membrane. This hollow-fiber membrane preferably has an average diameter of the lumen between 20 μm to 500 μm, preferably of 200 μm.

In one embodiment, the outer shape of the schematic cross section of the hollow fiber membrane is round, or circular.

But there are also other geometric figures of the schematic cross section of the hollow fiber membrane conceivable, such as star-like figures or figures with alternating convex and concave-like elements, which may preferably arise by increasing the surface of the hollow fiber membrane.

In one embodiment, a membrane, which in this embodiment is in the form of a hollow-fiber membrane, has at least three layers which are in contact with the respectively adjacent, directly contacting layer (ie a first layer with a second layer, and this second layer with a third layer). are linked to one another by covalent or non-covalent or covalent and non-covalent bonds or interactions, preferably linked to one another without delamination.

In one embodiment, the layer thickness of the layer formed as a selection layer in the dry state is 30 nm to 50 μm, preferably 30 nm to 200 nm.

In one embodiment, the layer thickness of a second layer, preferably the middle layer in the dry state, is 20 nm to 200 μm, preferably 30 nm to 50 μm, more preferably 30 nm to 200 nm.

In one embodiment, the layer thickness of a third layer, which is formed as a support layer, in the dry state 1 micron to 500 .mu.m, preferably 20 .mu.m to 200 .mu.m, in particular 25 to 100 .mu.m, more preferably 25 to 35 .mu.m, in particular 35 .mu.m.

In one embodiment of a membrane which is configured as a hollow-fiber membrane, a first layer, preferably the inner layer (selection layer), comprises a polymer which is selected from cellulose acetate, in particular a cellulose acetate having an acylation degree between 0.5 and 3, cellulose ester, cellulose diacetate and / or mixed esters. In particular, this first layer, preferably the inner layer, is formed as a selection layer, which particularly preferably comprises cellulose acetate.

In one embodiment of a membrane, which is configured as a hollow fiber membrane, a second layer, preferably the middle layer, at least one polymer which is formed from cellulose acetate, in particular a cellulose acetate having a degree of acylation between 0.5 and 3, cellulose ester, cellulose diacetate and or a mixed ester thereof and an additive, preferably an adhesion-promoting additive, which is preferably amino-functional, which is selected from polyethyleneimine and / or a polyamine, in particular a polymer which has reactive groups and / or elements.

Previous definitions of additive and reactive groups and / or elements is also valid for this.

In one embodiment of a membrane, which is configured as a hollow-fiber membrane, the second layer, preferably the middle layer, comprises cellulose diacetate and polyethyleneimine. Preferably, the second layer, preferably the middle layer, is formed as a selection layer.

In one embodiment of a membrane configured as a hollow fiber membrane, a third layer, preferably the outer layer, comprises at least one polymer selected from polyimine, polyimide, polysulfone, polyethersulfone, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacryalimide, polyethersulfone or mixtures from which are sulfonated and / or non-sulfonated, or sulfonated and / or non-sulfonated groups. Preferably, this third layer, preferably the outer layer, is formed as a support or carrier layer. Preferably, this third layer, preferably the outer layer, comprises polyetherimide.

• • Bereitstellung mindestens einer ersten klaren Spinmasse, aufweisend ein Material für die mindestens erste Schicht
• • Bereitstellung mindestens einer zweiten klaren Spinnmasse, welche von der ersten klaren Spinnmasse verschieden ist, und ein Material für die mindestens zweite Schicht aufweist
• • Koextrusion der mindestens zwei Spinmassen durch eine Spinndüse, aufweisend eine Anzahl an konzentrischen Ringen entsprechend der Anzahl bereitgestellter Spinnmassen, wobei mindestens ein erster Ring zur Aufnahme und/oder Extrusion mindestens einer ersten Spinnmasse, und mindestens ein zweiter Ring zur Aufnahme und/oder Extrusion mindestens einer zweiten Spinnmasse, welche von der ersten Spinnmasse verschieden ist, befähigt sind, wobei die mindestens zwei konzentrischen Ringe um einen zentralen Rundkanal angeordnet sind, welcher zur Aufnahme oder Extrusion oder Aufnahme und Extrusion eines Agens, bevorzugt eines Fällungsagens, bevorzugt Wasser befähigt ist
• • Bereitstellung eines Spülbades, welches befähigt ist, den Gehalt an verwendeten Lösemittel(n), welche(s) enthalten ist in vorgehend erhaltener Membran, zu reduzieren, vorzugsweise zu minimieren, vorzugsweise das/die verwendete(n) Lösemittel vollständig zu entfernen.

Also according to the invention is the process for producing the membrane, which comprises the following steps:

• Providing at least a first clear spin mass comprising a material for the at least first layer
• Providing at least one second clear dope which is different from the first clear dope and has a material for the at least second layer
• Coextrusion of the at least two spin masses through a spinneret, comprising a number of concentric rings corresponding to the number of spunbonds provided, at least one first ring for receiving and / or extruding at least one first dope, and at least one second ring for receiving and / or extruding at least a second spinning mass which is different from the first spinning mass, wherein the at least two concentric rings are arranged around a central circular channel which is capable of receiving or extruding or receiving and extruding an agent, preferably a precipitating agent, preferably water
• Providing a rinsing bath which is capable of reducing, preferably minimizing, the content of solvent (s) used which is contained in the previously obtained membrane, preferably completely removing the solvent (s) used.

• • Trocknung der vorhergehend erhaltenen und behandelten Membran oder Hohlfaser, diese Membran aufweisend.

In one embodiment, the method still has the following step, which may follow:

• Drying of the previously obtained and treated membrane or hollow fiber comprising this membrane.

• • der Gruppe Celluloseacetat, insbesondere ein Celluloseacetat mit einem Acylierungsgrad zwischen 0,5 und 3, Celluloseester, Cellulosediacetat oder Mischester davon; oder
• • der Gruppe Polyethylenimin, Polyamin, Polyvinylamin, aminhaltige Copolymere, Poly-L-Lysin, Oligoamin oder Mischungen daraus; oder
• • der Gruppe Polyimid, Polyimin, Polysulfon, Polyethersulfon, Polyetherimid, Polyethylenimin, Polyvinylpyrrolidon, Polymethylmethacrylimid, Polyethersulfon und/oder sulfonierte bzw. nicht-sulfonierte Derivate davon;
• • sowie Mischungen vorstehend genannter Polymere.

The clear spinning solution has at least one polymer, which is preferably selected from

• The group of cellulose acetate, in particular a cellulose acetate having an acylation degree between 0.5 and 3, cellulose ester, cellulose diacetate or mixed esters thereof; or
• The group polyethyleneimine, polyamine, polyvinylamine, amine-containing copolymers, poly-L-lysine, oligoamine or mixtures thereof; or
• The group polyimide, polyimine, polysulfone, polyethersulfone, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide, polyethersulfone and / or sulfonated or non-sulfonated derivatives thereof;
• • and mixtures of the aforementioned polymers.

In one embodiment, the dope comprises at least one solvent which is capable of dissolving the aforementioned polymers and thereby producing a clear dope.

In one embodiment, the spinning mass comprises organic solvents which are preferably at least partially miscible with water, preferably selected from dimethylacetamide, pyrrolidone, N-methylpyrrolidone, dimethylsulfoxide, formamide, N-methylformamide, primary alcohols, secondary alcohols, tertiary alcohols, dioxane, tetrahydrofuran or mixtures thereof.

In one embodiment, the method comprises the step that at least one first dope can come into contact with at least one second dope, preferably by coextrusion of a first dope with at least one second dope, preferably by providing and using a spinneret. Preferably, a hollow fiber nozzle is used as the spinneret. In this case, over one or more concentrically arranged annular channels previously described spinning mass / n are extruded, while at the same time a liquid or viscous agent is pressed through the centrally located circular channel. This agent is preferably water, and initiates the precipitation reaction in the phase inversion process. Furthermore, the step comprises that said membrane or hollow-fiber membrane is freed from the solvent by a final washing process. This washing step is followed by drying of the membrane or hollow-fiber membrane thus obtained and washed, which preferably takes place in a hot air stream. Advantageously, at least one spinning composition described above comprises a material or polymer which is capable of a selection layer such as previously defined, while at least one second spinning mass advantageously comprises a material / polymer which is capable of forming a support or carrier layer. The term dope is also used synonymously with the spinning dope. Preferred methods for producing said membrane or said hollow-fiber membrane are spinning processes, particularly preferably the phase inversion process, the dry-wet spinning process or the melt-spinning process.

Likewise, according to the invention, the use of the membrane or the hollow-fiber membrane, comprising at least two layers, is characterized in that the at least two layers are covalently and / or non-covalently bonded to one another, preferably delamination-free, in processes of peritoneal dialysis, in particular in the process for the regeneration of the dialysate, in hemodialysis, in reverse osmosis, in processes for power generation in osmotic power plants, as well as processes of gas separation, pervaporation and in nano-, ultra-, micro- and particle filtration.

Determination of the delamination strength of a membrane

Since in the production of a multilayer membrane, in particular a hollow-fiber membrane with simultaneously extruded layers, a time-delayed delamination can take place, an investigation method for determining the delamination strength of a membrane is required, which is described below. For this one manufactures small modules with an approx. 10 cm long single fiber. The fibers are first filled inside with water and then hydrophilized from the outside for about 10 s with a solution of 50% isopropanol in water. After complete removal of the alcohol, the fiber is stored overnight at 85 ° C in water. If necessary, the duration can also be extended. Then, the hollow fiber is rinsed at room temperature from the lumen side with water permanently so that a significant water leakage can be observed. Then, a water pressure is applied from the outside of the fiber, the height of which is determined by a pressure gauge. The applied pressure is a static pressure which has the same value at each point of the fiber. The pressure is slowly increased until the water leakage from the lumen side is no longer observed. At this limit pressure either the inner layer has collapsed due to the external pressure or the entire fiber has been compressed, so that the flow in the lumen is omitted. Which of the two situations is present, is decided by the fiber is cut across and then examined by light microscopy.

The following Table 1 shows the results of the delamination tests for the fibers of the various examples. Table 1 Fiber from example Maximum applied pressure [bar] Detachment of the inner layer annotation 1 <1 Yes Fiber delaminates in wet storage 3 6 No 4 2 No 5 7 Yes 6 3 No

The results show that the membrane of the invention with covalent or covalent and non-covalent interactions between the layers compared to the reference fiber of Example 1 has a multiple increased resistance to delamination, preferably, the layers of the membrane according to the invention with a pressure of up to 3 bar , preferably of up to 5 bar, preferably of up to 7 bar are not separable from each other, so delamination-free.

In one embodiment, the aforementioned pressure is designed as an applied external pressure which acts on the membrane.

Measurement of cation retention and urea permeability

For the characterization of a membrane, in particular a hollow-fiber membrane comprising a cellulose acetate-containing layer, the conversion of cations, in particular Na ⁺ , Ca ²⁺ , K ⁺ or Mg ²⁺ or Combinations thereof and urea measured and compared. For this purpose, the lumen side of the fibers of a hollow fiber membrane is flowed through once with a solution consisting of 226 mM glucose, 2.5 mM CaCl ₂ , 141 mM NaCl and 25 mM urea in water at a flow rate of 50 ml / min. The dialysate side contains a defined volume of 550 ml of an isoosmotic glucose solution in water. This volume is enclosed in a pressure-tight manner so that the dialysate side has a constant volume over the duration of the experiment. The solution is circulated at a flow rate of 1000 ml / min. The experiment is carried out at room temperature.

Now, the concentration changes for sodium cations, calcium cations and urea on the dialysate side of the hollow fiber membrane are determined time-dependent. During sampling, the volume of fluid removed is replaced by an equal volume of a solid punch, which is screwed into the fluid reservoir.

The concentrations can be determined with known analyzers, such as the Cobas Integra 400 from Roche.

From the initial concentrations and the concentration changes, the transport parameters of the membrane can be calculated.

The sodium permeability for membranes of the invention as determined in this manner is preferably 20-30 mmol / m ² d. The urea permeabilities are preferably 20-30 g / m ² d. The values can also be higher or lower.

To calculate the values given above from the measured data, a urea gradient of 0.86 g / l and a sodium gradient of 140 mM across the membrane were used.

All range data contained in the patent specification are inclusive of the specified range limits.

The following examples may explain the invention in more detail. All percentages of concentration are in mass percentages [w / w]. The viscosities of the solutions were determined with a Haake VT550 rotational viscometer at 40 ° C.

EXAMPLES

Example 1: Reference experiment without fixation of the layers

An inner, lumen-side oriented polymer solution and an outer polymer solution were extruded through two concentrically arranged channels of a spinneret. Water was supplied via a centrally arranged circular channel for the precipitation of the polymer solutions. The spinning material for the backing layer, which here forms the outer layer, consisted of 20% Udel 3500 polysulfone and 5% polyvinylpyrrolidone K90 and 1% water and is dissolved with stirring in dimethylacetamide. The viscosity of the solution was about 11500 mPas. The spinning material for the selection layer, which forms the inner layer here, consisted of 30% cellulose diacetate having a molecular weight of 29 kD and an acetyl content of 40% (# 22188, Sigma / Aldrich) dissolved in dimethylacetamide pa while stirring. The viscosity of this solution was included about 15200 mPas. The temperature of the nozzle block was 20 ° C. The extruded hollow fiber passed through an air gap of 250 mm before immersing in a water-filled precipitation bath at a temperature of 42 ° C. This was followed by a rinse, which was heated to 75 ° C. The fresh water supply of the connected baths was 2.6 l / min. The hollow fiber was then dried at 95 ° C. The take-off speed of the fiber was 250 mm / s. The dry fiber was reeled. One bundle of hollow fibers consisted of 2300 fibers with a total area of 0.4 m ² . The fiber inside diameter was 200 μm. The fiber outer diameter was 261 μm. The thickness of the dry inner layer was on average 500 nm. The resulting fiber had a selectivity of urea against mono- and divalent cations. To check the adhesion of the inner and outer layer, a differential pressure directed from outside to outside was applied to a wet-laid membrane and the limit pressure was determined, which led to the detachment of the inner layer from the outer layer. The result is shown in Table 1.

Example 2: Preparation of a dope for the inner polymer layer

A polymer solution containing cellulose [Sigma / Aldrich # 22188] in dimethylacetamide pa (DMAc) was treated with a polyethyleneimine of 0.044 g / ml (Sigma / Aldrich # 40.872 to 7; M _n = 10000 g / mol) in DMAc adjusted to a concentration of 30% cellulose acetate and 0.1% polyethyleneimine. An appropriate amount of a polyethyleneimine solution (0.044 g / g in DMAc) was added rapidly to a cellulose acetate solution with stirring. The mixture was then stirred at 45 ° C. for as little as possible without air bubbles for 30 minutes. Subsequently, the solution was diluted 1: 1 (w / w) with DMAc pa and stirred for a further 30 min, so that a homogeneous solution was formed. The addition of the polyethyleneimine solution increased the viscosity of the solution. The resulting dope was clear and had a slightly yellowish color. The viscosity of the diluted solution was between 600 and 800 mPas. It is understood that the polyethyleneimine can be replaced by other amines and polyamines, provided that the corresponding mixture with the cellulose ester leads to a clear spinning mass and after reaction with the cellulose ester enough free amino groups remain to interact with a component of the outer mass can.

Example 3: Spinning a two-ply hollow fiber membrane with a polyimide / polyethyleneimine system

The spinning mass of the selection layer, which here forms the inner layer produced according to Example 2, consisted of 15% cellulose diacetate [Sigma / Aldrich # 22188) and 0.05% polyethyleneimine (Sigma / Aldrich # 40,872-7; M _n = 10,000 g / mol) in Dimethylacetamide pa The polymer blend is clear even at higher polymer concentrations of 29% cellulose diacetate with 0.2% polyethylenimine. The relative proportions of the two polymers can in principle be chosen freely as long as a clear mass results, which still has to be spinnable in terms of its viscosity and results in a layer according to the invention which is selective against cations with simultaneous urea permeability. The spinning mass of the backing layer, which here forms the outer layer, consisted of a solution of 20% polyetherimide (Ultem 1000) in DMAc pa The support layer of the fiber is thus hydrophobic and requires hydrophilization before use. It is understood that such a layer can be obtained by further additions also in hydrophilic form. Thus, a mixture of 17.5% polyetherimide with 2.5% polyvinylpyrrolidone gives a hydrophilic adhesive backing layer. The spun masses were extruded over a hollow fiber spinneret with two concentrically arranged mass channels. Water was squeezed out via a centrally arranged channel of the hollow-fiber spinning nozzle, which filled the lumen of the fiber and led to the phase separation of the spinning masses. The temperature of the spinning block was set at 5 ° C. The fiber, after exiting the block, was passed through a 50 mm long air gap. The take-off speed was 250 mm / s. The temperature of the water-filled precipitation bath was 20 ° C. In the subsequent rinse, a temperature gradient of 20 ° C was set to 60 ° C. Here it must be ensured that the fiber is adequately freed from the solvent, since during drying otherwise thread breaks occur in the system or insufficient performance of the fiber. The drying of the fiber took place between 120 and 130 ° C. After the fiber had dried, the selection layer thickness was 100 nm, the support layer thickness of the fiber was about 35 μm. The lumen diameter was 200 μm.

The fibers were collected into bundles and further processed into dialysis modules. Prior to fiber characterization, the lumen side of a dialysis module was filled with water and hydrophilized from the outside for about 10 seconds with a 50% isopropanol / water mixture. This was followed by a heat treatment at 90 ° C. in the water-filled module overnight, which is known to the person skilled in the art by the term "annealing". Then the sodium, calcium and urea permeability of the fiber was determined. It was typically 23-30 g / m ² d for urea and 23-32 mmol / m ² d for sodium. The calcium permeability at a concentration difference of 2.5 mM across the membrane was below the detection limit. To check the adhesion of backing and selection layer, a differential pressure directed from outside to outside was applied to a wet-laid membrane and the limit pressure was determined, which led to detachment of the selection layer from the backing layer. The result is shown in Table 1 above.

Example 4: Spinning a two-ply hollow fiber membrane with a polyimide / polyethyleneimine / PMMI / polyethersulfone system

The spinel composition of the selection layer, which here forms the inner layer prepared according to Example 2 without the dilution step described therein, consists of 30% cellulose diacetate [Sigma / Aldrich # 22188] and 0.1% polyethyleneimine (Sigma / Aldrich # 40,872-7; _n = 10000 g / mol) in dimethylacetamide pa

The dope of the support layer, which forms the outer layer here, consists of a mixture of polyethersulfone (Radel A-100) and polymethylmethacrylimide (PMMI) known under the trade name Pleximid. A mixture of 20% polyethersulfone and 2% pleximide in dimethylacetamide gave a clear dope with a viscosity of 814 mPas measured at 40 ° C. A pure Pleximidmasse could not meaningfully spin because of the low molecular weight of the polymer. The lower molecular weight of the pleximide should also be the cause of the relatively good miscibility with the polyethersulfone. A complete miscibility is not given. The spun masses were extruded over a hollow fiber spinneret with two concentrically arranged mass channels. Water was squeezed out via a centrally arranged channel of the hollow-fiber spinneret, filling the lumen of the fiber and leading to the phase separation of the spinning masses.

The spinning conditions were chosen analogously to the conditions of Example 3.

The resulting fiber exhibited selectivity to mono- and divalent cations and exhibited urea permeability.

The selection layer adhered in the pressure load test.

Example 5: Spinning a two-layered hollow fiber membrane with a charged polymer system

The spinning material of the selection layer, which here forms the inner layer prepared according to Example 2 without the dilution step described therein, consisted of 30% cellulose diacetate [Sigma / Aldrich # 22188] and 0.1% polyethyleneimine (Sigma / Aldrich # 40,872-7; M _n = 10000 g / mol) in dimethylacetamide pa The spinning mass of the support layer, which forms the outer layer here, consisted of 20% polyethersulfone and 4% sulfonated polyethersulfone mixed in a solvent mixture of dimethylacetamide and pyrrolidone in a ratio of 1: 1. The degree of sulfonation of the polyethersulfone is to be chosen so that no water solubility is given. The spun masses were extruded over a hollow fiber spinneret with two concentrically arranged mass channels. Water was squeezed out via a centrally arranged channel of the hollow-fiber spinneret, filling the lumen of the fiber and leading to the phase separation of the spinning masses. The temperature of the spinning block was set at 20 ° C. The fiber, after exiting the block, was passed through a 200 mm long air gap. The take-off speed was 250 mm / s. The temperature of the water-filled precipitation bath was 40 ° C. In the subsequent rinsing bath, a temperature of 70 ° C was set. Here it must be ensured that the fiber is adequately freed from the solvent, since during drying otherwise thread breaks occur in the system or insufficient performance of the fiber. The drying of the fiber was carried out at 90 ° C. After drying the fiber, the selection layer thickness was 500 nm and the support layer thickness of the fiber was about 40 μm. The lumen diameter was 203 μm. The fibers were collected into bundles and further processed into dialysis modules. Prior to characterization of the fiber, the lumenal side of a dialysis module was first filled with water and hydrophilized from the outside for about 10 seconds with a 50% isopropanol / water mixture. The resulting membranes exhibited selectivity to mono- and divalent cations, typically between 5 and 20, without the membrane being previously annealed. The membranes were permeable to urea. To check the adhesion of the selection and support layer, a differential pressure directed from outside to outside was applied to a wet-laid membrane and the limit pressure was determined which led to the detachment of the inner layer from the outer layer. The result is shown in Table 1 above.

Example 6: Spinning a three-layer membrane with a polyimide / polyethyleneimine system

The dope of the selection layer, which here forms the inner layer, consisted of a solution of 15% cellulose diacetate (Sigma / Aldrich # 22188) in dimethylacetamide. The dope of the adhesion-promoting middle layer prepared according to Example 2 consisted of 15% cellulose diacetate (Sigma / Aldrich # 22188) and 0.05% polyethyleneimine (Sigma / Aldrich # 40,872-7; M _n = 10,000 g / mol) in dimethylacetamide pa The dope of the backing layer , which forms the outer layer here, consisted of polyetherimide (Ultem 1000) which was dissolved at 20% in DMAc. The three spun masses were coextruded through three concentrically arranged channels of a hollow fiber spinneret. Water was pressed through a centrally located channel that filled the lumen of the fiber and triggered the phase separation of the three spinning masses. The temperature of the spinning block was adjusted to 10 ° C. The fiber, after exiting the block, was passed through a 50 mm long air gap. The take-off speed was 250 mm / s. The temperature of the water-filled precipitation bath was 16 ° C. In the subsequent rinse, a temperature gradient of 20 ° C was set to 60 ° C. Here it must be ensured that the fiber is adequately freed from the solvent, since during drying otherwise thread breaks occur in the system or insufficient performance of the fiber. The drying of the fiber took place between 120 and 130 ° C. After drying the fiber, the selection layer thickness was about 60 nm, the thickness of the adhesion-promoting middle layer was about 40 nm, the support layer thickness of the fiber was 35 microns. The lumen diameter was 170 μm. The middle, adhesion-promoting layer and the selection layer could not be distinguished by electron microscopy. The relative layer thicknesses resulted from the measured fluxes of the two spinning masses. The fibers were collected into bundles and further processed into dialysis modules. Before characterizing the fiber, the lumen side became a dialysis module filled with water and hydrophilized from the outside for about 10 s with a 50% isopropanol / water mixture. This was followed by a heat treatment at 90 ° C. in the water-filled module overnight, which is known to the person skilled in the art by the term "annealing". Then the sodium, calcium and urea permeability of the fiber was determined. It was typically 23-30 g / m ² d for urea and 23-32 mmol / m ² d for sodium. The calcium permeability at a concentration difference of 2.5 mM across the membrane was below the detection limit. To check the adhesion of the layers, a differential pressure directed from outside to outside was applied to a wet-laid membrane and the limit pressure was determined, which led to the separation of the layers. The result is shown in Table 1 above.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 4276172 [0003]
• CA 2707818 A1 [0003]
• US 4164437 [0003]
• US 5156740 [0004]
• EP 0286091 B1 [0004]
• EP 0359834 B1 [0004]
• US 7393195 [0005]

Cited non-patent literature

• M. Mulder, Basic Principals of Membrane Technology, Second Edition, Kluwer, 1996, pages 71 to 91 [0005]

Claims (29)

Membrane having at least two layers, wherein the at least two layers each comprise at least one polymer and with respect to the material-forming material are different from each other, characterized in that the at least two layers are at least partially covalently connected to each other without delamination. Membrane according to claim 1, characterized in that the at least two layers with a differential pressure ≤ 3 bar, preferably ≤ 5 bar, preferably ≤ 7 bar are not separable. Membrane according to at least one of the preceding claims, characterized in that the membrane has a selectivity of urea to sodium of 5 to 10 without the use of an annealing step. Membrane according to at least one of the preceding claims, characterized in that the at least two layers are coextruded layers. Membrane according to at least one of the preceding claims, characterized in that at least one layer is formed as a selection layer. A membrane according to claim 5, characterized in that the selection layer comprises at least one polymer which is selected from cellulose acetate, preferably a cellulose acetate having an acylation degree of 0.5 to 3, cellulose esters, and mixed esters thereof. Membrane according to claim 5 or 6, characterized in that the selection layer still has at least one further additive. A membrane according to claim 7, characterized in that the additive is formed as an adhesion-promoting additive, which preferably has reactive groups, more preferably is amino-functional. Membrane according to claim 7 or 8, characterized in that the additive is selected from polyethyleneimine or polyamine or mixtures thereof. Membrane according to at least one of claims 5 to 9, characterized in that the selection layer in the dry state has a layer thickness of 30 nm to 50 microns, preferably from 30 nm to 200 nm. Membrane according to at least one of claims 1 to 4, characterized in that at least one layer is formed as a support layer. Membrane according to claim 11, characterized in that the support layer comprises at least one polymer which is selected from (a) polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide, or mixtures thereof; or (b) sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherimide, sulfonated polymethylmethacrylimide, or mixtures thereof; or (c) polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide and sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherimide, sulfonated polymethylmethacrylimide, or mixtures thereof. Membrane according to claim 11 or 12, characterized in that the support layer in the dry state has a layer thickness of 1 .mu.m to 500 .mu.m, preferably of 35 .mu.m. Membrane according to at least one of the preceding claims, characterized in that the membrane is designed as a hollow fiber membrane. Membrane according to claim 14, characterized in that the hollow fiber membrane has an average diameter of the lumen of 20 microns to 500 microns, preferably of 200 microns. Membrane according to at least one of claims 14 or 15, characterized in that the hollow-fiber membrane has at least one layer which is configured as a selection layer comprising cellulose diacetate and polyethyleneimine. Membrane according to at least one of claims 14 to 16, characterized in that the hollow-fiber membrane has at least one layer which is designed as a support layer which comprises polyetherimide. Membrane according to at least one of claims 14 to 16, characterized in that the hollow-fiber membrane has at least one layer which is designed as a support layer comprising polyethersulfone and polymethylmethacrylimide. Membrane according to at least one of claims 14 to 16, characterized in that the hollow-fiber membrane has at least one layer which is designed as a support layer comprising polyethersulfone and sulfonated polyethersulfone. Membrane according to at least one of claims 14 to 16, characterized in that the hollow-fiber membrane has at least one layer which is designed as a support layer comprising polyetherimide and polyvinylpyrrolidone. Membrane according to at least one of the preceding claims, characterized in that the membrane has three coextruded layers. Membrane according to claim 21, characterized in that at least one layer in the dry state has a layer thickness of 30 nm to 50 microns, preferably from 30 nm to 200 nm, at least one second layer in the dry state, a layer thickness of 30 nm to 50 microns, preferably from 30 nm to 200 nm, and at least one third layer in the dry state has a layer thickness of 1 .mu.m to 500 .mu.m, preferably 35 .mu.m. Membrane according to at least one of claims 21 or 22, characterized in that at least one layer comprises cellulose diacetate. Membrane according to at least one of Claims 21 to 23, characterized in that at least one second layer comprises cellulose diacetate and polyethyleneimine. Membrane according to at least one of claims 21 to 24, characterized in that at least one third layer comprises polyetherimide. A process for producing a membrane according to any one of the preceding claims comprising the steps of: Providing at least a first clear spin mass comprising a material for the at least first layer Providing at least one second clear dope which is different from the first clear dope and has a material for the at least second layer Coextrusion of the at least two spin masses through a spinneret, comprising a number of concentric rings corresponding to the number of spunbonds provided, at least one first ring for receiving and / or extruding at least one first dope, and at least one second ring for receiving and / or extruding at least a second spinning dope which is different from the first dope, the at least two concentric rings being arranged around a central circular duct which is capable of receiving or extruding or taking up and extruding an agent, preferably a precipitating agent, preferably water, characterized in that the clear spinning masses comprises at least one polymer or material capable of reacting or at least one polymer and material capable of reacting, in particular material capable of chemical crosslinking. A method according to claim 26, characterized in that at least one first dope comprises at least one polymer which is selected from the group cellulose acetate, in particular a cellulose acetate having a degree of acylation of 0.5 to 3, cellulose esters or mixed esters thereof or at least one polymer which is selected from the group Celluloseactat, in particular a cellulose acetate having a degree of acylation of 0.5 to 3, cellulose esters, or mixed esters thereof and at least one contains further additive, preferably an adhesion-promoting amino-functional additive which is selected from the group polyethylenimine or a polyamine or polyethyleneimine and a polyamine. A method according to claim 26, characterized in that at least one second dope comprises at least one polymer which is selected from Polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide or mixtures thereof; or Sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyetherimide, sulfonated polymethylmethacrylimide or mixtures thereof; or Polyimine, polysulfone, polyethersulfone, polyimide, polyetherimide, polyethylenimine, polyvinylpyrrolidone, polymethylmethacrylimide and sulfonated polysulfone, sulfonated polyethersulfone, sulfonated polyvinylpyrrolidone, sulfonated polymethylmethacrylimide or mixtures thereof. Use of the membrane according to at least one of the preceding claims in peritoneal dialysis, in particular for regeneration of the dialysate, blood purification, in particular for hemodialysis, reverse osmosis, power generation in osmotic power plants, gas separation, pervaporation, nano, ultra, micro or particle filtration.