Patent ID: 7485249

Claim:
A method of manufacturing a membrane with a double layer membrane wall whose layers consist of different polyacrylnitrile copolymers so that the layer forming one surface of the double layer membrane is blood-compatible whereas the layer forming the other surface of the double layer membrane is tissue-compatible, said method comprising the steps of: preparing, separately, a first polymer solution which contains a blood-compatible polymer comprising at least one of polyacrylnitrile copolymer P(AN-co-NVP) with a fraction of NVP between 18.0 and 20.9 mol-%, heparinized polyacrynitrile copolymer P(AN-co-APMA) with a fraction of 3.8 mol-% APMA, a mixture thereof and a mixture of at least one of polyacrylnitrile copolymer P(AN-co-NVP) with a fraction of NVP between 18.0 and 20.9 mol-% and heparinized polyacrylnitrile copolymer P(AN-co-APMA) with a fraction of 3.8 mol-% APMA with polyacrylnitrile, and a second polymer solution which contains a tissue-compatible polymer comprising at least one of polyacrylnitrile copolymer P(AN-co-NVP) with a fraction of NVP between 4.8 and 6.1 mol %, and a mixture thereof with polyacrylnitrile by dissolving the respective polymer in a solvent such that both polymer solutions remain in the form of polymer mixture solutions in a homogeneous state, bringing the two polymer solutions into contact with each other in the nozzle of an extruder so as to form a layered polymer solution compound arrangement, and extruding the two polymer solution compound arrangement from the nozzle of the extruder into a coagulation bath where it is subject to a phase inversion thereby forming a double layer membrane with a blood-compatible material surface at one side thereof and a tissue-compatible surface at the other side thereof which is at least partially freed from all non-membrane forming components.