Membranes having improved performance

A process for preparing a permselective asymmetric hollow fiber membrane, comprising

• a) dissolving at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyamides and polyacrylonitriles;
• and at least one hydrophilic polymer in at least one solvent to form a polymer solution;
• b) extruding said polymer solution through an outer ring slit of a nozzle with two concentric openings;
• c) extruding a center fluid through the inner opening of the nozzle;
• and thereafter
• d) washing the membrane obtained;
• e) treating said membrane with a salt solution containing from 0.5 wt.-% to 12 wt.-% of a physiologically tolerable salt and no physiologically intolerable salts subsequently to washing;
• and thereafter
• f) drying said membrane and, optionally, sterilizing said membrane by steam treatment.

A diffusion and/or filtration device comprising a membrane prepared by

• a) dissolving at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyamides and polyacrylonitriles;
• and at least one hydrophilic polymer in at least one solvent to form a polymer solution;
• b) extruding said polymer solution through an outer ring slit of a nozzle with two concentric openings;
• c) extruding a center fluid through the inner opening of the nozzle;
• and thereafter
• d) washing the membrane obtained;
• e) treating said membrane with a salt solution containing from 0.5 wt.-% to 12 wt.-% of a physiologically tolerable salt and no physiologically intolerable salts subsequently to washing;
• and thereafter
• f) drying said membrane and, optionally, sterilizing said membrane by steam treatment.

A method for at least one of hemodialysis, hemodiafiltration, and hemofiltration of blood, the method comprising preparing a membrane by

• a) dissolving at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyamides and polyacrylonitriles;
• and at least one hydrophilic polymer in at least one solvent to form a polymer solution;
• b) extruding said polymer solution through an outer ring slit of a nozzle with two concentric openings;
• c) extruding a center fluid through the inner opening of the nozzle;
• and thereafter
• d) washing the membrane obtained;
• e) treating said membrane with a salt solution containing from 0.5 wt.-% to 12 wt.-% of a physiologically tolerable salt and no physiologically intolerable salts subsequently to washing;
• and thereafter
• f) drying said membrane and, optionally, sterilizing said membrane by steam treatment, and
• performing the at least one of hemodialysis, hemofiltration and hemodiafiltration of blood using said membrane.

A method for at least one of bioprocessing;

• plasma fractionation;
• and the preparation of protein solutions, the method comprising preparing a membrane by
• a) dissolving at least one hydrophobic polymer selected from the group consisting of polysulfones, polyethersulfones, polyamides and polyacrylonitriles;
• and at least one hydrophilic polymer in at least one solvent to form a polymer solution;
• b) extruding said polymer solution through an outer ring slit of a nozzle with two concentric openings;
• c) extruding a center fluid through the inner opening of the nozzle;
• and thereafter
• d) washing the membrane obtained;
• e) treating said membrane with a salt solution containing from 0.5 wt.-% to 12 wt.-% of a physiologically tolerable salt and no physiologically intolerable salts subsequently to washing;
• and thereafter
• f) drying said membrane and, optionally, sterilizing said membrane by steam treatment, and
• at least one of treating a substance to be bioprocessed, fractionated and prepared into a protein solution using said membrane.