Patent ID: 6423232
Filing Date: 2002-07-23
Classification: A61L,B01D

Abstract:
A process for manufacturing apparatus for the treatment of blood or plasma by extra-corporal circulation, for preventing activation of the contact phase and comprising a semi-permeable membrane in the form of a flat membrane or a bundle of hollow fibers, based on polyacrylonitrile bearing fixed negative charges, characterized in that it comprises the following steps:preparing a solution comprising: at least one polyacrylonitrile bearing fixed negative charges, at least one neutral polymer, at least one solvent for said polyacrylonitrile and for the neutral polymer, optionally, at least one non-solvent for the polyacrylonitrile; extruding the solution in order to form a hollow fiber or a flat membrane; simultaneously with extrusion, in the case of the preparation of a hollow fiber, or after extrusion in the case of the formation of a flat membrane, solidifying the membrane obtained by a phase inversion process by partial or total contact of the extruded product with a liquid or gaseous fluid which is chemically inert with respect to the said polymers; washing the flat membrane or the hollow fiber obtained; optionally, treating the flat membrane or the hollow fiber with glycerol; preparing a semi-permeable membrane from the flat membrane or assembling a bundle of hollow fibers from the hollow fiber; mounting the flat membrane or the bundle of hollow fiber in a case and, optionally fixing caps to the case; sterilizing the medical apparatus obtained; and in that the amount of neutral polymer is adjusted such that:the overall ionic capacity of the semi-permeable membrane, based on polyacrylonitrile bearing fixed negative charges and containing a neutral polymer, is negative; the overall ionic capacity of the semi-permeable membrane, based on polyacrylonitrile bearing fixed negative charges and containing a neutral polymer, is, as an absolute value, not more than 10% less than the overall ionic capacity of the same semi-permeable membrane which contains no neutral polymer; the semi-permeable membrane based on polyacrylonitrile bearing fixed negative charges and containing a neutral polymer complies, before sterilization, with the following two electrical characteristics: the electrokinetic index â€œIâ€  of the semi-permeable membrane containing a neutral polymer, which is equal to Log10(|Z|/R), i.e. to the logarithm, in base 10, of the ratio |Z|/R of the Zeta potential â€œZâ€ , as an absolute value, expressed in microvolts, of the surface of the membrane intended to come into contact with blood or plasma, to the electrical resistivity â€œRâ€  of the membrane, expressed in ohm.centimetres, is less than or equal to 0.8, and the Zeta potential â€œZâ€  is negative.