Hollow fibers for outside-in-dialysis applications

A porous hollow fiber, said fiber comprising:

• (a) a tubular body comprising a wall region and defining a lumen surrounded by said wall region, and
• (b) said wall region comprising an outer surface, an inner surface, said wall region extending in a radial direction from said outer surface to said inner surface, wherein said inner surface defines said lumen, said outer surface and said inner surface are generally concentric with each other, and said wall region and said lumen extend in an axial direction;
• wherein:
• (i) said wall region comprises a porous fiber composition containing a mixture of a polysulfone polymer and a hydrophilic polymer;
• (ii) said wall region comprises a bulk layer and a selective layer, wherein the bulk layer supports the selective layer and the selective layer is located radially outwardly from the bulk layer, and said selective layer is selective for exclusion of passage of albumin therethrough so that said porous hollow fiber has an albumin sieving coefficient of less than approximately 0.01;
• (iii) said wall region comprises a plurality of radially extending elongated macrovoids located in said bulk layer;
• and
• (iv) said porous hollow fiber has a permeability for water through said wall region of at least approximately 6 mL/(h·mmHg·m2).

A method of producing a hollow fiber, said method comprising:

• forming an emergent fiber from a triple concentric spinneret having a bore liquid channel, a dope channel annularly surrounding said bore liquid channel, and a shower channel annularly surrounding said dope channel, by flowing a bore liquid through said bore liquid channel, flowing a dope liquid through said dope channel, and flowing a shower liquid through said shower channel;
• and
• stretching said emergent fiber as said emergent fiber passes through a coagulation bath while being pulled at a take-up velocity,
• wherein said triple concentric spinneret, said bore liquid, said dope, said shower liquid, and said coagulation bath are provided at temperatures within a 5 degrees C. range of each other,
• wherein said bore liquid comprises a fiber forming polymer composition containing an organic solvent, and
• wherein said shower liquid and said coagulation bath comprise respective higher concentrations of a non-solvent compared to said bore liquid.