| abstract |
Semipermeable membranes are disclosed for purifying aqueous biological fluids. The membranes are particularly suitable for purifying extracorporeal blood via hemodialysis. The membranes, preferably configured as hollow fibers, are made from a hydrophilic polymeric material, preferably cellulose acetate. Features of the membranes include an ultrafiltration coefficient (KuF) of about 15 to about 55 mL/hr/mmHg/m<2> (thus termed "high-flux" type membranes), a urea mass transfer coefficient (KoV(urea)) of at least 38x10<-><3> cm/min, and a ratio of KoV(urea)/KuF of at least 2.5x10<-><3>. Hollow fibers of such membranes suitable for hemodialysis have a lumen diameter of about 175 to about 210 mu m and a wall thickness of about 10 to about 35 mu m. According to disclosed methods for making the membranes, a melt comprising about 32 to about 40% w/w cellulose acetate, about 5 to about 10% w/w glycerine, and about 50 to about 67% w/w polyethylene glycol is extruded to make hollow fibers; the fibers are cooled, cold-stretched, water-leached, and replasticized using a glycerine solution. |