| 摘要 |
Unitary membranes (10, 10a) made of a plastic, semipermeable material having parallel tubular passages (23, 23a) passing longitudinally from end to end of the membrane may be made by extruding the plastic material through an extrusion orifice (36) exhibiting the cross-sectional shape of the membrane. Mandrel means are applied through the orifice (36) to displace plastic material in a manner corresponding to the pattern and shape of the parallel tubular passages (23, 23a). After the extruded plastic material is hardened, the mandrel means are separated from the hardened plastic material to open the tubular passages (23, 23a). |
