| abstract |
The invention relates to a method for manufacturing a polyvinylidene fluoride multi-core ultrafiltration membrane tube, which comprises the following steps: blending two or more polyvinylidene fluorides with different weight average molecular weights, and dissolving the polyvinylidene fluorides in a polar solvent to prepare a high-viscosity spinning dope; and extruding the spinning dope out of a multi-core spinning nozzle at a constant speed by a gear metering pump, wherein the formed porous newly-generated membrane filament generates phase inversion separation in a first stage and a second stage coagulation bath after passing through a certain distance of an air section. After rinsing and post-treatment processes, the membrane tube not only can bear high radial pressure from the outside to the inside, but also can bear large axial tension. The pure water stable flux is about 200 L/(m<2>.hr.bar). By controlling the medium compositions of core liquid and the coagulation bath, the manufactured membrane tube can be applied to manufacturing external-pressure type membrane modules or immersion-type membrane modules. |