Porous hollow fiber membranes and method of making the same

a method of making a porous hollow fiber membrane comprising:

• forming said hollow fiber membrane according to a dry-wet spinning method or a wet spinning method while using the following components:
• a spinning dope containing a base polymer as material forming said porous hollow fiber membrane,
• an additive for facilitating a phase separation of said spinning dope,
• a solvent compatible with both, said base polymer and said additive, and a mass of micropartilces insoluble in said solvent, wherein said microparticles are uniformly dispersed in a liquid medium and have an average particle size within the range of 1 to 20 um;
• wherein an amount of the additive and/or the particle size is adjusted to enhance the coagulation action of the microparticles;
• and
• a coagulation liquid for forming the hollow fiber membrane, to obtain a spun hollow fiber membrane, and extracting said additive with cold water or water at a temperature from 40 to 90 degree C.;
• and
• extracting said microparticles by immersing said spun hollow fiber membrane into an extracting solution effective to dissolve said microparticles but ineffective to dissolve sad base polymer;
• wherein said hollow fiber membrane has a permeability;
• and wherein a particle cutoff is within the range of 1 to 10 um;
• and a pure water permeate flow is equal to or higher than 30,000 L/m2/hr/100 kpa.