Porous membrane, process for producing porous membrane, process for producing clarified liquid, and porous-membrane module

摘要

A porous membrane with the membrane wall constructed of a hydrophobic polymer and a hydrophilic polymer, wherein when the membrane wall is divided into 3 sections in the film thickness direction to form region “a” containing one wall surface A of the membrane wall, region “c” containing the other wall surface C and region “b” between region “a” and region “c”, the hydrophilic polymer content ratio Ca in region “a” is greater than the hydrophilic polymer content ratio Cc in region “c”, and the mean pore size of the wall surface C is larger than the mean pore size of the wall surface A.

主权项

1. A process for producing a porous membrane whose membrane wall is constructed of a hydrophobic polymer and a hydrophilic polymer, wherein when the membrane wall is divided into 3 sections in the film thickness direction to form region “a” containing one wall surface A of the membrane wall, region “c” containing the other wall surface C and region “b” between region “a” and region “c,” the hydrophilic polymer content ratio Ca in region “a” is greater than the hydrophilic polymer content ratio Cc in region “c,” and the mean pore size of the wall surface C is larger than the mean pore size of the wall surface A, which comprises a solidifying step in which an internal solidifying solution is discharged from the internal fluid channel of the double-tube nozzle, while a membrane-forming solution, comprising a hydrophobic polymer, a hydrophilic polymer, a good solvent for both of these polymers and a non-solvent for the hydrophobic polymer, is discharged from the external fluid channel of the double-tube nozzle, for solidification in the external solidifying solution,
wherein a portion of the hydrophilic polymer is removed using an oxidizing agent-containing aqueous solution, either during or after the solidifying step.