Patent ID: 8420211

Claim:
A porous polyimide membrane of a three-layer structure, comprising: two surface layers (a) and (b); and a macrovoid layer interposed between the surface layers (a) and (b), wherein the macrovoid layer comprises a partition wall joined to the surface layers (a) and (b), and plural macrovoids surrounded by the partition wall and the surface layers (a) and (b), with an average void diameter in a membrane plane direction of from 10 to 500 μm, each of the partition wall of the macrovoid layer and the surface layers (a) and (b) has a thickness of from 0.1 to 50 μm and has plural pores having an average pore diameter of from 0.01 to 5 μm, the pores being in communication with each other and also in communication with the macrovoids, and the membrane has a total membrane thickness of from 5 to 500 μm and a porosity of from 70 to 95%.