POROUS MULTILAYER FILTER AND METHOD FOR PRODUCING SAME

摘要

Provided is a porous multilayer filter which can trap ultrafine particles and in which permeability is high and treatment can be performed at a high flow rate. A porous multilayer filter is characterized by including a support layer 2 composed of a porous expanded PTFE sheet, and a filtration layer 3 composed of a porous expanded PTFE sheet which is different from that of the support layer 2, wherein at least a liquid-to-be-treated inflow surface of the filtration layer 3 is subjected to hydrophilization treatment, the filtration layer 3 and the support layer 2 are fusion-bonded to each other at a boundary therebetween to form a multilayer structure, pores of the support layer 2 three-dimensionally communicate with pores of the filtration layer 3, and pores surrounded by a fibril skeleton of the filtration layer 3 are smaller than pores of the support layer 2.