CRYSTALLINE POLYMER MICROPOROUS MEMBRANE, METHOD FOR PRODUCING THE SAME, AND FILTER FOR FILTRATION

摘要

To provide a membrane capable of efficiently collecting fine particles for a long period of time, disclosed is a polytetrafluoroethylene microporous membrane wherein the mean pore size in the surface of the membrane is larger than the mean pore size in the back thereof and the mean pore size continuously changes from the surface toward the back.