POROUS MEMBRANE AND METHOD FOR MANUFACTURING THE SAME

摘要

PURPOSE: A porous membrane and a method for manufacturing the porous membrane are provided to obtain a high mechanical strength and a excellent water transmission degree to stably control transmission amount. CONSTITUTION: A porous membrane has a bead structure including a plurality of spherical crystallites. A plurality of macro voids which are divided by a plurality of spherical crystallites are formed on the outer surface. Each spherical crystallite is a microporous spherical crystallite in which many minute holes are formed on the surface. Water transmission degree which is measured at under nitrogen pressure of 1.0 - 1.5 kg / cm^2 is 1.20(ml/cm^2)·(min)-1·(kg/cm^2) -1 or greater. A rejection about a particle having a diameter of 0.07μm is 99% or greater. A compaction index which is defined as the following equation is 0.50 or less. Equation:(Lp1.0 - Lp1.5) / Lp1.0 IN the equation lp1.0 is the water transmission degree measured under 1.0 kg / cm^2 pressure and Lp1.5 is the water transmission degree measured under 1.5 kg / cm^2 pressure.