METHOD FOR PREPARING POROUS SEPARATION MEMBRANE COMPRISING ELASTIC MATERIAL POROUS SEPARATION MEMBRANE PREPARED BY SAID METHOD AND SECONDARY BATTERY COMPRISING SAID SEPARATION MEMBRANE

摘要

The present invention relates to a method for preparing a porous separation membrane and particularly to a method for preparing a porous separation membrane comprising an elastic material to a separation membrane prepared by the method and to a secondary battery comprising the separation membrane. According to one aspect of the present invention a porous separation membrane is provided in which an elastic material is homogeneously distributed in a polymer at a weight ratio of 40:60 to 5:95 and which has an elongation at a breakage value of 250% or more at room temperature in the direction of low elongation strength. According to another aspect of the present invention a method for preparing a porous separation membrane comprises the steps of: forming an extruded sheet by extruding a mixture of a polymer and an elastic material at a weight ratio of 95:5 to 60:40 through an extruder; forming a membrane by annealing and drawing the extruded sheet; and forming the porous separation membrane by heat setting the drawn membrane. According to the present invention a porous separation membrane having improved stability by decreasing the heat shrink rate and significantly increasing elongation at breakage can be provided.