PROCESS FOR PREPARING A COPOLYESTER

摘要

PURPOSE: Development of microporous membranes with sufficiently large pores for some purpose, such as water treatment and micro filtration, has been demanded. CONSTITUTION: A method of producing a microporous polyolefin membrane having relatively large pore size and sharp pore size distribution comprises the steps of: preparing a solution comprising 5 to 40 weight % of a polyolefin composition containing an ultra-high-molecular-weight polyolefin having a weight-average molecular weight of 5 X 10¬5 or more, and 95 to 60 weight of a solvent; extruding the solution through a die lip; quenching the extruded solution into a sheet; and stretching the sheet at an areal stretching ratio of 1.01- to 1.4-fold.