| 摘要 |
<p>PURPOSE:To prepare the subject novel porous membrane having an excellent floating fine material-catching property and useful as a precise gas or liquid filter employed in a semiconductor industry by biaxially stretching a polytetrafluoroethylene seme-calcination product in a high stretching surface ratio. CONSTITUTION:A polytetrafluoroethylene semi-calcination product (calcination degree is preferably 0.40-0.85) is biaxially stretched in a stretching surface ratio of at least 40 times to provide the objective porous membrane having a specific surface area of >=15m<2>/g, preferably 16-40m<2>/g, and an average pore diameter of <=0.2mum, preferably <=0.05mum.</p> |
