| 摘要 |
PURPOSE:To obtain the subject porous film having approximately uniform pore diameters and high porosity by compression molding powder of polytetrafluoroethylene resin for molding prepared by suspension molding, burning, making into a film form, piling plural sheets of the films, thermally fusing and drawing. CONSTITUTION:Powder of polytetrafluoroethylene resin for molding prepared by suspension molding is compression molded to give premolded articles of polytetrafluoroethylene. The premolded articles are burnt at >= the melting point of unburnt polytetrafluoroethylene, made into a filmy state, two or more films of the premolded articles are piled, integrated at a temperature (100-300 deg.C) >=the melting point of burnt polytetrafluoroethylene resin and stretched or biaxially orientated at a temperature (19-320 deg.C) <= the melting point of the resin to give the objective porous film having 40-80% porosity and >=99% removal ratio of uniform particles having 0.2mum diameter or having 40-80% porosity and >=3kg/cm<2> bubble point. |
