| 摘要 |
PURPOSE:To obtain a membrane of which the filtering capacity is enhanced without requiring the pretreatment of a support, by casting a polymer solution for forming a semipermeable membrane onto a nonwoven fabric having a two- layered structure wherein low and high density nonwoven fabric layers are laminated. CONSTITUTION:A polyester fiber web containing 20-80% of a non-stretched polyester fiber is used as a low density layer and the fineness thereof is set to 1-3 denier and the air permeability thereof is set to 5-50cc/cm<2>/sec. The web is prepared by a dry process. A wet nonwoven web receiving no calender processing and formed by using a modified cross-section fiber with fineness of 15 denier or less is used as a high density layer and the air permeability thereof is set to 0.1-5cc/cm<2>/sec. Two kinds of these webs are integrally laminated and subjected to calender processing at 150-250 deg.C so as to set air permeability to 0.1-4.5cc/cm<2>/sec. This web is used as a support to form a membrane. |
