| 摘要 |
PURPOSE:To prepare a filter having large charge quantity, by processing a split composite fiber web formed from a multilayer film composed of two or more kinds of thermoplastic resins different in m.p. into a nonwoven fabric and subsequently applying corona charge treatment to said fabric. CONSTITUTION:For example, a multilayer film formed by laminating a low m.p. thermoplastic resin such as polyethylene and a high m.p. thermoplastic resin such as crystalline polypropylene is slit and subsequently split. Next, the film is formed into staple fibers and formed into a nonwoven fabric molding by a carding apparatus and fused under heating to form a nonwoven fabric which is, in turn, brought to an electret state by corona discharge to be formed into an electret filter. This filter has large charge quantity and proper pressure loss and is excellent in the collection efficiency of fine particles. |
