| 摘要 |
A process and apparatus for producing a non-woven, especially a non-woven electret, fiber sheet provides for directing the non-woven fibers at a collecting surface and into an electric field between at least one electrode and the collecting surface. This process, in which the fibers are collected in the electric field, enables economical production of a non-woven electret fiber sheet of a single layer structure having a large amount of polarized charges (giving a total electric charge per unit area of at least 7 x 10<-><1><1> Coulomb/cm<2>), and a weight per unit area of at least 60 g/m<2>, preferably greater than 80 g/m<2>. The non-woven electret sheet may have the large amount of electret charge throughout its thickness and/or a uniform weight distribution and thus have excellent dust collecting properties. |
