| 摘要 |
A web of plastic material presenting filtering properties comprises a porous layer interconnected with a first non woven layer of plastic fibers. The porous layer is formed by heating another nonwoven of plastic fibers, having a lower plasticizing temperature than the fibers of the first non woven, to at least the plasticizing temperature of the fibers of the other non woven but below the plasticizing temperature of the fibers of the first non woven. The first nonwoven consists of polyester fibers and the other nonwoven, e.g., of polypropylene fibers. An apparatus for manufacturing such a web comprises a central roller, and endless felt band partially slung around said central roller, a heating member and a cooling element. In one embodiment the apparatus comprises a heatable central roller, a second endless metal band engaging a coolable second roller, said heatable central roller and an endless felt band partially surrounding the heatable central roller and a part of the metal band engaging said heatable central roller, non-woven material being passed between said endless metal band and said felt band (FIG. 2). In an other embodiment the central roller is a coolable central roller, heating means being accommodated opposite a region of the central roller and a part of the metal band engaging said part of the central roller. The felt band engages the central roller before and after the region opposite the heating means (FG. 3).
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