Non-woven bi-layer material, specially with long-term filter properties, and process for its manufacture

摘要

A description is given of a multi-layer filter material composed of non-woven fabrics, which are prepared from fibres or filaments of identical or different polymers, the filter material being composed of a deep bed filter and a fine filter, both of which have a homogeneous density perpendicular to their surface, and are connected together in such a manner that the surface occupied by the connection points does not exceed 75% of the total filter surface. …??The deep bed filter has a thickness 2- to 20-times that of the fine filter layer and the deep bed layer and the fine filter layer have a different packing density. …??A process for the production of the filter material is also described.