Nonwoven material of two or more layers, in particular with long- term filter properties and manufacture thereof

摘要

There is disclosed a multilayered filter material comprising nonwovens made of fibers or filaments of identical or different polymers, said filter material being composed of a depth filter and a fine filter which both have a homogeneous density perpendicular to their surface and have been joined together in such a way that the area covered by the bonding dots does not exceed 75%. The depth filter is from 2 to 20 times thicker than the fine filter, and they have different densities. There is also disclosed a process for manufacturing the filter material.