Mono- or multi-layered filter material and process for its preparation

A mono- or multi-layer filter material comprises at least one layer composed thereof from cellulose, glass fibers, synthetic fibers or a mixture and impregnated with a binder consisting of an epoxy resin and a curing agent. The curing agent comprises a first cross-linking at a lower temperature and a second curing agent, cross-linking at a higher temperature curing agent so that the epoxy resin is gradually curable depending on the temperature.