Method of filtering a fluid and a filter medium therefor

摘要

The present invention relates to a filter medium comprising a pre-filter layer (41), an intermediate layer (42), and a fine fiber layer (43). The pre-filter layer (41) comprises fibers having a diameter and a porosity P 41 ; the intermediate layer (42) comprises fibers having a diameter and porosity P 42 , and the fine fiber layer comprises fibers having a diameter and porosity P 43 . The diameter of the fibers and the porosity P 42 of the intermediate layer (42) is larger than the diameters of fibers and the porosities P 41 and P 43 of the pre-filter layer (41) and the fine fiber layer (43).