Nonwoven fabric for filter and filter for engine

摘要

A nonwoven fabric for a filter excellent in cleaning efficiency and trapped matter retention volume is constructed by two or more different kinds of fibrous layers placed one over the other. The nonwoven fabric has an average pore size from 30 mu m inclusive to 60 mu m inclusive and a total pore area at 0.011cm<2>/cm<2> or more with respect to an entire surface of the nonwoven fabric. The average pore size is calculated according to a bubble point method as defined in ASTM F-316-80 with use of a Coulter Porometer II.