Patent ID: 6991113
Filing Date: 2006-01-31
Classification: B01D

Abstract:
1. A process for manufacturing a nonwoven fabric for a filter excellent in cleaning efficiency and trapped matter retention volume constructed by two or more different kinds of fibrous layers placed one over the other, the nonwoven fabric having an average pore size from 30 μm inclusive to 60 μm inclusive and a total pore area at 0.011 cm 2 /cm 2 or more with respect to an entire surface of the nonwoven fabric, the average pore size being calculated according to a bubble point method as defined in ASTM F-316-80 with use of a Coulter Porometer II, said process comprising: placing two or more fibrous layers differing in density one over the other, each fibrous layer being composed of adhesive fibers and fibers to be adhered to said adhesive fibers, mixed at a certain ratio; subjecting the fibrous layers to a physical bonding by intertwining the fibers; subjecting the fibrous layers to a thermal treatment while fusing part of the fibers for adhesion to compose a multi-layered member of a certain shape; applying a liquid to a surface of the multi-layered member, the surface having a larger fibrous density than the opposite surface of the multi-layered member; and performing a calendar processing to the multi-layered member by allowing the one surface of the multi-layered member into contact with a first roller heated at a certain temperature, while allowing the opposite surface thereof into contact with a counterpart second roller at an ambient temperature, the temperature of the first roller being higher than the temperature of the second roller.