FILTER MEDIUM AND PROCESS FOR PRODUCTION OF THE SAME

摘要

A filter medium made of a nonwoven fabric of untrafine-denier filaments having a mean filament diameter of 0.05 to 1.8µm which is obtained by subjecting a nonwoven fabric or web constituted of bicomponent filaments made of a water-soluble thermoplastic resin and a water-insoluble thermoplastic resin to dissolution in a hydrophilic solvent or extraction with a hydrophilic solvent in such a way that part of the water-soluble thermoplastic resin remains in the fabric or web, wherein ultrafine-denier filament bundles having a mean width of 3 to 100µm account for 1 to 20% of the surface area of the nonwoven fabric and the lengthwise and widthwise tensile strength (B) (kgf/5cm) of the nonwoven fabric and the basis weight (A) (g/m<SUP>2</SUP>) thereof satisfy the relationship: 100 x (B)/(A) > 5 The filter medium exhibits high collection performance and liquid permeability and is useful as the filter for liquid fuels such as diesel engine fuel.