Patent ID: 7947142

Claim:
A process for making a pleated filter comprising: a) forming a monocomponent monolayer nonwoven web of continuous monocomponent polymeric fibers by meltspinning, collecting, heating and quenching the monocomponent polymeric fibers under thermal conditions sufficient to form a web of partially crystalline and partially amorphous oriented meltspun fibers of the same polymeric composition that are bonded to form a coherent and handleable web having a Gurley Stiffness of at least 100 mg and which further may be softened while retaining orientation and fiber structure, b) forming rows of pleats in the nonwoven web, and c) cutting the pleated web to a desired size and shape to form a pleated filter element comprising a self-supporting porous monocomponent monolayer matrix of fibers bonded to one another at at least some points of fiber intersection and having an average initial submicron efficiency of at least 15% at a 1.52 meters/sec face velocity, wherein the heating and quenching are performed by heating the meltspun collected web to a temperature sufficient to at least soften or melt amorphous portions of the fibers but not sufficient to melt crystalline portions of the fibers, and then quenching the heated web.