| 摘要 |
Cylindrical fibrous structures comprising a fibrous mass of nonwoven, synthetic, polymeric microfibers wherein the microfibers are substantially free of fiber-to-fiber bonding and secured to each other by mechanical entanglement of intertwining, the fiber structure having a substantially constant voids volume over at least a substantial portion of the structure and, preferably, a graded fiber diameter structure, both as measured in the radial direction. The structures are particularly useful as depth filters. The process for preparing such fibrous structures comprises the steps of: (a) extruding synthetic, polymeric material from a fiberizing die and attenuating the extruded polymeric material to form microfibers by the application of one or more gas streams directed toward a rotating mandrel and a forming roll in operative relationship with the mandrel; (b) cooling the synthetic, polymeric microfibers prior to their collection on the mandrel to a temperature below that at which they bond or fuse together, thereby substantially eliminating fiber-to-fiber bonding; and (c) collecting the cooled microfibers on the mandrel as a nonwoven, synthetic fibrous mass while applying a force on the exterior surface of the collected microfibers by the forming roll; wherein the process variables are controlled to form the cylindrical fiber structure with at least the major portion of the fibrous mass having a substantially constant voids volume. |
