Abstract: A composite staple fiber, wherein a polymer component A and a polymer component B are alternately arranged in a fiber horizontal cross-section; the fiber periphery is entirely covered with the polymer component A; both the polymer component A and the polymer component A have a substantially flat shape; the lengthwise ends of the polymer component B are located 0.05 to 1.5 &mgr;m from the fiber surface; and the weight ratio of the polymer component A to the polymer component B is from 90/10 to 10/90. The composite staple fiber of the present invention is not peeled or split by a carding and a needle punching treatments, but is divided and split in the subsequent water jet entanglement, resulting in flat ultrafine fibers having a sharp-edged structure.

Abstract: This invention relates to filling material composed of crimped fibers joined together at one end with a high density, and having crimps located in mutually deviating phases, while the other ends of the fibers stay free, and a process for manufacturing such filling material. The filling material exhibits superior bulkiness and thermal insulation, since the recovery force or resiliency of the crimps located in mutually deviating phases causes the fibers to spread sufficiently to contain a large quantity of air among themselves.