Sheath-core composite fiber and multifilament

Abstract

A sheath-core composite fiber is composed of two or more polymers, wherein a core component having a multifoliate shape with three or more projections is completely covered by a sheath component in a fiber cross-section of the sheath-core composite fiber, while having a ratio of the maximum thickness Smax of the sheath component to the minimum thickness Smin of the sheath component, namely Smax/Smin of 5.0 or more. A multifilament is composed of the core component of this sheath-core composite fiber. The sheath-core composite fiber and multifilament are suitable for the achievement of a good textile that is comparable to natural silk.

1 - 11 . (canceled) 
     
     
         12 . A core-sheath composite fiber comprising two or more types of polymers and having a cross section containing 1) a core component possessing a multilobar shape with three or more convex portions and 2) a sheath component completely surrounding the core component, with a maximum thickness S max  and a minimum thickness S min  of the sheath component having a S max /S min  ratio of 5.0 or more. 
     
     
         13 . The core-sheath composite fiber as set forth in  claim 12 , wherein the core component of a multilobar shape has a groove existing at the apex of each convex portion and extending toward a center of gravity of the core component, and a ratio of GN/GM between distance GM from the center of gravity G of the core component to a bottom M of the groove and a distance GN from the center of gravity G of the core component to an apex N of the convex portion is 1.1 to 1.5. 
     
     
         14 . The core-sheath composite fiber as set forth in either  claim 12 , wherein two or more core components are separated by the sheath component, and each of the separated core components has a multilobar shape. 
     
     
         15 . The core-sheath composite fiber as set forth in  claim 14 , wherein core components are separated by the sheath component, and mutually adjacent core components are of polymers having different melting points. 
     
     
         16 . A multifilament comprising the core component of the core-sheath composite fiber as set forth in  claim 12 . 
     
     
         17 . The multifilament as set forth in  claim 16 , wherein an average interfiber space distance is 5 to 30 μm, and having a space structure in which the interfiber spaces with distances of less than 5 μm account for 10% to 50%. 
     
     
         18 . The multifilament as set forth in  claim 17 , wherein the space structure has space proportion is 30% to 80%. 
     
     
         19 . The multifilament as set forth in  claim 17 , comprising two or more types of crimped fibers formed of polymers having different melting points, wherein the crimped fibers coexist uniformly. 
     
     
         20 . The multifilament as set forth in  claim 17 , comprising a fiber of a multilobar shape having a three or more convex portions in the cross section of the fiber. 
     
     
         21 . The multifilament as set forth in  claim 17 , comprising a fiber having a groove at an apex of each convex portion in the cross section of the fiber, and wherein a ratio of MN/D between a distance MN from a bottom M of the groove to an apex N of the convex portion and the fiber diameter D is 0.04 to 0.20. 
     
     
         22 . A fiber product partially containing the core-sheath composite fiber or the multifilament as set forth in  claim 12 .