Core-sheath composite fiber and method for producing same

Abstract

Provided is a core-sheath composite fiber which is easily moldable into a composite material or the like and is also excellent in strength. The core-sheath composite fiber comprises a core member containing polyamide and a sheath member containing modified polyethylene, and the core member has a melting point higher by at least 170° C. than a melting point of the sheath member.

What is claimed is: 
     
         1 . A core-sheath composite fiber comprising:
 a core member containing polyamide as a main component; and   a sheath member containing modified polyethylene as a main component, wherein   the core member has a melting point higher by at least 170° C. than a melting point of the sheath member.   
     
     
         2 . The core-sheath composite fiber according to  claim 1 , wherein a composite material including the core members has a polygonal cross-section. 
     
     
         3 . The core-sheath composite fiber according to  claim 1 , wherein the core-sheath composite fiber is used for a fuel tank. 
     
     
         4 . A method of producing a core-sheath composite fiber, comprising steps of:
 selecting polyamide as a main component of a core member and modified polyethylene as a main component of a sheath member such that the core member has a melting point higher by at least 170° C. than a melting point of the sheath member; and   melting the sheath member by heating and welding the sheath member to the core member.   
     
     
         5 . A method of producing a core-sheath composite fiber, comprising steps of:
 bundling together core-sheath composite fibers produced by the method of producing a core-sheath composite fiber according to  claim 4  and melting sheath members by heating; and   forming a composite material having a polygonal cross-section by extruding the bundle of the core-sheath composite fibers including the melted sheath members using cold pressing.   
     
     
         6 . The core-sheath composite fiber according to  claim 2 , wherein the core-sheath composite fiber is used for a fuel tank.