High strength polyethylene fiber

Abstract

A polyethylene fiber having high strength, which was not easily obtained by methods such as the conventional gel spinning method, includes crystals derived from a monoclinic crystal having a size of 9 nm or more. The tensile strength of the fiber can be 30 cN/dtex or more. This high strength polyethylene fiber is produced by mixing an ultrahigh molecular weight polyethylene with a mixed solvent of a good solvent for polyethylene and a poor solvent for polyethylene to form a polyethylene dope, extruding the dope through an orifice, cooling the extruded dope, and drawing it into a filament yarn.

1 . A high strength polyethylene fiber, comprising a crystal derived from a monoclinic crystal having a size of 9 nm or more. 
   
   
       2 . The high strength polyethylene fiber of  claim 1 , wherein the fiber has a tensile strength of 30 cN/dtex or more. 
   
   
       3 . The high strength polyethylene fiber of  claim 1 , which is produced by mixing an ultrahigh molecular weight polyethylene having an intrinsic viscosity of 8 dL/g or more with a mixed solvent comprising solvent (A) as a good solvent for polyethylene and solvent (B) as a poor solvent for polyethylene in a mixing ratio of solvent (A) to solvent (B) within a range from 20:80 to 99:1 by weight to form a mixed dope having a polyethylene concentration of 0.5% by weight or more and less than 50% by weight, extruding the dope through an orifice, cooling the extruded dope, and drawing it into a filament yarn. 
   
   
       4 . The high strength polyethylene fiber of  claim 3 , wherein solvent (A) has a viscosity index for polyethylene of 0.6 or more, and solvent (B) has a viscosity index for polyethylene of 0.6 or less. 
   
   
       5 . The high strength polyethylene fiber of  claim 1 , which contains 5 ppm or more of a solvent having a viscosity index for polyethylene of 0.6 or less.