Liquid crystal polyester fiber, method for producing the same, and use of the same

Abstract

The present invention provides a method for producing a liquid crystal polyester fiber, the method comprising a step of spinning a liquid crystal polyester that has a glass transition temperature and a melting point, both observed by differential scanning calorimetry, and that has a flow initiation temperature of 250° C. or higher, followed by a heat treatment at 230° C. or lower. Even though the heat treatment is conducted at a low temperature, the obtained liquid crystal polyester fiber has a high strength.

1 . A method for producing a liquid crystal polyester fiber, the method comprising a step of spinning a liquid crystal polyester that satisfies the following features (a) and (b):
 (a) a glass transition temperature and a melting point are observed by differential scanning calorimetry, and   (b) a flow initiation temperature is 250° C. or higher, which is followed by a heat treatment at 230° C. or lower.   
   
   
       2 . The production method according to  claim 1 , wherein the liquid crystal polyester is a liquid crystal polyester having a structural unit derived from a compound selected from phthalic acid and isophthalic acid in an amount of 20% by mole or more of the total structural units in the polyester. 
   
   
       3 . The production method according to  claim 1 , wherein the liquid crystal polyester is a liquid crystal polyester having a glass transition temperature of 150° C. or lower, which is determined by differential scanning calorimetry. 
   
   
       4 . The production method according to  claim 1 , wherein the liquid crystal polyester is a liquid crystal polyester having a melting point of 250° C. or higher, which is determined by differential scanning calorimetry. 
   
   
       5 . The production method according to  claim 1 , wherein the liquid crystal polyester fiber obtained after the heat treatment has double or more of strength compared to the strength of liquid crystal polyester fiber prior to the heat treatment. 
   
   
       6 . A liquid crystal polyester fiber obtained by the production method according to  claim 1 . 
   
   
       7 . The liquid crystal polyester fiber according to  claim 6 , the fiber having a tensile strength of 10 (cN/dtex) or higher when measured at a temperature of 23° C. 
   
   
       8 . A nonwoven fabric comprising the liquid crystal polyester fiber according to  claim 6 .