Liquid crystal polyester fiber and producing method thereof

Abstract

Provided is a liquid crystal polyester fiber having high strength, high elastic modulus, high abrasion resistance, excellent processability, and little thermal deformation at high temperature, and also provided is a production method thereof. A liquid crystal polyester fiber, characterized in that the peak half-value width of the endothermic peak (Tm1) observed when measuring by differential calorimetry under rising temperature conditions starting at 50° C. and increasing 20° C./min is 15° C. or higher, the polystyrene-converted weight-average molecular weight is between 250,000 and 2,000,000 inclusive, the peak temperature of the loss tangent (tan δ) is between 100° C. and 200° C. inclusive, and the peak value of the loss tangent (tan δ) is between 0.060 and 0.090 inclusive. A mesh fabric comprising the liquid crystal polyester fiber. A production method for melt liquid crystal polyester fiber, characterized in that liquid crystal polyester fiber obtained by melt-spinning is subject to solid-phase polymerization, and subsequently heat treated at a stretch ratio of at least 0.1% and under 3.0% at a temperature at least 50° C. higher than the endothermic peak temperature (Tm1) as observed when measuring by differential calorimetry under rising temperature conditions starting at 50° C. and increasing 20° C./min.

1 . A liquid crystal polyester fiber having: a peak half-value width of 15° C. or more at an endothermic peak (Tm1) observed by a differential calorimetry under a temperature elevation condition of 20° C./min from 50° C.; a weight-average molecular weight in terms of polystyrene of 250,000 or more and 2,000,000 or less; a peak temperature of a loss tangent (tan δ) of 100° C. or more and 200° C. or less; and a peak value of the loss tangent (tan δ) of 0.060 or more and 0.090 or less. 
     
     
         2 . The liquid crystal polyester fiber according to 1, wherein the fiber has a strength fluctuation rate of 10% or less. 
     
     
         3 . A mesh fabric comprising the liquid crystal polyester fiber according to  claim 1 . 
     
     
         4 . A producing method of a melt-spun liquid crystal polyester fiber characterized in that a liquid crystal polyester fiber made by a melt spinning is polymerized in a solid phase and then heated at a temperature of an endothermic peak (Tm1)+50° C. or more by a stretch rate of 0.1% or more and less than 3.0%, wherein the endothermic peak is observed by a differential calorimetry under a temperature elevation condition of 20° C./min from 50° C. 
     
     
         5 . The producing method according to  claim 4 , wherein the heated fiber is taken up under a yarn route regulation with yarn route guide in a range of 1 cm or more and 50 cm or less from an exit portion of a heating region.