High strength and low shrinkage polyester yarn and process for its preparation

Abstract

Disclosed is a high strength and low shrinkage polyester yarn, which has tenacity of 7.4 g/d or higher, elongation at break of 19 to 26%, shrinkage percentage of 2% or lower, and respective thermal-stress peaks of 3×10 −2 to 7.5×10 −2 g/d and 8.0×10 −2 to 10.5×10 −2 g/d at temperature ranges of 100 to 140° C. and 230 to 240° C., and process for its preparation. The high strength and low shrinkage polyester yarn is advantageous in that it has desirable resistance to external load and excellent dimensional stability, and is very useful as an industrial yarn with uniform shrinkage and excellent dimensional stability during a post-process for application to tarpaulin and truck covers.

What is claimed is:  
     
         1 . A high strength and low shrinkage polyester yarn, which has tenacity of 7.4 g/d or higher, elongation at break of 19 to 26%, shrinkage percentage of 2% or lower, and respective thermal-stress peaks of 3×10 −2  to 7.5×10 −2  g/d and 8.0×10 −2  to 10.5×10 −2  g/d at temperature ranges of 100 to 140° C. and 230 to 240° C.  
     
     
         2 . The high strength and low shrinkage polyester yarn as set forth in  claim 1 , wherein a ratio of a yarn's thermal-stress peak at a temperature range of 230 to 240° C. to a thermal-stress peak at a temperature range of 100 to 140° C. is 1.3 to 3.0.  
     
     
         3 . The high strength and low shrinkage polyester yarn as set forth in  claim 1 , wherein a shrinkage force of the polyester yarn within a first 5 sec after the start of shrinkage is 4.5×10 −2  to 6.5×10 −2  cN/d, and the shrinkage force of the polyester yarn thereafter is 1.5×10 −2  to 3.5×10 −2  cN/d.  
     
     
         4 . The process for preparing a high strength and low shrinkage polyester yarn by the direct spinning drawing process, comprising: 
 (a) spinning a melted polyester polymer at a speed of 383 to 490 m/min;    (b) drawing a spun polyester yarn in a total draw ratio of 5 to 6.4; and    (c) relaxing a drawn polyester yarn at 230 to 250° C. by a godet roller with a relaxation ratio of 9 to 13%.    
     
     
         5 . The process according to  claim 4 , wherein the relaxation is performed through a first relaxation step and a second relaxation step, and a relaxation distribution ratio of the first relaxation step to the second relaxation step is 9:1 to 1:9.