High tenacity polyester yarns

Abstract

This invention relates a fully drawn high tenacity yarn and a process for making the same from a partially oriented polyester feed yarn in a drawing process comprised of two stages.

1 . A fully drawn, untextured filament yarn made from a polymer containing at least 85% polyethylene terephthalate and having a relative viscosity less than or equal to 25 LRV, the yarn having a tenacity greater than 7.4 grams per denier and an elongation greater than 10%.  
     
     
         2 . The fully drawn, untextured filament yarn of  claim 1  further characterized by a toughness factor (TF) of greater than about 17, wherein the toughness factor (TF) is calculated according to: TF=DR×T×(1+E B /100) and wherein; DR is the total draw ratio, T is the tenacity in grams per denier and EB is the elongation at break.  
     
     
         3 . The yarn of claims  1  or  2 , wherein the polymer LRV in yarn is less than or equal to 22.  
     
     
         4 . The yarn of claims  1  or  2 , wherein the polymer further comprises a chain branching additive.  
     
     
         5 . The yarn of  claim 3  wherein the chain branching additive is trimethyl trimellitate present in an amount of about 1 to 500 parts per million.  
     
     
         6 . Threads made from the yarn of claims  1 - 5 .  
     
     
         7 . Fabrics made from at least a portion of the threads of  claim 6 .  
     
     
         8 . A partially oriented feed yarn for drawing and forming an untextured filament yarn made from a polymer having a relative viscosity less than or equal to 25 LRV and having 140%-160% elongation at break.  
     
     
         9 . The yarn of  claim 8  having denier per filament in the range of 2.5 to 9.0.  
     
     
         10 . A process of making a partially oriented feed yarn, comprising the steps of: 
 supplying a polymer having a relative viscosity of less than or equal to 25 LRV through a spinneret;    extruding at least a single filament;    passing the filaments through a quench delay and a hybrid quench zone; and    coalescing the filaments into a yarn bundle and interlacing.    
     
     
         11 . The process of  claim 10 , further including a process of stepwise drawing of the partially oriented feed yarn bundle, comprising the steps of: cold drawing; followed by heated drawing, to form a fully drawn, untextured filament yarn.  
     
     
         12 . The process of  claim 10 , further including a process of drawing the partially oriented feed yarn bundle in a single heated step to form a fully drawn, untextured filament yarn.  
     
     
         13 . The process of  claim 10 , wherein the process has a total draw ratio of about 2.2 to about 2.5  
     
     
         14 . The process of  claim 10 , wherein the first step has a feed roll which feeds the yarn to a first step draw roll.  
     
     
         15 . The process of  claim 10 , further including a first godet for heating and feeding the yarn to the second step of drawing.  
     
     
         16 . The process of  claim 10 , further including a second godet for heating and annealing the yarn and feeding the yarn to the relaxation step.  
     
     
         17 . The process of  claim 10 , further including interlacing the yarn prior to winding up.