High tenacity polyester yarns
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.