Polymer plastic strapping from polyethylene terephthalate

Claim 1

A process to produce high tensile polyester extruded strap using as a starting material a polyester resin obtained from the polymerization of terephthalic acid and ethylene glycol, said process comprising the steps of drying said polyester resin while in granular form to a final moisture content of about 0.2% by circulating hot dried air at about 300° F. through the granular polyester resin, keeping the dried polyester resin in a heated hopper to prevent moisture reabsorption by the polyester resin, said polyester resin being kept dried in the hopper by circulating hot air through the polyester resin at about 300° F., extruding the polyester resin in a nondegrading temperature range of between 482° F to 572° F., quenching the extrudate by cooling the same to about 122° F. and stretching the extrudate in two consecutive steps at a temperature of about 212° F., the draw ratio in the first stretching step being about 4 to 1 and the stretching ratio in the second stretching step varying between 2 to 1 and 2.5 to 1 to obtain a total stretching ratio varying between 8 to 1 and 9 to 1, the resulting polyester strap having a tensile strength of at least 75000 p.s.i. and an elongation at break of 8%.