Production of high tenacity, low shrink polyester fiber

In a continuous process for the production of high strength polyester yarn with enhanced low shrinkage comprising spinning molten polymer of high relative viscosity to form a multifilament yarn, feeding the yarn to a draw roll system to draw the yarn, said draw roll system comprising a pair of heated draw rolls, then overfeeding the drawn yarn from said heated draw rolls to a relaxation roll system, thereby reducing its shrinkage, and winding the yarn to form a package in a continuous process, the improvement comprising maintaining the traveling yarn about said pair of heated draw rolls for a period of at lest 0.25 seconds, maintaining the air temperature in the region about said traveling yarn for said period at a temperature of at least 220.degree. C., said draw rolls each having a surface temperature of at least 220.degree. C. and a substantial portion of its surface with a surface roughness value of at least 50 microinches, whereby said yarn is heated sufficiently to obtain a substantial relaxation between said heated draw rolls and said relaxation roll system, thereby providing yarn having an intrinsic viscosity of at least 0.78, a dry heat shrinkage DIN.sub.177 of less than 2.0%, a dry heat shrinkage DIN.sub.200 of less than 4.5, and a tenacity of at least 7.2 grams per denier.