Patent ID: 7108818

Claim:
A process for the production of a drawn polyethylene terephthalate yarn which translates to a high tenacity dimensionally stable tire cord, the process comprising: (a) extruding a molten melt-spinnable polyethylene terephthalate having an intrinsic viscosity of at least about 0.8 through a shaped extrusion orifice having a plurality of openings to form a molten spun yarn; (b) solidifying gradually said molten spun yarn by passing said molten spun yarn through a solidification zone which comprises (i) a retarded cooling zone and (ii) a cooling zone adjacent said retarded cooling zone, wherein said cooling zone, said yarn is rapidly cooled and solidified in a gaseous atmosphere; (c) withdrawing at sufficient speed said solidified yam from said solidification zone to form a crystalline partially oriented yarn; and (d) hot drawing said crystalline partially oriented yarn at a total draw ratio between 1.5/1 and about 2.5/1 to produce a drawn yarn having an effective crosslink density (N) between about 10×10 21 and about 20×10 21 crosslinks per cubic centimeter; thereby obtaining a drawn yarn with a terminal modulus of at least 20 g/d.