High modulus polyester yarn for tire cords and composites

A process for production of a drawn polyethylene naphthalate yarn, comprising:

• (a) extruding a molten crystallizable polyester polymer having an intrinsic viscosity of at least 0.6 through a shaped extrusion orifice to form a molten spun yarn,
• (b) solidifying the molten spun yarn by passing it through a solidification zone,
• (c) withdrawing the solidified yarn at a sufficient undrawn take-up speed to form a partially oriented yarn of birefringence of at least 0.030, and
• (d) hot drawing the partially oriented yarn to a total draw ratio of at least 1.3/1 to form a drawn yarn.

A process for production of a drawn polyester yarn having a T.sub.g greater than 100.degree. C., comprising:

• (a) extruding a molten crystallizable polyester polymer having an intrinsic viscosity of at least 0.6 through a shaped extrusion orifice to form a molten spun yarn,
• (b) solidifying the molten spun yarn by passing it through a solidification zone,
• (c) withdrawing the solidified yarn at a sufficient undrawn take-up speed to form a partially oriented yarn of birefringence of at least 0.030 and a melting point elevation in the range of 3.degree.-23.degree. C., and
• (d) hot drawing the partially oriented yarn to a total draw ratio of at least 1.3/1 to form a drawn yarn.

A process for production of a drawn polyethylene naphthalate yarn, comprising:

• (a) extruding a molten crystallizable polyester polymer having an intrinsic viscosity of at least 0.6 through a shaped extrusion orifice to form a molten spun yarn,
• (b) solidifying the molten spun yarn by passing it through a solidification zone,
• (c) withdrawing the solidified yarn at a sufficient undrawn take-up speed to form a partially oriented yarn of birefringence of at least 0.030 and the melting point elevation is the range of 3.degree.-23.degree. C., and
• (d) hot drawing the partially oriented yarn to a total draw ratio of at least 1.3/1 to form a drawn yarn.

A process for production of a drawn polyester yarn having a T.sub.g greater than 100.degree. C., comprising:

• (a) extruding a molten crystallizable polyester polymer having an intrinsic viscosity of at least 0.6 through a shaped extrusion orifice to form a molten spun yarn,
• (b) solidifying the molten spun yarn by passing it through a solidification zone,
• (c) withdrawing the solidified yarn at a sufficient undrawn take-up speed to form a partially oriented yarn of birefringence of at least 0.030, and
• (d) hot drawing the partially oriented yarn to a total draw ratio of at least 1.3/1 to form a drawn yarn having a tenacity of at least 6.5 g/d and dimensional stability of less than 5%.

A process for production of a drawn polyethylene naphthalate yarn, comprising:

• (a) extruding a molten crystallizable polyester polymer having an intrinsic viscosity of at least 0.6 through a shaped extrusion orifice to form a molten spun yarn,
• (b) solidifying the molten spun yarn by passing it through a solidification zone,
• (c) withdrawing the solidified yarn at a sufficient undrawn take-up speed to form a partially oriented yarn of birefringence of at least 0.030, and
• (d) hot drawing the partially oriented yarn to a total draw ratio of at least 1.3/1 to form a drawn yarn having a tenacity of at least 7.5 g/d and dimensional stability of less than 5%.

A process for production of a drawn polyethylene naphthalate yarn, comprising:

• (a) extruding a molten crystallizable polyester polymer having an intrinsic viscosity of at least 0.6 through a shaped extrusion orifice to form a molten spun yarn,
• (b) solidifying the molten spun yarn by passing it through a solidification zone,
• (c) withdrawing the solidified yarn at a sufficient undrawn take-up speed to form a partially oriented yarn of birefringence in the range of 0.030 to 0.30, and
• (d) hot drawing the partially oriented yarn to a total draw ratio of at least 1.3/1 to form a drawn yarn having a tenacity of at least 7.5 g/d and dimensional stability of less than 5%.