Patent ID: 10844168

Abstract:
A method for producing ultra-high intrinsic viscosity (IV) polyester resin pellets from a resin that contains one or more comonomers in an amount of up to 30 mol%. The method includes extruding a polyethylene terephthalate polyester starting material having a starting IV (IVst) meeting the following relationship: 0.65 dL/g <IVst <0.9 dL/g, to form resin particles having no more than 0.05 dL/g of IV lift due to solid-state polymerization, then latent heat crystallizing the resin particles to form crystallized particles having a variation of IV of no more than 0.05 dL/g across any dimension of the crystallized particles. The crystallized particles are then solid state polymerized to a final IV (IVf) of at least 0.9 dL/g to form the ultra-high intrinsic viscosity (IV) polyester resin pellets. During the solid state polymerizing the IV lift rate is at least 0.012 dL/g/hr.