PRODUCTION OF POLYETHYLENE TEREPHTHALATE RESIN HAVING HIGH VISCOSITY

摘要

PROBLEM TO BE SOLVED: To convert a low-viscosity polyester such as reclaimed polyester resin product and off-grade polyester resin into a high-viscosity polyester. SOLUTION: An aromatic tetracarboxylic acid dianhydride is added in an amount of 0.1-2 pts.wt. to 100 pts.wt. of a polyethylene terephthalate resin and the mixture is melted and kneaded with a twin-screw extruder having >=3 kneading zones. The kneading zone of the twin-screw extruder is preferably composed of a combination of a back-feeding flight or a back-feeding kneading disk at the resin extrusion side and at least one kneading disk at the resin feeding side.