METHOD AND APPARATUS FOR MAKING CRYSTALLINE POLYMERIC PELLETS AND GRANULES

摘要

A method and apparatus for underwater pelletizing and subsequent drying of crystallizing polymers to crystallize the polymer pellets with out subsequent heating is shown in FIG. 5. High velocity air or other inert gas is injected into the water and pellet slurry line (120) toward the dryer near the pelletizer exit (102) at a flow rate from about 100 to about 175 m3/hour, or more. Such high-speed air movement forms a vapor mist with the water and significantly increases th speed of the pellets into and out of the dryer such that the polymer pellets leave the dryer with sufficient latent heat to cause self-crystallization within the pellets. A valve mechanism in the slurry line (150) after the gas injection further regulates the pellet residence time and a vibrating conveyor after the dryer helps the pellets to achieve the desired level of crystallinity and to avoid agglomeration.

主权项

1. A method for processing crystallizing polymers into pellets using an apparatus including an underwater pelletizer and a dryer, said method comprising:
extruding strands of a crystallizing polymer through a die plate for cutting in said underwater pelletizer; cutting the polymer strands into pellets in a cutting chamber of said pelletizer; transporting said pellets out of said cutting chamber to said dryer as a water and pellet slurry, and injecting a high velocity gas into said water and pellet slurry to generate a water vapor mist and enhance the speed of the pellets into and out of said dryer, with said pellets retaining sufficient internal heat upon exiting said dryer for crystallization of said pellets, a speed of said high velocity gas being faster for smaller pellets than for larger pellets; and storing the hot pellets in a heat retaining or heat insulating container.