Processing of polyethylene terephthalate pellets e.g. for extruding film, includes initial kneading at just below glass transition temperature

摘要

Polyethylene terephthalate pellets are fed through a series of evacuated feed hoppers (8, 9) to a planetary roller extruder (3) where they are worked mechanically under vacuum without melting at a temperature that is at least 10[deg]C below the glass transition temperature, preferably at 130[deg]C. The rollers have an intermeshing spiral pattern of pins to continually expose new surfaces.