Technology Unit

A gear pump (38) conveys the concentrated polymer phase through a short conduit to a vacuum devolatilizing extruder or mixer (40). Molten stabilizer is injected
into the short conduit at injection point (38) a from the stabilizer addition apparatus. The mixed stream of concentrated polymer phase and stabilizer enters the inlet of vacuum devolatilizer (40). The devolatilizer (40) comprises a large horizontal cylindrical chamber inside which is mounted on a horizontal stirring shaft which extends over the length of the chamber and is driven by a motor outside the chamber. The stirrer shaft is provided with a number of paddles which agitate the concentrated polymer phase as it flows along the chamber thereby both assisting the removal of volatiles from the polymer by continuously exposing new surface, and also mixing the stabilizer and polymer.

At the end of the horizontal devolatilizer chamber the concentrated polymer phase flows into a shaft provided with a screw impellor which drives the polymer
along the shaft and into an underwater pelletizer, fed with water chilled at (42). The polymer pellets are washed and spun dried at (44) to form pellets suitable for
bagging or baling at (46).