PURPOSE: To purify a crude polymer without contamination with foreign matter, by discharging a contaminating polymer from a position near the screw support of a vented-screw devolatilizing extruder and discharging volatile impurities and part of the polymer from the vent.
CONSTITUTION: A crude methyl methacrylate- or styrene-based polymer containing volatile impurities is introduced into a feed inlet 6. The screw has flights of different directions on the left and right sides, so that foreign matter such as friction pieces at the screw support 4 can be discharged from an exit 8 and foreign matter at the support 5 is discharged from an exit 9. Therefore the purified polymer leaving an exit 7 is completely freed from any foreign matter. In addition, each of the vents 1 and 2 is on a side and has a descending slope, so that the vent gas can be easily discharged and at the same time the polymer entrained with the vapor of the impurities is also discharged. Thus, the polymer in the purification apparatus will never be contaminated with degraded polymer or the like.
MUNEKUNI HAJIME
YAMAGA TADASHI
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