Automatic continuous filtration of molten plastics - with intermittently displaced band filter

摘要

Process for filtering molten plastic material through a band filter moved intermittently by external traction through a filtering chamber sealed by plugs of plastic material formed at the entry and exit points of the band. While the band is stationary the temp. at the entry and exit points is kept low enough to maintain the seal, but when the band is to be displaced the temp. is raised so that the plugs are softened sufficiently at the edges to allow the band to move. The band may be moved automatically and its displacement predetermined. The temp. is pref. raised just to release the band and immediately reduced again after the required displacement. The filter is more effective than previous similar devices. It avoids loss of material from the plugs and the necessity of braking the band motion.