Pelletized brominated anionic styrenic polymers and their preparation and use

Abstract

Despite the frangibility of additive-free granules of brominated anionic styrenic polymer, it has been found possible by use of special mechanical processing to provide pellets of unadulterated brominated anionic styrenic polymer having a bromine content of at least about 50 wt % and in which at least about 70 wt % (preferably at least about 75 wt %) of the pellets are retained on a standard US No. 40 sieve and no more than about 30 wt % (preferably no more than about 25 wt %) are retained on a standard US No. 5 sieve. In preferred embodiments such pelletized anionic styrenic polymer is brominated anionic polystyrene having a bromine content of at least about 67 wt %, e.g., in the range of about 67 to about 71 wt %. Also preferred are pelletized brominated anionic styrenic polymers in which the melt flow index (ASTM D 1238-99) at 220° C., 2.16 kg is at least 4 g/10 min and preferably is at least 5 g/10 min. Another embodiment of this invention is a method of preparing pelletized unadulterated brominated anionic styrenic polymer which method comprises: A) forming strands of molten unadulterated brominated anionic styrenic polymer; B) submitting said strands to cooling and downwardly directed forced air flow on a porous conveyor belt whereby said strands are broken into pellets; and C) causing said pellets to drop into a classifier that removes fines from the pellets.

Dependencies are inferred from the claim text.