Dry recovery of isobutylene-styrene copolymer

Thermoplastic copolymers of aliphatic and aromatic olefines prepared in the presence of a Friedel-Crafts catalyst and a solvent are recovered by heating the resulting dispersion to a temperature above the boiling point of the solvent at atmospheric pressure, at a sufficient pressure to maintain the solvent in the liquid phase, flashing the dispersion down to atmospheric pressure and working the product so obtained to reduce the residual solvent content. Copolymers of styrene, p-methyl-, a -methyl-p-methyl-, p-ethyl-, p-chloro-, p-bromostyrene, vinyl naphthalene and indene with isobutylene or methyl-2-butene-1, preferably having 35-70 per cent of combined aromatic monomer, are prepared in methyl, ethyl or propyl chloride, fluorochlorinated hydrocarbons or vinyl chloride, using boron fluoride or aluminium chloride as catalyst at temperatures below 0 DEG C., preferably below - 70 DEG C., may be used. In examples, a styrene-isobutylene copolymer dispersion, prepared in a methyl chloride solution with an aluminium chloride catalyst and in which the formation of hydrogen chloride is neutralized by magnesium oxide, calcium carbonate or a quaternary ammonium hydroxide, is treated by (i) passing to a direct single-stage heater (Figs. 1, 3), through a pressure-reducing valve to a flash chamber 6, which encloses a double drum drier 7, where the dried polymer is worked and removed to an extruder; (ii) passing either through a heater 3 (Fig. 2), and a separator 16, or through a boiler 21 to flashing valves 17 and 24 and to an extruder 14; and (iii) by passing through a heater (Fig. 3), to a flash drum 4, and then either to a heater 9, directly to a flash drum 10 or through an intermediate flash drum 13 at a lower pressure to an extruder 11, or alternatively to a pressure drum 19 where it is heated and compressed before discharge or passage to a flash drum 10 for hot working in the extruder. Specifications 631,272 and 682,695 are referred to.