Solution Polymerization PS
By polymerizing styrene in solution many problems associated with heat transfer and the physical movement of viscous mass are reduced. But the solvent recovery and chain transfer reactions pose new challenges. In 1955 Distrene Ltd. (UK) started production of PS by solution polymerization process.
Styrene and solvent (toluene or ethylbenzene) are blended together and then pumped to the top of the first reactor which is divided into three heating zones. In the first zone the solution is heated to start up the polymerization reaction. The polymerization reaction in the second and the third zones of the first reactor and the three zones of the second reactor is exothermic and cooling coils are used to take heat out of the system By the time reaction mixture reaches the third reactor the polymerization reaction starts to slow down, so the reaction mixture is reheated.
From the third reactor the polymer is then run into a devolatilising vessel in the form of thin strands. At a temperature of 225°C the solvent, residual monomer and some very low molecular weight polymers are removed, condensed and recycled. The polymer is then fed to extruder units, extruded as filaments, granulated, lubricated and stored to await dispatch.
Solution-modified bulk polymerization
a) Reactors; b) Degasser; c) Dye mixer; d) Extruder; e) Water bath; f) Granulator; g) External lubrication; h) External lubricating agent; i) Polymer; j) Pure styrene; k) Monomer and solvent
