PRECIPITATION OF POLYSTYRENE FROM TOLUENE WITH HFC-134A BY THE GAS PROCESS

Precipitation of polystyrene from toluene solution using HFC-134a as a ntisolvent was investigated. In this gas antisolvent (GAS) precipitati on process, the pressurized HFC-134a was dissolved into a 20-g toluene solution containing 5 and 10 wt % polystyrene. The pressure required to expand toluene and cause precipitation of polystyrene by HFC-134a w as observed to be much lower than that required by the frequently used antisolvent carbon dioxide. At a temperature of 293 K and a pressure of 5.17 bar, 67 and 74.5% yields were obtained for holding times of 50 and 120 min, respectively. The cloud-point pressure was found to be l inearly dependent on temperature. Almost the same yield was obtained f or any arbitrary combination of temperature and pressure having the sa me binary volume expansion. The volume expansion was found to be the m ajor factor influencing yield. The operation with a higher pressure an d a lower temperature would result in a higher yield.