Today, almost all processes carry out polymerization and impregnation in a one –step process. The reaction occurs in a single reactor designed to control the temperature and pressure of the reaction.
Styrene monomer and water is charged to the reaction kettle equipped with an agitator. Various chemicals are added to affect suxpension of the monomer in water and to control the polymerized bead growth,molecular weight and other parameters necessary to produce the desired product. The polymerization is an exothermal reaction and is controlled by reactor temperatures and pressures, as well as various catalysts.
In the second phase of the process, the blowing agengt is added under pressure and impregnates the soft polystyrene beads.The total batch cycle takes a little less than twelve hours.When completed, the entire batch consisting of water and the impregnated polystyrene beads are dumped to de-watering systems.
Finishing Operations
Following the de-watering process, the beads are transferred to dryers for drying. The conditions used to polymerize the beads play a controlling part in determining the exact shape and or skew ness of the particle size distribution. The dried beads are then screened through state-of-the-art systems to provide the desired size cut.Various surface lube system are added at this point prior to packaging eliminate potential lumping during pre-expansion.
