Polypropylene Pellets by Bulk Polymerisation in Liquid Propylene

Polypropylene is propylene strung into long chains. In the bulk process the propylene itself is the liquid: kept liquid at 30–40 atm, it polymerises at 60–80 °C on a catalyst of titanium tetrachloride on magnesium chloride. Letting the pressure down boils off the unreacted propylene and leaves a powder, which is extruded into pellets. Natta found the regular (isotactic) form in 1954. The picture: our diagram of reactor, flash and pelletiser.