Process for producing expandable particles of propylene polymer

摘要

The invention relates to expandable olefin bead polymers which comprise a blowing agent with a boiling point of from -5 to 150° C., selected from the group consisting of alkanes, alkanols, ketones, ethers and esters. The particles are unfoamed and have a bulk density above 500 g/l, and can be foamed to a bulk density below 200 g/l after storage for one hour at room temperature in free contact with the atmosphere. They are prepared by impregnating polyolefin pellets in suspension in a pressure vessel with the blowing agent, cooling the batch below 100° C., reducing the pressure and isolating the particles.