Spherical expandable thermoplastic beads, e.g. of polystyrene - prepd. by conditioning thermoplastic granules in an aq. medium contg. a soluble phosphate, adding blowing agent and impregnating

摘要

In the prodn. of virtually spherical, expandable particles of a thermoplastic polymer, particles of the polymer are first suspended in an aq. medium contg. a difficultly soluble phosphate as suspension agent and opt. a second surface active agent. The polymer particles are them conditioned by holding the suspension at above the softening point of the polymer for >=1 hour. A volatile blowing agent is then added to the conditioned particles and impregnation of the particles with the blowing agent is promoted by holding the mixt. for >=1 hour under gas tight conditions at a temp above the softening point of the polymer. Process is esp. useful for making expandable (co)polystyrene beads, using blowing agents such as butane, isobutane, pentane, neopentane, hexane, heptane, etc. The process prevents agglomeration of the particles and breaking of the suspension during treatment and gives separate virtually spherical expandable beads.