Anti-lumping compounds for use with expandable polystyrene beads

Abstract

An anti-lumping agent for use with expandable polystyrene beads is disclosed. The expandable polystyrene beads comprise a styrene or styrene derivative polymer in combination with a blowing agent. Typical blowing agents are C3-C6 hydrocarbons, with pentane being especially preferred. The anti-lumping agents include block copolymers formed from blocks of ethylene oxide and propylene oxide. Preferably, the copolymers have a number average molecular weight of from about 4,000 to 15,000, and a hydrophilic-lipophilic balance number of from about 16 to 29. The anti-lumping agents significantly reduce the lumping potential of the expandable polystyrene beads, especially when they are expanded to low densities of from about 1.5 to 0.75 lbs. per cubic foot, and more preferably to densities of from about 1.2 to 0.85.

Dependencies are inferred from the claim text.