PURPOSE: To obtain title copolymer particles which can provide foamed products having excellent heat resistance and high extent of expansion, by suspending styrene/maleic anhydride copolymer particles in an aqueous medium, adding to the suspension a blowing agent and a solvent which dissolves the particles, and impregnating the particles with the agent and the solvent.
CONSTITUTION: Styrene copolymer particles containing 2W25% of maleic anhydride and having an average degree of polymerization of 500W4,000 are prepared by block-polymerizing styrene and maleic anhydride by the use of a catalyst and pelletizing the polymer through an extruder. The foamable styrene copolymer particles of the purpose are prepared by suspending the pellets in an aqueous medium by the use of a dispersing agent, such as polyacrylate salt and methylcellulose, adding to the suspension a solvent which dissolves the pellets, such as benzene, toluene or xylene, and a blowing agent, such as propane or n-butane, and impregnating the pellets with the solvent and the blowing agent.
SASAKI HIDEAKI
MAEDA TETSUJI
