| 摘要 |
PURPOSE:To obtain advantageously the titled polymer particles of a desired particle diameter and a narrow particle diameter distribution, by suspension- polymerizing a styrene monomer in two stages of different temperatures in the presence of a blowing agent by using both of low-temperature-decomposable and high-temperature-decomposable polymerization initiators. CONSTITUTION:Small particles of a blowing agent-containing expandable styrene polymer having a particle diameter distribution adjusted to a range within an average particle diameter + or -20% are suspended in an aqueous medium. A low-temperature-decomposable polymerization initiator whose decomposition temperature for obtaining a 10hr-half life is 50-80 deg.C is added to the suspension, and the blowing agent is vaporized in the course of bringing the temperature to a first-stage polymerization temperature and is fed at a rate of 3-15g per liter of the space capacity of the polymerization vessel. A styrene monomer to which a high-temperature decomposable polymerization initiator whose decomposition temperature for obtaining a 10hr-half life is 80-120 deg.C and a blowing agent are added to the reaction system, and the whole is subjected to the first- stage polymerization at 40-100 deg.C and subjected to a second-stage polymerization at 100-150 deg.C to obtain the titled polymer particles.
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