EXPANDABLE THERMOPLASTIC RESIN PARTICLES, THERMOPLASTIC PRE-EXPANDED PARTICLES, AND THERMOPLASTIC EXPANSION-MOLDED ARTICLE

An in-mold expanded mold article can be produced inexpensively and easily by using the expandable polystyrene-type resin particles. However, expanded mold articles are not sufficient in dimensional stability under a high-temperature environment for a long period of time upon use of relatively-high-temperature applications such as a thermal insulating material for pipes, a heat-insulating material for roofs, an automotive member, a thermal insulating material for solar systems or the like because the monomer that forms the polymer in the expanded mold article is styrene. The expansion-molded polystyrene article has thus a drawback that it is not suitable for those applications which require heat resistance as a disadvantage. Further, even higher heat-resistant performance is required in these application fields in recent years. The object of the present invention is to provide an expandable thermoplastic resin particle having improved heat resistance. The problem is solved by an expandable thermoplastic resin particle comprising a polymer obtained from a monomer composition comprising 60 to 80 parts by weight of ±-methylstyrene and 40 to 20 parts by weight of acrylonitrile, wherein a content of residual monomeric components in the particle is not more than 0.5% by weight.