Abstract:
The present invention relates to a styrene-based resin having a weight average molecular weight Mw′ as determined by the GPC-MALS method of 1,000,000 or more and 5,000,000 or less, a degree of long-chain branching of 0.2 or more per 1,000 styrene units, and a tetrahydrofuran-insoluble matter of 0.1% by weight or less (including 0), the styrene-based resin being free from a component derived from a polyfunctional monomer in a molecular chain thereof. In a method for producing this styrene-based resin, in an impregnation step of adding a polymerization initiator and a styrene monomer in an aqueous medium, thereby impregnating the polymerization initiator and the styrene monomer in the seed particle at a temperature at which polymerization of the styrene monomer does not substantially proceed, the amount of the styrene monomer is 20 to 200 parts by weight based on 100 parts by weight of the seed particle; and in an additional impregnation polymerization step of graft polymerizing the styrene monomer on the styrene-based resin, the addition amount of the styrene monomer is 50 to 700 parts by weight based on 100 parts by weight of the seed particle, and the content of the styrene monomer in the seed particle is held at 10% by weight or less.
Abstract:
Provided are: expandable acrylic resin bead and expanded acrylic resin bead, both having excellent moldability and capable of providing a foamed molded article that generates less soot during combustion and has a low decomposition gas generation speed; and a foamed molded article obtained through in-mold molding the expanded acrylic resin beads.The expandable acrylic resin bead is composed of an acrylic resin and a physical blowing agent impregnated therein. The acrylic resin contains a methacrylic ester component (A) and an acrylic ester component (B). The content of the component (A) is 85 to 99 mol % with respect to a total 100 mol % of the component (A) and the component (B). At least one of the component (A) and the component (B) contains a component having a polycyclic saturated hydrocarbon group. The glass transition temperature of the acrylic resin is 112 to 125° C.