| CPC C08F 279/02 (2013.01) [C08F 2/22 (2013.01); C08L 25/12 (2013.01); C08L 2203/20 (2013.01); C08L 2203/30 (2013.01)] | 17 Claims |

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1. A styrene-based thermoplastic resin composition comprising:
(A) a graft copolymer obtained by graft-polymerizing, in the presence of a conjugated-diene-based rubber, (a) a monomer mixture containing at least an aromatic vinyl-based monomer and an acrylic acid ester-based monomer; and
(B) a vinyl-based copolymer obtained by polymerizing (b) a monomer mixture containing at least an aromatic vinyl-based monomer and a vinyl cyanide-based monomer and containing substantially no acrylic acid ester-based monomer,
wherein said styrene-based thermoplastic resin composition contains a component insoluble in acetone,
the acetone-insoluble component contains a structural unit derived from said acrylic acid ester-based monomer,
a content ratio (d1) of said structural unit is 1 to 7 mass % with respect to 100 mass % of said acetone-insoluble component; and
a ratio (d2/d3) is 4 to 75 between the following:
the content ratio (d2, mass %) of said structural unit derived from said acrylic acid ester-based monomer in said acetone-insoluble component, with respect to 100 mass % of the mass obtained by subtracting the mass corresponding to said conjugated-diene-based rubber contained in the insoluble component from the mass of said insoluble component; and
the content ratio (d3, mass %) of a structural unit derived from said acrylic acid ester-based monomer in the acetone-soluble component, with respect to 100 mass % of the soluble component in said styrene-based thermoplastic resin composition.
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