Patent ID: 8609754

Claim:
A flame-retardant thermoplastic resin composition, comprising: a graft copolymer (A) comprising a rubbery polymer, a vinyl cyanide compound, and a vinyl compound copolymerizable with the vinyl cyanide compound, graft-polymerized together, a vinyl copolymer (B) comprising a vinyl cyanide compound and a vinyl compound copolymerizable with the vinyl cyanide compound, polymerized together, and a phosphoric flame retardant (C), wherein the vinyl copolymer (B) has a mass-average molecular weight of 90,000 to 160,000, an amount of the phosphoric flame retardant (C) is 5 to 20 parts by mass relative to 100 parts by mass of a sum of the graft copolymer (A) and the vinyl copolymer (B), a content CB 1 of vinyl cyanide units in an acetone-insoluble fraction of a mixture of the graft copolymer (A) and the vinyl copolymer (B) is 25.0 to 30.0% by mass relative to a total mass of the graft copolymer (A) and the vinyl copolymer (B), a content CB 2 of vinyl cyanide units in an acetone-soluble fraction of the mixture of the graft copolymer (A) and the vinyl copolymer (B) is 25.0 to 30.0% by mass relative to the total mass of the graft copolymer (A) and the vinyl copolymer (B), and an absolute value |CB 1 −CB 2 | of a difference between CB 1 and CB 2 is 0.1 to 2.5% by mass relative to the total mass of the graft copolymer (A) and the vinyl copolymer (B).