Rubber modified vinyl-based graft copolymer, and thermoplastic resin composition containing same

A thermoplastic resin composition comprising:

• a rubber-modified vinyl-based graft copolymer having a core-shell structure, in which a shell is formed by graft polymerization of a monomer mixture to a core comprising a rubber polymer,
• wherein the monomer mixture comprises about 30 wt % to about 80 wt % of an aromatic monomer comprising an alpha position-substituted aromatic vinyl-based monomer represented by Formula 1 and an aromatic vinyl-based monomer other than the alpha position-substituted aromatic vinyl-based monomer, wherein the alpha position-substituted aromatic vinyl-based monomer and the aromatic vinyl-based monomer other than the alpha position-substituted aromatic vinyl-based monomer are present in a weight ratio of about 0.5:1 to about 5:1;
• about 10 wt % to about 30 wt % of a vinyl cyanide-based monomer;
• and about 10 wt % to about 30 wt % of a maleimide-based monomer:
• wherein R1 is a C1 to C5 alkyl group and Ar is a substituted or unsubstituted C6 to C20 aryl group or a substituted or unsubstituted C7 to C20 alkylaryl group;
• and
• an aromatic vinyl-based copolymer resin,
• wherein the thermoplastic resin composition has an Izod impact strength of about 20 kgf·cm/cm to about 40 kgf·cm/cm, as measured on a ¼″ thick specimen in accordance with ASTM D256, a melt-flow index of about 3 g/10 min to about 5 g/10 min, as measured at 200° C. under a load of 10 kg in accordance with ISO 1133, and a Vicat softening temperature (VST) of about 110° C. to about 130° C., as measured under a load of 5 kg in accordance with ASTM D1525.