Core-shell copolymer, method for preparing the same and thermoplastic resin composition including the same

A core-shell copolymer, comprising:

• a core;
• and
• a shell surrounding the core,
• wherein the core includes a conjugated diene-based monomer-derived repeating unit and a phosphate-based cross-linking agent-derived cross-linking part, the phosphate-based cross-linking agent represented by the following Formula 1,
• wherein the shell includes a first alkyl (meth)acrylate monomer-derived repeating unit, a second alkyl (meth)acrylate monomer-derived repeating unit, and a sulfonate-based ionic monomer-derived repeating unit, the sulfonate-based ionic monomer represented by the following Formula 2,
• wherein the core is 68 parts by weight to 92 parts by weight and the shell is 8 parts by weight to 32 parts by weight, based on a total of 100 parts by weight of the core-shell copolymer,
• wherein the core has a swell index of 2.7 to 10.9,
• wherein the shell includes 1 weight percent (wt %) to 16 wt % of the sulfonate-based ionic monomer-derived repeating unit, based on the total weight of the shell, and
• wherein the shell has a weight average molecular weight of 105,000 g/mol to 645,000 g/mol:
• wherein
• R1 and R2 are each independently an alkylene group having 1 to 30 carbon atoms, and
• R3 and R4 are each independently hydrogen or a methyl group, and
• wherein
• R5 is a single bond or an alkylene group having 1 to 30 carbon atoms,
• R6 is hydrogen or a methyl group,
• M is potassium (K), sodium (Na), or hydrogen, and
• n is 0 or 1,
• wherein the swell index of the core is measured by immersing the core into toluene for 24 hours, and obtained by the following equation:
• swell index=weight of the core swollen in toluene/weight of the core after drying the swollen core to remove toluene.