Polyester copolymer having excellent strength, and product comprising the same

A polyester copolymer comprising

• 1) residues of dicarboxylic acid components comprising terephthalic acid;
• and
• 2) residues of diol components comprising isosorbide, cyclohexanedimethanol, and non-cyclic diol,
• wherein the copolymer comprises the isosorbide residues, cyclohexanedimethanol residues, and non-cyclic diol residues respectively in the content of 4 to 20 mol %, 65 to 85 mol %, and 11 to 31 mol %, based on the total number of moles of the diol component residues, and
• satisfies the following Mathematical Formula 1:
• 30<(X*Y)/(Z*W)<1000 [Mathematical Formula 1]
• in the Mathematical Formula 1,
• X is storage modulus (unit:
• MPa) of the polyester copolymer at 40° C.,
• Y is glass transition temperature (unit:
• ° C.) of the polyester copolymer,
• Z is melting point (unit:
• ° C.) of the polyester copolymer, and
• W is heat of fusion (unit:
• J/g) of the polyester copolymer.