POLYESTER RESIN AND POLYESTER RESIN COMPOSITION USING SAME

PROBLEM TO BE SOLVED: To provide polyester resin compositions low in gas permeability and high in glass transition point. SOLUTION: Polyester resin compositions comprise 5-100 pts.wt. polyester resin composed of repeating units represented by the formula: -CO-R1-CO-O-R2-O- (wherein -CO-R1-CO- is composed of 10-90 mol% 4,4'-sulfonebenzoic acid residue, 90-10 mol% isophthalic acid residue, and 10-0 mol% other diol residues; and -O-R2-O- is composed of 5-100 mol% ethylene glycol residue and 95-0 mol% other diol residues) and having an intrinsic viscosity [η], measured at 25 deg.C in a mixed solution of tetrachloroethane and phenol at a weight ratio of 1:1, of not less than 0.3 dl/g and a glass transition temperature, measured by the DSC, of not lower than 70 deg.C and 100 pts.wt. polyethylene terephthalate resin.