NORMAL PRESSURE CATION DYEABLE POLYESTER AND FIBER

摘要

Disclosed is a normal pressure cation dyeable polyester which can be cation-dyed under normal pressure and has high strength. Specifically disclosed is a normal pressure cation dyeable polyester, which is a polyester copolymer having an ethylene terephthalate as the main repeating unit, wherein a sulfoisophthalic acid metal salt (A) and a compound (B) such as a sulfoisophthalic acid phosphonium salt are contained in an acid component constituting the polyester in such amounts that both the two mathematical formulae are fulfilled. Preferably, the polyester copolymer has a glass transition temperature of 70 to 85°C and an intrinsic viscosity of 0.55 to 1.00 dL/g. Also disclosed is a polyester fiber produced by conducting the melt spinning of the polyester copolymer.