| abstract |
(57) [Summary] [Structure] A polyester obtained by copolymerizing an isophthalic acid component containing a metal sulfonate group in an amount of 1 mol% or more and a specific non-reactive phosphorus compound consisting of a phosphonic acid type anion and a phosphonium cation in an amount of 0.01 to Modified polyester blended with 0.3% by weight. [Effect] The thickening phenomenon is suppressed, the degree of polymerization can be sufficiently increased, and the polyester can be melt-molded into fibers, films, etc. without impairing the excellent mechanical properties. For example, it can be used as a high-strength cationic dye-dyeable polyester fiber or an alkali-soluble component of a splittable conjugate fiber, and its industrial significance is extremely large. |