| abstract |
An undrawn polyester yarn comprising 0.2 to 10% by weight of a polymer having a recurring unit structure represented by the following formula (1): <IMAGE> (1) wherein R1 and R2 stand for substituents consisting of optional atoms selected from C, H, N, O, S, P and halogen atoms, with the proviso that the sum of the molecular weights of R1 and R2 is equal to or more than 40, and n is a positive integer, and having a molecular weight equal to or more than 1000, the elongation increase ratio (I) of the undrawn polyester yarn, represented by the following formula (2), being equal to or more than 8%: <IMAGE> (2) wherein ELb stands for the residual elongation (%) of the undrawn yarn and ELo stands for the residual elongation (%) of a corresponding undrawn polyester yarn substantially free of the polymer represented by the formula (1). |