PURPOSE: The titled inexpensive fibers, prepared by melt spinning a polyester consisting of four repeating components units in a specific proportion, having a uniform thikness, a high strength and modulus, and suitable for tire cords, etc.

CONSTITUTION: A polyester, obtained by polymerizing monomers, e.g. p-acetoxybenzoic acid, containing carboxylic acid, hydroxyl and acyloxy groups, and consisting of repeating four units of 40W60mol% units, expressed by formulaI, and derived from p-hydroxybenzoic acid, etc. 10W20mol% units, expressed by formula II, and derived from 1,2-bis(p-carboxy-phenoxy)ethane, etc. 10W20mol% units, expressed by formula III, and derived from terephthalic acid, etc. and 20W 30mol% units, expressed by formula IV, and derived from bisphenol A, etc. in the total amount of the four components ≥90mol%, and capable of forming an anisotropic melt is melt spun at 280W 350°C, and preferably heat-treated to give the aimed fibers.