Polyester fiber and method for the production thereof
 A polyester fiber having a tenacity of at least 4.0 g/d is formed from a copolyester having a degree of polymerization of from 80 to 100 of which copolyester 1.0 to 2.0 mol % of its acid component has a metal sulfoisophthalic group and 0.5 to 1.9 weight % of which copolyester is provided by a glycol component provided by glycol having a molecular weight of from 400 to 6000. The polyester fiber is readily dyed with basic dyes. The polyester fiber can be prepared by spinning the copolyester at a shear rate of.ltoreq.10.sup.4 sec.sup.-1, a spinning draft ratio of .ltoreq.250, a back pressure of the spinneret of.gtoreq.40 kg/cm.sup.2 and a shear stress of .ltoreq.(Q+0.7).times.10.sup.7 dyne/cm.sup.2, where Q is the mass output rate per single hole (g/min). 
Toray Industries, Inc.
C D
C08G D01F
inventional inventional
Takehiko Keizo Tadayuki
Miyoshi Sano Matsumoto