by the reaction of ethylene glycol and terephthalic acid or its derivatives fiber forms which can be produced from the polymer are filaments staple and tow polymerization is accomplished using an ester of dihydric alcohol and terephthalic acid traditionally polyester filaments are produced by forcing the molten polymer at a temperature of about 290 u00b0 c through spinneret holes followed by air cooling combining the single fiber into yarns and drawing or stretching the yarns several times their original length to orient the long chain molecules and gives the fibers and consequently the yarn strength in one process in the prior art for continuous copolymerization wherein for example terephthalate acid and ethylene glycol are fed into a polymerizer of a type well known in the art and as polymer is produced the solid product is moved to a chipper then moved to a melting stage next to an extruder and extruded through a spinneret die for melt spinning to produce the fiber in the continuous process described above in one preferred aspect the isophthalic acid ipa and glycol are combined in a reactor with terephthalic acid with the ipa being held at the selected level to provide the ipa pet polymer of the invention in a preferred embodiment and a best mode the mole percentage of ipa is held in the range of 1 8 2 0 which yields a level of 1 4 1 8 ipa by weight the precisely controlled copolymer is then chipped melted and extruded to form fibers this copolymer is designated as a virgin resin in one example fiber made from one of such resins in designated p 472 which has about 1 7 ipa this fiber was made into.