Abstract: Described is a process for producing linear polyesters of improved whiteness and reduced yellowness by esterification of aromatic dicarboxylic acids or transesterification of their bis(lower alkyl) esters with or without aliphatic dicarboxylic acids with diols to form bisdiol esters and their oligomers and further condensation of these preproducts to spinnable polyesters, which comprises adding to the esterification, transesterification or polycondensation hatch from 0.5 to 15% by weight of phosphorus-containing modifiers and conducting the polycondensation initially in the melt to an IV from 0.4 to 0.55 dl/g and thereafter in solid phase to an IV from 0.62 to 0.72, the indicated IV values being measured at 25.degree. C. in dichloroacetic acid. The phosphorus-containing modifiers used preferably have the formula V or VI ##STR1## where R.sup.6 is alkylene or polymethylene of 2 to 6 carbon atoms or phenyl and R.sup.5 is alkyl of 1 to 6 carbon atoms, aryl or aralkyl, in the cocondensed state.

Abstract: The present invention relates to a process and a device for forming a transfer tail on winding bobbins of high-speed winding frames by use of an auxiliary thread guide which is swivelled over a predetermined track at a predetermined speed and, subsequently, passes the yarn over to the reciprocating thread guide. It is possible to obtain a transfer tail of adjustable and reproducible length even at high winding speeds.