INFUSIBLE SYNTHETIC FIBRES AND PROCESS FOR PRODUCING THE SAME

The invention relates to infusible synthetic fibres having a chemical structure of the polymer cyclised at the macromolecular level, said structure containing aromatic groups formed by oxygen bonds and having an oxygen limit index of over 45 %, a filament length density ranging from 0.9 to 1.33 dtex, a filament tenacity of minimum 2 cN/ dtex, a tear strength of 0.3 to 0.75 GPa, a breaking elongation of 13% to 18 % and a content of mass oxygen of 11 % to 17 %, preferably of 13 to 15 %. The process for producing infusible fibres consists in treating the polyacrylonitrile cable with a content of acrylonitrile of minimum 95 ... 98% in an air environment heated in three temperature steps, with controlled stretching. A controlled and uniform filament length density is ensured, the fibre can be worked as textile, it does not flow, melt, or burn in contact with a flame and extinguishes after removing the heat source without eliminating noxious chemical compounds, does not shrink and does not creep at temperatures of over 250 degree C. Inventia se refera la fibre sintetice ignifuge, care au o structura chimica a polimerului ciclizata la nivel macromolecular, care contine grupari aromatice formate prin legaturi de oxigen si are un indice limita de oxigen de peste 45%, o densitate de lungime pe filament de 0,9...1,33 dtex, o tenacitate pe filament de minimum 2 cN/dtex, o rezistenta la rupere pe filament de 0,3...0,75 GPa, o alungire la rupere 13...18% si un continut de oxigen masic de 11...17%, de preferinta 13...15%. Procedeul de obtinere a fibrelor ignifuge consta in tratarea cablului poliacrilonitrilic cu un continut de acrilonitril de minimum 95...98%, in mediu de aer, incalzit in trei trepte de temperatura, cu etirari controlate. Se asigura o densitate de lungime pe filament controlata si uniforma, fibra poate fi prelucrata textil, in contact cu flacara nu curge si nu se topeste, nu arde si se stinge dupa indepartarea sursei de caldura fara a elimina compusii chimici sub forma de noxe si nu se contracta si nu se alungeste la temperaturi de pana la 250 degree C.