Patent ID: 6258916
Filing Date: 2001-07-10
Classification: D01F

Abstract:
A process for obtaining yarns and fibres based on polyamide-imide, which have an improved thermomechanical behavior, comprising:a) forming a reaction mixture of toluylene diisocyanate, aromatic anhydride and an aromatic diacid with recycled dimethylalkyleneurea (DMAU), heating the reaction mixture, and after heating adding dimethylalkyleneurea (DMAU) to form a spinable solution of a polymer,b) spinning the spinable solution of the polymer, the polymer having an inherent viscosity .gtoreq.0.8 dl/g, in dimethylalkyleneurea (DMAU) into an aqueous coagulating medium containing 30 to 80% by weight of dimethlalkyleneurea (DMAU) and from 20 to 70% by weight of water to form filaments, the polymer consisting essentially of:amide-imide chain sequences (A) of formula: ##STR7##amide chain sequences (C) of formula:--NH--Ar.sub.1 --NH--CO--R--CO--imide chain sequences (D) of formula: ##STR8##in which:Ar.sub.1 denotes a tolylene divalent aromatic radical,Ar.sub.2 denotes a trivalent aromatic radical,Ar.sub.3 denotes a tetravalent aromatic radical,R denotes a divalent aromatic radical,the chain sequences (A) being present in a proportion of 0 to 100%,the chain sequences (C) being present in a proportion of 0 to <100%,the chain sequences (D) being present in a proportion of 0 to 100%,the sum of the chain sequences (A)+(C)+(D) being equal to 100%, wherein the proportion of sequence (D) is 20 to 100% when sequence (A) is absentc) drawing the filaments obtained to a ratio of at least 2.times.,d) removing the residual solvent from the filaments with water by washing, distilling the residual solvent into a recycle dimethylalkyleneurea stream and a water stream, recycling at least a portion of the recycle dimethylalkyleneurea stream to the step for forming the reaction mixture, and drying the filaments, ande) overdrawing the filaments at a temperature of at least 250.degree. C., to a ratio of at least 2.times., with the result that the total draw ratio is at least 5.times..