Abstract: The present invention relates to a process for obtaining PAI fibers by spinning PAI in solution and to the fibers thus obtained. They are obtained by dry or wet spinning into dimethylalkyleneurea followed by removal of the solvent and overdrawing at high temperature. The yarns and fibers obtained are produced from PAI based on tolylene or meta-phenylene diisocyanate, and on an aromatic acid anhydride and/or an aromatic dianhydride, and optionally on one or a number of diacid compounds. They exhibit an outstanding thermomechanical behavior and make it possible to gain access to very low linear densities.

Abstract: The present invention relates to a process for obtaining PAI fibres by spinning PAI in solution and to the fibres thus obtained. They are obtained by dry or wet spinning into dimethylalkyleneurea followed by removal of the solvent and overdrawing at high temperature. The yarns and fibres obtained are produced from PAI based on tolylene or meta-phenylene diisocyanate, and on an aromatic acid anhydride and/or an aromatic dianhydride, and optionally on one or a number of diacid compounds. They exhibit an outstanding thermomechanical behavior and make it possible to gain access to very low linear densities.

Abstract: Directly shapeable clear solutions of polyamide imides and a method for preparing same are provided. The solutions are obtained by polycondensation in .gamma.-butyrolactone (.gamma.BL) in substantially stoichiometric proportions between toluylene diisocyanate and an aromatic acid anhydride, and by dilution in (.gamma.BL) to give a solution allowing them to be processed at a later stage. Yarns and fibers made from said solutions are also described.

Abstract: The present invention relates to solutions which can be directly shaped in anhydrous dimethylalkyleneurea, based on a polyimide obtained from an aromatic dianhydride and an aromatic diisocyanate.It also relates to the process for the production of the above solutions, as well as to a process for spinning these solutions and to the yarns and fibres thus obtained.

Abstract: The present invention relates to a process for obtaining semiordered polyamides-imides.More particularly it consists in performing the polycondensation in two separate stages:1) reaction between a part of an aromatic diisocyanate and all of the trimellitic anhydride in the presence of dimethylalkyleneurea of pH.ltoreq.7 until the intermediate compound has dissolved,2) successive addition of one or more aromatic diacids and of the remainder of the diisocyanate in the dimethylalkyleneurea of pH.ltoreq.7 until the polyamide-imide obtained has dissolved completely.The semiordered polymers thus obtained have a Tg lower than the random polymers, and this makes them easier to convert.