Abstract: The invention is an amine-oxide process for the production of a cellulose moulded body, wherein a suspension of cellulose in an aqueous tertiary amine-oxide is converted into a cellulose solution which is moulded and passed through an aqueous precipitation bath. A moulded body is obtained which, optionally after washing, is treated with a crosslinking agent. The cellulose solution contains a substance whereby the crosslinking agent may be activated. The process according to the invention allows the production of fibres having effectively controllable fibrillation properties.

Abstract: This invention relates to a process for the production of a cellulose molded body according to the amine-oxide process, which results in a molded body having reduced and effectively controllable fibrillation properties.

Abstract: There are disclosed flame-retardant, high temperature resistant polyimide fibers of the general formula ##STR1## wherein n is an integer larger than 1, A is a tetravalent aromatic group and R is at least one divalent aromatic group. These polyimide fibers have been heat-treated in the unstretched state and have a maximum shrinkage of 14% when heated to a temperature of 400.degree. C. These polyimide fibers are produced by initially spinning crude fibers from a solution of the appropriate polyimide in an aprotic organic solvent, preferably according to the dry-spinning method, which solution optionally contains additives. The crude fibers obtained are washed with water to remove the solvent. The washed crude fibers are dried to a moisture content of less than 5% by mass, are subjected to a heat treatment at a temperature of between 315.degree. C and 450.degree. C, are cooled and, if desired, are crimped and cut to staple fibers.

Abstract: In preparing polyimides by heating a solution of intramolecular tetracarboxylic acid dianhydrides and organic diisocyanates in an aprotic organic solvent in the presence of a polymerization accelerator, a catalytic amount of an alkali metal hydroxide is used as the polymerization accelerator. By this process, polyimides having high molecular weights are produced in a simple manner. The polyimides produced exhibit a high-temperature resistance.

Abstract: To produce flame-retardant thermostable new homopolyimides having structural units of the general formula ##STR1## by reacting 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride with an overall equimolar amount of 2,4- and/or 2,6-toluene diisocyanate, the reaction is carried out in the presence of a polymerization accelerator. The new homopolyimides have a glass transition point of at least 320.degree. C. and are processible to moulded articles exhibiting a similarly good structural strength as could hitherto be observed in mixed polyimides only. Furthermore, the new homopolyimides can be spun to fibres.

Abstract: To produce mixed polyimides having structural units of the general formulae ##STR1## wherein n is an integer larger than 1 and R represents a divalent aromatic residue, a solution of an intramolecular tetracarboxylic acid dianhydride mixture including 50 to 99% by mol benzophenone-3,3',4,4'-tetracraboxylic acid dianhydride and 50 to 1% by mol pyromellitic acid dianhydride is heated in a polar aprotic solvent and is admixed with an altogether equimolar amount of 2,4- and/or 2,6-toluenediisocyanate and/or methylenebis(phenylisocyanate). The mixed polyimides according to the invention are readily soluble in organic solvents, are flame-retardant and exhibit a good thermostability.