Abstract: A process for producing fibers or films by the steps of:a) preparing an aromatic polyamide by polycondensation of dicarbonyl dihalides or mixtures thereof with at least two diamines in N-alkyllactams as a solvent, the polycondensation being of at least 90 mol %, based on the total amount of dicarbonyl dihalides in the reaction mixture, of compounds of the formula I or mixtures of such compoundsHal--OC--Ar.sup.1 --CO--Hal (I)with at least 90 mol%, based on the total amount of diamines in the reaction mixture, of compounds of the formula II and optionally III or mixtures of such compoundsH.sub.2 N--Ar.sup.2 --NH.sub.2 (II), H.sub.2 N--Ar.sup.3 --NH.sub.2 (III)where Ar.sup.1, Ar.sup.2 and Ar.sup.

Abstract: A process for maintaining or increasing the tensile strength of fibers of aromatic copolyamides which are formed from a major portion of para-monomers and are soluble in organic aprotic and polar solvents. The process involves storing the fibers in alkaline media after production by wet or dry spinning processes, after treatment of the dry or wet spun fibers, and storing the fibers in an aqueous environment having a pH of at least 10. The tensile strength of the fibers is retained or increased.

Abstract: A macroporous, asymmetric, hydrophilic membrane is described, which contains a copolyamide which has the following recurring structural units:(A) --OC--Ar.sup.1 --CO--and also three different structural units of those mentioned below:(B) --NH--Ar.sup.2 --NH--(C) --NH--Ar.sup.3 --NH--(D, E, F) --NH--Ar.sup.2 --Z--Ar.sup.3 --NH--where the symbols Ar.sup.1, Ar.sup.2, Ar.sup.3 and Z have the following meaning:Ar.sup.1 is a 1,4-phenylene or another bivalent C.sub.6 -C.sub.r aromatic or heteroaromatic radical in which radical the bonds are in para or comparable coaxial or antiparallel position, Ar.sup.2 and Ar.sup.3 are 1, 2 phenylene, 1,3-phenylene or 1, 4-phenylene radicals and Z is one of the following bivalent radicals --O--, --CH.sub.2 --, --C(CH.sub.3).sub.2, --C(CF.sub.3).sub.2 --, --SO.sub.2 --, --NHCO--, or --O--Ar.sup.2 --O--.

Abstract: Reprocessing mixtures which contain organic solvents and constituents of low volatility and may contain water: includes introducing the mixture into a concentration apparatus of a solvent recovery system, concentrating the mixture in the concentration apparatus by evaporating off a portion of a readily volatile fraction and feeding this readily volatile fraction to a separation column. A portion of the concentrated mixture from the concentration apparatus is conducted away into a separation apparatus where the constituents of low volatility are separated off from the concentrated mixture and ejected from the solvent recovery system. The concentrated mixture is conducted away, freed from the constituents of low volatility, from the separation apparatus.

Abstract: Fiber materials from synthetic polymers, wherein the synthetic polymer is a homogeneous alloy consisting essentially of.alpha.) poly-N-vinylpyrrolidone (PVP) and.beta.) at least one homo- or copolyaramide having at least one recurring structural unit of the formula (I) ##STR1## where E.sup.1 and E.sup.2 are identical or different and each is a divalent aromatic or aliphatic radical.

Abstract: An aromatic copolyamide which is soluble in organic copolyamide solvents and contains recurring structural units of formulae I, II and III ##STR1## in which at least some of the radicals R.sup.1 are a group of formula --OC--R.sup.2 --CO--, in which R.sup.2 is a divalent aromatic radical having valence bonds in the para-position or in a comparable coaxial of parallel position to one another, and in which the remaining radicals are as defined.

Abstract: There are described aromatic copolyamides which are soluble in organic polyamide solvents and which consist essentially of recurring structural units of the formulae Ia, Ib and Ic on the one hand and Ia, Ib and Ie on the other[--OC--R.sup.1 --CO--NH--R.sup.2 --NH--] (Ia), [--OC--R.sup.1 --CO--NH--R.sup.3 --NH--] (Ib),[--OC--R.sup.1 --CO--NH--R.sup.4 --NH--] (Ic), [--OC--R.sup.1 --CO--NH--R.sup.7 --NH--] (Ie),where R.sup.1 and R.sup.7 are divalent aromatic radicals whose valence bonds are in the para or a comparable coaxial or parallel position relative to one another, R.sup.2 is a radical of the formula III ##STR1## and R.sup.3 and R.sup.4 are radicals of the formula IV ##STR2## where Z is --O--, --S--, --CO--, --SO.sub.2 --, C.sub.1 -C.sub.10 -alkylene or --O--R.sup.1 --O-- and R.sup.6 is in each case hydrogen or an inert substituent.The mole fractions of the individual structural features in the copolyamides are defined within selected limits.

Abstract: Aromatic copolyamides are described which are soluble in organic polyamide solvents and which essentially consist of the recurring structural units of the formulae Ia, Ib and Ic ##STR1## wherein R.sup.1 and R.sup.4 are divalent aromatic radicals, the valency bonds of which are in the para position or in a comparable coaxial or parallel position relative to one another, R.sup.2 is a radical of the formula III ##STR2## and R.sup.3 is a radical of the formula IV ##STR3## The mole fractions of the individual structural features in the copolyamides are fixed within selected limits. Fibers composed of the copolyamides claimed are distinguished by a high stretchability.

Abstract: Aromatic copolyamides are described which are soluble in organic polyamide solvents and contain at least 95 mol % of repeating structural units of the formulae ##STR1## and up to 5 mol % of structural units E and/or F containing m-bonds and being derived from aromatic dicarboxylic acids (E') and/or aromatic diamines (F'), the sums of the molar proportions of structural units A+E and the molar proportions of structural units B+C+D+F being essentially the same. In these formulae, --Ar-- is a divalent aromatic radical whose valence bonds are in the para or comparable coaxial or parallel position, --R is hydrogen, lower alkyl radicals, lower alkoxy radicals or halogen, and R' is a direct bond, a polymethylene chain of 2 to 6 carbon atoms, --O--, --S--, --CO-- or --SO.sub.2 --, or a group of the formula --O--Ar'--O--, in which Ar' has the same meanings as Ar.

Abstract: The invention relates to a process for separating N-methyl-2-pyrrolidone (NMP) from aqueous solutions which are obtained in industry, inter alia, in the production of heat-resistance polymers such as polyamides and polyimides.According to the invention, the extractants used are phenols which are sparingly soluble in water, are aliphatically monosubstituted and/or polysubstituted in the nucleus and have 4 to 16 carbon atoms in the straight-chain or branched, saturated or unsaturated aliphatic radical and have a boiling point which is preferably at least 20.degree.-25.degree. C. above the boiling point of NMP. If necessary, an inert, viscosity-reducing diluent is added.