Abstract: Titanocenes of the formula I ##STR1## in which R.sup.1 are cyclopentadienyl.sup..crclbar. groups and R.sup.2 and R.sup.3 are aromatic radicals which are substituted in both ortho-positions by fluorine and, in addition, are substituted by an acyloxy group are suitable as photoinitiators for the photopolymerization of ethylenically unsaturated compounds.

Abstract: Titanocenes of the formula I ##STR1## in which R.sup.1 are cyclopentadienyl.sup..crclbar. groups and R.sup.2 and R.sup.3 are aromatic radicals which are substituted in both ortho-positions by fluorine and, in addition, are substituted by an acyloxy group are suitable as photoinitiators for the photopolymerization of ethylenically unsaturated compounds.

Abstract: Titanocenes of the formula I ##STR1## in which R.sup.1 are cyclopentadienyl.sup..crclbar. groups and R.sup.2 and R.sup.3 are aromatic radicals which are substituted in both ortho-positions by fluorine and, in addition, are substituted by a pyrrylalkyl group, amidoalkyl group or imidoalkyl group, are suitable as photoinitiators for the photopolymerization of ethylenically unsaturated compounds.

Abstract: Titanocenes with, for example, .pi.-cyclopentadienyl ligands in which one or two carbo- or heterocyclic aromatic rings are bonded to the titanium, the aromatic rings being substituted by fluorine in at least one of the two ortho-positions relative to the metal-carbon bond and being substituted by at least one free or etherified or esterified polyoxaalkylene radical, are suitable as photoinitiators for the photopolymerization of ethylenically unsaturated substrates.

Abstract: Titanocenes containing two 5-membered cyclodienyl gropus, for example cyclopentadienyl, and one or two 6-membered carbocyclic or 5- or 6-membered heterocyclic aromatic rings which are substituted by a fluorine atom in at least one of the two ortho-positions to the titanium-carbon bond and contain, as further substituents, a substituted amino radical, are suitable as photoinitiators for radiation-induced polymerization of ethylenically unsaturated compounds.

Abstract: Titanocenes with, for example, .pi.-cyclopentadienyl ligands in which one or two carbo- or heterocyclic aromatic rings are bonded to the titanium, the aromatic rings being substituted by fluorine in at least one of the two ortho-positions relative to the matal-carbon bond and being substituted by at least one free or etherified or esterified polyoxaalkylene radical, are suitable as photoinitiators for the photopolymerization of ethylenically unsaturated substrates.

Abstract: Titanocenes with, for example, .pi.-cyclopentadienyl ligands in which one or two carbo- or heterocyclic aromatic rings are bonded to the titanium, the aromatic rings being substituted by fluorine in at least one of the two ortho-positions relative to the metal-carbon bond and being substituted by at least one free or etherified or esterified polyoxaalkylene radical, are suitable as photoinitiators for the photopolymerization of ethylenically unsaturated substrates.

Abstract: A flexible, printed circuit with excellent adhesion of the printed tracks, which is obtained by coating one side of a metal foil without an intermediate layer with a polymer consisting of a polyamide, polyimide or polyamide-imide containing siloxane groups, which is obtainable by crosslinking a silicon-modified polyamide prepolymer, polyamide-acid prepolymer or polyamide-amido-acid prepolymer of the formula I, heating the coated metal foil in the temperature range from 50.degree. to 300.degree. C. till a tack-free coating is obtained, exposing the opposite side of the coated metal foil, which side is provided with a photolacquer, through a photo mask, and developing the exposed metal foil.

Abstract: Flexible base materials consisting of a metal foil and a film, firmly adhering thereto without an interlayer, of a polyamide/polyimide block copolymer of the formula I, or of a polyamide/polyimide copolymer prepared from a polyamide acid block of the formula IVa or Va and a dicarboxylic acid dichloride of the formula XI and a diamine of the formula XII.The individual symbols are defined in claim 1.The base materials according to the invention are suitable for the preparation of flexible printed circuits.

Abstract: Flexible base materials consisting of a metal foil and a film of a polyamide, polyamide-imide and/or polyimide, firmly adhering thereto without an intermediate layer, the film being obtained by heating a polyamide, polyamide-amidoacid and/or polyamide-acid containing the structural units of the formulae I and II.The individual symbols are as defined in claim 1.The base materials according to the invention are useful for the production of flexible printed circuits.

Abstract: A novel improved process for separating mixtures of 3- and 4-nitrophthalic acid is described. The said process comprises treating a mixture of 3- and 4-nitrophthalic acid, which mixture is free from inorganic acid residues, in an aqueous-organic medium containing 1-20 percent by volume of water, at a temperature of between 20.degree. and 100.degree. C., stepwise with a base capable of forming salts of 3- and 4-nitrophthalic acid, which salts are essentially insoluble in the reaction medium, the treatment being carried out by adding base until a pH value of about 2.8 is obtained, separating the precipitating product consisting mainly of a 3-nitrophthalic acid mono-salt, subsequently precipitating, by the addition of further base, a product consisting principally of a 4-nitrophthalic acid salt, and finally converting the resulting nitrophthalic acid salts separately into the corresponding free acids, and optionally purifying these.