Bayer Aktiengesellschaft

Harald Gleinig

Karl Linhart

Kurt Breig

Roderich Raue

Gunther Boehmke

Bernd Berger-Lohr

Reinhold Hornle

Hans-Peter Kuhlthau

Klaus Schubert

Hans-Heinz Molls

Jochen Koll

Klaus-Friedrich Lehment

Dorde Jovcic

Jurgen Lahrs

Claus Gosling

Dieter Pawellek

Reiner Skerhut

Gottfried Dick

Friedrich Kunert

Concentrated stable solutions of cationic azo dyestuffs of the formula ##STR1## wherein A denotes the radical of an aromatic-carbocyclic or aromatic-heterocyclic diazo component,

Process for the preparation of solutions of cationic azo dyestuffs

Concentrated, stable solutions, with a low salt content, of cationic azo dyestuffs of the formula ##STR1## wherein A denotes the radical of an aromatic-carbocyclic or aromatic heterocyclic diazo component,

Preparing concentrated azo dye solutions using nitrite salt as both

Leather dyeing agents, which can be obtained by concentrating, by means of a membrane separation process, the mother liquors, which are produced in the salting-out process in the preparation of organic dyestuffs which are water-soluble or which contain groups imparting water-solubility, the mother liquors having an extinction in the absorption maximum which is .gtoreq.500, with a layer thickness of 10 cm, and by drying the concentrate, if appropriate.

Leather dyeing agents and their preparation: membrame separation of dye

To prepare concentrated solutions of cationic polyazo dyestuffs of the formula ##STR1## in which R represents hydrogen or methyl and

Process for the preparation of solutions of cationic polyazo dyestuffs

Polynitrated diaryl compounds of the formula given in the description are reduced with 1-2 mols of sulphides, or compounds which donate sulphide ions, per mol of nitro group in the presence of 0.5-10 mols of ammonia per mol of starting compound at 30.degree.-110.degree. C. to give nitroamino-diaryl compounds, for example 4,4'-dinitro-dibenzyl-2,2'-disulphonic acid is reduced to 4-nitro-4'-amino-stilbene-2,2'-disulphonic acid.

Process for the partial reduction of polynitrated diaryl compounds

Pulverulent preparations with a low dust content, in particular dyestuff powders, are obtained when the customary dustproofing agents are not added before the drying process and also are not sprayed directly onto the product to be dustproofed, but are allowed to act on the pulverulent product in the form of an aerosol. The average particle size of the aerosol is less than 10.mu..

Process for the manufacture of preparations with a low dust content

Cationic dyestuffs of the general formula ##STR1## wherein R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 - to C.sub.4 -alkoxy, nitro or halogen,

Process for the preparation of cationic dyestuffs

Cationic dyestuffs of the general formula ##STR1## wherein R.sub.1 represents hydrogen, C.sub.1 -C.sub.4 -alkyl, C.sub.1 - to C.sub.4 - alkoxy, nitro or halogen,

The preparation of hydrazone dyestuffs of the formula ##STR1## wherein R.sup.13 and R.sup.14 independently of one another represent hydrogen, C.sub.1 -- to C.sub.4 --alkyl, C.sub.1-- to C.sub.4-- alkoxy or halogen, in particular chlorine or bromine, and

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Odenthal, Germany

Harald Gleinig