Hoechst Aktiengesellschaft

Siegfried Schiessler

Ernst Spietschka

Erwin Dietz

Wolfgang Tronich

Manfred Urban

Helmold Von Plessen

Gustav Kapaun

Hans-Tobias Macholdt

Jorg Gitzel

Reinhard Zunker

Eberhard Fischer

Frank Alfter

Hans-Gerd Elinkmann

Novel isoindoline pigments of the formula (I) ##STR1## in which R.sup.1 is --CN and R.sup.2 is CN or a 5- to 7-membered hetero-cycle;

Isoindoline pigments

Biscationic acid amide and imide derivatives and processes for their

The conventional condensation of naphthalene-1,4,5,8-tetracarboxylic acid with 1,2-diaminobenzene gives the resulting naphthoylenebisbenzimidazole isomers together in the cis and trans form. It is desirable to shift the isomer ratio of the mixture obtained toward the desirable trans product and to reduce the amount of cis product obtained. It is also desirable to develop a process of preparation which optimizes the yield and improves the waste water situation. This object is achieved according to the invention by subjecting virtually stoichiometric amounts of the starting compounds to a precondensation at 60.degree. to 110.degree. C. in an aqueous medium and then completing the condensation in the aqueous medium in a second stage at 130.degree. to 180.degree. C.

Preparation of vat dyes and pigments of the perinone series

Pigment preparations consisting of organic pigments and basic additives of the general formula I

Pigment preparations

A process for the preparation of pigment preparations of the anthanthrone series, which comprises subjecting anthanthrone crude pigments to aqueous pearl milling in the presence of dispersants of the formulae

Process for the preparation of pigment preparations of the anthanthrone

The .alpha.-modification of cis-naphthoylenebis(benzimidazole) is unstable in many media and up to date has therefore only been used as a vat dye. However, according to the invention, the .alpha.-modification can readily be used for pigmenting in the mass polyolefins such as polyethylene, polypropylene or analogous copolymers. During pigmenting, the pigment which is prepared in a conventional manner, is stable in that modification and produces strong red dyeings.

Use of the alpha-modification of cis-naphthoylenebis(benzimidazole) for

Process for preparing 1,3,6,8-tetrabromopyrene by brominating pyrene in aqueous suspension with simultaneous reoxidation of the resulting hydrogen bromide to bromine by means of an oxidizing agent, which comprises reacting pyrene in a highly concentrated aqueous suspension having a pyrene-water weight ratio of 1:1.2 to 2 with bromine at temperatures of 40.degree. to 65.degree. C. with simultaneous reoxidation of the resulting hydrogen bromide to bromine using an oxidizing agent, completing the bromination by heating the reaction mixture to temperatures of 70.degree. to 130.degree. C., reducing excess bromine with a reducing agent to hydrogen bromide and subjecting the 1,3,6,8-tetrabromopyrene formed, preferably without intermediate isolation, to an alkaline aftertreatment at temperatures of 40.degree. to 100.degree. C. within the pH range 8.5 to 12.

Process for preparing 1,3,6,8-tetrabromopyrene

Process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid (called 'NTC' below) and its 1,8-monoanhydride in a high degree of purity, which comprises dissolving impure NTC or impure NTC-1,8-monoanhydride as the tetra-alkali metal salt of NTC in water in known manner, removing any insoluble impurities present, bringing the clarified solution to a pH value of 4-5 below 45.degree. C., separating off the di-alkali metal salt of NTC which thereby crystallizes out and converting the latter into free NTC or into free NTC-1,8-monoanhydride by treatment with a strong acid at 20.degree. to 100.degree. C.

Process for the preparation of naphthalene-1,4,5,8-tetracarboxylic acid

This invention relates to a process for the preparation of a very pure copper phthalocyanine pigment of the .alpha.-modification which comprises dissolving crude copper phthalocyanine in a 80 to 86% sulfuric acid isolating the copper phthalocyanine sulfate formed, hydrolizing the sulfate and grinding the copper phthalocyanine thus obtained in an aqueous-organic medium.

Process for preparing copper phthalocyanine pigments of the

N,N'-dimethyl-perylene-3,4,9,10-tetracarboxylic acid diimide is obtained as a valuable pigment of a pure red shade, by reacting perylene-3,4,9,10-tetracarboxylic acid anhydride at low temperatures with a dilute aqueous solution of at least the four-fold molar amount of methylamine. The so-obtained bis-ammonium salt of the bis-N-methyl amide is then heated without isolation to effect ring closure while splitting off two mols of water and two mols of methyl amine. The product can be used without any finish operation or can be after-treated to yield a pigment of an exceptionally high transparency or of a good hiding power.

Process for the preparation of a

Highly pure .alpha.-copper phthalocyanine is obtained when a product regenerated from .alpha.-copper phthalocyanine sulfate by hydrolysis with water is aftertreated in an aqueous medium containing a polar organic non-aromatic compound which is water-soluble or liquid. The aftertreated product has an especially high tinctorial strength, is very easily dispersible and has a very pure reddish-blue shade.

A process for the preparation of highly pure organic pigments which comprises converting organic dyestuffs having various degrees of purity into dyestuff salts capable of being isolated by means of suitable acids which dissolve the impurities contained in the dyestuff, separating them from the acid, recovering the dyestuffs in pure form from the dyestuff salts by the action of water and subjecting the isolated dyestuff in aqueous organic or aqueous-organic medium to a mechanical fine dispersion. By this process the dyestuff formed by the decomposition of the dyestuff sulfate is obtained in highly pure form and can extremely well be brought into a finely dispersed form so that it can be brought into pigment form already by short-time grinding. During the preparation and isolation of the dyestuff sulfate the sulfuric acid is obtained in such a high concentration that it can be regenerated in an economical manner and any ecological charge is avoided.

Process for the preparation of highly pure halogenated phthalocyanine

A process for the purification of optionally substituted crude phthalocyanines wherein a phthalocyanine is introduced into a 84 to 88 % sulfuric acid, the phthalocyanine sulfate formed is subjected to a crystal growth at 60 - 100.degree. C in an inert gas atmosphere, the phthalocyanine sulfate is isolated and the phthalocyanine is recovered by hydrolysis with water. By this process a phthalocyanine sulfate is formed in a coarse crystalline form which can easily be filtered and which furtheron can easily be processed to a valuable pigment of the .alpha.-modification.

Process for the purification of copper phthalocyanine

Contaminated sulfuric acid which may contain water, organic compounds and inorganic salts is converted to almost pure concentrated sulfuric acid by passing the acid through a Pauling plant and distilling the concentrated contaminated acid. Addition of nitric acid improves the decomposition of organic compounds and ammonium salts of the contaminated acid.

Process for the regeneration of sulfuric acid

Two-step-process for regenerating dilute sulfuric acid which may contain organic and inorganic impurities such as heavy metal salts. In the first step the impure acid is distilled in vacuo and in the second step concentrated in a Pauling apparatus.

Growing community of inventors

Bad Soden am Taunus, Germany

Siegfried Schiessler