GB462548A - Improvements in or relating to the manufacture of dyestuffs of the indanthrone series - Google Patents

Abstract

Indanthrone dyestuffs are manufactured in a fine state of subdivision by precipitating them from a vat at a temperature below 35 DEG C., preferably between 15 and 35 DEG C., in the presence of a vatting assistant comprising a water-soluble condensation product of epichlorhydrin or dichlorhydrin with ammonia or an alipatic primary amine. The precipitation of the dyestuff in the leuco or oxidized form is preferably brought about slowly with uniform agitation, e.g. by the gradual addition of salt in solid form or in solution followed by oxidation of the leuco compound by air or oxidizing agents, either in the original suspension or after filtering it off and resuspending it in water. The dyestuffs may also be precipitated by cooling below 5 DEG C. The process is applicable to the treatment of crude dyestuffs, whereby purification is simultaneously effected. In examples: (1) 3 : 3<1> - dibromo - N - dihydro-1 : 2 : 2<1> - 1<1>-anthraquinoneazine is vatted by the action of sodium hydrosulphite with the addition of the condensation product of dichlorhydrin with ammonia, and the vat is stirred until the dyestuff is precipitated, after which complete oxidation is ensured by air-blowing; (2) 3 : 3<1> - dichloro - N - dihydro - 1 : 2 : 2<1> : 1<1>-anthraquinoneazine is vatted by the action of sodium hydrosulphite with the addition of the condensation product of epichlorhydrin with monomethylamine, and the leuco compound is precipitated by adding salt, and oxidized with the sodium salt of m-nitrobenzenesulphonic acid; (3) the monobromomonochloroindanthrone obtained according to example 15 of Specification 357,536 is vatted by the action of sodium hydrosulphite with the addition of the condensation product of epichlorhydrin with ethylenediamine, and the leuco compound is salted out and oxidized by air; (4) the indanthrone dyestuff containing bromine and chlorine described in example 4 of Specification 357,536 is vatted as in (1) and the leuco compound is salted out and air-blown; (5) trichloroindanthrone (prepared by treating indanthrone in nitrobenzene suspension with sulphuryl chloride) is dissolved in concentrated sulphuric acid, precipitated by pouring the solution into water and vatted by the action of sodium hydrosulphite, after which the condensation product of epichlorhydrin with ammonia is added and the leuco compound is salted out, filtered off, suspended in water and oxidized by air. The products are suitable for dyeing by the pigment pad reduction method, for printing, and for the preparation of redispersible dyestuff powders. Specification 438,523 also is referred to.