GB521509A - Improvements in or relating to the manufacture of lake pigments - Google Patents

Abstract

521,509. Lakes. IMPERIAL CHEMICAL INDUSTRIES, Ltd. Nov. 17, 1938, No. 33472. Convention date, Nov. 17, 1937. [Class 2 (iii] In the' manufacture of insoluble rosinated calcium salts of acidic azo dyestuffs, especially Lithol Red, the lake producing reaction is carried out in the presence of a sulphuric acid ester (preferably in the form of an alkali metal salt) of an aliphatic alcoholic compound containing at least 8 carbon atoms in its alcoholic radicle, or a mixture of such compounds, the said ester or mixture of esters being preferably added, e.g., in an amount from 1-5 per cent. of the weight of the pigment, to the undeveloped azo dye subsequent to the completion of coupling but prior to the formation of the rosinated calcium salt. In an example, 2-naphthylamine-1-sulphonic acid is diazotized and coupled with #-naphthol, and the resulting dyestuff, in the form of its sodium salt, is boiled in aqueous solution with I Wood rosin which has been saponified with caustic soda, with the addition of lauryl sodium sulphate. B Wood rosin saponified with caustic soda is then added and the mixture is boiled with calcium chloride solution, producing a bluish red or maroon pigment. Alternatively, the lauryl sodium sulphate may be added to either dyestuff component prior to coupling, or to the suspension of the precipitated pigment prior to or during its development at elevated temperature. The rosins may be replaced by other grades, e.g., M gum rosin.