GB675244A - Improvements in the production of coloured artificial thread-forming substances and of threads, foils, and the like therefrom - Google Patents

Abstract

Artificial thread-forming substances such as cellulose esters and ethers, viscose, superpolyamides, superpolyurethanes, polyesters, polyacrylonitrile, and polyvinyl chloride, are coloured by incorporating in them a pigment consisting of a water-insoluble ester of a leuco vat dyestuff of the anthraquinone series and a monocarboxylic acid having up to 7 carbon atoms. Leuco vat dyestuffs of dibenzanthrone, isodibenzanthrone, dibenzpyrenequinone, indanthrone, flavanthrone, or pyranthrone may be esterified with carboxylic acid anhydrides or halides which do not contain hydrophilic groups, e.g. acetyl anhydride or chloride, or benzoyl chloride. The esterification may be carried out with the dry leuco compounds in inert solvents or diluents, if desired in presence of acid binding agents, such as alkali acetates, pyridine, or quinoline, but the aqueous solution of an alkali leuco compound may be directly treated with the esterifying agent. The vat dyestuffs themselves may be reacted with the esterifying agents in the presence of metals having a reducing action such as zinc or aluminium. By carrying out the latter process in the presence of pyridine or quinoline, the reducing metal may be dispensed with in some cases, e.g. in the case of indanthrone. The carboxylic acid esters of leuco vat dyestuffs of the anthraquinone series may be added to spinning solutions or masses. The threads or fibres obtained are coloured in a manner fast to washing and light and stable to aqueous alkalies and acids. The colourings are vat stable so that when a mixed fabric of undyed cotton and viscose rayon or viscose staple fibre, which has been obtained from a spinning solution coloured in the described manner, is subsequently vat dyed, the viscose rayon retains its original colour. In an example, 2.5 parts by weight of the acetic acid ester of leucodibenzanthrone in a fine powdered form are added to 1,000 parts by weight of viscose containing 75 parts of cellulose. The viscose is then spun to form threads of a permanent deep red - brown shade. In another example, the acetic acid ester of the leuco compound of the vat dyestuff resulting from alcoholic potash fusion of bz-1-benzanthronyl-1-amino-anthraquinone is dispersed in a small proportion of a solution of cellulose acetate in presence of a reaction product of ethylene oxide and octyl alcohol. The pigment preparation is dried and rolled. It is then stirred into a cellulose acetate spinning solution. In a similar manner, a pigment preparation of the acetic acid ester of leuco-N,N1-dihydro-1,2,21,11-anthraquinoneazine (leucoindanthrone) may be obtained and may be incorporated in a spinning solution of polyacrylonitrile. Specifications 24604/08, [Class 2], 337,741, [Class 2 (iii)], and 506,803, are referred to.