GB563181A - Improvements in the dyeing of cellulose acetate textile materials - Google Patents

Abstract

Cellulose acetate textile material is subjected to the action of a 23-40 per cent aqueous solution of caustic alkali, the temperature and duration of the treatment being such that the acetyl value is not reduced by more than 7, and is then washed and thereafter is dyed with a direct dyeing dye for cellulose acetate. Materials which have been pre-treated with the caustic alkali are more deeply dyed by the cellulose acetate dyes, e.g. 1 : 4-diamino-anthraquinones, and the dyeings are more resistant to fading when exposed to an acid atmosphere, e.g. one containing combustion products of coal gas. The caustic alkali may be sodium or potassium hydroxide. The treatment is useful in the dyeing of yarns of high denier and high filament count. The action of the alkaline agent may be stopped by washing with water and neutralizing with acid. In an example, a cellulose acetate fabric is subjected while free from tension to the action of a 33 per cent solution of caustic soda for 30 seconds. The fabric is washed and then dyed in a bath containing Celliton Blue AF, xylene and turkey-red oil mixture, and water at 80 DEG C. In another example, cellulose acetate fabric is treated with a 37.5 per cent caustic potash solution for 60 seconds and then after washing, it is dyed with a solution containing S.R.A. BLUE IV, xylene and turkey-red oil mixture, and water at 80 DEG C. The Specification as open to inspection under Sect. 91 comprises also the use of other alkaline reagents for the pre-treatment, e.g. sodium silicate, barium hydroxide, sodium phosphate, methylamine, propylamine, and tri-ethanolamine, and the treatment is described as applicable to cellulose ester materials in general and to films. This subject-matter does not appear in the Specification as accepted.