Cellulosic fibres salt solution processes

Azoic dyeing of cellulosic fibres is a process that is used only to a small extent today. In this process, an azo pigment is formed by chemical reaction within the fibre. The cotton fibres are first impregnated with an appropriate coupling component such as the anilide of 3-hydroxy-2-naphthoic acid, 156, under aqueous alkaline conditions. The fibre is then treated with a solution of a stabilised diazonium salt, in which the... 

Another cellulose product is rayon. This is really cellulose itself, temporarily modified so that it can be dissolved and processed to give films or fibres. The starting materia) (from wood, cloth, or paper) is impregnated with concentrated NaOH solution. Addition of CS2 allows some of the OH groups to react to give a xanthate salt that is soluble in water. 

Regenerated cellulose films and hollow fibres used in haemodialysers have been prepared by a method known as the cuprammonium process. Cellulose is dissolved in a solution of ammonia and cupric oxide. The complex cupric salts are water-soluble and cellulose is regenerated by treatment with acid. Cuprophan is prepared by this process. 

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