Unshrinkable finishes

Many of the unshrinkable finishes based on chlorine or other oxidizing agents reduce the wet-fastness of acid dyes. A few examples of the nature of the effect are quoted from I.C.I. Dyehouse Technical Information Publication No. 536 for dyeings on wool rendered unshrinkable by the combined peracetic acid and sodium hypochlorite method of the Wool Industries Research Association (Table 15.6). Only effect on shade has been recorded because alterations with regard to staining of adjacent fibres are insignificant. 

The washing test applied to the first five was that of the I.S.O. (Mechanical Mild Wash at 40°C (104°F) for 30 minutes) and for the remainder the S.D.C. No. 2 test (50°C (122°F) for 45 minutes. The figures show that there is a loss of fastness of 1 to 2 gradings with the level-dyeing acid dyes, but none with the premetallized or fast acid dyes. Different unshrinkable finishes would not give exactly the same results but they could be expected to be of the same order. Shrink-resisting processes are usually applied to goods which are washed frequently, and it follows that the use of the molecularly-dispersed acid dyes is undesirable. 

The Procilan dyes are 2 1 metal complexes containing groups which form stable chemical links w ith the wool fibre. This confers even better wet fastness than is associated with the normal 2 1 metal complex dyes. This property makes them especially useful for dyeing wool which has received an unshrinkable finish and which is intended for garments requiring frequent washing. The application of the Procilan dyes will be described in Chapter 22. 

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