Thermofixation method

The Thermosol process of Du Pont, or similar thermofix methods, are used extensively for continuous dyeing of materials made of polyester alone or when mixed with other fibres. The process, see Fig. 23.11, is... 

Useful diazo dyes (Figure 2.72), not much used for CA, which have excellent fastness properties on PES, are suitable for application by the thermofixation method, i.e. padding an aqueous dispersion on to PES fabric and then fixing by baking at c. 200 °C for 1 minute. 

Blends of polyester with cotton (qv) or viscose are first dyed with disperse dyes, then with sulfur dyes (see Fibers, polyester Fibers, regenerated CELLULOSics). Disperse and sulfur dyes can also be appHed simultaneously in a pad—dry—thermofix/chemical reduction pad—steam sequence. In this case, the sulfur dyes cannot be used in thein reduced form because of the effect of the sodium sulfide on the disperse dye. Therefore, this method is confined to the solubilized sulfur dyes or sulfur dyes in the dispersed form. 

These methods 2, J, and 4) are only used when applyiag fiber-reactive dyes. In all methods thermofixation conditions are 60—90 s at 190—220°C depending on the choice of disperse dye. In method (/) the chemical pad is caustic and hydrosulfite for vat dyes, and alkaU and salt for fiber reactives. This is the most popular method ia the United States. 

Disperse polyester, polyamide, acetate, acrylic and plastics fine aqueous dispersions often applied by high temperature/ pressure or lower temperature carrier methods dye may be padded on cloth and baked on or thermofixed azo, anthraquinone, styryl, nitro, and benzodifiiranone... 

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