Dyeing & Printing Auxiliaries

The dyes used in this mass colouration are specific for a particular substrate and are classified with regard to their chemical constitution, substantivity to the fibre type and method of application.

To achieve the best dyeing results the following criteria are important:

• Levelness and optimum depth/shade of the dyeing
• Dye solubility/dispersing property of the dye
• Good fastness properties

Printing Chemicals

Using one of several printing methods, printing ink, paste or dispersion is applied to the fabric and then fixed to the fibre by heat or heat and steam. Excess dye is removed from the fabric by washing and detergent scouring and the fabric is subsequently dried. Printing styles can be broadly classified into direct, dyed, discharge and resist. Printing methods vary with machinery and include: block printing, roller printing, screen printing (table, flatbed, rotary), spray printing and foam printing.

The types of dyes used in textile printing are usually the same classes that confer substantively to given fibre types in the exhaust dyeing process. There are several types of printing in vogue e.g. Pigment, Vat, Reactive, Disperse, Rapid, Naphthol/Base.

Today, with the use of a suitable binder, pigments can be applied to all types of fibres. The ease of application and the fact that washing-off of the prints is unnecessary, has contributed to the popularity of Pigment Printing.