Pigment dyeings, fastness requirements

Starch finishes are still used in India. Starch cannot be incorporated into pigment pad-bath formulations since it interferes with the final fastness requirements of pigment dyeings. 

Phenolic moulding powders Temperature requirements moderate up to 170°C but reducing atmosphere present. Only moderate light fastness requirements as compounds become brown. Spirit and water soluble dyes Red toners Simple monoazo pigments ... 

The textiles printing industry has an appreciable interest in P.Y.17 and applies it in the form of pigment preparations. Where its fastness properties satisfy the specifications and where the use requirements are not too demanding, the pigment is also utilized for spin dyeing purposes. Manufacturer recommendations include media such as polyacrylonitrile and cellulose acetate fibers, on which 1/3 SD pigment prints exhibit a lightfastness which is equal to step 5 on the Blue Scale. 

P.R.262 is a comparatively recent product which affords bluish shades of red. P.R.262 is recommended for polypropylene spin dyeing, but possesses all-round suitability for other applications, as long as the requirements do not exceed the fastness properties of this class of pigments. 

The dyes are vatted in the usual way and added to the dyebath, which is then adjusted to pH 10 by the addition of sodium bicarbonate, and the dyeing is carried out at 95°C (203°F). Oxidation of the pigment requires treatment with sodium percarbonate or perborate at 95°C (203°F) because the action of atmospheric oxygen is slow. The vat dyes offer an opportunity to dye a limited range of shades of excellent all-round fastness. 

---