Pigment dyeing is a comparatively recent addition. In the
process of pigment dyeing no actual chemical reaction takes place between
the dye and the fabric. Instead, what happens is that the pigments gets
seated on the fabric with the help of binders. There is a challenge in
pigment dyeing. Pigments are not soluble in water and shows no affinity for
fiber. So, conventional dyestuff-based dyeing conditions are not feasible
for pigment dyeing. To come to terms with such limitations, a new kind of
pigments have been formulated for use in fibres. These are maintained in a
stable dispersion in the medium of water by anionic surfactants. This type
of pigment is known as pigment resin color (PRC), primarily used in
printing. Some of the popular pigments used in fabrics are given here.
- Yellow colour: Acetoacetic acid anilide pigments
- Red: Azoic pigments
- Blue or green: Phthalocyanine pigments
Difference between a dye and Pigment in context fibre dyeing is
explained in the following section.
| Pigments |
Dyes |
| Pigment coloring is done by dispersion of fine
particles. These are in sizes smaller than 1 micron. They contain around
108 mol of molecules per particle. They get attached to the fibres in
this original state. |
In contrast, dyestuffs tend to fix on fibre with
individual molecule (in some cases, however with several molecules) |
A good pigment dyeing system should ideally come with the follow innovative
features.
- Doing without wet processing: results in Preventing water pollution
along with high Productivity.
- Binder: For improving crock fastness
- No thermo-migration : This makes even dyeing on both the sides
- Excellent Fastness properties
A typical process of pigment dyeing for cellulosic
textile materials consists of padding the textile materials with a Dye bath.
The dye bath contains anionic or neutral colour dispersions of pigments.
Along with the pigments it also contains anionic binders, acid-liberating
catalyst, anti-migrating agents, and other types of additives. Then the
textile materials are dried at high tempratures, this cures the film-forming
binders and pigment colours firmly on the textiles.
Key
features of a good pigment dyeing system