Pigments - 1
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Pigments for use in pigment printing should have certain properties. Thus the shades produced by them should exhibit good fastness to light, washing, gas fading, chlorine, acids, alkalies, peroxide, perspiration and especially abrasion. The emulsion thickenings made by using them should give sharp impressions, develop good brilliancy and have good reproducibility. The suitability of pigments in textile printing depends on the particle size, particle size distribution, degree of dispersion, electrical charge, specific gravity, crystal structure and stability, hardness etc.
The dispersion of the pigment is generally done by milling in the presence of an emulsifying agent or a dispersing agent. If over-milling is done, the primary pigment particles are broken and tis is accompanied by loss of brilliancy, resulting in dulling of the final shade of the prints. A kneader type of milling machine is used for the purpose, since it produces a highly dispersed and concentrated pigment paste in a minimum of processing time.
