Wednesday, August 23, 2017

Printing Paste Ingredients and their Functions

Ingredients of Printing:
Printing means localized application of dyes on the fabric according to design. For printing it is required to produce printing paste. Printing paste is a viscous paste which is made from pigments, thickeners and many of chemical. A good printing paste is mainly responsible for good printing effect. So it is very important to make a printing paste. There are different types of ingredients are used to make printing paste. 
Printing paste
Fig: Printing paste
Generally following ingredients are used in printing paste:
  1. Dyestuffs or pigment.
  2. Wetting agents.
  3. Thickener.
  4. Solvents dispersing agents.
  5. Defoaming agents.
  6. Oxidizing and reducing agents.
  7. Catalyst and oxygen carrier.
  8. Acid and alkali.
  9. Career and swelling agent.
  10. Miscellaneous agent
Printing Paste Ingredients and their Functions:

1. Dyes/Pigments:

Functions:
  • Attraction of dyestuff to the fiber due to presence of auxochrome.
  • To achieve color effect on the fabric.
  • To produce required shade.
Example: Vat, Azoic, Reactive, Direct dye etc.

2. Wetting agents:

Functions:
  • To wet the fabric as well as dyestuff.
  • To reduce surface tension of water allowing the dyestuff for easy penetration into fiber.
  • To obtain smooth paste.
  • To dissolve the dyestuff in the paste.
Example: Olive oil, T.R oil, Caster oil, Lissapol N, Animal oil, Glycerine.

3. Solvents/Dispersing agents/Solution acids:

Functions:
  • To get bright design,
  • To assist dye penetration,
  • To spread dye molecules evenly in the paste,
  • Assist dye fixation,
  • To prevent aggregation of dye molecules in the highly concentrated of the dye.
  • To prevent precipitation.
  • To increase solubility of the dyes.
  • To make proper printing shade.
Example: Urea, Glycerine, Desirable, Alcohol, Acetone, Diethylene glycol, Thio diethylene glycol.

4. Thickener:

Functions:
  • To give required viscosity to the printing paste
  • To prevent premature reactions between the chemicals contained in the print paste.
  • To hold the ingredients of the print paste on the fabric.
Example: Na-alginate, Fine gum, British gum, CMC.

5. Defoaming agents:

Functions:
  • To prevent the foam generation during printing.
Example: Silicone, Defoamers, Sulphated oil, Perminol KB, Emulsified pine oil.

6. Oxidizing agents:

Functions:
  • To develop the final color during steaming or in the subsequent after treatment.
  • Assists to dye fixation.
Example: Sodium chlorate, Potasium chlorate, Sodium nitrate, Resist salt, Ammonium chlorite, Ludigol, Na or K dichromate.

7. Reducing agents:

Functions:
  • Used for reduction of different dyes.
  • Used for mainly in discharge printing.
  • To destroy color from the ground of fabric.
  • To make the insoluble dyes to soluble.
Example: Sodium hydrosulphite, Stanus chloride etc. Rongolite-C.

8. Catalyst and oxygen carrier:

Functions:
  • To prevent fiber damage during steaming.
  • Accelerate the final color development by oxidation.
  • Reduce the risk of oxidation.
Example: Copper sulphide, Ammonium vanadate, Potassium ferrocyanide.

9. Acids/Alkalis:

Functions:
  • To maintain pH.
  • To develop the color or printed fabric.
  • To fix dye on the fabric permanently.
Example: Organic acid, Alkali KOH, NaOH, Na2CO3, Pottasium carbonate, Sodium bicarbonate, Sodium acetate.

10. Swelling agents:

Functions:
  • To create the big size holes of the fibers.
  • Helps to swell the fiber structure.
  • To reduce crystallinity.
  • Help the easy penetration of dye molecule inside the fiber polymer.
Example: Polyethylene glycol, Phenols, DEGDA (Di-ethylene glycol diacetate)

11. Carrier:

Functions:
  • Used for fixing disperse dyes on polyester or polyester wool blends at temperature below 105oC.
Example: Diphenol, Ortho-phenol, Tri-chloro benzene

12. Miscellaneous agent:

Functions:
  • Assist fixation of dyes.
  • Absorb moisture from air.
  • Facilitates subsequent washing off.
Example: Urea, Glycerine etc.

13. Mild oxidizing agent:
During steaming of ago color, the partial color can be destroyed by the effect of reducing. To secure of this condition, mild agent is used.

Example: Ludigol, Resist salt.