Friday, January 1, 2010

Pigment Dyeing

Pigment dyeing is not really "dyeing" in it's truest form because the pigments stick on the fabric with the help of binders.. Pigments are insoluble in water. They exist in the form of finely ground molecules, milled for garment dyeing purposes into a paste. When anionic dispersing agents are added, a slightly negative charge is present, thus the foundation for pigment dyeing is born. When a positively charged cationic pre-treat is added to the fiber a magnetic bond is formed. The process is complete when a cationic binder is added to "lock" the pigment into place.In pigment dyeing no actual chemical reaction takes place between the dye and the fabric.

 
The pigment dyeing process is generally a three step process such as
1.Cationisation of the fabric or giving electric charge to the fabric by a  powerful cationic pretreatment.

Pigment dyeing is an electrical process whereby the goods to be dyed are given an electrical charge opposite that of the pigment.  When the pigment is added to the bath, the opposite electrical charges attract each other, much like the north and the south poles of two magnets.  Because of the electrical nature of the process.
A typical recipe for cationizing Step
• Cationic Imparting Agent
• Wetter
• Acetic Acid for pH control
The cationic agent is applied with a wetting agent and acetic acid onto the fabric in the batch or commercial dyeing machine. After a period of time, the fabric is rinsed.
2.Pigment exhaustion on the fabric
The pigments are first mixed with water and a dispersing agent that imparts an anionic charge to the pigments. This solution is added gradually to the dyeing machine. The temperature of the bath is slowly increased and the machine is held at the dyeing temperature for up to 20 minutes. The fabric is held at an elevated temperature to increase the adsorption of the pigments.
A typical recipe for this step
• Pigment colorants
• Dispersing agent
3.Binder application :-A binder used in the exhaust pigment dyeing procedure for fixing   pigment colors.Binders are commonly acrylic polymers with nonionic and cationic nature. It improves crock and wash fastness.After the pigment is exhausted , the binder is fed into the dyeing machine and exhausted onto the fabric over a period of time. Acetic acid is added to the bath, which facilitates binder polymerization, then the fabric is rinsed, the dyeing machine is drained, and the fabric is extracted.
Dyeing Process Flow Diagram


A Process flow diagram for pigment Garment dyeing process 
 
Advantages of pigment dyeing

1.Its applicable to a wide range of textiles and wide gamut of colors available. Some brilliant fluorescent pigments are available for special applications and fashion items. 
2.The process of pigment dyeing can also be relatively cheap.
3.The process chemicals are less toxic , environmentally friendly and least polluting.
4.The color fades with the repeated use , just like denims.
Limitations of Pigment Dyeing
1.Color fading could be a problem if not desired, and can only be kept intact with further chemical treatments.
2.The abrasion resistance and hand could be unsatisfactory depending upon the pigment, binder and softener used.
3.Dark and deep shades are better produced with other dyestuffs rather than pigments.

Further Readings

Yarn dyeing with blue 3 GK
http://www.icidyes.com/ingrain_dyes_textile.html

6 comments:

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  2. hello,
    thanks for ur information about pigment dyeing....this will be help full for me . bt i want to know that what will be the Ph of dyeing bath...can u plz inform ..
    thanks
    shabbir

    ReplyDelete
  3. Hello,
    Can I dye yarn by pigment?

    Thanks
    Jahid

    ReplyDelete
  4. Yes,you can dye yarn with pigment dyes.

    ReplyDelete
  5. I really like your blog. I really appreciate the good quality content you are posting here for free. May I ask which blog

    platform you are using?

    Dyes And Pigments Importers In Delhi

    ReplyDelete
  6. Its really awesome blog
    thanks for sharing

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