Thursday, August 5, 2010

Cotfix Hot Brands - Printing Dyes

Our cyanuric chloride based, Cotfix 'H' brand dyes forms various chemical linkage with hydroxyl groups of cellulose. These dyes are low substantive and high fixation dyes most suitable for dyeing and printing of cotton, viscose, cuprammonium rayon and natural silk. The dyeing temperature is 80°C.


METHOD OF DYEING: By Exhaust Dyeing:
Take well pre-scoured fabric and ensure that the pH of the fabric is 7, if require adjust pH by adding Acetic Acid. Take soft water for dyeing, if the water is hard, add sequestering agent to achieve best result.
Set the dye bath at 50ºC and add pre-dissolve dye in two portion and run for 10 min.
Add 5 gms./lit. Common salt for deep shade (2.5 gms./lit. for pale shade) and run for 10 min. start raising temperature to 80ºC - 85ºC in 30 min.
During raising temperature, 20 gms./lit. Common salt (10 gms./lit. for pale shade) after first 10 min. and add 25 gms./lit. Common salt (8 - 10 gms./lit. for pale shade) after another 10 min. and continue dye for 15 min. after reaching the temperature to 80ºC - 85ºC.
Add Alkali slowly in 15 min. and continue dyeing for further 45 - 75 min.


SALT AND ALKALI REQUIREMENTS FOR REACTIVE HOT DYES
COTFIX – H BRAND DYES IN PRINTING
In conventional one-step printing with reactive dyes, urea is used to increase solubility of the dyestuffs and to improve dyestuff migration from the printing paste to the textile fiber.
Minimization or even substitution of urea is possible in the one-step method by controlled addition of moisture.
Another option is the two-step printing method, involving the following steps:
• Padding of the printing paste
• Intermediate drying
• Padding with alkaline solution of fixating agents (especially water-glass)
• Fixation by means of overheated steam
• Washing steps (to remove thickeners and improve fastness properties).
The process is carried out without urea.
A typical recipe for the printing paste is given below:
Thickening stock solution:
Fixation is carried out by means of overheated steam (90 °C to 125 °C).

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