These dyes are of particular interest in the dyeing and printing of cellulosic fibers, such as Cotton, Linen, Viscose, Cup ammonium and Polynosic rayons.
`M' Brand Dyes are highly reactive requiring comparatively milder conditions in dye fixation. They are primarily of interest in dyeing at normal room temperature (about 25-35ºC) using Soda Ash or Sodium Bicarbonate.
`M' Reactive Dyes are applicable to cellulosic textiles by Batch - wise, semi-continuous and Continuous methods in conventional textile machinery like Open-vat, Package, Jet, Jig, Winch and Padding Mangle.
Some important considerations in Reactive cold brand dyeing:
Effect of Ca ++ and Mg ++ on Reactive Dyestuffs.
Parameter | Effect | Impact |
Solubility | Reduced Solubility Particularly with Greens and Turquoises | Can cause dye spotting Unlevel dyeing Loss of dye from recipe (economy) Difficulties in washing-off (reduced fastness) Staining machinery (and subsequent fabric batches) Reduced “RFT”; and increased possibility of customer complaint. |
Aggregation | Increased Aggregation | Can cause dye spotting Unlevel dyeing Loss of dye from recipe (economy) Difficulties in washing-off (reduced fastness) Staining machinery (and subsequent fabric batches) Reduced “RFT”; and increased possibility of customer complaint. |
Inadequate removal from within the fiber during preparation | Can cause “cloudy” dyeing or even white precipitates on the fiber | Unlevel dyeing Reduced “RFT”; and increased possibility of customer complaint. |
Bicarbonate in the Dye bath:
It is quite common, many dye house managements ignore the testing of hardness of water time to time. They just find fault either with process chemicals or dyes but just ignore the potential dangers of bicardbonate in process water!.
Practical Dangers to “Right First Time” Dyeing of Bicarbonate:
Issue | Effect | Impact |
Bicarbonate turns to carbonate on heating (equation 1) | The exhaustion and migration phase which should be under neutral conditions is alkaline | Premature hydrolysis with loss of economy of recipe. More loose dye than expected to wash-off after dyeing; with loss of wet fastness |
Bicarbonate turns to carbonate on heating (equation 1) | The exhaustion and migration phase which should be under neutral conditions is alkaline | Premature Fixation before Migration. Unlevel dyeing ; expensive re-processing. |
Unpredictable bicarbonate content | Poor shade reproducibility in terms of both Lab – Bulk; and Bulk - Bulk | Expensive Shading Additions. Loss of time, “RFT” and money. |
a. The residual Peroxide and chlorine on the bleached fabric will yield poor depths due to the destruction of dyestuff molecules.
b. Higher moisture content of the dyestuff i.e., more than 3.5%, also yields poor depth of shades.
c. A good neutralization with acetic acid after dyeing is necessary.
d. Use Non-ionic low foaming detergents for soaping.
Chemical requirements: (For MLR 1:7 to 1:15)
Depth | Salt | Soda |
0.1 – 0.5% | 30 gms/liter | 3 gms/liter |
0.5 –1.0% | 35 gms/liter | 4 gms/liter |
1.0—2.0% | 40 gms/liter | 5 gms/liter |
2.0—4.0% | 55 gms/liter | 7 gms/liter |
Above 4% | 70 gms/liter | 10 gms/liter |
Dye Dissolution:
The dissolving of cold brand dyes is a crucial step, which determines the colour yield, repeatability and lab to bulk reproducibility.
- If the shade we are going to be dyed is a tri-chromatic one, i.e., a combination of three dyes, each dyestuff in the combination should be weighed separately and put into separate containers.
- Each dye should be dissolved separately using 1:15 MLR ratio i.e., for 1 kg of dye 15 liters of water should be used.
- First the dye should be pasted thoroughly, with a little cold water into a uniform colloidal mass. Then add hot water of 60°C and dilute.
- Filter through fine bolting cloth and the mix the three dyes.
- Do not add urea directly to the solid dye powder. If large quantities
Of dyestuff is dissolved, add 1/10th by weight of urea to dissolved solution to improve dissolution.
Sampling/Shading/Addition of Dyes during dyeing (Sampling procedure):
1. Do not compare any sample taken just after the addition of salt against the standard shade. This will mislead you.
2. Take sample 30 minutes after the addition of soda for light & medium shades and 45 minutes for dark and v.dark shades.
3. Wash Cold- ½ minute
4. Wash Hot – 60°C- ½ minute
5. Neutral soap – boil – ½ minute
6. Neutral soap – boil – ½ minute
7. For dark and very dark shades, do 6 soaping of ½ minute duration.
8. Cold wash.
10. Check shade.
11.If shade is not matching, and if you want to make 10 or 20 or 30% addition in total, drain the running bath up to ½ volume, refill with fresh water, then add the required dye (pre-dissolved, filtered) in two portions, continue dyeing for another ½ half. Do not make any addition of salt or soda into the bath.
After Treatments:
- After dyeing is over, drain the bath.
- Do one cold wash – overflow.
- Do one cold wash.
- Do one Hot wash @ 50°C
- Neutral soap 0.5 to 1.0 g/l at 80 to 90°C for 15 minutes.
- Hot wash at 80°C – 10 minutes.
- Cold wash – 10 minutes.
- Softening treatment (Cationic if necessary) 1 – 2%
(All the above information were given under good faith and does not carry any warranty)
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