There are some common problems in India maximum textile dyeing house for example poor wet rubbing fastness in dark shade (Dark maroon burgandany, dark red etc).
In exhaust reactive dyeing method (60 degree Celsius dyeing temperature) following variable factor has to be checked: -
1) Material/liquor ratio.
5) Water Hardness and Ph.
6) Proper selection of dye.
We will directly approach to the root cause of the problem.
Case Study I
Material=2/4 count (cotton Yarn)
Material/ Liquor ratio =1; 20
Machine = Cabinet dyeing machine
Reactive Red SYG (local) =4.0% owf
Reactive Yellow RD (Local) =1.4% owf
Reactive Navy Blue SGL (Local) =0.2% owf
Common salt=80 gpl, Soda ash=5 gpl+ caustic soda=1 gpl
Dyeing process: -dyesaltsoda exhaust dyeing process (60 degree temperature dye).
Wet Rubbing fastness is coming (normal) =2 (ISO; 105-X12)
After investigation of above problem following two factors was observed which was creating problem (bottom mentioned)
Water hardness: Water hardness was observed 420 ppm. In dyeing bath after local sequestering agent (1 Gram /liter) addition also poor wet rubbing fastness was observed.
Selection of Dye
From Filter paper test (Figure I) it was clearly observed that dye precipitation was there before draining of dye liquor in lab trail.
From Filter paper dropping test (Fig II) each and every stage of dyeing shows that precipitation is there after using 1 gram per liter sequestering agent (local also). It clearly shows precipitation starts from salt stage (minor) at soda + caustic soda stage (maximum precipitation) in lab stage.
Fig IIIFilter paper dropping test we have used glycerin in dye dissolving then also dye precipitation was observed from salt (Minor) at fixation stage (Maximum precipitation).
Fig IV-Filter paper dropping test used local sequestering agent in dye dissolving also then also dye precipitation was observed.
Finally (local) Reactive Red SYG was replaced by polyfunctional reactive dye (From colourtex) recipe was: M/C=50 KG-
Cora fix Rubine GDN (colourtex); -2.52% owf.
Reactive Yellow RD (local): -1.6% owf
Reactive N. Blue SGL (local): -0.14% owf
Common salt=80 gram per liter, soda ash=5 gram per litre+caustic soda=1 gram per liter.
Process: -Dyesalt----sodas exhaust process (60 degree Celsius dyeing temperature).
In Bulk trail dye was dissolved with (local) wetting agent +sequestering agent (local) along with warm water (50 Degree Celsius). Then in machine before addition of dye sequestering agent (1 gram per litre) was used also.
Process: sequestering agent (1 gpl), room temp, 20 minute running------Dissolved dye added slowly--- Common salt(II installment),40 degree Celsius---temp rise to 60 degree Celsius(1 Degree rise in temperature)60 degree Celsius ,30 minute holding time----dissolved soda ash in two installment at 15 minute gap---60 minute holding timebefore caustic soda addition check samplecaustic soda in two installment---shade ok draincold washneutralizationsoap (at boil,20 minute)hot wash(2)cold washcheck sample for rubbing fastness checking
Fig V-shows bulk trail of each and every stage of dyeing no precipitation was observed (Filter paper dropping test).
Fig VI:-shows wet rubbing fastness improvement observation (ISO-X12) in yarn stage then after weaving stage (patti) along with regular running process (yarn).
Wet rubbing fastness=3(ISO-X12).
Dye dissolving in wetting agent plus sequestering agent shows uniformity from each and every stage of dyeing (See filter paper dropping test Fig V)
Note: The readers are requested to take trial in first in laboratory then go for bulk trial. This article is written in good faith for problem solving attitude.
About the Author:
The author is working with Colourtex Industries Ltd. Surat as the Product Manager for Reactive Dyes.
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