City University, Bangladesh. Department: Textile engineering. Academic project about blend dyeing in one bath dyeing process.

1. Department of Textile Engineering
Prepared by: Anik Deb
Batch: 17th

2. Dyeing method of Polyester Cotton (PC) Blended Fabric in Single Bath Process for Saving
water, energy and time with high temperature & high pressure.
1. Abstract:
In this research, the process of dyeing (polyester/cotton) blend fabrics using disperse &reactive
dyestuffs in one bath dyeing method. In this method dye fiber reaction was good, and they
created more stable covalent bond. The color and rubbing fastness properties of the
polyester/cotton fabric was assessed. Shade% was measured by spectrophotometer after dyeing
the sample. The data obtained shows that it is possible to dye polyester/cotton fabrics with
disperses &reactive dyestuff. The dyed samples showed good rubbing and washing color
fastness properties within the range of color. The color depth and the color ratio was good which
was showed by spectrophotometer.
2. Key words: Dyeing recipe, materials and method, limitation, physical test, cost analysis.
3. Introduction:
The traditional method of dyeing polyester/cotton blends involves the use of various two-bath
processes which are claimed to impart high wet fastness but are time-consuming and therefore
expensive to operate. Several attempts having the past had been made to reduce these to one-bath
processes, for example ICI have developed a rapid one-bath method using a mixture of selected
disperse and reactive dyes. Others have suggested modification of the cotton component using
hydrophobic aromatic compounds to allow one-bath dyeing of these blends either with disperse
dyes or with reactive disperse dyes .With these approaches in mind we have studied the use of
the ICI Procinyl reactive &disperse dyes, introduced in1958, which combine the properties of
disperse and reactive dyes. The selection of these blend fibers ensured sufficient comfort
resulting mainly from the use of cotton fibers, as well as suitable mechanical properties such as
the tensile strength characteristic of synthetic fibers. However, the presence of both components
(polyester/ cotton) in textiles causes some difficulties in the dyeing process (Gejdzicki, 1998).
Polyester fibers show a hydrophobic character, and swell to a very small extent in the water bath.
Hence, the access of the dyestuff molecules to the fibers inside is very difficult (Arslan, 2001).
This fact, together with an absence of active chemical groups in polyester's macromolecules
makes it impossible to apply the majority of dyestuffs apart from disperse dyes (Bhattacharya,
1992). On the contrary, hydrophilic cellulose fibers may easily undergo swelling in water. Owing
to this phenomenon, the dyestuff molecules first adsorbed on the fiber surface may diffuse into
the fiber interior. Subsequently, bonding interactions between the dyestuff and cellulose may be
formed (Legrini et al., 1993). In spite of their advantages, polyester fibers are difficult to dye
(Yediler et al., 2000). The often applied pressure method requires a suitable, intricate apparatus
which causes great energy consumption. In order to obtain intensive color strength of polyester
fibers, dispersing or carrier material agents are often added to the dye bath (Perez et al., 2002).
These agents can often cause sensitization of the human skin. Moreover, the small amount of
them left on the polyester fibers reduces color fastness to light (Neamtu et al., 2002). It is
possible to eliminate disperse dyestuffs and the detrimental auxiliary agents by the application of
natural polymer such as chitin in the textile finishing processes (Montazer, 2001). Here, we

3. research about the process of dyeing polyester/cotton fabrics using disperse/reactive dyestuffs in
one bath dyeing process.
4. Materials and method:
4.1 dyeing recipe:
Dyes:
1. Reactive dye yellow: 3.5ml or 0.035gm. 2. Disperse dye yellow: 6.5ml or0.065gm.
Total dye required: 10ml or 0.1gm.
Sample weight: 10gm, Dispersing agent: 16ml, Sequestering agent: 4ml, Wetting agent: 4ml,
Anti creasing agent: 8ml, Leveling agent: 8ml, Salt: 20ml, Soda: 40ml, PH=9-12, Detergent:
20ml, M: L: 1:20
Additional water: 200- (16+4+4+8+8+20+40+20)
= 80ml.
Measurement of Dye Solution:
Sometimes we prepare stock solutions to take the proper amounts of dyes & chemicals. It is done
when we have to take a very little amount because it is not impossible to measure in digital
balance.
Let, we have to make 1% stock solution of dye.
1% stock solution means, a solution of 100ml water which contains 1 gm. solid dyes. If the dye
is in liquid form then, 1% stock solution means, a solution of 99 ml water which contains 1ml
liquid dyes. For the stock solution the formula of the “Dye” will be --
Shade % = 1 owf
Fabric wt. = 10 grams. Total liquor = (20×10) = 200 ml
Dye % = (Shade % ÷ Stock solution %) × fabric wt.
So that for the above data, required dye is-----
Dye= (1%/1%).10=10ml.

4. So, we need 10ml dye solution to dye the 10 gram fabric.
Now, the problem is we have to add the dye solution in the bath by using the pipette. When we
do it manually then we cannot measure proper amount of solution. By seeing the level of
solution in the pipette we take the dye solution. We may take little more or less amount of
solution in the bath. Let, we take 0.1ml more or less dye solution instead of 10ml dye solution.
Here, we take 0.1ml dye solution more or less than the required dye solution. After dyeing with
that we get proper shade.
4.2 Dyeing Procedure:
1. Ser the dye bath with substrate at 50c temperature and add dispersing agent, leveler, acetic
acid and other auxiliaries, then run the dye bath for 5-10 minutes.
2. Add both dyes and raise the temperature 90- 130 @ 1-2 C/min
3. Add glauber salt and Soda ash, run the bath for one to two hours at the same temperature.
4. Lower down the bath temperature to 70 – 80 over 10-15 minutes.
5. Drip the dye bath and carry on the after treatment process.
After Treatment Process:
1. Rinse twice with hot and cold water.
2. Treat the fabric with suitable fixing agent for improving the wet fastness properties of dyed
goods.
3. Soap wash according to recommendation.
4. Rinse twice with hot and cold water and then
5. Neutralize with acetic acid.

5. 4.3 Fiber and dye-specific properties
To understand why so much effort is spent on dyeing PC blends despite the problematic cost
situation, it is worthwhile looking at some fiber and dye-specific aspects. Reactive dyeing have
to be fixed in an alkaline medium usually soda ash alone or in combination with caustic soda are
used to set the pH at 10.8-13.5. This greatly reduces the yield of common disperse dyes.
4.4 Sensitivity to reduction
some reactive dyes are extremely sensitive to reducing agents. This sensitivity is found at all
steps in the process, especially after application of the dyes. Although some disperse dyes are
sensitive to reduction during the dyeing phase, reductive clearing is normally carried out after
dyeing as it improves the fastness properties of the dyed substrate.
4.5 Fixation conditions
Reactive dyes are water-soluble and are therefore fixed to the cellulosic fiber in a moist medium.
In conventional continuous dyeing methods, that means fixation in saturated steam. However,
the disperse dyes used for Polyester is fixed by thermo soling, i.e. at temperatures of around 210-
220°C. Cellulosic fibers have a tendency to discolor in such conditions As a result of these
completely different dyeing requirements, multistep processes using several liquors have been
developed for continuous dyeing of PC blends.
4.6 Effect of humidity in dye bath solution:

6. 5. Limitations:
1. Due to Limitations in lab accessibility, it was not possible to follow all laboratory trials in
production for different shade%.
2. Due to limitations of lab dyeing machine dyes of different brand could not be used.
3. Due to lack of testing machine all the test could not be tested.
From the above discussions we can easily find out that the limitation to get the RFT dyeing is the
manual measurement of dyes and chemicals. If we can minimize this problem then we can get
the Right First Time dyeing. For increasing RFT efficiency this problem should be minimized.
I am trying to find out the solutions of this problem. The solutions are given below-----
Use Exact Amount of Chemicals:
We face problems to get RFT efficiency in bulk production because of not measuring the exact
amount. If we indicate the proper amount use in lab then during the bulk production we may not
face problems to get RFT Dyeing.
Such as, if we use 1.01 gm. dye in lab then we need to write the exactly that amount. So during
the bulk dyeing people will calculate according to the 1.01 gm. dye.
Dyed sample for 1% shade:
Fig: polyester cotton(pc) blend Fabric

7. 6. Physical test of dyed sample:
1. Color Fastness to Rubbing :( AATCC)
Results which we can achieve in Normal Conditions are
Sample condition Grey scale result
Dry: 4-5(acceptable)
Wet: 4(acceptable)
2. Color fastness to washing: ISO 105 CO6 (After wash with multifiber)
The test was occurred by 40c.
Test description Result
Color change in shade staining in acetate: 4-5
Color change in shade staining in cotton: 4-5
Color change in shade staining in nylon: 4-5
Color change in shade staining in polyester: 4
Color change in shade staining in acrylic: 4-5
Color change in shade staining in wool: 4-5
3. Color fastness to light :( AATCC)
Sample Grade
Test no: 1 4
Test no: 2 4
Test no: 3 4
4. Color fastness to perspiration :( AATCC)
Sample Grade
Color change in acidic solution: 4
Color change in alkaline solution: 4-5

8. 5. Shade match in spectrophotometer view:
Sample color % ratio is shown by following figure.
7. One bath dyeing cost analysis for industrial bulk production:
Graphical Representation of Amount of Time

9. The graph showed that the one bath dyeing method required 1010 min time where as two bath
method needed 1100 min. So that the one bath dyeing method saves 90 min. As a result the one
bath dyeing method provides the following benefits:
 Production will be increase.
 Labor cost will be decrease.
 Product can be delivers to the buyer within certain time. So buyer will satisfy to the
company’s authority.
 Save machine running cost. I.e. electricity, gas, and power cost.
Cost Saves for Extra Time
 1KW hour = 1 unit of electricity
 1 unit cost =5.5Tk (Approximately)
 Dyeing machine is 60 KW capacity
 So it consume 60×1=60 unit per hour
 Cost =60×5.5 =330Tk/hr
Since one bath dyeing method save 90 (1 hour 30 min) minutes, So it saves 330×1.5= 495Tk
(approx.) energy cost. So proposed one bath dyeing method saves 880Tk/1000kg (approx.) with
90 minute time.
Conclusion:
P/C blend fabrics were successfully dyed by one-bath one-step dyeing process. This process was
not cumbersome as other process because here all the existing chemicals were used which has
not needed any special requirements. The novelty of undertake study is successful by
maintaining the right process with the existing dyes and chemicals as is to give complete shade
gamut, which will open up new avenues to dyeing factory owner to cater to the blend dyeing
needs of the textile processors. The work is based on the well established process of dyeing
however will emerge in readymade dyes as option to dyers to get rid of cumbersome shade
matching at their end. Also, this one-bath one-step dyeing process has potential in offering
savings in time, energy, water and labor. This process can be able to save approximately Tk.880
per 1000 kg of fabric with 90 minutes time. This research work demonstrates the specific
possibility of a commercially acceptable dyeing process for P/C blend using one bath method.