Department of Textile Engineering Management (43rd Batch), Bangladesh University of Textiles
Profit increasement of any organization depends on the cost efficiency & time management of the organization and customer satisfaction depends on the quality & price of the product. The exhaust dyeing technique is the most common method for the application of reactive dyes and cold pad dyeing technique is another uprising method for the application of reactive dyes. In exhaust dyeing, there are needs steam and salt which doesn’t needs in cold pad batch dyeing process.
So, the dye fixation is done by salt and batching gradually in exhaust dyeing process and cold pad batch dyeing process. Environmental responsibility is best achieved in cold pad batch application since little or no electrolyte is required, and dye fixation rate is higher than dye fixation rate of exhaust dyeing process. The specific findings of this research are to get the required time & cost of the exhaust dyeing and cold pad batch dyeing processes and to get the actual dyed fabric shade quality of the exhaust dyed and cold pad batch dyed fabric so that we can aware which process is more profitable for a dyeing company.
Required time for the exhaust and cold pad batch dyeing are measured by calculating the time of each process which are needed for the completion of these dyeing. Then, cost of the exhaust and cold pad batch dyed fabrics are calculated by using the dyes & chemical cost sheets, utility cost sheets. Also, shade quality of exhaust and cold pad batch dyed fabrics are acquired by using data color machine. Here, Quality is determined based on the CMC report which can get from the data color machine. There has also other tests for quality checking but here showed only CMC test.
The total cost of exhaust and cold pad batch dyed fabrics are calculated by adding dyes & chemical cost and utility cost. Manpower cost is not added in the total cost of exhaust and cold pad batch dyed fabric costs because the salary of employees of exhaust and cold pad batch dyeing section which information is needed for determining manpower cost, is a confined information and company cannot share that information with others. In future, if the salary of the employees can collect then that will help to calculate more accurately the total cost and will get more accurate result from this research project.
OBJECTIVES
Dyeing is a crucial step for textile industry because most of the final output of readymade garments are made by different types of dyed fabrics which has so much demand among people. The cost of dyeing in fabric affects greatly in total cost of dyed fabric which decreases the profit of any dyeing companies. Somehow if we can reduce the cost of dyeing process, it will increase the profitability of any textile company. Exhaust dyeing is most popular fabric dyeing method in the world because of its lower process cost & better quality of the fabric.
In Bangladesh, almost 80% to 85% dyeing factories are following this process. Despite there has some restriction in Cold Pad Batch Dyeing but the use of CPB dyeing system is increasing day by day. The cost of Cold Pad Batch dyed fabric are also not so much higher than Exhaust dyed fabric and quality of the CPB dyed fabrics are also close to or better than Exhaust dyed fabrics. The main aim of this research is to find out the dyeing process that is more profitable for any dyeing industry.
The specific objectives to meet the research goal have been provided as follows:
To identify the dyeing process that provides better quality of fabric.
To measure the cost difference between exhaust and CPB dyeing processes.
To measure the time required for dyeing in both processes
To determine which process is more economic friendly for any company.
INTRODUCTION
In the fast-changing world, we need to update continuously if we want to compete with others. The focus of any business is to earn profit and it can gain through some ways and reducing the cost of making & the production time are of them. Alongside it’s also necessary to maintain quality of the product. Bangladesh textile and apparel industry is seeing a remarkable change in terms of sustainability. A huge amount of water and energy are being consumed during dyeing processes.
Profitability crisis and environmental issues are being a great concern for the industry now. Factories here in Bangladesh are struggling to remain competitive, maintaining global stringent compliance requirements, and keeping sustainability intact. However major point is to consider that changing towards sustainability does not make any adverse effect on the quality of the finished product. Exhaust dyeing is a widely used process in Bangladesh where Cold Pad Batch (CPB) dyeing process is ignored through the long journey of Bangladesh textile industry for knit fabric.
But now this scenario is changing because day by day companies are concern about the environment and they want to do business by which the environment will not damage so much, and they can deliver quality product and get maximum profit. Comparing with Exhaust dyeing method, Cold pad batch method is relatively more environment friendly due to high dye fixation and non-requirement of thermal energy and the quality of fabric is good and cost friendly.
There are a few literatures review about the comparison of Exhaust dyeing and Cold Pad Batch dyeing in terms of time, quality & cost. Maximum research paper is published with different evaluation of Exhaust dyeing and its properties. As a result, it is hard to find direct comparison of Exhaust dyeing and CPB dyeing. Hence, there is a literature gap of this studies.
The aim of this research is to find out the dyeing process that is more profitable for any dyeing industry. This thesis report consists of 05 sections including literature review discussed in sections 1.0, materials and methos discussed in section 2.0, analysis discussed in section 3.0, results & discussions discussed in section 4.0 followed by conclusion in section 5.0. The necessary raw data and data analysis have been provided in the appendix section at the end of the report.
LITERATURE REVIEW
The textile and apparel industry in Bangladesh is seeing a remarkable change in terms of sustainability. A huge amount of water and energy are being consumed during dyeing processes. Profitability crisis and environmental issues are being a great concern for the industry now. Factories here in Bangladesh are struggling to remain competitive, maintaining global stringent compliance requirements, and keeping sustainability intact.
However major point is to consider that changing towards sustainability does not make any adverse effect on the quality of the finished product. Exhaust dyeing is a widely used process in Bangladesh where Cold Pad Batch (CPB) dyeing process was ignored through this long journey of Bangladesh textile industry for knitted fabric.
CPB dyeing is higher quality dyeing method for woven and knitted cellulosic fibres. The process reduces the use of salt, water, energy, and dyestuff, chemical and thus significantly reduces the chemical concentration of effluent. CPB dyeing attempts the utmost cost-effective and advantageous approach of dyeing cotton with reactive dyestuffs. The elimination of salt addition also supports the minimum energy and water consumptions; hence rendering it more eco-friendly and fixation of dye is also much higher.
Dyeing
Dyes express different affinities for the various facets of growing crystal, they produce striking patterns of color that are determined by the host crystal’s symmetry [1]. Dyeing of wool fabrics with these new anthraquinone compounds as natural dyes has been studied. The values of dyeing rate constant, half-time of dyeing and standard affinity have been calculated and discussed. The effect of dye bath pH, salt concentration, dyeing time and temperature were studied. Color strength values and the dye uptake were high [2]. One review covers supercritical fluid dyeing of polyethylene terephthalate to the most recent results obtained for the dyeing of other synthetic and natural textiles [3].
Dyeing Process
One study was developed with a new process to desize, bleach, and dye starch-sized cotton fabrics in one bath using enzymes [4]. One article review three potential eco-friendly system applicable to textile dyeing processes to minimize salt and water consumption. Application of enzymatic processing, the use of biodegradable organic salts, various surface modifications of cotton to reduce the volume of effluent and total dissolved solids [5].
Dyeing Mechanism both for Exhaust and CPB dyeing
The batch dyeing mechanism of material with reactive dyes is the exhaustion of dye in presence of electrolyte or dye absorption and fixation under the influence of alkali. Dyes create covalent bond with fabric by following:
D-SO2-CH2-CH2-OSO3Na + OH-Cell → D-SO2-CH2-CH2-O-Cell + NaHSO3 chemical reaction [6].
In one research, an attempt was taken to develop efficient dyeing method of widely used cotton and polyester blend knitted fabric by the simple modification of recognized two bath cotton/polyester blend dyeing process. They revealed result with outstanding efficiency in terms of process time, water consumption and cost minimization maintaining all quality parameters as required [7].
One study is done with Bogolan dyeing technique, deeply rooted in Mali. It uses local clays from Niger River region and a leave extract from Nagalama trees [8]. CPB method for dyeing cotton involves ultrasonic energy resulting into a one third decrease in batching time. The study showed that the use of ultrasonic energy not only shortens the batching time but the alkalis concentrations can considerably be reduced [9].
Dyeing Classification
Dye
Based on Application
Based on Source
Based on Chemical structure
Basic
Natural
Azo
Acid
Anthraquinone
Direct
Benzodifuranone
Reactive
Polyamide
Disperse
Synthetic
Indigoid
Mordant
Aromatic
Solvent
Phthalocyanines
Sulfur
Aryl carbonium
Vat
Nitro and Nitroso
The classification of textile dyes has become essential due to the remarkable increase in the type and number of dyes. One article reviewed the structural classification of these dyes by the following functional groups: Anthraquinone, azo, phthalocyanine, sulfur, indigo, nitro, nitroso, etc. taking into account their chemical structures [10]. Natural colorants cover all the dyes and pigments derived from plants, insects and minerals, i.e., derived from natural resources.
The dyeing with natural colorants was one of the oldest techniques practiced by the ancient civilization people [11]. Natural and synthetic dyes are compounds of great interest since they play an important role in our everyday life. The broad variety of technical and industrial applications, which is used for dyeing or printing of textile, paper, leather and other materials. Some of these dyes are toxic, carcinogenic and can cause skin and eye irritation [12].
Critical Factors to be considered in these two Dyeing Processes
The variables which influence the levelness and exhaustion of dyeing of acid dyes on nylon in reused dyebaths have been examined. These factors included electrolyte concentration, pH, and other dyeing conditions such as flow rate, liquor ratio, temperature, and rate of dye addition. This study revealed that reused dyebaths involve critical factors which a dyer should be controlled to produce successful level dyeing.
These factors influence surface texture, density of fabrics, interweaving mode of yarns, gloss of fibers and yarns, twist degree of yarns and so on [13]. A dynamic model for the dyeing process has been developed and this allows the fuzzy controller to be fine-tuned by computer simulation. Results of the control system simulation showed very satisfactory tracking performances of the pH profiles [14].
Quality of Exhaust and CPB Dyeing
Quality of Exhaust Dyeing
Exhaust dyeing required a high level of control over a range of reactive dyeing process variables for improved and efficient dyeing properties of new hetero-functional reactive dyes [15]. Modification of cotton fibre with cationic agents is one of the most effective ways to realize its salt-free reactive dyeing. A result showed that cationization level of cotton fibre increased with the increasing dosage of 3-chloro-2-hydroxypropyl trimethylammonium chloride, leading to enhanced dye uptake [16]. One study found that, color yields of dyeing carried out by using pure water and pure salt are higher than for dyeing carried out by using soft water and salts supplied from dye houses [17].
Quality of CPB Dyeing
A research showed that, the fixation of reactive dye is higher (80%~90% for non-aqueous dyeing vs. 40%~50% for traditional dyeing), resulting in cotton fabric achieving a deeper shade after dyeing [18]. One result showed that, the dye up-take could reach nearly 100% without any salt as accelerating agent. Since just a little water was used in the process, hydrolysis of reactive dyes was restrained, fixing rate was increased, and the apparent color depth of the dyed sample was much better than traditional water bath dyeing [19].
Another research showed that, the use of ultrasonic energy in CPB during batching stage resulted into an improvement in K/S and % fixation values. Also, a significant decrease of four hours in batching time (from 12 to 8 h) is achieved. The reduced batching time provides one and half time more production in the given time [20].
Challenges of Exhaust and CPB Dyeing
Exhaust Dyeing Challenges
Some study showed, existence of naphthol, vat dyestuffs, nitrates, acetic acid, soaping chemicals, enzymatic substrates, chromium-based materials, and heavy metals as well as other dyeing auxiliaries, makes the textile dyeing water effluent extremely toxic [21]. Traditional dyeing of cotton fabrics with reactive dyes has produced many environmental problems. Different substituents on the dyes had a little effect on the ultraviolet-visible absorption maximum wavelength [22].
To achieve salt-free and low-alkaline reactive cotton dyeing, ethanol-water mixture with high concentration of ethanol in volume was employed as medium for cotton fabrics dyeing by reactive dyes [23]. Colorants and chemicals introduced serious environmental hazards that are mainly resulted in effluent loading, containing the toxic, carcinogenic, and mutagenic substances, to natural environment.
Another review observed the challenges to environment posed by the dyes and chemicals present in spent dye bath, progress in possible remedies in dyeing wastewater treatment including the nanotechnology; and particularly discusses the studies based on the dyeing effluent samples collected from the local textile processing industries [24].
Textile dyeing effluent is considered as one of the most environmentally unfriendly industrial processes. The study aimed to review the different types of textile dyes use in the industrial processes and their contribution to environmental pollution in South Asian countries. The result showed that some physicochemical parameters of the dyeing effluents (COD, TDS and BOD) exceeded their standard limits [25].
CPB Dyeing Challenges
According to an article, in CPB dyeing it is difficult to make amendments to off-shade batches so pressure to get things right first time and requires fabrics to have completely uniform moisture and temperature throughout to achieve optimum results [26]. Another article showed that in CPB dyeing the dyed fabric production rate is low, requires least 12hours batching time for dye fixation and requires an intermediate drying process after bleaching [27].
Potential of CPB Dyeing
One study proved that in CPB dyeing total savings on electricity and Steam energy (Birr)=14+225=239 Ethiopian Birr for a lot of 100 kg fabric or approximately 2.39 Birr per kg of fabric. From the above economic analysis, assuming that the factory producing 80 tons per month of 100% cotton knitted fabric having 180 GSM or daily production of approximately 3 tones would have savings in steam cost 18% [28]. According to average economic growth scenario, the global water demand is expected to be 1500 billion m3 in 2030.
Therefore, sustainability of water resources and protection against contamination are important issues all over the world on behalf of avoiding global freshwater crisis in the future. A cleaner production assessment study was carried out in a textile mill employing cotton and polyester fabric finishing–dyeing.
The focus was the minimization of water and chemical consumptions and wastewater generations in the mill [29]. Environmental responsibility is best achieved in cold pad batch application since little or no electrolyte is required, dye fixation is at ambient temperature, and fixation is high. One study represents general methodology of cold pad batch dyeing (CPB) of cotton fabric with reactive dyes and gives approach to eco-friendliness of this process [30].
Another study proved that, CPB dyeing is the significant cost saving and waste reduction, as compared to other dyeing methods. Total elimination of the salt and other specialty chemicals such as anti-migrant, levelling agents and fixing agents and optimum utilization of dyes which reduces the chemical cost and waste load of effluent [31].
Materials & Methods
Materials
Fabric:
100% Cotton Single jersey knitted fabric of 160 GSM was scoured and bleached in Impress Newtex Composite Textiles mill by the conventional alkali (NaOH) boil scouring followed by peroxide (H2O2) boiling methods. These fabrics were boiled with mild soda ash (Na2CO3) and bleached with peroxide (H2O2 ).
Dyes and Chemicals:
Felosan Fox LF (Supplied by CHT), Heptol DCS (Supplied by CHT), Contavan GAL (Supplied by CHT), Heptol SF4 (Supplied by CHT), Maxbrite-4BKS (Supplied by Hunsman), Everzol-Yellow LX (Supplied by Dyeing), Everzol Red ED-3B (Supplied by Dyeing), Everzol Black B 133% (Supplied by Dyeing), Glubar Salt (Supplied by Hunsman), Caustic Soda (Supplied by Hunsman), Hydrozen Peroxide (Supplied by Majesta Chemical ltd.), Neutra Acid (Supplied by Majesta Chemical ltd.).
Experimental planning and design
A precise research plan was prepared before starting the experimental work. This plan was designed based on the cold pad batch and exhaust dyeing cost, time . Times, costs, quality and other necessary details of the cold pad batch and exhaust dyeing process to be collected were outlined in the experimental design. The required amount of each time and cost for both cold pad batch and exhaust dyeing process was calculated based on the experimental design. The quality of cold pad batch and exhausted dyed fabric was also measured based on the experimental design. Experimental design is essential so that materials, time, energy, and money are not wasted while experimenting.
Dyeing Methods
Cold Pad Batch Dyeing Method
The fibre reactive dyes which were used in this study. The dye solution was prepared in warm water (40ºC) to ensure complete dissolution of dye. A separate solution containing alkali, sodium silicate and wetting agent was prepared using the concentrations. Both dye and chemical solutions were mixed prior to carrying out the padding operation. The dye recipe used was the same as used for dyeing by exhaust method in a soft flow machine by the mill. The objective was to determine the difference in colour value by comparing the two methods.
The scoured and bleached dry fabric was passed through dye and chemical mixture and squeezed through pad rolls at 80% wet pick up. The fabric was batched on a roller, covered with polyethylene to prevent from drying and rotated for a period of 12 hours at a slow motion say 5 r.p.m-6 r.p.m. The dyed fabric was rinsed with cold and hot water followed by soaping with 2 g/l sodium carbonate and 5g/l non-ionic soap. Soaping was carried out at boil for 15 minutes.
Exhaust Dyeing method
With a view to implementing this process in the textile mills after optimizing the process conditions, the cotton knitted fabric dyed in a soft flow dyeing machine in a knitting, dyeing, and finishing mill were collected. These fabrics were dyed and washed in a textile mills. The typical dyeing process of one of the dyes that were used under this study.
ANALYSIS
Time Analysis of Cold Pad Batch Dyeing process
Total required time for 71 kg 100% cotton knit fabric dyeing is as follows:
Process Name
Required time (minute)
Slitting
22 minutes
Singeing
10 minutes
Scouring & Bleaching
40 minutes
Stentering(dry)
15 minutes
CPB Padding
10 minutes
Batching
720 minutes
Washing
45 minutes
Stentering (Finish)
12 minutes
Compacting
8 minutes
Total Time
882 minutes or 14.7 hours
Required Time for Cold Pad Batch dyed fabric
In Cold Pad Batch dyeing process, the required time for dyeing of 100 kg fabric are remains almost same as 71 kg fabric dyeing. So, the required time for Cold Pad Batch dyeing of 100 kg 100% Cotton S/J 160 GSM Fabric are 882 minutes or 14 hours 42 minutes.
Time Analysis of Exhaust Process
Total required time for 681 kg 100% cotton knit fabric dyeing is as follows:
Process Name
Required time (in minute)
Scouring, Bleaching & Dyeing
420 minutes
Slitting
140 minutes
Stentering
90 minutes
Compacting
55 minutes
Total Time
705 minutes or 11.75 hours
Required pretreatment Time for Cold Pad Batch dyed fabric
In this dyeing process, the required time for 100 kg knit fabric scouring, bleaching & dyeing are remains same as 420 minutes because time depends on the machine capacity. Because if the amount of fabric is higher than machine capacity, then the required time will be increased. For 100 kg knit fabric, slitting, stentering, compacting times are gradually 22 minutes, 15 minutes, and 8 minutes.
Process Name
Required time for 100 kg fabric dyeing (in minute)
Scouring, Bleaching & Dyeing
420 minutes
Slitting
22 minutes
Stentering
15 minutes
Compacting
8 minutes
Total Time
465 minutes or 7.75 hours
Required Time for Exhaust dyed fabric
So, the required time for Exhaust dyeing of 100 kg 100% Cotton S/J 160 GSM Fabric are 465 minutes or 7 hours 45 minutes.
Cost of Cold Pad Batch Dyed Fabric
Dyes & Chemical Cost
For 71 kg 100% Cotton S/J 160 GSM Fabric:
Required cost of chemicals & dyes for Cold Pad Batch dyed fabric
Dyes & Chemical Name
Required amount
Total Cost for each Dyes & Chemicals in BDT
Colorcontin SAN
0.25kg
24.371
Sarabid LDR
0.125kg
2.77
Soda ash light
2.5kg
70.57
Caustic Soda
3.495L
272.39
Felosan Fox LF
0.71L
17.91
Heptol DCS
0.568L
76.68
Contavan GAL
0.507L
49.08
Heptol SF4
0.152L
20.10
Hydrozen Peroxide
1.826L
106.73
Neutra acid
0.72L
1980.00
Everzol Black B 133%
0.61
195.45
Everzol Red ED-3B
0.36
157.07
Everzol-Yellow LX
0.385
186.81
Total cost
3159.93 BDT
Then 1 kg 100% Cotton S/J 160 GSM Fabric’s Dyes & chemical cost are 44.50 BDT.
Utility Cost:
Utility cost are 2 types. One is steam cost and another is electricity cost.
Steam cost for 71 kg knit fabric Cold Pad Batch dyeing is as follows:
Process name which needs steam
Required amount of steam for per kg fabric (In Kg)
Per kg cost of steam(In BDT)
Total cost of steam per kg fabric dyeing(In BDT)
Total steam cost for 71 kg fabric dyeing(In BDT)
Drying before Padding
0.287
1.60
0.46
32.66
Drying by Padding
3
1.60
4.8
340.8
Total Steam Cost for 71 kg CPB dyed fabric
373.46 BDT
Total steam cost for 1 kg Cold Pad Batch dyed fabric 5.26 BDT.
Electricity cost for 71 kg knit fabric Cold Pad Batch dyeing is as follows:
Machine name
Required amount of electricity for 71 kg fabric dyeing (In KWH)
Per KWH Cost of Electricity (In BDT)
Total electricity cost for 71 kg fabric dyeing(In BDT)
Motor
5.06 KWH
10.51 BDT
53.2 BDT
Total electricity cost for 1 kg Cold Pad Batch dyed fabric is 0.75 BDT. So, total utility cost for 1 kg CPB dyed fabric is 6.01 BDT.
Manpower Cost: Required manpower cost for 1 kg CPB dyed fabric is 17.28 BDT.
Others Cost: Water treatment costs, Machine process costs, Space costs are included in this cost section. The total others cost for 1 kg CPB dyed fabric is 1.85 BDT.
Total cost of 1 kg CPB dyed fabric
Dyes & Chemical Costs
44.50 BDT
Utility Cost
6.01 BDT
Manpower Cost
17.28 BDT
Others Cost
1.85 BDT
Total Cost
69.64 BDT
So, total cost of 1 kg CPB dyed fabric is 69.64 BDT.
Cost of Exhaust Dyed Fabric
Dyes & Chemical Cost
For 681 kg 100% Cotton S/J 160 GSM Fabric:
Required dyes & chemicals cost for Exhaust dyed fabric
Dyes & Chemical Name
Required amount (Kg)
Total Cost for each Chemicals in BDT
Proder JTFL AC
2.043 kg
53.69
Jingen SQ PBS
3.746 kg
404.83
Jingen LUB HGS
5.448 kg
410.45
Jingen STRS 200
2.043 kg
161.17
Soda ash
40.86 kg
1153.47
Hydrozen peroxide
13.620 kg
796.09
Jintexyem OEM
2.043 kg
163.70
Jin. Neutra Acid
5.45 kg
13433.22
BIO J1085
6.81 kg
2136.38
Jingen EZ BPA
3.405 kg
1164.17
Jingen LV CL-225
4.086 kg
364.43
Glauber salt
65.376 kg
1259.19
Jingen SP AWP
2.724 kg
573.21
Pearl Soft Cat
1.703 kg
85.73
Everzol-Yellow LX
0.041
19.89
Everzol Red ED-3B
0.0816
35.60
Everzol Black B 133%
0.8853
283.66
Total Cost
22498.89 BDT
Then 1 kg 100% Cotton S/J 160 GSM Fabric’s dyes and chemical costs are33.04 BDT.
Utility Cost: Utility cost are 2 types. One is steam cost, and another is electricity cost.
Steam cost for 681 kg knit fabric Exhaust dyeing is as follows:
Process name which needs steam
Required amount of steam per kg fabric (In Kg)
Per kg cost of steam
(In BDT)
Total cost of steam per kg fabric dyeing
(In BDT)
Total steam cost for 681kg fabric dyeing
(In BDT)
Dyeing & Post Washing
4.43
1.60
7.1
4835.1
Then, steam cost for 1 kg Exhaust dyed fabric is 7.1 BDT.
Electricity cost for 681 kg knit fabric Exhaust dyeing is-
Machine name
Required amount of electricity for 681 kg fabric dyeing (In KWH)
Per KWH Cost of Electricity (In BDT)
Total electricity cost for 681 kg fabric dyeing (In BDT)
Motor
90.71 KWH
10.51 BDT
953.4 BDT
Then, electricity cost for 1 kg Exhaust dyed fabric is 1.45 BDT. So, total utility cost for 1 kg Exhaust dyed fabric is 8.55 BDT.
Manpower Cost: Required manpower cost for 1 kg Exhaust dyed fabric is 21.68 BDT.
Others Cost: Water treatment costs, Machine process costs, Space costs are included in this cost section. The total others cost for 1 kg Exhaust dyed fabric is 2.17 BDT.
Total cost of 1 kg Exhaust dyed fabric:
Dyes & Chemical Costs
33.04 BDT
Utility Cost
8.55 BDT
Manpower Cost
21.68 BDT
Others Cost
2.17 BDT
Total Cost
65.44 BDT
So, total cost of 1kg Exhaust dyed fabric is 65.44 BDT
Quality Analysis of dyeing process:
Here quality of dyed fabric is measured by the shade quality, color fastness and rubbing fastness of the fabrics. Shade quality is measured by Spectrophotometer or Data-color machine. In that machine, Color Matching Cabinet (CMC) test is done through which we got all the parameters of the shade of the fabric.
Parameters that are observed during CMC test or color difference test are:
DE/ Delta E (Color Difference):
Pass, fail or warning depending on its quality. If DE result is not passed, then say not ok. DE is also called Total Color Difference and, in the industry, usually 0.75 to 1.0 (Commercially) is not called Warn, 0 to 1.0 is called Pass and above 1.0 is called Fail.
DL / Delta L (lightness or Darkness):
How light or dark the color depends on the value of this delta L. Its value can be either (+) or (-); If,
👉Result value (+) means shade lighter 👉 Result value (-) means shade darker.
Db / Delta b (Yellowness or Blueness):
The value of delta B / Db determines how yellowish or bluish the shade is, it has two types +/-. If the value is + here, it will be assumed to be yellowish. And if the value is – then it will be assumed as Bluish. That is, you need to check the delta b / Db result to know whether the seed is on the yellowish or blueish side.
Dc / Delta C:
Dc / Delta C determines the chroma or brightness of the shade. This value is of two types, one (+/-). Here if the value is + then the seed will be brighter and if the value is (-) then the seed will be pulsed.
Acceptance range of these parameters:
CMC De:
0.0 -0 .75= pass will show
0.75-1.0=Warn will show
1- Above = Fail will show
DL [lightness]:
Value (+) = lighter shade
If value (-) = darker shade
Da [red/green]:
value (+) = Said Reddish (less green)
If value (-) = Shaded Greenish (less red)
Db [yellow/blue]:
value (+) = shade yellowish (less blue)
If value (-) = shade bluish (less yellow)
Metamerism index:
If below < .50 = pass/ok
If above 0.50 =fail /Shade not ok
Shade quality of CPB dyed fabric
Here we select Navy color CPB dyed fabric. We compared this dyed fabric with PANTONE 19-3832 TCX of navy-blue color in Data-color machine. Here are the measured parameters and charts-
Table – 12: Shade quality chart of Cold Pad batch dyed fabric
Observation
CMC decision
CMC DE
DL
Da
Db
DC
DH
Metamerism index
1st
PASS
0.41
-0.98
0.09
-0.12
-0.12
-0.09
0.00
2nd
PASS
0.39
-0.98
-0.01
-0.13
-0.13
0.00
0.10
3rd
PASS
0.40
-0.98
0.09
-0.07
-0.03
-0.11
0.06
Shade quality of Exhaust dyed fabric
Here we select Navy color Exhaust dyed fabric. We compared this dyed fabric with PANTONE 19-3832 TCX of navy-blue color in Data-color machine. Here are the measured parameters and charts-
Rubbing is done in two ways like as wet and dry. Rubbing fastness depends on the nature of the color and depth of the shade. The pressure of the rubbing machine was 9N and cycle time was 10 times. The color fastness to rubbing is categorized from 1 to 5 where higher the number better the fastness. Here, testing is done in both Exhaust and CPB dyed fabric sample which size was 14/5 cm. The result of the test is-
For Exhaust dyed fabric, the dry rubbing is 4 to 5 and wet rubbing is 2 to 3. On the other hand, for CPB dyed fabric, the dry rubbing is 4 to 5 and wet rubbing is 3 to 4. There doesn’t have any difference in dry rubbing of both Exhaust and CPB dyed fabric but the wet rubbing value of CPB dyed fabric is higher than Exhaust dyed fabric. So, the color fastness to rubbing of CPB dyed fabric is better than Exhaust dyed fabric.
Color Fastness to washing
10/4 cm size specimen was taken from both Exhaust and CPB dyed fabric and 10/4 cm size specimen was taken from multi-fibre fabric. Then, 50 ml detergent and 50 ml sodium perborate were taken with both exhaust and cpb dyed sample and kept at C for 30 minutes in different rota wash machine and then rinse the samples twice with cold water and dry at C by hanging. The change of shade and degree of staining of both Exhaust and CPB dyed fabric was measured in the grey scale and staining scale where the value was 4 to 5 for both fabrics.
Table-14: Change of shade & degree of staining of CPB and Exhaust dyed fabric
Multi-fiber fabric
Acetate
Cotton
Nylon
Polyester
Acrylic
Wool
Value of CPB dyed sample
4 to 5
4 to 5
4 to 5
4 to 5
4 to 5
4 to 5
Value of Exhaust dyed sample
4 to 5
4 to 5
4 to 5
4 to 5
4 to 5
4 to 5
As, the color fastness to washing is same for both CPB and Exhaust dyed fabric, so there has no difference in color fastness to washing in both CPB and Exhaust dyed fabric.
RESULTS & DISCUSSION
Results Time: –
Figure: Required total time for Cold Pad Batch and Exhaust dyeing (in hour)
The required time for CPB dyeing of 100 kg fabric are 882 minutes or 14.7 hours.
The required time for Exhaust dyeing of 100 kg fabric are 465 minutes or 7.75 hours.
The required time for CPB dyeing of knit fabric is 47% higher than the required time for Exhaust dyeing of knit fabric.
Cost: –
Figure: (i) Dyes & Chemicals and (ii) Utility Costs for 1 kg fabric of Cold Pad Batch and Exhaust dyeing process (In BDT)
Figure: (i) Manpower and (ii) other costs for 1 kg fabric of Cold Pad Batch and Exhaust dyeing process (In BDT)
Dyes & Chemical costs of CPB dyed fabric is 25.8% higher than Exhaust dyed fabric.
Utility cost of Exhaust dyed fabric is 29.7% higher than CPB dyed fabric.
Manpower cost of Exhaust dyed fabric is 20.3% higher than CPB dyed fabric.
Other cost of Exhaust dyed fabric is 14.75% higher than CPB dyed fabric.
The total cost of 1 kg Cold Pad Batch (CPB) dyed fabric is 6% higher than the cost of 1 kg Exhaust dyed fabric.
Quality: –
By using CPB dyed fabric sample, 3 out of 3 sample get pass indication by CMC test. On the other hand, by using Exhaust dyed fabric sample, 2 out of 3 sample get pass indication by CMC test. Moreover, color fastness to rubbing of CPB dyed fabric is better than exhaust dyed fabric and color fastness to washing of CPB dyed fabric is same as Exhaust dyed fabric. Comparing with the CMC report and color fastness to rubbing of both CPB and Exhaust dyed fabric we can say that the quality of CPB dyed fabric is better than Exhaust dyed fabric.
So, despite the quality of Cold Pad Batch dyed fabric is better than Exhaust dyed fabric, Exhaust dyeing process is more profitable for any dyeing industry. Because in Cold Pad Batch process needs more time & cost than Exhaust dyeing process which ultimately increases the profit of any dyeing company.
CHALLENGES
This research is done based on bulk production’s cost, time, quality. In bulk production, it was very much tough to find out same specification of 100% Cotton Single jersey fabric of 160 GSM with Navy color dyed fabric in both Cold Pad Batch (CBP) and Exhaust dyeing section.
Calculating the required steam & electricity cost for the production was difficult because steam & electricity cost are not separately calculated in each section of the factory.
The access of the testing lab for outsiders of the factory was limited, it was hard to get the access of dyeing lab for the testing of shade quality by data-color machine.
Production is done shift wise but sometimes it takes more than 8 hour or 1 shift. That’s why there faced some difficulties to calculate the process times.
Collecting the cost of chemical & dyes was another complex task because it’s a confined information and no factory wants to share the information so easily.
LIMITATIONS
For quality analysis, here we showed only shade analysis through data-color machine. Due to the lack of time and access in the testing lab, the color fastness test can’t be done.
Total salary of the workers & employees of each section was not possible to collect that’s why here didn’t added the manpower cost with the total cost of the 100kg dyed fabric.
Cost per unit of water, steam and electricity are taken from reliable sources.
FUTURE RESEARCH DIRECTION
The manpower cost, water neutralization cost and some other lower costs of both cold pad batch and exhaust dyeing sections are not included in the total dyeing cost. If these costs are included with the cost of Cold Pad Batch (CPB) and Exhaust dyed fabric than that cost will be more acceptable, and we can differentiate more accurately which process is more profitable for any dyeing company. In this research project only applied most usable quality test method which is data-color test that’s used widely in dyeing factories for determining the quality of dyed fabric. There has color fastness test, shrinkage control test, color absorbency test which can be used to determine the quality of dyed fabric and by which the quality of both fabrics can differ more precisely.
CONCLUSION
The results obtained from this study allow us to conclude that compared to traditional Exhaust dyeing methodology, CPB dyeing technology consumes less steam & electricity but needs more chemicals than Exhaust dyeing process. Cold Pad Batch (CPB) dyeing process has the capability of continuous production, and the reduced dyeing auxiliary concentration leads to minimize the waste effluent. In CPB dyeing process, no salt or small amount of salt and steam are required, and the rate of dye fixation is at ambient temperature is high. Despite salt or small amount of salt used in Cold Pad Batch (CPB) dyeing process and the quality of dyed fabrics are also better, Cold Pad Batch dyeing process is not so much economic friendly process for dyeing factory. For a factory profit is the main target, but in Cold Pad Batch dyeing process needs comparatively more time and cost. That’s why Exhaust dyeing is more economic friendly and profitable process for dyeing factory. Also, there has some restrictions in Cold Pad Batch dyeing process like as, only those fabric can be dyed in this process which are constructed by cotton fibre. We hope in future this restriction will overcome by developed techniques and technology.
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