Dyeing Cotton Knit Goods without Bleaching (Part-1)

Scope of Dyeing Cotton Knit Goods without Bleaching Operation for Energy Saving and Cost Reduction (Part-1)
Md. Palash Hossain
Department of Textile Engineering
Dhaka University of Engineering & Technology (DUET)
Email: palashsakal@yahoo.com




ABSTRACT
Several samples of single jersey cotton (knitted) fabric of 180 GSM were colored through conventional and selective process (pretreated without bleaching). Both types of samples were judged after dyeing with specific shade of single and tri-chromatic. Spectrophotometer (Data Color 650) CMC result passed for specific shade region for three primary colors red (0.5%), blue (0.5%) and yellow (0.1%). In case of tri-chromatic shade it was found that 0.5% shade also possible without bleaching operation. In addition, characterization of the bleached and unbleached dyed samples was done through investigation of different fastness properties. The unavoidable cost analysis revealed the appreciable outcomes of the work.

Key words:
Bleaching, cotton knit fabric, light shade, shade matching, color fastness, energy saving, cost effective

Abbreviations: PPC= Padma Poly Cotton, CMC= Color Measurement Committee, WTP= Water Treatment Plant, ETP= Effluent Treatment Plant

1. INTRODUCTION
Energy is one of the most important ingredients in any industrial activity [1]. However, its availability is not infinite. Global energy crisis, as well as high cost of fuels resulted in more activities to conserve energy to maximum extent. The textile industry retains a record of the lowest efficiency in energy utilization and is one of the major energy consuming industries. About 34% of energy is consumed in spinning, 23% in weaving, 38% in chemical wet processing and another 5% for miscellaneous purposes. Power dominates consumption pattern in spinning and weaving, while thermal energy is major for chemical wet processing.

Textile industries are consuming large quantity of water, which is expensive to buy, treat, and dispose. Major portion of water is used for wet processing of textile (60 to 70 %). Keeping this in mind there is acute need of energy and water conservation programmed to implement as earlier as possible.

Knit dyeing process is one of the most crucial and dominating sector in Bangladesh, as Bangladesh earns around 40% of its foreign currency by this sector [2] .So steps should be taken to make this sector stronger by reducing processing time, production cost and by saving environment. Process time is a very important factor for a dyer, because a dyer delivers his product within lead time that is given by the buyers. To deliver product, dyer must reduce his dying time. In this competitive world reduction of processing cost in also a major factor because higher production cost leads lower demand of the product. Hence it is very challenging task for the dyer. Moreover, it is of utmost necessity to keep our environment free from pollution of different chemicals used in dyeing factories. So to save environment a dyer should use the least chemicals that are most essential for performing dyeing. In order to perform the cotton knit dyeing process efficient, reduction of process time and reduction of chemicals in the preparatory stage play a significant role. However without using peroxide in the preparatory process, it could be possible to obtain desired shade after dyeing. But actually up to the scope of searching through internet or books, no relevant research works were found in a justified way.

To run with the processing heads, focusing on scouring, bleaching and so on can be initiated here.

Natural fibers (cotton) are yellowish or off-white in color due to color bodies present in the fiber and contain oils, fats, waxes, minerals, leafy matter and motes as impurities that interfere with dyeing and finishing. The process of destruction of yellowish or off-white color bodies is called Bleaching and The process of removing of impurities and make good absorbency is called Scouring.

1.1 Objectives with rationales

  1. The cost of a process includes the amount of process time, no. of processing stage and amount of chemicals. Henceforth reduction of process time, chemicals reduce the cost.
  2. Another focus lies with reduction of processing time this also depends on how many processing stage are occupied. Since in this experiment bleaching is not conducted, it saves a lot of time which is economical.
  3. Since waste water is hazardous for environment, in this process as bleaching is not done. So extra chemicals do not add on as effluent.
  4. If process stages are increase more than require amount of energy will also be more. In the bleaching process need huge amount energy to operate the machine. Here bleaching operation is totally ignore. So it saves sufficient amount of energy. That makes the process easier, safe and cost effective.
2. MATERIALS AND METHODS

2.1 Materials
2.1 Raw materials

Table 1: Information of used cotton fiber

Parameter
Value
Origin
CIS (Uzbekistan)
Staple Length
11/8 "
Grade
SM
Mic
4.53
Mat
0.87
Rd
79.3
+b
11.0

Table 2: Fabric specification

Parameter
Value
Fabric type
Single jersey
Type of cotton
100% cotton combed yarn
Yarn count
26S
GSM (Gram/Square Meter)
180

2.1.2 Dyes and chemicals:
Table 3: Name of used dyes

Name of dyes
Trade name
Country
Reactive dye
Novacron Red FN-2BL
Switzerland
Novacron Yellow FN-2R
Novacron Blue FN-R

Table 4: Name of used chemicals

Name of chemicals
Name of  the company
Wetting agent
Dysin
Sequestering agent
Dysin
Antifoaming agent
Dysin
Caustic soda(NaOH)
Dysin
Hydrogen peroxide(H2O2)
Dysin
Peroxide killer
Dysin
Stabilizer
Dysin
Acetic acid
Dysin
Detergent
Dysin
Leveling agent
Dysin
Gluber salt
Dysin
Soda ash (Na2CO3)
Dysin
Anhydrous sodium carbonate
James H.Heal
ISO Standard soap
James H.Heal
L-Histidine hydrochioride monohydrate
James H.Heal
Sodium chloride (Nacl)
James H.Heal
Disodium hydrogen orthophosphate dihydrate
James H.Heal

2.1.3 Machineries
Table 5: Specification of used machineries

Name of Machine
Model
Brand
Origin
Infra Red lab dyeing machine
Supermat
Sandolab
TAIWAN
Washing and dry cleaning color fastness tester
415/8
James H. Heal
UK
Crock master color fastness to rubbing tester
670 hand driven crock master
James H. Heal
UK
Spectrophotometer
Model-600
Data color
USA
Light box
CAC-60
Verivide
UK
Combined laboratory oven dryer
HX30
James H. Heal
UK

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