Now You Know 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

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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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