Investigation into Cotton Knit Dyeing With Reactive Dyes To Achieve Right First Time (Rft) Shade
Hossain, Md. Ibrahim
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Abstract The present situation of dying process in Knit sector is well established & successful. But there are new challenges arising everyday which are trying to unsettle this progress. The process can be improved more if some new technology is introduced under precise condition making sure that the quality of production is not degraded. The knit dyeing process of cotton is almost entirely using Reactive Dyes & Exhaust methods, which are still undoubtedly successful. But there are some problems which were not previously taken into consideration due to flexible market situation, now the business is very complex and competitive. So now some of them are playing vitally in the ratio of profit with quality. The first & the foremost target of any industrial production are to produce in the least time with maximum quality. At present days our knit dyeing industries are affecting with reduction of profit margin, economic crisis in countries, energy crisis etc. In such hostile condition the industries should concentrate very carefully on the duration of unit production, making the dyeing right in the minimum process steps. That’s why intense control of process should be done to get as much as close towards right-first-time dyeing. The “right first time” (RFT) approach to dyeing requires management, supervisors, and operators to focus on close measurement and follow-up of all aspects of the production system to ensure that each step is operating as specified. Goal-oriented product specifications are met on first-pass processing, so material is not held in-process for dye additions or rework dyeing. Rapid corrective action is taken when any defect is identified in the process or product. Operator and technical teams define and implement longer-term solutions to more frequently occurring breakdowns or disruptions in the process. Fixation levels for reactive dyes, when doing deep dyeing, can be as high as 70%. Tests in several factories in Bangladesh have shown that currently fixation ranges from 40-65%. If, on average, the fixation is 50% then about 20% of the dye is essentially being wasted. If 20 kg of dye is used to dye a batch of 200 kg of fabric then 4 kg is being wasted per batch. If, on average, dye costs Tk.460 per kg then this is a loss of Tk.1840 per batch. If a factory dyes 1,000 tones of fabric each year, using 100,000 kg of dye and wastes 20% because of poor fixation, this is the equivalent of a loss of Tk. 9,200,000 per year (approximately US$ 117,949). This fixation level can increase achieving RFT shade by changing the variables (pH, time, temperature, liquor ratio, dyeing process, process parameters-different types of salt, alkali etc.), by modification the cellulose (cationization), reducing water hardness. In this experiment it was studied most of the parameters related to RFT concepts. Among them 22 points were summarized through which it can achieve the RFT shade. All these factors were discussed in details. It was also worked to utilize the 3M (Man, Machines and materials). For this dyeing workers were trained to not using more or less dyes, chemicals, machines were ensured accurate parameters and raw materials quality were tested in every lot. Among the 22 RFT factors the water hardness effect on reactive dyes fixation was worked more. For this experiment there was used three reactive dyes namely, Dychfix Red 3BXF, Dychufix Yellow 3RXF, Dychufix Navy Blue 2GLXF. Their fixation efficiency was observed by using at different dosing the chelating agent Liang710. It was also studied the change in color fastness due to using at different dosage of sequestering agent. The result was compared among the sample dyed without chelating agent and sample dyed with chelating agent.