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Fabric Dye

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Assignment: Fabric Dye Dyeing is a procedure that involves addition of color to products of textile such as yarns,fabrics and fibers. Dyeing is usually carried out in a special solution that contains dyes and specific chemical material The quality of color fastness is dependent on 2 factors. foremost selection of appropriate dye depending on the textile material to be decorated and secondly selection of the proper method for dyeing the fabric, yarn or fiber(Smith,McClure,2003).
Different materials are utilized during the process of textile dyeing. These include. fiber, water, cloth or yarn. Apart from these materials, a host of other process chemicals are included. These are. acids such as formic and acetic, alkalis such as sodium carbonate, NaOH and potassium hydroxide, bleaches such as sodium chlorite, sodium hypo chlorite and hydrogen peroxide, dyes such as pigment, disperse and vat, salts such as sodium chloride, stabilizers from sodium nitrate, sodium silicate and organic stabilizers, auxiliary finishes such as softener and fire retardant. There are various methods that are used for textile dyeing. First there is application of color by use of various techniques of dyeing for various kinds of fiber and at various phases of the textile production procedure. These techniques include. stock dyeing, direct dyeing, yarn dyeing, top dyeing, piece dyeing, dope dyeing, piece dyeing, garment dyeing and solution pigmenting (Smith, McClure, 2003).
There following are processes that are generally used when dyeing textile materials. batch and continuous, semi-continuous, and pigment dyeing process. Batch dyeing process is also known as exhaust dyeing and is the most common and popular technique for dyeing textile materials. The word exhaust is used to refer to this technique since this process allows dye to be transferred gradually from a moderately huge volume dye bath to the material being dyed. It also takes a longer time. Thus the dye is intended to ‘exhaust’ starting from the dye bath to the material. In this technique, textile materials can be readily dyed at any phase during their assembling into the preferred textile product which comprises of yarn, fiber, garment or fabric. Some of the machines used in batch dyeing process can perform at temperatures of 1000 0 C. Batch dyeing technique can be optimized by. first replacing conservative overflow-flood rinsing techniques with processes like drain and fill or use of other techniques such as smart rinsing (especially for fabrics), suitable recycling of rinsed water fo the subsequent session and finally recycling of dye bath if at all technical considerations permit (Smith, McClure, 2003).
The continuous dyeing procedure involves feeding textile materials continuously or constantly into dye range. The speeds range from 50 to 250 m per minute. Continuous dyeing process is also a well-liked method of dyeing and commands 60% of the total yardage of the dyed products. This process comprises of the following. application of dye, fixation of dye with chemicals or heat and eventually washing. This method is most appropriate for fabrics that are. Continuous dye ranges are intended for dyeing blends of cotton and polyester. Continuous and to a certain extent semi-continuous processes of dyeing are both less prone to consumption of water as compared to batch dyeing. It however results in residues being highly concentrated. For optimization of this method, latest adoption of dispensing techniques, whereby the chemicals are dispensed on-line as distinct streams (Theodore, Dupont, Ganesan, 2000).
They only get mixed at the instance just before they are conveyed to the applicator. Semi-continuous dyeing on the other hand comprises of pad-jig, pad-roll, and pad-batch. The fabric is foremost impregnated using dye-liquor in what is referred to as padding machine. It is then exposed to batch wise curing in a jigger. Alternatively storage with a slow rotation for several hours can also be done. This curing is performed at room temperature in the pad-batch whereas in pad-roll, this process is performed at increased temperature by employment of a heating chamber. Thus Fixing of the dye onto the fiber is enhanced by use of these two methods. After this process of fixation, there is thorough cleansing and rinsing in continuous washing machines of the fabric in full width. Pigment dyeing is a newly added technique. In this process, there is no actual reaction of chemicals that takes place between the fabric and the dye. What actually occurs is that pigments get seated on the material aided by binders. The main challenge in this technique is the fact that pigments are insoluble in water and displays no affinity for fiber. Thus conservative dyestuff-supported dyeing situations aren’t possible for pigment dyeing. To overcome such challenges, a new type of pigments has been devised for application in fibers.
The sector of textile dyeing and finishing consumes huge quantities of water together with significant amounts of complicated chemicals. Firms operating in the textile sector are being faced with considerable challenges, several of them related with the acquirement and discarding of these important raw materials. Specifically the costs brought about by mains supply of water and disposal of effluent are on the rise and firms need to solve these challenges so as to remain competitive and save money. Good Practice Guide outlines that it is feasible for firms to bring down their effluent and water costs by a whopping 20% or even more by adopting low-cost and no-cost changes. There are 3 main areas where water is mostly used in the processing of textile. These include. pre-cleaning and rinsing of yarn or fabric before printing or dyeing, the printing or dyeing operation, soaping and later on after-treatment and finally the process of rinsing (Christie, 2007).
The other areas that can also use water include water for cooling purposes, cleaning, ion exchange, steam drying and boiler. Water is thus allocated to the above 3 areas providing suitable consideration to other smaller ancillary uses of water in addition to the huge process consumers. Process uses of water include. dye house, process cooling, washing or rinsing and the processes of scouring, finishing, and bleaching. Water use can be reduced by such simple options as repairing leaks and faulty valves, turning off running hoses and taps and turning off water especially when machines are off. Water use can also be reduced by application of advanced methods such as reducing the amount of process phases, recycling cooling water, re-using process water, countercurrent rinsing/washing and reduction of process water usage(Christie, 2007).
There are several sustainable dyes that can be made by use of less water. These include. reactive dyes which contain a reactive group that builds a chemical bond under alkaline condition with cotton fiber. These types of dyes provide bright and fast colors, and they account for more than 70% of the dyes that are used for cotton. Vast amounts of salt are required to make the dye migrate from the dye bath onto the fiber and also the fixation and exhaustion rates for dyes that are reactive are comparatively low. Thus for usual reactive dyes ,the rate of fixation is mostly less than 80% which results in wastage of dye and removal of the unfixed dye needs and extensive washing and rinsing with hot water. Suppliers of dye are now offering advanced dyes that permit higher fixation and exhaustion rates while at the same time utilizing less than half of salt required with normal reactive dyes. As more and more mills attain experience with these new dyes and gain confidence that they provide savings in water, energy and chemical reduction, their adoption should significantly increase (Harriet, 2008).
Almost all the chemicals utilized in textile processing are in most cases not maintained on the fiber but are eventually washed off by use of water. This effluent finally finds its way to the environment and thus local community in one way or another. This therefore calls for effective management of the same so as to reduce its impact not only to the environment but also the cost the company would incur in its treatment The strength of effluent and its subsequent treatment costs can thus be highly reduced by controlling the amount of each chemical and water used, replacing the highly polluting chemicals with less polluting ones. Simple options for reducing the strength of effluent include recipe optimization whereby the recipes are checked whether they have been mixed to the right specifications and whether the specific chemical used is really important to the process. In some instances it is possible to attain a 20-50% reduction in chemical by just reviewing use of recipes and chemicals. This correspondingly reduces effluent biological oxygen demand (BOD) by 30-50% and reduces the costs of disposing effluent. Other effective methods include dosing control-checking for proper calibration of dosing systems and if manual, then operators should be supervised on how they control and measure dosing, instrumentation, pre-screening chemicals, pre-screening raw materials, chemical substitution and finally chemical re-use and recovery. Some firms are required to correct the PH of the last effluent before dumping it to sewer by using alkali or acid to dose it. Thus use of additional chemicals can be eliminated by examining the available waste streams and thus neutralizing of one stream with another can be considered (Kate, 2008).
Effective chemicals, effluent and water management is a process that is ongoing. It thus requires constant commitment from management and may entail rewriting processes or introduction of improved systems to maintain any improvements done. The phases for implementing a chemical, effluent and water management program entail. establishing a management team, planning the program, carrying an audit to determine chemicals and water use together with effluent production, identifying all opportunities for reduction of chemical and water consumption, assessing the feasibility of different options, implementing solutions, monitoring the options implemented, reporting of cost savings and progress to the workforce, and finally managing initiatives to increase and maintain savings(Theodore,Dupont,Ganesan,2000).
References
Christie. R.M (2007). Environmental Aspects of Textile Dyeing. New York: Woodhead Publishing Ltd.
Harriet, H. (2008). From Fiber to Fabric:The Essential Guide to Quiltmaking Textiles. New York: C &amp. T Publishing Inc.
Kate, F. (2008). Sustainable Fashion and Textiles:Design and Journeys. New York: Earthscan.
Smith B, McClure V. (2003). Fabric Dyeing for Beginners. New York: Collector Books.
Theodore L, Dupont R,Ganesan K.(2000). Pollution Prevention:The Waste Management Approach to the 21st Century . New York: Lewis Publishers.
http://www.wrap.org.uk/sites/files/wrap/GG062.pdf