There are four stages of manufactures in which color may be applied to textile materials. Solution/dope dyeing Pigments of dye stuffs are dispersed in the spinning solution where the fibers are manufactured. There are some difficulties in this process of obtaining color on fabric.
Fibers are dyed in their loose state where the fibers are less tangled and dyed thoroughly. Fiber dyeing is expensive to produce. There is better penetration of the dye into the fiber which produces a higher degree of color fastness on fabrics. Direct, sulfur, vat and developed dyes are used on cellulose fibers.
Yarn Dyeing:
Yarns are dyed by three methods namely, skein dyeing, package dyeing and beam dyeing. Yarn dyeing is best adapted to large quantity dyeing. Gingham, chambrays, denims and madras are dyed by this method.
Fabric/solid/piece dyeing:
Dyeing the gray fabric either in woven or knit, open or tubular form, in continuous, semi continuous or batch process to get a solid color.Dyeing is followed by an after treatment to fix the dye or to wash out the excess dye to improve the fastness.Various types of dyeing machines are used for both continuous and Batch process.Every dye system has different characteristics in terms of versatility, cost,tension of fabric, use of carriers,weight limitations etc.
It shall provide sufficient movement for the liquor to penetrate uniformity into every parts of the goods.The liquor movement shouldn’t be so vigorous that it damages the fine materials.Machine must be constructed of a material which will withstand prolonged boiling with acid or alkaline solutions.Heating arrangement should be such that uniform temperature could be maintained.There should be some means of adding the concentrated dyestuff solution in such a way that it becomes well diluted before it comes into contact with the goods.All moving parts and electric motors should be protected against the corrosive action of steam atmospheric conditions
Pad Dyeing :
This process is carried out using mechanical means (pad-batch wetting).The dying liquor is distributed homogeneously onto the fabric (i.e. also the dye is distributed homogeneously).In a second stage the dye penetrates into the fabric and is then fixed. At the end of the process the material is washed.Pad dyeing is carried out with the fabric in open width form.The fabric is passed through a solution of concentrated dye liquor and is then squeezed evenly by a pair of heavy rollers to force the dye into the fiber.All the operations are carried out on a single machine.
Fabric, at first loaded into the machine, carry out treatments following a predetermined cycle, unload the machine and finally wash it thoroughly before starting a new cycle. This working process is extremely flexible and suitable for processing small lots: for example, it is possible to a carry out a scouring treatment on a single machine, and then a bleaching one followed by a dying process.All these operations can be carried out with different degrees of automatisation.
In fully automated dye houses all steps going from the preparation of recipes and laboratory trials to dyestuffs and chemicals feeding, material transportation, loading and unloading of machines and control of dyeing parameters (e.g. level,heating,Injection at selected speed PH temperature,etc) are performed under computing guidance.
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