Dyeing, Bleaching and Integrated Textile Processing Sector

The integrated textile industry is engaged in production of yarn, fabric and finished goods from raw fibers. Initially, raw fibers are transformed into yarn, thread or webbing. Then the yarn is converted into fabric in looms. Fabric then dyed or printed to convert into finished product. In short, process flow is like fibre manufacturing/preparation, yarn manufacturing, fabric production and finishing processes.

Yarn Manufacturing:
Staple i.e. natural, regenerated natural and man-made fibers are transformed into yarn through grouping and twisting operations. Other fibers are processed using spinning operations. Vegetable fiber yarn manufacturing involves ginning, fibre blending, carding, combing and twisting while animal fiber yarn manufacturing involves scouring, fiber blending, carding, combing and twisting.

Fabric Manufacturing:
Fabric manufacturing involves winding, warping, section  warping, beaming, sizing, weaving and knitting. Winding, warping, section  warping, beaming,  involve transferring yarn from one type of package to another  to facilitate subsequent processing and placing into looms. Sizing is a process wherein sizing compounds are applied to yarn to bind the surface fiber together and to protect the yarn against abrasion  during weaving. The main sizing compounds are starch, gelatin,oil, wax and manufactured polymers such as poly vinyl alcohol, polysteyerene, polyacrylic acid  polyacetates.The sized wrap is dried by hot air or by steam. 

The most important operation of fabric manufacturing is weaving and knitting. Weaving is done using looms. Knitting is a method of converting yarn into fabric by intermeshing loops which are formed with the help of needles.

Finishing Process:

These processes enhance the appearance, durability and serviceability of the fabric and make the fabric worthy of apparel making. These finishing processes are called wet processing since extensive water is used to carry out these processes.

Preparation treatments consist of desizing, scouring, bleaching, gassing or singeing, mercerizing.

Bleaching :

To improve the whiteness of grey fabrics bleaching is carried out. Commonly sodium hypochlorite and sodium chlorite or hydrogen peroxide are used. Per-acetic acid bleaching is sometimes used for synthetic fibers that cannot be bleached using hydrogen peroxide.

Dyeing:

Dyeing is the application and fixing of dye to a substrate. Textiles are dyed using a wide range of chemicals and dyestuff. Dye may be reactive or dispersant. Reactive dye are used for cotton fibers while dispersant dye are used in manmade fibers. Auxiliary chemicals and bath conditions are used to accelerate the dying  action. The dye is then fixed using heat  and a wash removes unfixed dyes and chemicals and fibers of fabric. 

Printing:

Printing produces designs on the fabric by applying a colourant or other reagent ,usually in a paste or ink.

Stentering :

Stentering straightens and dries fabrics using hot air,resulting in the desired finished products.

Machine Finish:

This is a process  where width of fabrics is fixed.