DYEING

INTRODUCTION TO DYEING

Day by day dyeing technology is changing for providing more coloration facility, more dyeing machine productivity, more upgraded dyed product, better safety, lower wet processing time, higher quality of textiles, more consistency of dyes in the textile fabric & finally for human comfort. In textile wet processing and synthetic dyeing there are various types of machinery are used from dyeing pretreatment to finishing which vary with dye brand to brand according to their dyeing technology.

Over the years for textile fabric processing we saw a lot of development through which we can provide a wide range of textile product with different coloration appearance & which are used for different purpose. With the aid of textile machine now most delicate fabrics with different finish is provided which could not think at past. Usually there are three types of fabric.

i. woven fabric
ii. knitted fabric
iii. non-woven fabric

All of the above fabric categories have different derivatives. Among them Woven fabric has a great versatility. That can be used in home textile as well as fashion. New technology machinery provides versatility not only by varying the structure of woven fabric manufacturing but also varying in processing such as in coloration & by different finishes.

This web site contains some information on woven fabric processing machinery with their technical data as well as their component & advantages provides through their machine. It also contains some necessary picture & diagram which helps to be familiar with the dyeing machine. This project also contains dyeing brand information, dyes manufacturing country & silent feature.

FLOWCHART OF WOVEN FABRIC DYEING

                                    GRAY FABRIC INSPECTIO
                                                      ↓ 
                                     STITCHING & BRUSHING
                                                      ↓
                                               SINGEING
                                                      ↓
                                                DSIZING
                                                      ↓
                                               SCOURING
                                                      ↓
                                  BLEACHING MERCERISING
                                                      ↓
                  DYEING   ←                                   →     PRINTING
                          ↓                                                                 ↓
                                                FINISHING

BRIEF DESCRIPTION OF EACH STEP OF DYEING
SINGEING
Singeing is the first step of dyeing. Singeing is important for a fabric to provide a smooth finish. Woven fabric goods usually contain protruding fibers from textile yarns. Singing process is used to remove those protruding fibres from the surface of the fabric. The fabric is passed in to a flame and these protruding fibers are burned out. Some time copper plate is used remove the fibre. For printing, singing is most essential to improve the surface smoothness by eliminating the pilling and fibres.

DESIZING
Desizing is an important dyeing preparation step. During weaving sizing material is used to increase the strength of warp yarn. The sizing material is hydrophobic in nature. That’s why it must be removed before dyeing. Desizing is the process to remove the size material from the fibre. There are many chemical to remove the size material. Enzymes are the most popular material to used in sizing process.

SCOURING
Scouring is one of the most important processes of textile fabric dyeing. All of the natural fibre contains natural oil and wax. Before dyeing, those oil and wax must be clean for smooth and proper dyeing. The Scouring is a cleaning procedure that used to eliminate those oil, wax from fibers, yarns, or fabric by soaping. For scouring process alkaline solutions are typically used; however, Solvent solution may be used in some case. The parameter of scouring procedures like temperature, chemicals, and time vary with the type of fabric and fibre types. Impurities are including natural materials, dirt lubricants and other. Residual tints antistatic agents, water-soluble sizes, used for yarn verification.

BLEACHING
Bleaching is a complex process. The most common bleaching agents include sodium chlorite, hydrogen peroxide, sulfur dioxide gas and sodium hypochlorite. All the natural fibre contains a natural color which is harmful for dyeing shade matching. For example the cotton has natural yellowish shade. So it is important to remove the natural color from the fibre. Bleaching is a used to eliminate the natural color from the fibre and prepare the fabric for further process. According to the types of fibre the bleaching chemical is selected. Hydrogen peroxide is most popularly used bleaching agent for cotton and cotton blends.
MERCERIZING
Mercerization is used to increase appearance, luster and dye ability of textile fibre. Mercerizing is a semi-continuous or continuous chemical process used for cotton and cotton/polyester goods.Room temperature must be maintain during this process, causes the twisted ribbon-like cotton or cotton polyester blend fabric to swell into a round shape and to contract in length. This causes the fiber to become more lustrous than the increase in strength original fiber,  by as much as 20 percent, and increase its affinity for dyes during dyeing

DYEING
Dyeing is proper way to coloration of textile material (fibre, yarn, woven fabric, knitted fabric, non-woven fabric). Suitable dyestuff, dyeing machine and dyes chemical is required for achiving proper dyeing shade. There are four types of dyeing,

1. Fiber Dyeing
2. Yarn Dyeing
3. Fabric Dyeing 

4. Garment Dyeing

PRINTING
Printing is the process to make colors on the textile materials with the presence of thickener to give sharp design. The thickener will be removed after the printing process to make softer handle.
Classification of Textile Printing
1. Direct Printing: Printing on material directly with the ink on the designed goods.
2. Reverse Printing: Printing on the goods by printing ink on background.

Textile Printing Process 

1. Fabric Preparation
2. Silk Screen/Rotary Screen/Roller Preparation
3. Print paste Preparation
4. Print ink preparation
5. Printing on fabric
6. Drying
7. Fixing
8. Washing and Soaping
9. Final Drying

FINISHING

Finishing is the last steps of dyeing. Actually dyeing finishing is required for quality assurence of dyed fabric. There are different types of finishing those actually depends on buyer requirment.
There are two types of finishing:
i. Chemical finishing
ii. Mechanical finishing.

Chemical finish: Here finishing effect is brought out by means of chemical. Some examples are:
i. Optical finishing
ii. Resin finishing
iii. Antimicrobial finishing

Mechanical Finishing: Here finishing effect is brought out by means of mechanical application. Some examples are:
i. Calendaring
ii. Heat setting

iii. Brushing
iv. Compacting.

Wish you good luck-------------------------------------------
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