METHODS OF DYEING (YARN):-

Methods of yarn Dyeing:

When dyeing is done after the fiber has been spun into yarn, it is called yarn dyeing. In this method, the dyestuff penetrates the fibers to the core of the yarn. Yarn dyeing is slightly difference from woven or knit dyeing. Dyed yarns are used for making stripe knit or woven fabrics or solid dyed yarn fabric or in sweater manufacturing.

Different Types or Methods of Yarn Dyeing:-

Yarn is dyed either as hanks or wound on to compact reels known as packages, mounted on hollow spindles. There are many forms of yarn dyeing: skein (hank) dyeing, package dyeing, warp beam dyeing & space dyeing.

A. Package Dyeing:-

Package dyeing is a mature technology that is one of the most commonly used methods of yarn dyeing. The term package dyeing usually denotes for dyeing of yarn that has been wound on perforated cores. The dye flows through to the yarn package with the help of the deliberate perforations in the tube package. Once full exhaustion is brought about, the carrier of colored yarn is consequently removed from the vessel.

Fig: Package dyeing (Photo: Getty images)

Ref by printerest.

The package which is wound may be of polyester, cotton, viscose or acrylic. The weight of the package varies from 500 g to 2 kg each. The other names for package dyeing is cop, cheese and cone dyeing.

B. Hank Dyeing:-

Hank dyeing is an another methods of dyeing yarn. The yarns are loosely arranged in skeins or hanks (skein is the length of a yarn wound in a loose coil). Then they are hung over a bar and immersed in a dyebath. In this method, the color penetration is the best & the yarns retain a softer feel. The process of dyeing yarn in the form of hanks or skeins is carried out by both hand & machinery. It is also called skein dyeing.

Fig: Hank dyeing ref by printerest.

C. Space Dyeing:-

Space dyeing is a technique used to give yarn a unique, multi-colored effect. While a typical skein of yarn is the same color throughout, a skein of space dyed yarn is two or more different colors that typically repeat themselves throughout the length of the yarn. Space dyed yarn is sometimes referred to as dip dyed yarn. The secret to space dyeing yarn involves the use of a special chemical called a mordant. The purpose of a mordant is to help permanently fix the dye to the yarn after the space dyeing process.

D. Warp Beam Dyeing:-

Beam dyeing is the much larger version of package dyeing. An entire warp beam is wound on to a perforated cylinder, which is then placed in the beam dyeing machine, where the flow of the dye bath alternate as in the package dyeing. Beam dyeing is more economical than skein or package dyeing, but it is only used in the manufacture of woven fabrics where an entire warp beam is dyed. Knitted fabrics, which are mostly produced from the cones of the yarn, are not adaptable to beam dyeing.

Process , Flow Chart for 100% Cotton Yarn (Dark/Medium/Light Shade):

Dyeing process can be varying depending on the individual procedure of a textile engineer or a dyeing master. Now I will give typical flow chart of cotton yarn dyeing.

Pretreatment

Batch loaded

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Demineralization (50˚C, 20 min; pH=4.5)

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Scouring & bleaching (100˚C×40 min.)

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Drain

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Rinse

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Drain

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Neutralization with acid (50°C ×20 min)

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Hot Wash with peroxide killer (60˚C, 20 min.)

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Drain

Dyeing

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Leveling agent & Salt (60° × 20 min; PH=6)

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Color dosing (60°C×20 min.)

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Run time = 10 min. (60°C)

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Color migration (80°C × 20 min.)

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Cooling (60°C)

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Level Check

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Soda dosing (60°C×30 min.)

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Dyeing run (Dark shade :60°C×60 min; Medium shade: 60°C×40 min; Light shade: 60°C×

30 min)

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Dyeing sample check

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(If Ok)

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Drain

After-treatment

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Rinse (with cold Water)

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Neutralization after dyeing (50°C×20 min.)

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Drain

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Soaping (Hot wash)

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Drain

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Rinse

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Add finishing chemical (60°C×20 min)

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Drain

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Unload.

Ref :-https://textilelearner.net