Spinning - (Wet Spinning): The viscose solution is metered through a spinneret into a spin bath...

Spinning - (Wet Spinning): The viscose solution is metered through a

spinneret into a spin bath containing sulphuric acid, sodium sulphate, and zinc sulphate.

Once the cellulose xanthate is neutralized and acidified, rapid coagulation of the rayon filaments occurs which is followed by simultaneous stretching and decomposition of cellulose xanthate to regenerated cellulose.

Stretching and decomposition are vital for getting the desired tenacity and other properties of rayon.

Chapter 3 Different regenerated Cellulosic Fibres

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Other regenerated cellulose fibres:Cuprammonium or cupro rayon:Manufacturing Process of Cuprammonium Rayon Like Viscose Rayon, cuprammonium rayon is also a

regenerated cellulose fibre. Cotton linters are used as the source of cellulose for this rayon.

Ammonical copper oxide solution is also known as cuprammonium hydroxide solution.

Cuprammonium hydroxide solution is a solvent for cellulose.

When a solution of cellulose in cuprammonium hydroxide is diluted with water or treated with dilute sulphuric acid, the cellulose is regenerated or reprecipitated. By using a spinnerette, filaments of this regenerated cellulose can be produced.


Manufacture of Cuprammonium Rayon

The source of cellulose for this rayon is cotton linters, the purification of cotton linters is carried out in two stages:

a. Mechanical Treatmentb. Chemical Treatment

Mechanical Treatment

The cotton linters are transported in bales in highly compressed state and the object of the mechanical treatment is to loosen them and to remove loosely bound impurities such as dust sand, seed residues etc.


Manufacture of Cuprammonium Rayon b. Chemical TreatmentThe mechanically opened and purified cotton

linters are boiled under pressure for several hours with dilute soda ash ( Na2Co3) solution (2%) to which a little amount of caustic soda may be added.

The natural fatty matter present in the cotton is converted into soluble substance by the action of soda ash and thus removed from cotton linters.


Dissolution of Cellulose

In this, a solution of hydrated copper sulphate in 300-400 liters of water is introduced in a vessel at ordinary temperature with stirring.

Some sugar is also added followed by caustic soda solution to form copper hydroxide.

linters in water are added to the above mixture to form copper cellulose.

The copper cellulose is filtered to remove the liquid, well ground and dissolved in a solution of ammonia in water.


Spinning Solution

By adding certain compounds to the cuprammonium cellulose solution, the solution is made more suitable for spinning. These compounds include glycerine, glucose, tartaric acid, citric acid, oxalic acid, sugar etc.

Stretch Spinning

In the spinning process, the cuprammonium cellulose solution is discharged through nozzles ( spinnerette) into a solution of sulphuric acid in the form of relatively thick threads which are subsequently pulled( stretched ) to very fine filaments.


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Properties: Tenacity: 1.7-2.3 g/d (dry), 1.1-1.35 g/d

(wet) Elongation at break: 10-19% (dry), 17-

33% (wet) D.P.: 500 Cross section: Round Recovery from stretch: Good MR%: 11%

Chapter 3 Different regenerated Cellulosic FibresPolynosic: In other words, Polynosic is a regenerated cellulose

fibre which, when wet remains stronger and distorts less than either Cuprammonium or Viscose. Polynosic means many fibrils, The Intl. Organization for standardization prefers the name modal.

Properties: Tenacity: 3.9 g/d (dry), 2.9 g/d (wet) Elongation at break: 11% (dry), 13 %(wet) D.P.: 450-500 Cross section: Round Recovery from stretch: Good MR%: 11.8%

Chapter 3 Different regenerated Cellulosic FibresTancel:Tencel is a natural, manmade, biodegradable fibre which made

from wood pulp. General name is Lyocel. Tancel is solvent spun cellulosic fibre

of new generic class produce a clear viscose solution which is treated and spun into a bath contain dilute solution of the solvent. Tencel is the best fibre among regenerated cellulose fibres. The fibre is called CF0001 in USA.

Properties:Tenacity: 3.5 (dry), 2.5 (wet)Elongation: 11.8%X-section: RoundSpecific gravity: 1.56MR%: 11.5100% biodegradable. Tencel has a very high absorption capability, and a very

smooth surface.

Chapter 3 Different regenerated Cellulosic FibresBlending process: This solution of Na- cellulose xanthate

cellulose is blends in a big horizontal mixer to balance any irregularity and to get more uniform quality of final product.

Viscose is blends: because —It is not fully synthetic.Its cost lower than natural fibre.

By blending fibre, we can improve absorbency of lower absorbent fibre such as polyester.

Chapter 3 Different regenerated Cellulosic FibresSpecial viscose:Evlan: Evlan is viscose rayon staple fibre used by

the carpet trade. It has a smoother cross-section than standard viscose. It has a higher crimp usual. It has a higher strength than usual and this gives durability. Evlan has been widely used since its introduction in 1962. Evlan is used for Carpets.

Topel: This fibre is an x-section cellulosic fibre. It

has much less affinity for water, in which it swells only very little. It has good resistance to caustic alkali, a properly useful in package dyeing. It is used for blending with cotton for better appearance, handle and drape.

Chapter 3 Different regenerated Cellulosic FibresEnd use of viscose rayon:Apparel: Accessories, blouses, dresses, jackets,

lingerie, linings, sportshirts, sportswear, ties, work clothes

Home Furnishings: Bedspreads, blankets, curtains, draperies, sheets, slipcovers, tablecloths, upholstery

Industrial Uses: Industrial products, medical surgical products, nonwoven products, tire cord

It is used in making umbrella cloths and protective cloths.

It is used as sewing embroidery threads and in making (Special type of rope yarn).

Viscose + cotton: This blend is used for reducing cost

Differentiate between four re-generated fibers:.Properties Viscose rayon Polynosic Cupro Cotton

1. Tenacity

2. Elongation at break

3. D.P.

4. Cross section

5. Recovery from stretch

6. MR%

1.5-2.4 (dry)0.7-1.2 (wet)

15-30% (dry)20-35% (wet)

250-300

Serrated

Poor

13%

3.9 (dry)2.9 (wet)11% (dry) 13% (wet)

450-500

Round

Good

11.8%

1.7-2.3 (dry)1.1-1.35

(wet)

10-19% (dry)17-33% (wet)

500

Round

Good

11%

3-5 (dry)3.6-6 (wet)

3-7%

5000

Flat/kidney shaped.

Good

8.5%

Spinning - (Wet Spinning): The viscose solution is metered through a spinneret into a spin bath...

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