What is is Viscose? |Flow chart of viscose rayon manufacturing: ||Description of Viscose manufacturing:

Viscose:

Viscose is a man mode ,natural polymeric  cellulose or regenerated cellulose or filament or staple fiber,viscose regenerated cellulose obtained by the viscose process .The name viscose was derived from the word “viscose” which describe the liquid state of the spinning sun.A viscose  solution is as thick as honey.

Basic unit or monomer:

                                         

N=175, cellulose  unit of Viscose

N=250, cellulose  unit for Cuprammonuim

N=300,cellulose unit for Polynosic

                                            

                                     Flow chart of viscose rayon manufacturing :

Preparation of wood pulp

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Steeping & Pressing

(Formation of soda cellulose &excess alkali is pressed out)

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Shredding

(In two or three hours formation crumbs)

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Ageing

(In atmospheric oxygen D.P fall of 800-350)

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Churning

(Xanthation or Sulphidising)

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Mixing

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Repening

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Spinning

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Drying

Description of Viscose Manufacturing

   

1.      Preparation of the wood pulp:

The starting metal is timber. It floats on rivers to the metals. Here the bark is removed and  the wood is chipped into pieces about  7/8×1/ 2×1/4 inches.The chips are treated with calcium bi-sulphite and then cooked with steam under pressure for about 14 hrs.Then bleached with hypochlorite and converted into paper boards sheets.

2.     Steeping & pressing:

The flat, white sheets of board contain about 90 -94% of pure cellulose. They are first conditioned by storing in a room at a definite humidity and temp. This conditioning is necessary. The sheets are then stacked vertically in the press and then soaked in a 17.5% solution of caustic soda for 1-4hrs. 

3.     Shredding :

The shredders are water cooled and will take 200 Jb of pressed soda cellulose at a time. In two or three hrs they break in up into fine Crumbs.

4.     Ageing:

Some depolymerisation occurs  and the degree of polymerization falls from about 800-350 in this process.The  higher the temp,the room rapidly does ageing  -which is mainly a process of depolymerastion.

5.     Churning:

About  10% of their own (crumbs) weight of carbon disulphide is added  and the crumbs and disulphide are churned up together , a deep orange ,  gelationous mass of sodium cellulose Xanthatevis formed. Churning is continued for about three hrs , the churns rotating at about 2 rpm.

6.     Mixing(solution):

In this mixers the sodium cellulose xanthate is stirred with dilute caustic soda for 4 to 6 hrs, the vessel being cooled. The xanthate dissolves to a clear –brown, viscose  liquid ,similar in appearance to honey this liquid ,similar in appearance to honey this liquid is known as “viscose” but is still too impure ,too acetated and too young to spin.

7.     Repening :

The viscose solution is stored for 4 to 5 days( at 10-18 )degree C and during storage it ripens .the whice whice is a available to determine when viscose is ripe enough to be spun is as given below –

Acetic acid test:

Before it is ripe the viscose solution will dissolve in 40% acetice acid but when it is viscose will precipitate in this acid.