Regenerated Fibers.pptx

Fibres

1. Regenerated Fibers From naturally occurring polymers

2. Introduction High potential in natural material Cannot be used in their natural state Chemically processed into a solution Extruded through a spinneret Cellulosic: Rayon, L yocell , Acetate, T riacetate Protein: Azlon – S oy silk, Silk latte

3. Viscose First man-made fiber is composed of regenerated cellulose Invented in France in 1884 Derived from French word “rays of light ” It was first sold as artificial silk Regenerated cellulosic fibre and cellulose is the raw material for producing this man made fibre Raw material is obtained from a special variety of wood called spruce

4. Flow Chart Preparation of wood pulp  ↓  Steeping & Pressing  (Formation of soda cellulose &excess alkali is pressed out)  ↓  Shredding  (In two or three hours formation crumbs)  ↓  Ageing  (In atmospheric oxygen D.P fall of 800-350)  ↓  Churning  ( Xanthation or Sulphidising )  ↓  Mixing  ↓  Repening   ↓  Spinning  ↓  Drying 

5. Cont.

6. Manufacturing Process

7. Cont. Purification of Cellulose Spruce trees are cut into timber. Their barks are removed and cut into pieces Pieces are treated with a solution of calcium bisulphite and cooked with steam under pressure for about 14 hours. The cellulosic component - unaffected by this treatment , Cementing material called lignin, - converted into its sulphonated compound which is soluble in water and washed off. Purifying the remaining cellulose with excess of water. After this it is treated with a bleaching agent ( sod. hypochlorite ) and finally converted into paper boards or sheets .

8. Cont. Conditioning of Wood Pulp The pulp sheets are cut in to the required dimension and are kept in a special room . Air moves freely among the divisors by means of ventilators, the temperature is maintained at 30 degcelcius . This process for desired moisture content Steeping Process ( mercerising ) The conditioned wood pulp sheets are treated with caustic soda solution ( about 17.5%). Swell cellulose fibre The cellulose is converted into soda cellulose . The sheets are allowed to soak become dark brown in colour. This takes about 1-14 hours. The caustic soda solution is drained squeezed

9. Cont. Shredding or cutting process The wet, soft sheets are passed through a shredding machine Cuts them into small bits Ageing Process The soda cellulose is stored in small galvanised drum s for about 48 hours at 28 deg C. Ageing process - Stimulate the action of polymerization Exposure of white crumb to oxygen . White crumb are aged to bring down degree of polymerization Helps in maintaining proper viscosity

10. Cont. Churning Process or Xanthation The crumbs of soda cellulose are transferred to rotating, air tight, hexagonal churners or mixers . Treatment of white crumb with carbon disulphide under controlled condition at 20-30 C to form a cellulose xanthate Sodium cellulose xanthate is formed during this process and the colors of the product changes from white to reddish orange . Mixing or dissolving Process A dilute solution of caustic soda is added , and stirred for 4-5 hours The sod.cell.xan . dissolves to give a clear brown thick liquor, similar to honey. This is called 'viscose'

11. Cont. Ripening Process To give a solution having best spinning qualities. Ripening is carried by storing the viscose solution for 4-5 days at 10 to 18 deg ( type of fiber being made ). The viscosity of the solution first decreases and then rises to its original value. Ripened solution is filtered carefully to remove air bubbles

12. Cont. Spinning Process Done by wet spinning Viscose solution is forced through a spinnerets Spinning Bath Sodium sulphate dissolves sod. cell. xanthate Sulphuric Acid converts xanthate into cellulose filament Glucose to give softness  Zinc sulphate gives added strength

13. Viscose Filament and Fibres

14. Quality of filament depends The temperature of the spinning bath The composition of the spinning bath. The speed of coagulation The period of immersion of the filament in the spinning bath. The speed of spinning . The stretch imparted to the filaments.

15. Application of Viscose Rayon