2. Rayons
According to FTC (Federal trade
commission):
A manufactured fiber composed of
regenerated cellulose in which
substituent have replaced not more
than 15 % of hydrogen of hydroxyl
groups
3. Viscose Rayon
Rayon is the oldest commercial manmade
fiber.
The process of making viscose was
discovered by C.F.Cross and E.J.Bevan in
1891
It is now manufactured abundantly as its
raw material is cellulose and is available in
large quantities in timber and vegetable
matter
4. Viscose Rayon
The viscose method is relatively
inexpensive and of particular significance in
the production of nonwoven fabrics.
It is not synthetic.
Its properties are more similar to cotton and
flax rather than polyester and nylon.
Viscose Rayon has silk like aesthetic and
good feel.
The name viscose was derived from the
word viscous, which mean liquid state of
spinning solution.
5. Manufacturing of viscose
rayon
Preparation of wood pulp
Steeping and pressing
Recovery of Caustic soda
Shredding
Aging
Churning (Xanthation or Sulphidising)
Mixing
Ripening
Spinning
7. Preparation of Wooden pulp
Soft wood trees are used
Wood is chipped into pieces about
0.9’’ X 0.5’’ X 0.25’’
Chips are treated with Calcium bi sulphite
Ca(HSO3)2 for 8 -12 hours
Chips are cooked with steam under
pressure for 14 hours to convert into pulp
form
Pulp is washed with water to remove
Calcium bi sulphite
Pulp is bleached with sodium hypo chlorite
(NaOCl) solution
Pulp is converted into paper board
9. Steeping and
pressing
The cellulose pulp sheets are steeped
in 17.5 % NaOH solution for 1-4 hours
It is then pressed to remove excess
solution
This process is called “ steeping”
Cellulose is swollen and liquid turn
brown
Excess of alkali is pressed out
This process is known as “ pressing”
Moist soda cellulose mass is obtained
10. Recovery of caustic soda
Moist soda cellulose is allowed to
diffuse through parchment
membranes to obtain pure caustic
soda
Recovery of caustic soda is important
for economic purpose
Used Caustic soda is concentrated
and mixed with fresh caustic soda to
12. Shredding
The shredding machine consists of
drum inside which high speed
revolving blades with serrated edges
are installed
Moist soda sheets are shredded and
converted into fine crumbs
14. Ageing
Carried out in stirring vessel
Very important for properties of fabric
Polymeric chains of cellulose are
degraded in the presence of
atmospheric oxygen at temp 20-25
degree centigrade
Completed in 1-2 days
15. Churning
Stainless steel air-tight rotating drum
It can rotate at about 2 rpm
Soda cellulose crumbs contain about 30%
cellulose
10% CS2 solution is added to soda cellulose
crumbs
Soda cellulose and CS2 are churned
together to form deep orange gelatinous
mass of sodium cellulose xanthate
Churning is completed after 3 hours
After completion of churning, sodium
cellulose xanthate is discharged
16. Mixing and blending
Dilute NaOH soln is added in sodium cellulose
xanthate and mixing is carried out for 4-5 hours
A clear viscous liquid is obtained which is
known as viscose
Viscose contains 6.5 % NaOH and 7.5 % of
cellulose
Different viscose solutions obtained from
different mixers are blended together along with
TiO2 to balance inequalities and to obtain
17. Uniform homogeneous mixture produces
better quality of Rayon
It is filtered to remove any un dissolved
particles
Air bubbles are removed
18. Ripening
It is very important part of manufacturing
process
The uniform homogenous viscous solution
is stored in stainless steel vessel at 10-18
◦C for 4-5 days for ripening
During ripening, first of all the viscosity of
solution falls down and then again reaches
to its original viscosity
19. When original viscosity reaches, this is
the proper time to spin the solution
and solution is immediately spun
20. Spinning
A ripened viscose solution is forced to a
centrifugal pump by compressed air, which
delivers it to filtering media and then glass
tubing which carries a spinneret jet
The centrifugal pump delivers the viscose
solution constantly and regularly
The spinneret is submerged in acid bath
Viscose solution comes out into acid bath
after passing through “spinneret” solidifies
into filaments owing to regeneration of
cellulose
Temp. of acid bath = 40~55 ⁰C
24. Properties of viscose rayon:
Tensile strength:
The tensile strength of normal viscose
rayon is 30000 – 46000 lbs per square
inch.
Elongation:
Normally it will elongate 17-25 % of its
original length before breaking.
25. Elastic properties:
At 2% extension it has elastic recovery of
60%
Specific gravity:
1.50 to 1.52
Effect of moisture:
It has moisture regain of 13%.
26. Effect of heat:
It begins to lose strength at 150
degree centigrade and decomposes at
205 degree centigrade.
Effect of sunlight:
It can withstand exposure to sunlight
without discoloration.
27. Chemical properties:
It can be attacked by oxidizing agents
like hydrogen peroxide.
Effect of Acids:
Can be attacked by hot dilute acids
and cold concentrated acids.
Effect of alkali:
It has high resistance to dilute alkali
and can be attacked by strong alkalis.
28. Resistance to insects:
Resistance to insects is good but can
be attacked by silver fish.
Microorganisms:
Resistance to mildews is much better
than cotton.
30. Major uses of Rayon:
Apparel: Accessories, dresses,
jackets, sport shirts, sportswear,
suits, ties, work clothes etc.
Home Furnishings: Bedspreads,
blankets, curtains, sheets,
tablecloths.
Hinweis der Redaktion
Serrated----- saw like
Galvanized----- stirring
For storage purpose------