Cellophane From .

Cotton Lin-
ter Pulp-A New Dimension in
P. R. Ra.aiwa.y
Cellulose Technology, in India

Cellophane or Cellulose Film, as process but with fast developing protects what it shows" and gives
it is called, is essentially regener- improvements. The subsequent the buyer a feeling of reassurance
ated cellulose. The history of development in 1927 of methods that he is able to See what he
regenerated cellulose may be of obtaining Moistureproof buys and that the product packed
considered to start with the Cellophane gave a boost to the is genuine and fresh. As more
discovery in 1892 by Cross, technical applications and the than 100 different types of
Bevan & Beadle that cellulose demand for this product for an Cellophane can be made suited
could be converted into a disper- ever widening variety of uses has to specified applications, no
sible form by treatment with been increasing day by day. The wonder that the position of
Caustic Soda followed by CS2, higher strength properties and Cellophane as a packaging
known as xanthation. A method the comparatively cheaper price medium is acclaimed as universal.
of coagulation and regeneration of cellophane are bound to
cellulose in the form of a film or sustain this product in competing It is a matter of pride that the
foil was subsequently patented with several other products 'like manufacture of Cellophane and
by Stearn in 1898. The Swiss Polyethylene, PVC etc. of more Rayon was pioneered in India by
scientist Bradenberger was, recent origin. Travancore Rayons in 1950, in
however, largely responsible for the post-independence years of
Cellophane, because of its
the initial work OD producing fast industrialisation of the
remarkable characteristics, is the
regenerated cellulose foil in country. From the initial 2-3 tons
most' popular and versatile
continuous sheets and his first per day production, we have been
medium in the field of flexible
patents for continuous casting growing and expanding in stages
packaging for reasons of its
machines were issued in 1911. and BOW we have four cellophane
sparkling transparency and
Bracenberger is also credited with plants with a capacity of 15-16
clarity, its superior properties of
the coining of the familiar trade tons per day. Corrspondingly,
protecting against moisture,
name Cellophane which is derived there are three coating machines
odour and gas, its smooth surface
from the first syllable of cellulose now, incorporating the latest
which imparts excellent printing
and the last syllable of the French technology in the field and we
characteristics, its high speed
word 'Diaphane' meaning trans- are now in a unique position to
performance on packaging
parent. The first plant for the
machines, its capacity to be produce as many as 33-40
production of Cellophane was
tailored economically-to meet a different types of cellophane to
erected in France bv La Cello-
variety of packaging requirements meet any designation or specifi-
phane followed shortly afterwards
and its ability to combine with cation required by the customer.
by Great Britain and the United
other packaging media both by Quantitatively, we are equipped
States u~ing thl"cnre Brlldpnht'r~t'r
extrusion coating and by lamin- to produce about 4-5 thousand ..
P. R. Ramaswamy ation. In other words, cellophane tonnes per year of cellophane,
Superintf'ndent is the only packaging material thus saving about 4-5 crores
The Travancore RayollsLimited that "shows what it protects and of foreign exchange. Along with

244 Ippta, July, Aug., & Sept .. 1~76 Vol. Xlll No.3
 this, we engage in regular supplies It may be apt to give a brief air has been displaced, the
of cellophane for Defence description of the process of pressure is raised to between
requirements and exports in Cellophane from Cotton Linters. 5-8 Kg. The contents are thus
1'. Cotton Linter Pulp: ··cooked" for a period of 2-6
sizable measure and contribute
substantially to the national hours depending on the viscosity
Cotton Linters are generally of to be attained in the product,
cause. different grades=-lst cuts, 2nd the characteristics of which are
Pioneering as in the achievement cuts, mill runs, and defibrated, determined by the concentration
of Cellophane production, Tra- An optimum blend of these ofthe alkali and by the time and
vancore Rayons has "beenthe grades is used. The process of temperature of the digestion.
first in India to establish the converting the linters into pure Thorough mixing of the linters
successful use of cotton linters cellulose pulp is donein batches. and alkaline liquor throughout
for viscose grade (dissolving
Raw Cotton Linters
grade) pulp. December 8, 1961,
I
marked the historic commission- Opening and Dry Cleaning
ing of the 10 ton Cotton Linter I
NaOH Digestion spent liquor
Pulp Plant in the Travancore
I
Rayons. Wood pulp (formerly Washing
imported and subsequently from I
NaoCI Bleaching &. Souring
indigenous sources) which was I
used as raw material for Cello-
phane manufacture gradually has Washing
been replaced oyer the years with
I
Soft Water
Cotton Linter Pulp. For some
years, Wood pulp was mixed To Vis ,
Hydro Extraction
For
cose sale
with Cotton Linter Pulp in
varying proportions and now we Slurry Drying &
have been able to emerge out Steeping Baling
into a happy situation in which
our entire Cellophane production The pressed bales of cotton the cooking period 'is essential
is on Cotton Linter Pulp. The linters are unwrapped and fed to the uniformfty of th~ product.
years preceding this were indeed into the opening and cleaning
machines where the physical When digestion is completed, the
trying periods for us not only in
impurities are cleaned and the eontents.vef the digester vessel
stabilising the rated production
linters are rendered into a are discharged or 'blown off'
of cotton Linter Pulp but also in
uniformly loose and fiuffiy state .under steam pressure through a
dovetailing the eharacteristics of
for pneumatic transport to the valve at the bottom of the
this new material into the viscose
processing to achieve the quality Digesters through a Mixing Mill digester. The linters and spent
and quantity of our Cellophane where the linters are mixed liquor fall into a steel wash tank
production. Trials are now under thoroughly with alkali containing where the liquor is drained off
way to utilise cotton linter pulp some detergent also. The requisite and the linters (which at this
•• for our Rayon production also batch weight of linters is thus stage will be brownish) are
and it is hoped that tangible charged into the Rotary Digester, thoroughly washed to ensure
results will be achieved in this after. which steam is admitted complete removal of the alkali
direction as well. into the Digester. When all the and the soluble 'degradation

Ippta, July, Aug. & Sept., 1976 Vol. XIII No.3 245
 product. of the original imp- air, the pulp gets dry to a mois- Fhe first stcp is the preparation
urities. Continuous washing of ture of 5-7~ and is compressed of alkali cellulose, Ccllulose in
thc brown stock is done on and delivered in bales of average the form of Cotton Linter Pulp
Dorr Washers which consist of weignt approz. 100-150 Kg. to shreddings is steeped in 17-20%
a rotary pan with spray jets and the consumers. Soda Lyc in Slurry Mixers. The
a vacuum pump to withdraw the pulp "absorbs NaOH, swells up
The following table gives a com-
wash waters. considerably and the cellulose
parison of the typical analysis of
our Cotton Linter Pulp as against gets converted to alkali cellulose
After washing, the brown stock
IS 3518 specification for chemical whicli is then pressed to remove
is pumped to Hollander chests
cotton for viscose Type land excess,liquids. Tne alkali cellulose
for bleaching. Sodium Hypo-
also against a Buckey's sample. is next shredded i.c. disintegrated
chlorite is the usual bleaching
agent and souring is done with
dilute Sulphuric Acid. It is ----=---------------------------
Buckeye
important during bleaching which Our typical
sample Sample
is an oxidative process to control
such factors as slurry consistency,
------------------------~-------
1 3 4
time, temperature, pH and
---------------=----------------
active CIa concentration, to
(i) Moisture percent Max. ".20 7.5
avoid degradation and atthe same
time to produce a cellulose (ii) Alpha Cellulose Min. 98.2 98 96.90
having the desired colour.
Thorough washing follows each (iii) Solubility in 7.14%
NaoH Max.· 2-4 2.0 3.60
stagc of the bleaching process
and special attention has to be (iv) Ether Soluble matter
paid to the quality of water used percent 0.07-0.15 0.1 0.10
in reducing iron content, ash,
silica etc. After final washing,
the purified linters now termed (v) Ash Content 0.1-0.2 0.1 O.tS
as 'finished pulp' are pumped percent max.
into large blending tanks which
(vi) Acid insoluble ash
ensures uniformity of chemical
and physical propcrties of the ppm Max. 75
pulp through large consignments. 50 56
(vii) IrOD as Fe ppm max. 30-100
The pulp is next hydro extracted
in screw presses to a moisture (viii) Calcium as Cao ppm 80-150 120
content of approx. 50 -55% and
the material is pneumatically (ix) Manganese as Mn ppm 0.20 0.20
transported to the viscose station
for viscose manufacture. (x) Copper No .. 0.3- 0.6 0.28

When drying is required, the (xi) Fluidity/Viscosity Rhes

hydroextracted pulp is conveyed (0.5 gm in tOO ml) 15-i7 16.5-18.0 Vis. 8.6
through a tunnel drier where, c.p. (0.5% CEO)
under carefully controlled tem-
perature and drculation of hot - -- ..-._--'-- ---------- -~----------------.

246 Ippta, July, Aug. & Sept., 1976 Vol. XIII No.3
 2. CeUopbaDe: in such a waytbat the tips of 'he
Cotton Linter Pulp lids' are immersed in a solution
-----":""""-"------ of 10-15% Sulphuric Acid And
NaoH Slurry Steeping
14-20% Sodium Sulphate at a
temp. 35-4SoC. In this bath,
Slurry Pressing the viscose is coagulated and
••
regenerated back a. a filin of
Shredder Cellophane. After this, the film
in continuous sheet form passes
Maturing over rollers through a series of
baths for completion of the
hydrolysis, expelling, CSt and
Xanthation
H2S. washing out of the
acid, desulphurisation, bleaching,
NaoH Dissolving softening and plasticising, sizing,
• dyeing etc. and finally the
Ripening important changes of drying,
humidification. The continuous
Filtration film is wound on large
rollers.

Coating &. Processing The Cellophane so produced is

plain and transparent. To import
special properties of moisture
Conversion
proofness, heat sealability etc.,
Outgoing Product the film is given further coating
treatment. This essentially con-
into a fluffy powder form is the ripening of the viscose. The sists of a nitrocellulose coating
and fed into a large giant drum, . viscose is kept for specified periods plasticized together with resins,
rotating at a slow speed and under low temperature. This is to waxes, dissolved in a solvent
fitted with a cooling jacket. Here, bring it to a suitable coagulating mixture composed of ethers and
during the retention period of the point and viscosity for casting as toluene. The plain film is passed
alkali cellulose in the drum, Cellophane. During this penod, through the coating bath then
"maturing" involving a certain viscose is filtered 2-3 times to
dried in a current of hot air and
controlled depolymerisation of remove all suspended impurities
the released solvents are
the cellulose molecules, occurs. and subjected to a high vacuum
recovered.
The matured alkali cellulose is to remove all trapped air bubbles.
then treated with CS2 in speciaIIy After proper ripening, the viscose Apart from Nitrocellulose
proteeted vessels and gets con- is pumped by special pumps to a lacquers, other agents are also
verted to an. orange coloured mass casting head. The lower part of used in formulating the surface
called cellulose xanthate. This the head consists of 2 lips made coating. The most common
mass is further dissolved under of special alloy, finely polished, among them are 'Saran' (Vi ny-
vigorous agitation in dilute NaOH fitted at an angle and having a ledene Chloride Acronitrile
tinder controlled temperature to very narrow adjustable slit all Copolymer) and Vinyl Chloride
give a thick honey like liquid along its width. The head is Acronitrile Copolymers By
termed 'viscose', The next step mounted on lead lined acid tanks adopting suitable surface coating
•

Ippta, July, Aug. & Sept., 1976 Vol. XlII No.3 247
compositions, cellulose films with handling, film wrap, protection indicate the wt. in !ms. of 10 Sq.
varying properties best suited for from dust, foreign particles etc. Metres of the film.
each type of packaging have I. S. 5012: 1968 gives the Ind ian
The various type of cellophane
been developed by us. Standard Specifications for
are identified by a rotation of
Cellulose Film. It is heartening
The packing and storage of letters and a few of the common
that "Trayophane" (which is
cellophane is also important, the symbols used with their meaning
the trade name of Travancore
main factors to be taken care of are as follows :
Rayons Cellophane) not only
being air humidity, temperature
complies with these specifications
: Transparent A Anchored but excels them in respectof
T
C Coloured certain characteristics like tensile
M : Moisture Proof
0 Opaque strength, elongation, burst
P : Plain
: Heatsealing U : Unsized, low surface strength etc. which can be
S
slippage attributed to the use of pure
xx.: Polymer Coated W : Wrap Twist high alpha Cotton Linter Pulp
as raw material. •
Eg; A designation MSA Tmenns From each of the above types, Reference:
that the film. is moisture proof, Cellophane is produced in Cellulosic Plastics: V.E. Yarsley
heatsealing, anchored and trans- different gauges, the common & W. Flarell Cellulosic Films in
parent. gauges being 300, 400, 600 which . Packaging I.l.P.

241 Ippta, July, Aug., & Sept., 1976 Vol. XlII Ne. 3