Jute is a long, soft, shiny vegetable fiber that can
be spun into coarse, strong threads. It is produced primarily from plants in
the genus Corchorus, which was once classified with the family Tiliaceae, and
more recently with Malvaceae. The Corchorus capsularis. "Jute" is the
name of the plant or fiber that is used to make burlap, hessian or gunny cloth.
Chemical
composition of jute fiber:
Cellulose - 65.2 %
Hemi- Cellulose 22.2 %
Lignin 10.8 %
Water Soluble 1.5%
Fat and Wax 0.3 %
Physical
Property of Jute Fiber:
1) Tenacity (g/den): 3.5 ~ 4.5 or (40-70 g/tex)
2) Length: 0.2-30 inch
3) Stretch and Elasticity: Not good and 2%
elongation at break
4) Resiliency: Not very good
5) Abrasion Resistance: Relatively good
6) Dimensional Stability: Good
7) Moisture Regain: 13.75%
8) Specific gravity: 1.48~1.50
9) Color: Yellowish, Yellow, Brown, Golden
10) Heat Resistance: Good
11) Specific Heat: 0.324
12) Diameter: 18 micron
13) Cross section: Uneven, Thick cell wall with
lumen.
Chemical
Properties:
1) Effect of Bleaching: Not affected by oxidizing
and reducing bleaching agents
2) Effect of acid: Destroyed by hot concentrated
acids. Dilute acid can't do harm to the fiber
3) Effect of alkali: strong alkali destroy the fiber
and strength reduces
4) Organic solvent: Resistant to organic solvents
5) Effect of Mildews: Better than cotton and linen
6) Effect of insects: Resistance is good
7) Dye ability: Good, easily dyed.
8) Electrical and thermal conductivity: Moderate
Bleaching
Process of Jute Fiber/Fabric-
Bleaching of Jute:
Although jute fibres contain considerable amount of impurities, jute materials are
generally bleached without prior scouring due to its alkali sensitivity. Jute
differs from linen in its high lignin content (about 11-12% dry weight). The
lignin, together with hemicelluloses, provides inter-cellular binding material
known as lamella, holding the fibre together. In contrast to linen, it is
neither desirable nor necessary to delignify jute. Jute is effectively bleached
by hydrogen peroxide while most of the lignin remains.
A consequence of the presence of lignin in bleached jute is that its whiteness
is not fast to light.
Bleaching Process:
Jute may be successfully bleached with sodium hypochlorite solution having 3-7
g/l available chlorine, using sodium carbonate to maintain pH of 10 to 10.5 at
room temperature for 1 to 2 hours. It is advisable to add 1 to 2 g/l wetting
agent, when the material is directly bleached without scouring. It is then washed and anti-chloride with 0.2% sodium
sulphate for 20 minutes at 50 ̊C.
Sodium chlorite is suitable for bleaching of jute. It removes more lignin than
hydrogen peroxide. Treatment of jute fabric with acidified 4% (o.w.m.) sodium
chlorite solution, pH 4 to 4.5 at 90 ̊C for 90 minutes improves the whiteness
of the materials.
The bleaching with hydrogen peroxide
causes a markedly lower loss of weight (10% as against 17.9% in chloride
bleaching) and slightly lower loss in strength.
In jigger machine, the recipe (% O.W.M.) of jute bleaching as follows:
- Hydrogen Peroxide of 50% : 3 to 6%
- Sodium Silicate : 6 to 8%
- Caustic Soda : 0.5 to 0.7%
- Nonionic Detergent : 0.2 to 0.5 %
- Chelating Agent : 0.05%
- pH : 10.5~11
- Temperature : 80 to 85 ̊C
- Time : 120 minutes
The
brightness of peroxide bleached jute material was found to increase when
pre-treated with an enzyme mixture containing cellulose and xylanase.
The conventional hydrogen peroxide bleaching requires high temperature which
may damage jute material.
So cold
bleaching may be carried out by treating the jute materials with a solution
containing -
6% hydrogen peroxide,
4% caustic soda,
4% sodium silicate,
2% soda
ash and
1% soap
- followed by 24 hours storing at room temperature. The whiteness
achieved may not be very high.
- In that case after completing 24 Hours bleaching process , the jute materials should be washed using clean water and then optical textile brighter can be used to achieve more brightness. Optical textile brighter can be used at 1~3 g/l to make the solution based on to dip the whole mount of jute material in the bucket/ tank. Dipping time may be : 1~ 2 hours.
Ambient temperature processing:
Some other main parameters and considerations regarding ambient
temperature processing as given as under:
Processing of jute is difficult due
to its complex chemical structure. Bleaching
of jute is done in such a way that it produces sufficient whiteness without damaging fiber. Dyeing process is also selected in such a way that it does not damage the fiber and at the same time
results in optimum fastness and dye uptake. Jute being bulky and hygroscopic, requires a considerable amount of water and thermal energy for its
processing and subsequent drying. Effluent released after processing
creates water pollution. Considering the resource management issues involved in jute
processing, including the ease of processing in
small operations, this study is focused on
performing both bleaching and dyeing at ambient temperature without using
thermal energy or sacrificing product
quality.
Ambient Temperature Bleaching Process :
The possibility of bleaching of jute
at Ambient temperature has been
explore using sodium persulphate as
peroxygen booster. The process is dependent on
four variables. hydrogen peroxide, sodium hydroxide, sodium silicate and
sodium persulphate, which has been
optimized by using the statistical technique,
central composite rotatable plan (CCRP).
A recipe using -
50 g/l of hydrogen
peroxide (50%),
30 g/l sodium hydroxide (Flake),
25 g/l sodium silicate,
5
g/l sodium persulphate,
5g/l non-ionic
surfactant and
0.25 g/l magnesium
sulfate
- is suggested to obtain an acceptable
level of whiteness without affecting the
strength. The method involve padding the fabric in the solution using 90 -
100% wet pick up and then batching for 3
hours followed by washing
DYEING PROCESS -
Ambient temperature dyeing Cellulose is the main component in jute which participates in the
dyeing of jute
fiber. So, all the dyes which are suit able for dyeing of cotton fiber can
be used for jute with some
modification. Considering both the fastness of
colour and cost of dyeing, reactive dyes
are found to be best for jute dyeing. It
was found after extensive study that
dichlorotriazine and vinyl sulphone reactive
dyes can be applied judiciously on jute
fiber at ambient temperature. Process involves exhaustion of dyes
on jute followed by fixation in alkali
bath.
It is important to note that -
70-80 g/l
glauber's salt is needed during exhaustion,
20-30 g/l sodium carbonate is required for fixation of dichlorotriazine and
5 g/l sodium
hydroxide
- is required for fixation of vinyl
sulphone reactive dye on jute.
Thanks for reading!
B.R
Zahidur
Executive- (Hameem Group)
