How to bleach & dyeing jute fiber/ Fabric?

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)