Jute:
Jute is one of the cheapest natural fibers and is second only to cotton in amount produced, and variety fibers are composed primarily of the plant materials cellulose and lignin. Jute is a long, soft, shiny vegetable fiber that can be spun into coarse, strong threads. In this article we will know about jute fiber and its bleaching process with details.
Jute is an inexpensive fiber used primarily for ropes, packaging and backing carpets due to its coarseness. With the rise of synthetics in the 1960s, jute lost some of its market to polypropylene. Its breaking strength is comparable to that of steel wire. Jute can be mixed with cotton for casual garments. Jute is extracted from the bark of the white jute plant, Corchorus capsularis and to a lesser extent from C.Olitorius (tossa jute). Jute fiber also called as the ―”golden fiber” is one of nature‘s strongest vegetable fibers and has high insulating and anti-static properties, moderate moisture regain and low thermal conductivity. Jute ranks second in terms of production. Bangladesh and India (West Bengal) are the main producers of jute in the world, with Myanmar and Nepal producing smaller quantities of jute. Of the various jute products manufactured, sacking contributes for the bulk. In addition, jute yarn and twines are also used for household textiles. It is also being blended with other fibers and used in cushion covers, toys, wall hangings, lamp shades and shoes. Use of jute in rigid packaging and reinforced plastic is increasing and is replacing wood pulp and paper. Geotextiles are also made from jute.
Bleaching Process of Jute Fiber and Fabric:
Although jute fibers 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 fiber 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.
Jute 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 antichlored 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% (on the weight of material or 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 chlorite bleaching) and slightly lower loss in strength.
In jigger machine, the recipe (% o.w.m.) of jute bleaching as follows:
Hydrogen peroxide (50%): 3 to 6%
Sodium silicate: 6to 8%
Caustic soda: 0.5 to 0.7%
Nonionic detergent: 0.2 to 0.5 %
Chelating agent: 0.05%
pH: 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 cellulase 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.
Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
