Bleaching of jute

The art of bleaching jute has received fresh attention as diversified jute products like decoratives, soft luggage, and upholstry material are in great demand now-a-days. Raw Indian jute is brown in colour and requires bleaching. Scorning of jute 

Hydrogen peroxide bleaching process is most suitable for bleaching jute fabrics and the bleached goods are suitable for making diversified jute products. 

Process involving only use of is not very suitable as above certain percentage 

Scouring and bleaching of jute with sodium chlorite with an acceptable whiteness can be achieved, but the process is a time consuming two step process. Moreover, sodium chlorite is metal corrosive and health hazardous. 

The use ofperacetic acid as ableaching agent for jute fabrics is reported [119]. The optimum bleaching results are obtained at 70°C around pH 6.5. The mild acidic condition is most suitable because of the fact that neither hydrocellulose nor 

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Defatted jute was prepared by treating it with alcohol-benzene (1 2v/v) mixture in a Soxhlet apparatus, washed well with alcohol and air dried. Bleaching of jute fiber was carried out with 0.7% sodium chlorite following a special method (17) KPM rayon sample was prepared by treating it with dilute soap solution, washed well and dried. 

There are some serious drawbacks with reference to the bleaching of jute. They are ... 

Bleaching of jute with followed by treatment with an aqueous solution of... 

A continuous or semi-continuous process for bleaching of jute fabric with chlorinated derivatives of cyanuric acid is developed [126]. The process comprises a preliminary treatment with boiling water, followed by impregnation of the materials with 0.4-0.6% aqueous alkaline solution, and then subjection of the material to steam treatment. Thereafter, the material is treated at 20-50 C with a mixture of trichlorocyanuric acid and cyanuric acid (with available chlorine content 7-15 g/1), containing sodium carbonate or bicarbonate. The pH of the solution is finally adjusted to 4-5 with acetic acid or phosphoric acid. The treated material is then bleached with H,0,. The time of treatment is usually 40-60 min, but can be extended to 2 h in the case of a heavy fabric with high lignin content. 

A cross-sectional view of kenaf is shown in Figure 3d. The ultimate cells are nearly cylindrical with thick cell walls. Kenaf fibers are shorter and coarser than those of jute. Both chemical (kraft) and mechanical pulps have been produced from kenaf, and successful demonstration mns of newsprint have been made for the Dallas Morning Nem, the St. Petersburg Times, and the Bakersfield Californian with a furnish of 82% kenaf chemithermomechanical pulp and 18% softwood kraft pulp. Kenaf fiber is also considered a substitute for jute and used in sacking, rope, twine, bags, and as papermaking pulp in India, Thailand, and the former Yugoslavia. RoseUe bleached pulp is marketed in Thailand. 

The improvement of photostability of jute fabric itself is an important matter to be given priority. Various processes have been developed in which bleached jute does not revert to its natural colour on exposure to light. The blocking of reactive phenolic groups by etherification or esterification is expected to arrest the yellowing process. The presence of some chromophore in dyes can cause absorption of near uv-radiation of sunlight and prevent discolouration. Bleached jute goods treated with copper-potassium dichromate (0.25% o.w.f) improve photostability over conventional bleached fabric [123]. 

A two step process [127] based on the preferential removal of lignin from the surface of jute fibres has been developed. In the first step the fabric is treated with either moist chlorine gas and aqueous chlorine solution or with an aqueous solution of hypochlorous acid at pH 6 and containing available chlorine equivalent to 5-10% (o.w.f). In the second step, the treated fabric is extracted with an aqueous solution of at least one compound selected from sodium hydroxide, phosphates, and sulphites an equivalent to 5-10% (o.w.f.). Finally, the fabric is washed, and is bleached by the conventional H Oj and/or hypochlorite method. 

Laccase Color Chromophore and pigments Discoloration of colored effluent Bio-bleaching of lignin containing fibers such as kenaf and jute. Biobleaching of indigo in denim for various effects... 

The appearance and feel of jute fabrics is much improved by the woolenizing process, and bleached and dyed fabrics appear to have commercial possibilities. The problem is the cost of the treatment, and to achieve similar effects more cheaply may require a deeper knowledge of the internal changes that take place within the fiber. 

Distinction between Raw and Bleached Products.—In the raw state, many textile fibres, such as flax, hemp, jute, etc., exhibit a colour quite distinct from white and in these cases the distinction between raw and bleached products is simple and is made by the eye. Other fibres, however, such as those of cotton and wool, are often white in the unbleached state and in such cases the distinction between the raw and bleached products cannot be made by the eye but requires investigation. 

Gokhale et al. (11) studied the application of a yeast cellulase-free xylanase in agrowaste materials, such as bleached bagasse pulp, jute fiber, and corncob powder. The best result was achieved using bleached bagasse pulp with a degree of hydrolysis of 19.4%. 

Substrate and its Preparation. The substrate used for grafting purpose were jute fiber (defatted and bleached) and KPM rayon yarn. Jute fiber under investigation was of Corchorus Capsularis variety. It was arbitrarily divided into three portions. The middle portion was chosen for the purpose of study. 

Dessicator atmosphere conditioned at R.H. of 75% and a temperature of 26°C. Twist/cm (jute fiber) = 1. Lignin content of bleached jute = 10%. 

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