Source: New Cloth Market


Abstract

Total wet chemical processing of jute has been carried outat ambient temperature starting from bleaching to dyeing with reactivedyestuff. Ambient temperature bleaching produces satisfactory whiteness andspent bleach liquor has been reused for bleaching of another batch of fibre.


Conventional hot hydrogen peroxide bleaching and subsequentdyeing of jute with reactive dyestuffs has also been done to make a comparisonwith the ambient temperature processed fibre. It has been found that whitenessIndex produced by ambient temperature process is slightly lower than thatproduced by conventional hot hydrogen peroxide bleaching but sufficient enoughfor carrying out dyeing in light shades and the dye affinity is always more incase of bleached fibre produced by ambient temperature process using hydrogenperoxide as bleaching agent.


So, it saves a lot of precious resources like thermal energyand water. The water effluent is also minimum resulting the process an eco-friendlyone.


Need For Chemical Processing Of Jute


Any product, whether it is diversified and value added juteproduct like upholstery, apparels, furnishing textiles etc. or jute fabric forpackaging, must have attractive look for customers' attraction. So, bleachingand subsequent colouration of bleached jute fabric in different shades, in asimple, cost effective and environment friendly way, is a challenge.


NIRJAFT has developed several processes relating topretreatment, bleaching and dyeing of jute. Bleaching and dyeing of jute atambient temperature is one of them.


Need For Ambient Temperature Process


  • 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 fibre
  • Dyeing process is also selected in such a way that it does not damage the fibre 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 juteprocessing, including the ease of processing in small operations, this studyis focused on performing both bleaching and dyeing at ambient temperaturewithout using thermal energy or sacrificing product quality.


Ambient Temperature Bleaching Process


The possibility of bleaching of jute at ambient temperaturehas been explored using sodium persulphate as peroxygen booster. The processis dependent on four variables Le. hydrogen peroxide, sodium hydroxide, sodiumsilicate and sodium persulphate, which has been optimised by using thestatistical technique, central composite rotatable plan (CCRP).


A recipe using 90 gpl of hydrogen peroxide, 25 gpl sodiumhydroxide, 20 gpl sodium silicate, 7.5 gpl sodium persulphate, 10 gpl non-ionicsurfectant and 0.5 gpl magnesium sulphate is suggested to obtain an acceptablelevel of whiteness without affecting the strength.


The method involve padding the fabric in the solution using100% wet pick up and then batching for 2 hours followed by washing.


Dyeing Of Jute at Ambient Temperature


Cellulose is the main component in jute which participate inthe dyeing of jute fibre. So, all the dyes which are suitable for dyeing ofcotton fibre 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 afterextensive study that dichlorotriazine and vinyl sulphone reactive dyes can beapplied judiciously on jute fibre at ambient temperature.

Process involves exhaustion of dyes on jute followed by fixation in alkali bath. 60-80 gpl glauber's salt is needed during exhaustion. 20 gpl sodium carbonate is required for fixation of dichlorotriazine and 4 gpl sodium hydroxide is required for fixation of vinyl sui phone reactive dye on jute.


Conclusions


NIRJAFT has developed several processes relating to pretreatment, bleaching and dyeing of jute. Bleaching and dyeing of jute at ambient temperature is one of them.


  • The ambient temperature processing technique is economic since it utilizes the minimum water and thermal energy


  • It requires no extra capital investment because conventional textile processing machinery can be used
  • The process produces minimum pollution since effluent is low


  • Reuse of chemicals for use in the next stage of operation makes the process even more economic


  • As the whole process is carried out at ambient condition, it is easy to control the processing condition


  • The health hazard problem to the labour is also minimised.



About the Authors


Authors are associated with National Institute of Research on Jute & Allied Fibre Technology (NIRJAFT)


Originally published in New Cloth Market: February 2010