Process Modification for Improvement in Conventional Reactive Printing of Cotton Fabric

Abstract

Current study was based on the imperative constituent’s replacement of the reactive printing paste for cotton printing. They are sodium alginate, sodium bicarbonate and urea. Although sodium alginate is a natural thickener and environment friendly, but its availability and cost are the major concern which motivated the researcher to replace it with some better constituent. Other main part of the printing paste recipe is urea. Urea is nitrogen containing compound and it causes water stream pollution. It supports the reactive dyes molecule in solubility and moisture management to the fabric. Moisture helps the dye shade to remain sharp and shine during steaming process. The third and final replacement was sodium bicarbonate. Alkali is prerequisite in printing as reactive dyes form covalent bond to cellulosic cotton in alkaline condition. However, alkali hydrolyzes the dye molecules as well. Also, it has detrimental effects towards environment. Sodium alginate was replaced with synthetic acrylic thickener and tamarind kernel powder after its carboxy methyl substitution. Its degree of substitution was dignified by using both dry and wet methods. 0.654 was the DS value with dry method and 0.661 was the DS value with wet method. Urea was replaced with nitrogen free polymer i.e. polyethylene glycol 400 which increased dye solubility. Sodium bicarbonate was replaced with tri chloro acetic acid. Tri chloro acetic acid dissociated at high temperature around 100℃ and became alkaline (as required for fixation) during steaming process of the printed fabric. Five Mono chloro triazine and one vinyl sulphone reactive dye was selected for reactive printing. One conventional recipe was prepared with sodium alginate (2%), sodium bicarbonate (2.5%) and urea (15%) and six modified recipes were prepared against standard recipe 1. Recipe 2 included acrylic synthetic thickener (3%) and the rest of the chemicals were same as recipe 1. Recipe 3 and 4 have mixed ratio of SA and AST. Recipe 5 was prepared by using TCAA (4%) and CMTKP (6%). Recipe 6 by adding PEG-400 (2%) in recipe 5. In recipe 7, PEG-400 (1%) reduction in recipe 6. All 7 seven recipes were used in 6 reactive dyes at two dose levels (2% and 4%). There were total 84 trials of reactive printing and each trial was accessed with 9 tests. Sum K/S and shade strength, penetration of the dyes into the fabric, staining on the white ground of the fabric, washing fastness (change in shade and staining), rubbing fastness (dry and wet), light fastness, perspiration fastness (acidic and basic), sharpness of the edges, fabric hardness and cost saving. After running 6 colours at different dose levels, it was confirmed that recipe 6 is best in all aspects. However, based on cost and results, recipe 7 had better outcomes than recipe 1.