Optimised chlorine-free bleaching systems for jute and jute/cotton blend fabrics

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">A sequential two-stage bleaching process using peracetic acid followed by hydrogen peroxide. has been developed specifically for jute and jute/cotton blend fabrics. A peracetic acid system is optimised for jute by the selection of suitable buffering and stabilising agents. A superior bleaching effect is obtained by using TSPP as a stabiliser in the presence of a phosphate buffer, under mildly alkaline conditions (<i>p</i>H 8.0-8.5), whereby excellent fibre brightness may be achieved at temperatures as low as 40-60°C. A conventional H₂O₂-Na₂SiO₃ system has also been further optimised for jute by the exclusive use of sodium metasilicate at high concentrations of 3.5-4.0 g/l. Sequential bleaching with these independently optimised system results in an excellent degree of overall fabric brightness, such that the 1st-stage peracetic acid bleach may be carried out at relatively low temperature (30-40°C). This combination process therefore offers an effective, environmentally favourable and energy efficient option to conventional peroxide-utilising and chlorine bleaching processes. A further advantage is that it may also be successfully extended to the bleaching of jute/cotton blends. Furthermore, fabric tensile strength loss is less than that observed with high temperature H₂O₂-Na₂SiO₃ bleaching and the tendency towards photoyellowing of the combination bleached fabrics is not adversely affected, despite the high level of fabric brightness achieved.</span>