Study On The Preparation Of Formaldehyde-free Discharge Agent And Its Application In Pigment Discharge Printing

Thiourea dioxide is drawing more and more attentions in textile industry because of its unique reducing ability.It releases no formaldehyde,and is free of heavy metal ions.However,TDO cannot be uniformly dispersed in the discharge paste,which inhibits TDO particles from passing through screens,and weakens its reducing ability to ground dyes.Furthermore,conventional steaming process is complicated and consuming high energy.In our study,the modified discharge agent TDO was prepared by grinding TDO in a non-aqueous media D5 in the presence of little water and 1%(mass percent)Tween-20.Thereafter mixed with selected thickeners,binders and other additives,the modified discharge agent TDO was used in pigment discharge printing of cotton and silk fabrics.Besides,a free steaming pressing process was developed and used in pigment discharge printing due to its energy conservation,environmental protection and water saving.The particle size,dispersion stability,whitedischarge ability and reducing stability of the modified discharge agent TDO under different water contents were studied,and the optimum ratio of water was determined in grinding process.By analyzing the compatibility and rheological property of thickeners,the handle and whiteness of the fabric samples,thickeners were chosen to adapt to the modified discharge agent TDO.The temperature,time,and the concentration of TDO in pressing discharge printing were optimized.Tensile strength tests,DSC and FT-IR were used to measure the influence of white discharge printing on the properties of printed fabrics.The crocking fastness,handle and K/S value of printed fabrics were tested to determine the optimum binders.Based on the above fundamental researches,the pressing process was applied in pigment discharge printing with modified discharge agent TDO.The results show that:(1)In grinding process,when water contents vary from 5%to 10%,the modified TDO exhibits higher dispersibility,narrower particle size and better whitedischarge stability;(2)The fabrics printed with thickener compound(PT-RV:emulsion=1:1)or TF-312C have better whiteness,handle and other performances;(3)The optimum pressing discharge printing is carried at 110? for 40 s with 10%concentration of modified discharge agent TDO,which has less influence on fiber structure and fabric properties similar to the conventional steaming process;(4)The binder APF101 and UDR-K have less effect on the color change of pigments,and can endow printed fabrics with better K/S values,colorfastness and handle.