Non-aqueous Softening Finishing For Cotton Fabrics

Low utilization of softener and wastewater pollution are the main problems for the traditional softening finishing(impregnation method) in aqueous bath. In order to solve the above problems and save water resources, novel softening finishing method is acquired.This paper focuses on a novel water-free softening finishing process of the softener/D5 suspension system for cotton fabrics. Decamethyl cyclopentasiloxane(D5) is introduced to be the finishing medium instead of water. It can significantly improve the utilization of imidazoline softener close to 100%, saving lots of water resources, which is of great significance for water conservation and wastewater reduction. Simultaneously the finishing temperature is lower,showing the advantage in reducing energy consumption. Moreover, D5 can be recycled after finishing by distillation technology. Hence the novel technology is expected to improve the utilization of imidazoline softener and remarkably reduce sewage emissions, achieving green dyeing and finishing.The preparation of the softener/D5 suspension system is the premise of softening finishing.Imidazoline softener and D5 are uniformly mixed by ball milling technology. The softener/D5 suspension system obtained can be in high concentration. Simultaneously it presents a good storage stability. During the softening finishing, it can be easily diluted with D5 according to the concentration desired.In the optimization of finishing process, the adsorption ratio of imidazoline softener is considered as the evaluation index. The optimal finishing process of imidazoline softener for cotton fabrics in D5 medium is as follows: the mangle expression before finishing 0%, finishing temperature 20 ℃, finishing time 5~10 min and bath ratio of D5 1:10. Compared to the traditional aqueous system, the softener/D5 suspension system shows significant advantages in reducing the finishing temperature, shortening the finishing time and remarkably improving the adsorption ratio of imidazoline softener.According to the SEM images of the finished cotton fabrics which are heated at different drying temperatures, the adsorption forms of imidazoline softener on fiber surface are different.When the drying temperature is lower than the melting point of imidazoline softener,imidazoline softener is adsorbed on fiber surface in the form of particles. Further increasing the drying temperature to the value higher than the melting point of imidazoline softener, a layer of adsorption film is formed on fiber surface. Because of the different adsorption forms, the softening mechanisms are variant. For the former, when there are relative motions between the interfaces, a series of micro-motions occurs, such as extrusion, deformation and sliding roll.Hence the friction coefficient of fiber is decreased, especially the static friction coefficient,improving the smoothness and softness of cotton fabrics. For the latter, the adsorption layer on the surface also decreases the friction coefficient of fiber. Additionally the R group in the molecular structure of imidazoline softener can easily rotate when subjected to external force.And it is easy for R group to return to the stress relaxation state, endowing cotton fabrics a soft and fluffy tactile.The adsorption kinetics of imidazoline softener on cotton fabrics in D5 medium and in water are investigated. The pseudo-first-order and pseudo-second-order kinetic models are utilized to analyze the kinetic data of imidazoline softener on cotton fabrics. The results indicate that the adsorption process follows the pseudo-second-order kinetics in both two systems.Simultaneously the adsorption rate of imidazoline softener on cotton fabrics in D5 medium is much faster than that in water.The basic properties of cotton fabrics finished by the softener/D5 suspension system are measured and characterized, in order to further investigate the finishing effect. The results show that the hand feeling of cotton fabricfabrics can be significantly and uniformly improved.Simultaneously the whiteness of cotton fabrics is not significantly affected. In addition, the softener/D5 suspension system is superior to the traditional one in softness and wash resistance of cotton fabrics.