Study On The Low-temperature And Environmental Pre-treatment Technology Of Cotton Knitted Fabric

Energy saving, environmental protection, and high efficiency are the sustainable development directions of dyeing and finishing industry. Energy consumption and pollution are the most urgent problems in traditional pre-treatment of cotton knitted fabric. Thus, it is imperative to develop environment-friendly, low-temperature and high-efficiency pre-treatment technology for cotton knitted fabric. It is recognized that enzyme scouring process, is one of the most potential processes for cotton pre-treatment. However, compared with alkali scouring, enzyme scouring process has some problems such as low impurity removal and wettability. In addition, enzyme scouring need advanced technology and has poor system compatibility, so it is difficult to realize large-scale applications of enzyme scouring process in cotton knitted fabric pre-treatment. In a word, improving the enzyme scouring effect, solving the compatibility problem and simplifying process are the key technologies to achieve low-temperature,environment-friendly and high-efficiency pre-treatment of cotton knitted fabric.Pectin removal and wettability used as index, scouring processes of pectinase, lipase and cellulose for cotton knitted fabric were optimized. The optimal compound enzyme scouring process was as follows: 2.5g/L pectinase, 3g/L lipase, 5g/L cellulose, pH=9, cotton knitted fabric was scoured at 70℃for 60min. After compound enzyme scouring, the knitted cotton fabrics had high pectin removal, soft handle and high wettability, which got close to alkali scouring level. Based on enzyme scouring of cotton knitted fabric, H₂O₂/TAED activated bleaching system was applied to bleach cotton knitted fabric. The optimal process was as follows: 5g/L TAED, pH=9, the scoured cotton knitted fabric was bleached at 70℃for 60min. The H₂O₂/TAED activated bleaching system endowed better handle, less damage to cellulose. The CIE whiteness of cotton knitted fabric can arrive at 70, and the wettability got close to alkali scouring level. The One-bath two-step process indicated that compound enzyme scouring process and H₂O₂/TAED activated bleaching system had good system compatibility, so it was feasible for one-bath process of cotton knitted fabric pre-treatment. The results of one-bath process indicated that the whiteness, wettability and strength loss of cotton knitted fabric can satisfy the need of backend processes, and one-bath process was a low-temperature, environmental protection and high efficient pre-treatment process of cotton knitted fabric.FTIR-ATR, SEM and KES indicated that impurity removal after compound enzyme scouring process was better than single enzyme because of the synergistic effect among pectinase, lipase and cellulose. FT-IR showed that the absorbance of cotton knitted fabric decreased at 1716.7cm^-1, which might be attributable to the decrease of the carboxylic ester in pectins and waxes, and EDS elementary analysis also proved this results. SEM showed that, most of the impurities were removed after compound enzyme scouring except some useful waxes, and the surface of primary cell wall was etched by cellulose, which enhanced the wettability of the cotton knitted fabric. In addition, the handle of cotton knitted fabric was measured by the Kawabata Evaluation System, which indicated that the handle of cotton knitted fabric after compound enzyme scouring was softer than alkali scouring process according to the four indexes of MIU, SMD, B and 2HB.