Study On The Blocking Problem Of Special Mineral Soil In Cotton Printing With Reactive Dyes

Sodium alginate is one of the most commonly used pastes for cotton fabric printing with reactive dyes,but its reserve is limited and the price is high.The special mineral soil in Guangxi is a new type of mixed layer clay with low price,abundant reserves and good stability,adhesion,expansion,thickening and thixotropic properties.After modification,it can replace sodium alginate as reactive dye printing paste.However,it is found that the special mineral paste is easy to block printing screens.For this reason,this project conducted a systematic study on the problem of screen blocking,and found out the main causes of screen blocking,and put forward a corresponding solution to solve the blocking problem,so that to provide guidance for the industrial application of special mineral soil paste.Firstly,sodium alginate(including 10% urea)was used as the original printing paste.According to the printing process,the cotton fabric was continuously printed to obtain the screen blocking grades,and then the block rating system was established.Furthermore,the effects of the fineness of special mineral soil,the particle size and content of hard particles,the solid content of the paste and the mass ratio with modifier-R on blocking performance and printing performance were investigated.And the counter-evidence method was used to understand the effect of the easy-drying problem of a color paste on blocking property,and the main reason caused the blocking problem was finally found.The results showed that,increasing the fineness of special mineral soil paste,removing the hard particles,reducing the solid content of special mineral soil paste and optimizing the amount of modifier-R can reduce the blocking problem,but it cannot completely solve the blocking problem of the special mineral soil paste encountered in the application process,so that it cannot meet the requirements of continuous printing production.The dominant reason caused the blocking problem is that the special mineral soil paste is much easier to dry than other conventional original pastes.Then,for solving the blocking problem of special mineral soil caused by easydrying,glycerol,polyethylene glycol-400,triethanolamine,caprolactam,urea,five commonly used moisturizers and a self-developed humectant-Z were used to modify the special mineral soil,and its effect on blocking performance and printing performance was investigated.The results showed that,the type,quantity and position of the hygroscopic group in the humectant not only affected the improvement in screenblocking resistance of the paste,but also affected the color yield of the reactive dye printing;Adding 9% of glycerol,4% of three Ethanolamine or 6% of polyethylene glycol-400 can reduce the blocking problem of the modified special mineral soil,but the color yield of the printed fabric surfaces was decreased significantly;adding 2% humectant-Z or 10% urea can solve the blocking problem,and almost without affecting the surface color yield of the printed fabric.Finally,the rheological property and printing property of three pastes,sodium alginate(including 10% urea),special mineral soil(including 2% humectant-Z)and special mineral soil(including 10% urea),were compared and analyzed.The composition and molecular structure of the humectant-Z were analyzed by infrared spectroscopy and organic element analysis.The structure-activity relationship between the humectant-Z structure and the printing performance was determined.The results show that,the special mineral soil(including 2% humectant-Z)and special mineral soil(including 10% urea)have obvious "shear thinning" characteristics and good viscosity recovery ability,and thixotropy;The reactivity of hydroxyl groups in Humectant-Z molecule with reactive dyes reduced due to its intramolecular hydrogen bonds,and the addition of 2% humectant-Z can not only can effectively solve the blocking problem of special mineral soil paste,but also the rheological properties and printing performances are comparable to traditional sodium alginate/urea reactive dye printing processes.The application of modified special mineral soil/humectant-Z(2%)printing process can realize urea-free printing and solve the problem of ammonia nitrogen in conventional sodium alginate/urea printing,which meets the requirements of environmental protection.