| Based on sol-gel and starch dissolution mechanism, different physical or chemical methods were used to modify starch in this work. At the same time, the use of modified starch in the different processes of papermaking industry obtained excellent practical effect. IR analysis, optical microscope, and Scanning Electron Microscope(SEM) were applied to characterize the structure and function of gel starch and dissolved starch.The novel development of this work is as follow:(1) Filler was wrapped with gel starch for the first time. It is another innovation among the surface modified technologies of filler;(2)In the recipe of coating color, latex is replaced with gel starch to increase the dosage of starch while decrease the dosage of latex;(3) It is the first time to explore a method which make the gel starch from not sufficiently cooking starch. In order to improve surface strength of paper and decrease dry capacity, high solid content of gel starch was used as sizing agent. (4) The dissolved starch solution can be used as sizing agent directly after its dissolution by NaOH/thiourea/urea, no need of cooking.The content and results of this work are as follow:(1) Based on the sol-gel mechanism, a novel filler wrapped with cationic gel starch was prepared successfully in wet end application through adopting new modified technology. The particle of this novel filler can be controlled. We also analysised the retention and drainage property, Zeta potential, and the properties of papers. The results revealed that, the cooking solid played an important role in the modification process, the mean diameter of filler was bigger as the cooking solid was higher. When the solid of starch was up to 30%, the novel filler had the optimal application effect, which had the highest filler retention compared with the raw paper, improved 37.5% of the ash content,41.1% of the tensile index,45.3% of the surface strength. (2) Based on the sol-gel mechanism, the gel starch was prepared in the coating system application through adopting new modified technology. This kind of gel starch was used to replace latex in coating color. The results revealed that, the low and the high shear viscosity, the water retention property of gel starch coating color were lower than cooking starch coating color. The papers surface sized with gel starch coating color had better properties than that sized with cooking starch coating color, such as CIE whiteness, smoothness, K&N value, surface strength. The optimal 6#(the dry dosage of GCC:Clay:Starch:Latex is 60:40:12:5) coating recipe had greatest property, it also indicated that it is feasible to replace latex with gel starch in coating color. (3) Based on the sol-gel mechanism, the gel starch was prepared in the surface sizing system application through adopting new modified technology. This kind of gel starch was used to prepare the high solid content of surface sizing agent. The results revealed that, the high solid content of gel starch solution improved the surface strength, physical strength and optical property of paper compared with 8% solid content cooking starch, but the papers surface sized with gel starch had worse water resistant property. (4) In order to decrease the viscosity of starch solution, a novel method of dissolving starch in NaOH/thiourea/urea solution was found. The results showed that, the dissolved starch solution had the lowest viscosity as the temperature of dissolution system was -10℃, and the dosage proportion of NaOH,thiourea,urea was 4:3:3.The papers surface sized with dissolved starch had better physical strength, opacity, smoothness, surface strength. When the solid content of dissolved starch was higher, the papers got better smoothness and surface strength.
|
PDF Full Text Request