Study On Improving The Folding Endurance Of Securities Paper

Due to the rapid development in nearly 10 years, China’s paper industry has become saturated. With the development of information technology,the output and demand of printing and writing paper have been decreasing. Specialty paper, due to its wide range of applications, has been developing rapidly in recent years. To improve its folding endurance,the influences of the beating degree of cotton pulp, the ratio of cotton pulp to synthetic fiber and softwood pulp, the type and dosage of polyacrylamide, and the effect of surface sizing on the folding endurance of security paper would be described in this study.This paper begins with the discussion on the effects of the beating methods on folding endurance, which indicated that the paper folding endurance was better when beat by Valley followed by PFI than that of using Valley individually. When the pulp’s beating degree reached to 34°SR by Valley beater, PFI refiner would be used to keep beating. The result shows that when the beating degree reached to 49°SR and 67°SR, the best folding performance appeared, with 8800 times and 10980 times, respectively.This paper also explored the optimal proportions of cotton pulp and synthetic fiber,and cotton pulp and softwood pulp. When the dosage of PVA fiber whose melting point is 70℃ was 20%, about 5% of increment was obtained on the folding endurance of the paper which was made by cotton pulp and PVA. When the dosage of softwood pulp was up to 10%, the folding endurance of the paper which was made by cotton pulp and softwood pulp together would be increased slightly.Studying the influence of the type and dosage of polyacrylamide on paper folding endurance was followed, which indicated that folding endurance of paper improved a lot with APAM addition. When the dosage of APAM was 0.4%, the folding endurance of the paper would increase by 28%.Double-sided sizing had significant effects on improving the folding endurance of security paper by using the sizing agent prepared with corn starch and polyvinyl alcohol.When the content of polyvinyl alcohol in the sizing agent was 10%, and the amount of the sizing agent was about 6 g·m-2, the tensile index and the folding endurance could be increased by 27% and 90%, respectively. When the paper containing PVA fibers was treated with surface-sizing, the folding surface, tensile index and tear index of paper can be improved significantly.