| Paper pulp raw material structure of the low proportion of long fibers, high proportion of short fibers and secondary fibers, caused the situation that most of paper had low dry strength. Rapid economic development and diversification social demand put forward higher requirements and standards of all kinds of paper dry strength, it also stimulated extensive research on the paper dry strength properties. The traditional paper dry strength agents starch, polyacrylamide and its derivatives were difficult to meet the needs of high-strength paper requirements; therefore we needed to look for an efficient, inexpensive, environmentally friendly and stable novel paper dry strength agent. Starch and chitosan had better enhancement effect on paper dry strength, and also had a higher chemical activity, which could be chemically modified to obtain better dry strength effect. In this paper, corn starch with nano-modified treatment, were grafted copolymerization with DTPA and chitosan further.The impact of the performance of modified starch, modified products and chitosan graft copolymer technology and its impact on pulp properties wereresearched in detail.Firstly, optimize the process of papermaking and adding dry strength agents. The optimum processing parameter:the sample pulp was mixed of 50% OCC (E) and 50% chemical bleaching pulp of softwood, after defibering the pulp, all kinds of dry strength agents were added, and then the mixture was stirred for 10min. After that the pulp was used to make paper which was dried in vacuum at 105℃.Then research and discuss the enhancement of various types of dry strength agent for paper, and study the optimal dosage of dry strength. The results showed that: Chitosan’s enhancement was better than that of starch, the system of starch and soy protein was used as dry strength, the effect was more obvious than alone, and the best fit ratio was 3:1 (starch to soy protein). The optimum amount of starch was 2% as a dry strength agents alone, the optimum dosage of chitosan and soy protein were 0.25% and 2%.Subsequently, the nano-modificated starch was chelated with DTPA, and the chelation process parameter and the performance of product were discussed. Study showed:chelation reaction optimum reaction temperature was 130℃, reaction time was 4h, solid-liquid ratio of lmg:1mL. Starch size was in the range of 200-400nm and nano-modified starch had poor thermal stability than the original.Finally, the synthesis and characterized of starch -DTPA-chitosan and its applied were researched. The results show that:the esterification occurred between of starch and starch-DTPA, the amidation occurred between of starch-DTPA and starch-DTPA-chitosan. Thermal stability:starch-DTPA<starch-DTPA-chitosan<starch, DSC melting temperature:starch<starch-DTPA<starch-DTPA-chitosan. Starch, starch-DTPA and starch-DTPA-chitosan enhanced tensile properties and tear properties of paper, and the effect was obvious in sequence. Starch-DTPA-chitosan and soy protein used together got the greatest degree of reinforcing effect on the breaking length, breaking length can reach 9.825km, enhanced 61.33% than blank samples representing not add dry strength agents. The effect was same to tear index. The most obvious effect is enhanced, tear index reached 5.92 mN·m2/g, increased 56.61%. |
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