Study On Characteristic Of ASA Neutral Sizing

Currently, the neutral and alkaline sizings are mainly AKD and ASA (Alkenyl Succinic Anhydride). The sizing efficiency of ASA is similar to that of AKD. However, with the lower cost, the faster curing rate and getting good sizing performance quickly after drying, ASA is suitable for the future development. APMP is one of the most widely used CMP, but it includes lots of anionic trash which is adverse to ASA sizing. The characteristic of ASA neutral sizing in Poplar APMP was studied in this paper mainly.Firstly, a self-made cationic starch as emulsifier was used to emulsify ASA, and the emulsifying technics of ASA was optimized simply. ASA emulsion which was prepared in the condition:m(emulsifier):m(ASA)=3:1, emulsifying time of2.5min and the amount of10%alum, had good sizing effect and stability.Secondly, the different effects of ASA, fillers and cationic additives on ASA sizing in APMP and HBKP of poplar were studied. The results showed that the dosage of ASA had a greater impact on sizing degree, specifically, a better sizing performance could be obtained at the dosage of0.2%ASA both in APMP and HBKP. However, the sizing effect in APMP was better than HBKP with the same dosage of ASA. Adding PCC of15%was beneficial to improve the sizing efficiency of ASA in APMP, whereas harmful in HBKP. Sizing performance in APMP was better with tale and GCC followed by PCC, but optical properties follow the opposite trend. Proper doses of cationic additives could promote the ASA sizing efficiency in APMP obviously. In the different fiber classifications of APMP, the sizing performance of fiber classification between100mesh and200mesh was best and above that of the original pulp.The effect of papermaking technics factors such as sizing pH, pulp concentration, pulp temperature, residence time of ASA in wet end, the order of adding wet end additives, the pressure, the drying temperature and drying time on the sizing performance of ASA were studied. The results showed that sizing pH had great influence on sizing. The sizing degree was better when the value of pH was from6to8. As the residence time of ASA in wet end and pulp temperature increased, the sizing degree slumped. The concentration of pulp must be controlled for better sizing effect. The different order of wet end additives led to a greater change of sizing degree. The drying temperature also had a great impact on sizing degree, the lower the temperature the worse the sizing degree.Besides, in order to explore the mechanism of ASA sizing, the migration of ASA in a paper in the drying process was investigated. It was observed that there was the phenomenon of migration of ASA in the drying process and the migration had a certain orientation, the temperature and difference of ASA emulsions could both affect the migration of ASA.