Study On Enhancement Of AKD Sizing And Its Mechanisms

Alkyl ketene dimer (AKD) as a kind of neutral/alkaline size is widely used in alkaline papermaking. Traditional AKD emulsion is used cationic starch as emulsifier, which has lower retention on fibers and need a long time to be cured. In this paper, AKD sizing efficiency enhancement was studied by increasing the retention of AKD on fibers and shortening time of curing, also the mechanism of AKD sizing efficiency enhancement was studied.Firstly, a novel self-made cationic resin was used to take place of traditional cationic starch as emulsifier to emulsify AKD wax, and the emulsifying technics of resinous AKD was optimized. A novel high efficient cationic resinous AKD emulsion was preparated, and its sizing efficiency was increased by 17% than that emulsifying by cationic starch.Secondly, the sizing technics of resinous AKD was studied. The factors such as retention system, sizing pH, the kind of fillers, the press pressure, the drying temperature and drying time were studied. Its applications in cotton pulp, hard wood pulp, OCC and wheat straw pulp were also studied.In order to study the mechanism of sizing efficiency enhancement of cationic resinous AKD, the Zeta potential of AKD emulsion and the retention of AKD in pulp were studied, and also SEM was used to study the microstructure of AKD in handsheets before dried and after dried. And the reason why cationic resinous AKD has higher efficiency than that emulsified by cationic starch was explained.Adding some wet end additives such as PAE, PA, PAC could improves Zeta potential of pulp and retention of AKD to improve the sizing effect. The results showed that AKD had its higher retention and better sizing effect when Zeta potential of the pulp was -5mV.Finally, the self-made cationic resinous AKD emulsion was produced through pilot experiment in paper mills. The results showed that it can get better profits about 0.5 yuan/t while the sizing effect was enhansed by 11% than that emulsified by cationic starch, and also the curing time was shortened.