Preparation Of Modified AKD Sizing Agent And Study On Its Sizing Mechanism

Alkyl ketene dimmers (AKD) had been widely used as typical internal sizes for alkaline papermaking. The purpose of this research were to improve the stability and sizing efficiency of AKD emulsion, resolve the problem of sizing lagging of AKD,make clear the sizing mechanism of AKD and expand the application area of AKD in papermaking. The main content can be got as follow.Firstly, the modification technology of natural polymer was studied involving cationic starch and cationic guar gum by homogeneous and semi-dry method respectively. Effect of performance of cationic modified natural polymer on AKD emulsion and sizing were discussed. It indicated that performance of cationic starch could significantly influence AKD sizing, and cationic guar gum had superior performance to improve AKD sizing.Secondly, the high positive charge density polymer---Polyethyleneimine(PEI) was used as emulsifier of AKD, The obtained optimum emulsify conditions were mPEI/mAKD=1/6, pH value at 3, emulsifying temperature at 70℃and emulsifying time 10min. Under these conditions, the particle sizes and Zeta potential of AKD emulsion were 1184 nm and +52.1mV, sizing degree of hand sheet could be up to 68 s. Besides, the AKD emulsion modified by PEI in pilot had high sizing degree and fast curing speedThirdly, the organic conceptional diagram was used as theoretical guidance, by adjusting monomers type and ratio, effect of HLB of polymer emulsifier on performance of emulsifying AKD were studied. The results showed that the polymer showed good emulsification property when the HLB value was 17 and the ratio of monomers(acrylamide:octadecyl acrylate:Diallydimetylammonim Chloride)were 4:7:10, the sizing degree of paper sized by AKD emulsified by polymer emulsifier at the dosage of 8% could be up to 63s, the curing yield of paper was 86%.At last, in order to discuss the application of AKD sizing agent in APMP paper sizing, the sizing promotion efficiency of cationic polymers had been compared. At the same time, Effects of retention system on AKD sizing were discussed. The result showed that at dosage of chitosan acetate was 0.2 wt% to AKD emulsion, the sizing degree could increase 140% higher than other sizing-promote agent. Sizing degree was better in dual-retention system than in single retention system. When the dosages of CPAM and Bentonite were 0.03 wt% and 0.4 wt% to fiber, the first retention rate and sizing degree increased about 7% and 197.56% respectively.