| High Yield Pulp (HYP) usually contains more anionic trashes due to its natural characteristics of high-yield pulping process, which is detrimental to sizing. It tends to deteriorate the application of HYP in high-grades paper. In paper industry, one traditional and widely way to solve these problems is to use anionic trash catchers (ATC) with high cationic charge density. How to affect sizing about ATC with different molecular weight, molecular structure, and charge density is still a vague issue. Thus, the effects of ATCs on controlling anionic trashes and promoting efficiency for AKD sizing were investigated integratedly, especially the effects of molecular weight of ATCs. The sizing degrees of paper sized with AKD were measured by three different methods including liquid penetration time, methanol/water critical absorption value and edge penetration value.The differences of separate sample preparation method and cumulative chemical addition method were first investigated and compared in measuring pulp Zeta potential and cationic demand of pulp filtrate, the results obtained were in consistency. Being less time consumed, the cumulative chemical addition method can be considered as a rapid method to screen the ATCs in controlling anionic trashes, which facilitated following experiments.Applying three kinds of PDADMAC. three kinds of PEI, and four kinds of HCS (three of them were LHCS) with different molecular weights showed that PDADMAC-5with high-molecular weight had the best effects in controlling anionic trashes and promoting AKD sizing efficiency of BCTMP; The molecular weight of PEI had little effect on the electrokinetic characteristic of the pulp. According to the liquid penetration time and methanol/water critical adsorption value of the paper sized with AKD. PEI-3with high molecular weight had better promoting efficiency, while the molecular weight of PEI had little effect on the edge penetration value of paper; The electrokinetic characteristics of the pulp changed little treated with different HCSs as well as PEIs. LHCS-3with lowest molecular weight had good promotion to AKD sizing.At last, the effects of PDADMAC-5. PEI-3. LHCS-3. PA, PAE and PAC on promoting AKD sizing were analysed comparatively. It was concluded that PAC was obviously inferior to the organic ATCs. At low dosages, ATCs with high charge density, such as PDADMAC, PEI and PA, had better effects on controlling anionic trashes and promoting sizing efficiency based on the liquid penetration time and methanol/water critical adsorption value of the paper sized with AKD. According to the edge penetration value of paper. PAE had better ability to improve the AKD sizing, while LHCS, PA, PDADMAC and PEI were similar. At high dosages. LHCS was the most effective polymer.PDADMAC. PEI. PA. PAE, LHCS and PAC were investigated in controlling anionic trash and promoting AKD sizing efficiency. In papermaking, the results will be beneficial for improving paper quality, lowering production cost and HYP application. |
