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Lijun Wang,Yiqian Zhang,Pedram Fatehi 한국펄프·종이공학회 2016 한국펄프·종이공학회 학술발표논문집 Vol.2016 No.10
1. Formation of DS-fixing agent PEC highly depends on the DS components, fixing agent molecular weight and its dosage, as very different phenomena can be seen in this study for different DS components, for polyamines with different molecular weight, and for the same polyamine used at a different dosage. 2. For fixing agent with enough low molecular weight and at enough low dosage, it can form loose and dispersible DS-fixing agent PECs, and increasing its dosage will produce denser and smaller PECs; for fixing agent with enough high molecular weight, it can directly form dense DS-fixing agent PECs, and increasing its dosage mainly increases the size of PECs; for fixing agent with medium molecular weight, its behaves between the two cases described above. 3. Although hemicelluloses modeled DS water showed that a small part of PECs formed are detectable by FBRM, the performance of DCS water 2 used in this study showed that DS-fixing agent PECs alone are generally too small to be detected by FBRM. 4. Based on the performance of DCS water 1 and DCS used in this study, it can be concluded that small CS particles undetectable by FBRM can be the “seeds” for producing larger particles detectable by FBRM, either by agglomerating the small CS particles or by depositing DS-fixing agent PECs onto the small CS particles. For the formation of FBRM-detectable particles, the agglomeration of medium sized CS particles (between 125nm-470nm in this study), or deposition of DS-fixing agent PECs onto such particles, seems critical.
Lijun Wang,Yiqian Zhang,Pedram Fatehi 한국펄프·종이공학회 2016 펄프.종이기술 Vol.48 No.6
Dissolved substances (DS) in papermaking suspension contribute a large portion of negativity to the total dissolved and colloidal substances (DCS). Compared to colloidal substances (CS), dissolved substances are clearly more difficult to be removed by fixing agents (FA). Formation of polyelectrolyte complexes (PECs) between fixing agents and dissolved substances plays a very important role in clarifying the mechanism of a fixing agent acting on DCS. This study, therefore, focused on the characteristics of PECs formed between fixing agents and dissolved substances. Three polyamines (PA) with different molecular weight and slight different charge density were synthesized and used as fixing agents, in four different kinds of water including, two kinds of DCS water separated from a same deinked pulp (DIP) but with different size and distribution of CS particles, and two kinds of DS water modeled by oxidized starch (OS) and hemicelluloses (HC). The formation of PEC in these systems and their corresponding characteristics were characterized using focused beam reflectance meter (FBRM), laser particle size analyzer (LPSA), turbidity meter, and charge detection. From the results, it is concluded that for a given DS component and a certain kind of fixing agent, the formation of DSfixing agent PECs highly depended on the molecular weight of the fixing agent and its dosage. A fixing agent with enough low molecular weight could form big but loose and dispersible DS-FA PECs, increasing its dosage would produce denser and smaller PECs; and a fixing agent with enough high molecular weight could directly form dense PECs, increasing its dosage increased the size of PECs. Depositing DS-FA PECs onto small CS particles also played an important role in forming new CS particles with larger sizes, and in this case, a fixing agent with higher molecular weight tended to produce more large particles.