The Study Of Amphoteric Polymer Of Fillers In Papermaking Retention System

The object is mainly doing researches about technologies and mechanisms for preflocculation of amphoteric polymer and filler, and it is the first to explore the stability of the new technology before applying it to actual production.Compared with the former filling theory, the preflocculation filling technology of amphoteric polymer is much superior at tensile and ash content when adding the same amount of filler.The order of adding cationic polyacrylamide(CPAM) has little or no effect on paper’s ash content but a significant impact on paper uniformity compared the technology of preflocculation of amphoteric polymer before and after adding CPAM. The optimum technology of producing preflocculations of amphoteric polymer is pulp+preflocculations+CPAM.The selected two kinds of amphoteric polymer and kinds of pulp and filler was applied to the feasibility study, which proved to be the widespread use of the technology.The preflocculation which was made of the selected two kinds of amphoteric polymer(amphoteric PVAm and strength agent ZQ) and PCC was measured the Zeta potential. Based on the result of this experiment, one can draw a conclusion that the surface of the preflocculation carries negative charge. On the one hand, the amount of the negative charges is different with the n+/n- value of selected two kinds of amphoteric polymer. Overall, PVAm carries more negative charges than that of ZQ as PVAm is neutral while ZQ is acidic.Besed on the SEM of the preflocculation, the size of the preflocculation is generally 10μm. The preflocculation has regular shape and its surface is formed by calcium carbonate which is recognized because the shape of it is cylinder or diamond. A conclusion could be drawn that one end of the particle glues together with those of other particles and the shape of the particles acts like scissors because each particle of calcium carbonate staggers one by one. The preflocculation stays almost on the corner where fibers interlace together rather than the upside of fibers.The formation mechanism of flocculate process amphoteric polymer and filler is explained combined with electrostatic field theory: according to the experimental results of PCD04 particle charge detector and Zeta potential, different sizes of negatively charged particles could be allowed into the flocculation respectively. Therefore, the flocculation is empty inside and has a positive electric field in centre of it, which makes calcium carbonate particles glue from ends of them and other ends act like scissors just as as shown in the SEM.The two kinds of amphoteric polymer were heated to the temperature of the headbox. The usage results of ZQ showed little difference before and after heat while PVAm sticked on the container inside, which showed a thermal stability problem. According to the experimental results of PCD04 particle charge detector and Zeta potential, the cationic group of PVAm hydrolyzes when heated to a certain temperature and infrared results indicates that the group is methylamino.The preflocculation of amphoteric polymer and filler which mixed with negatively charged particles was added into pulp. The paper sample analysis indicated that filler retention and paper ash content improved and the tensile index did not reduce that a conclusion could be drawn that the preflocculation of amphoteric polymer and filler with negatively charged particles inside is more compact and has strong shearing resistance.By using the orthogonal experimental design, the best dosage of chemicals of the technology is PVAm/ZQ 0.175%、GCC 30%、CPAM 0.067%.Techanisms for preflocculation of amphoteric polymer is explained based on electrostatic field theory, which is of great value in the guidance of adding amphoteric papermaking additives at the wet end.