Study On Preparation And Application Of Hyperbranched Cationic Polyacrylamide

In recent years, along with the papermaking wet operation system changing from acidicto neutral/alkaline, paper machine high speed development and the increasinglyimprovement of white water closed circulation degree, the current situation has a higherdemand for the retention rate, water filtration performance, and paper forming. Thus thequality and stability of the chemicals put forward higher requirements. Therefore, one of theimportant research works is to develop an efficient, environment friendly, andmulti-functional aids for the complicated papermaking wet-end system.Hyperbranched cationic polyacrylamide with novel multi-branched structure, propertiesand morphology, can overcome deficiency of linear polyacrylamide as paper additives.Compared to the linear polymers with the same molecular weight, they have a series ofcharacters including higher surface faculties degree, the lower viscosity of solution andsmaller hydrodynamics radius. For this reason, hyperbranched polymers can exhibit moreexcellent effects.The hyperbranched cationic polyacrylamide (SiO2/BCPAM) was synthesized by aqueousradical polymerization and in-situ polymerization method. Based on the study of the structuralcharacteristics, it was investigated as retention and drainage aid and strength agent in thepapermaking.In the aqueous solution of pentaerythritol, ammonium cerium nitrate, acrylamide (AM)and methacryloyloxyethyl trimethyl ammonium chloride (DMC) as the radical polymerizationof the monomers, to synthesize branched cationic polyacrylamide (BCPAM), then addedTEOS, it produced nano SiO2by hydrolysis and condensation, to crosslink the branchedcationic polyacrylamide to make hyperbranched cationic polyacrylamide (SiO2/BCPAM). Thestructure of the SiO2/BCPAM was characterized by FT-IR, NMR, TG, SEM, intrinsic viscositymeasurement and cationic degree. The effect of polymerization reaction system and processconditions on product quality was studied, and the optimun conditions of synthsis ofSiO2/BCPAM were as follows: reaction temperature50℃, reaction time3.5h, the initiatorconcentration was0.0275%(based on the total monomer mass), and the cationic monomerconcentration was10%.The strengthening effect of SiO2/BCPAM on bleached eucalyptus pulp and the optimumapplication condition were studied in this paper. The results indicated that the strengtheningeffect of SiO2/BCPAM to bleached eucalyptus pulp was best under the following conditions: the dosage of SiO2/BCPAM is0.5%, the reaction is2minutes, and the pH value of thesystem is7. Compared to the control sample, the burst, tearing and tensile index of the paperused SiO2/BCPAM increased by23.59%,12.44%and25.47%, respectively.The performance of SiO2/BCPAM as retention and drainage aids for the retention systemof bleached eucalyptus pulp was studied. Along with the increasing dosage of SiO2/BCPAM,the FPR and drainage rate of the pulp were improved, and the optimum dosage of S-CPAMwas0.5%(based on dry pulp). With the enhancement of the shearing, the prolonging of actiontime and the increasing of pH value, the performance of SiO2/BCPAM displays a trend ofdeclining. The branched structure of SiO2/BCPAM could impede molecular reconstructionand charge decay in a certain degree, and had a resistance to the high shearing, AndSiO2/BCPAM in alkaline systems still showed better retention and drainage effect, in theneutral system it showed the best effect. SiO2/BCPAM with bentonite particles composed theretention and drainage systems, showed more excellent effect than the unit system.