Performance Of Fixing Agents In Controlling Micro-Stickies In Recycled Newsprint Pulp

Currently, the development of papermaking industry is retarded by the shortage of forest resources. The utilization of recycled paper increased year by year in many countries. However, recycled paper consists of a big amount of impurities which causes many troubles in recycling and papermaking processes, among which stickies problem is the most serious one.Great attention should be paid on the optimization of mechanical and physical treatments to control or to eliminate stickies components effectively. Even so, micro-stickies, which belongs to dissolved and colloidal substances (DCS), will still be left in the system, and they can be only dealt with by biological or chemical treatments. Biological methods mainly use enzymes to decrease the size and tackiness of stickies, while most of the chemical methods are based on mechanisms of dispersed stablization, adsorption, surface passivation and fixation. Among them the chemical fixation with fixing agents is most widely accepted because it has remarkable effectiveness and it is very easy to be applied in papermaking process. Besides, fixation principles are also related to some of the other methods such as surface passivation, biological degradation, and dissolved air flotation, therefore, it is thought to be the very field that is worthy of being further investigated.In this paper, the microstickies control effects of some fixatives on properties of newsprint recycled pulp were investigated, which include inorganic polyaluminum chloride (PAC), organic polyamine (PA), polydiallydimethyl ammonium chloride (PDADMAC), and two high cationic starches (HCS) with different average molecular weights (HCS_HMw for the higher one and HCS_LMw the lower one). The results showed that the HCSs, no matter being used in its single form or in combination with a cationic polyacrylamide/bentonite microparticle retention system, increased pulp zeta potentials higher than the other fixatives did (also in single or combination with the microparticle retention aids), indicating that the HCSs were easier to be absorbed onto pulp fibers. Dosed in same amount of cationic charges, the HCSs can fix more DCS components to cellulose fibers than the other fixatives, giving the liquid phase of the pulp slurries...