Studies Of Two Types Of Retention And Drainage Aid Systems For Recycled Fibers

The impacts on the formation abilities of recycled fibers by two types of retention and drainage aid systems i.e. CPAM/Silica based aluminum modified microparticlate sol, CPAM/lignosulfonate oxides were investigated in this thesis.In the section of effects of retention and drainage aid by CPAM/ Silica based aluminum modified microparticlate sol, it was found that The stability of normal silica based microparticlate sol was not good but with acceptable effects of retention and drainage aid for the wet-web of paper machine. The efforts were made to improve its stabilities by chemical modification. The optimal chemical modification conditions were optimized, which was proposed as, addition of 0.10 times of aluminum ions to the mole of silicate in to the silica based gel with a reaction temperature of 25°C at pH 3 with a silica based gel consistency of 3% (v/v), after reaction, the mixture were maturated for 24 hours. In fact, after storing for 48 hours, the retention and drainage aid effects were still remained. If more aluminum ions were applied, the modified silica sol will become unstable again, its particles will loss the effects of retention and drainage aid. The principle of improvement the stability of aluminum ion modified silica based microparticlate sol could be explained as to provide some amount of positive charges on the surface of gel, the electro-potential of the gel particle surface were changed, which could prevent the dual electrocity layers from attack by the sodium ions.At the same time, it was found during the investigation on the Compozil system, that the effective particle diameters were requested as the linkage to form a micro-flocs of cellusic-fines with positive charges. While utilizing together with CPAM, because of long chain of CPAM molecules, the formed floCs were more bulky, therefore, the diameter of silica microparticles were requested. In a somewhat range, the retention and drainage aid effects shows the positive relations with the increasing specific surface areas of silica based microparticlate sol.In worldwide, very high intensive attentions and R&D activities have been focused on the comprehensive utilization of lignosulfonates from Black liquor. Activation of lignosulfonate by oxidizing with hydrogen peroxide at different application levels were carried out to produce derivatives as additives in wet-end chemicals of papermaking. Effects on improvement of retention rate and strength of handsheets were investigated by using of oxidized lignosulfonate alone and combining with CPAM for the paper making process of recycled fibers. The results show that oxidized lignosulfonates combining with CPAM can be used as bi-functional additives in wet-end of papermaking using recycled fibers.