Preparation And Flocculation Mechanism Of Modified Silica Sol

The preparation and their application in papermaking of aluminium modified silica sol (AMS) and boron modified silica sol (BMS) were first investigated in China. The retention and drainage efficiency of AMS and BMS were superior to that of imported silica sol NP882 and the retention and drainage efficiency of BMS was superior to that of AMS. The optimal conditions before modification were 8% alkali dosage, heat temperature T12 and heat time 90 minutes. And the optimal conditions of aluminium modification were modification degree A3, temperature T24 and reaction time about an hour. Or that of B/Si was 0.08-0.1.Ultrafiltration instrument was selected to condense BMS and its optimal conditions were 3.5kPa pressure with 10 million molecular weight membrane at room temperature. In order to improve the stability of high concentration silica sol, anion or no ion surface actives could be useful. 0.01% DBS was found to be the best dispersant and had almost no effect on silica sol which was in favor of its commerciality.Characteristic application process and electrochemistry performance of cationic polymers/modified silica sol (MS) were systemically studied, It was found that CS/MS microparticle retention and drainage aid system had better retention and drainage efficiency in the high shear condition than CS single retention aid system, meantime CS/BMS system was better than CS/AMS system. MS microparticle retention and drainage aid systems were applicable to pulp with high fines such as waste pulp and wheat straw pulp. Seen from the effects of MS microparticle retention and drainage aid systems on wood pulp and waste pulp, CS and CPAM/MS system had better retention and drainage efficiency than CS/MS system and CPAM/MS system. But CS/MS system had best retention and drainage efficiency in wheat straw pulp. In all pulp BMS had better retention and drainage effiency than AMS. CS/MS microparticle retention and drainage aid system was preferably applicable in pH value 4-8 and resin sizing systems with less than 3% aluminium sulfate. This system had good resist capability to electrolyte interfere so that cycle water with less than 100mM electrolyte could be used resulting in less water resource polluted and wasted.Flocculation mechanism of microparticle retention and drainage aid system was investigated with DDJ, Laser size instrument and paper formation which was a new ideal and simple method. The research results showed that in the addition of cationic polymer fibers and fines flocculated and broken up with high shear then more chain loops and tails were exposed and bridged by negative MS. Due to MS was microparticle and had high specific surface area and high negative charge density it made close fragments flocculated into smaller and more uniform and compact floc net so that it improved retention and drainage with excellent formation.