改性微粒硅溶胶的研制及应用机理研究

The preparation and their application in papermaking of aluminium modified silica sol (AMS) and boron modified silica sol (BMS) were first investigated in China. At the same time the structures and configurations of AMS and BMS were first time authenticated. The modified silica sol microparticle system was detailedly and systemically studied with colloid charge titration. On the research of flocculation mechanism the laser sizer was also first time used to determine the floc size. Results showed that sodium silicate was treated and acidification was carried out by means of strongly acid cation exchange resins and obtained almost sodium free acid sols. The acid sol obtained after acidification was then made alkaline.

Preparation and Flocculation Mechanism of Microparticle 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. At the same time the structures and configurations of AMS and BMS were first time authenticated. The modified silica sol microparticle system was detailedly and systemically studied with colloid charge titration. On the research of flocculation mechanism the laser sizer was also first time used to determine the floc size. Results showed that sodium silicate was treated and acidification was carried out by means of strongly acid cation exchange resins and obtained almost sodium free acid sols. The acid sol obtained after acidification was then made alkaline. The alkalization was carried out with sodium silicate so that concentration at the preparation could be enhanced and mitigate later condense. Low temperature was in favor of the rate control of particle aggrandizement and smaller and more uniform particles were achieved. The optimal conditions before modification were 8% alkali dosage,heat temperature T12 and heat time 90 minutes. Aluminium and boron modification of the surface were carried out by means of aluminate and borate in order to give particles better charge stability. 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. 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. Aluminium and boron modification project were feasible and reliable.Ultrafiltration instrument was selected to condense BMS and its optimal conditions were 3.5 kPa 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.AMS and BMS were analyzed by means of FT-IR, 29 Si-NMR, 11 B-NMR and 27 Al-NMR. The results showed that there were three kinds silicate anions such as Si(OSi)2 (OH)2 (Q2) ,Si(OSi)3 (OH) (Q3) and Si(OSi)4 (Q4) in unmodified silica sol NP882 surface. Because Al and boron were introduced to silica sol surface,there were only Si(OSi)2 (OH)2 (Q2) and Si (OSi)4(Q4) in AMS and BMS surface and (Q3) Si(OSi)3 (OH) were changed into Si(OSi)3 (OAl)3- and Si(OSi)3 (OB)3-. In the addition,the Al in AMS particles and B in BMS particles existed mainly in the form of AlO4 or BO4 tetrahedra linked with four Si atoms in the second coordination sphere. From TEM(transmission electron microscopy) AMS and BMS particles were not spherical and size were about 3nm. Furthermore BMS particle size was smaller and more uniform than AMS.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 100 mM 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.