【作者】 杨桂英；

【导师】 刘温霞；

【作者基本信息】 山东轻工业学院 ， 制浆造纸工程， 2008， 硕士

【摘要】 氢氧化镁铝为混合金属氢氧化物,是最常见的一类水滑石。实验中利用氯化镁和氯化铝混合物与稀碱液的共沉淀反应,合成了带正电荷的氢氧化镁铝胶体,并对制得的胶体进行了表征。然后利用氢氧化镁铝作为阳离子微粒,通过动态滤水仪和絮凝度分析仪研究其自身,及与阴离子聚丙烯酰胺、阳离子聚丙烯酰胺、阴/阳离子聚丙烯酰胺复合物等组成助留系统时,对纸料和填料的助留、絮聚情况,并用扫描电镜和透射电镜分析氢氧化镁铝助留系统的助留机理与特点。结果表明,氢氧化镁铝微粒为完整的结晶体,颗粒大部分呈六边形结构,结晶状态良好,最大粒度为200nm,平均粒径100nm左右。氢氧化镁铝胶体随胶溶时间的增加其Zeta电位逐渐增加,而且使得其对纸料的助留作用提高,对高岭土和滑石粉填料的絮聚作用增强。此外,利用适当的剪切作用可提高氢氧化镁铝的分散性能,并由此可提高其对纸料的助留作用和对填料的絮聚作用。然而,单独使用氢氧化镁铝对纤维及填料的助留和絮聚作用不是很强。其对高岭土的絮聚作用主要靠氢氧化镁铝松散聚集体的“桥联”作用,而对滑石粉主要靠电中和作用。当氢氧化镁铝与阴离子聚丙烯酰胺组成阳离子微粒助留体系时,对纸料的助留作用和对填料的絮聚作用较强,且氢氧化镁铝加入量越高,达到最大絮聚所需阴离子聚丙烯酰胺的量也越大,所引发的絮聚具有一定的抗剪切作用,尤其是加入氢氧化镁铝后所历的剪切作用越大,最后的纸料留着率越高。CPAM/氢氧化镁铝助留体系具有良好的助留作用,以先加CPAM后加氢氧化镁铝时对纤维的留着率较好,并且在中性偏碱性的时候助留效果最佳。氢氧化镁铝与CPAM联合使用时,先加CPAM与先加氢氧化镁铝的两种加入顺序均可大幅度提高对高岭土的絮聚作用,并以先加氢氧化镁铝时达到最大絮聚所需氢氧化镁铝的量较低,但两种加入顺序对高岭土填料的絮聚机理不同,先加CPAM后加氢氧化镁铝形成的是结构致密的高岭土絮聚体,而先加氢氧化镁铝后加CPAM形成的是结构松散的高岭土絮聚体。氢氧化镁铝与APAM/CPAM复合物组成的助留系统中,随着APAM/CPAM复合物质量比增大,对麦草浆的助留作用随之提高。带有阳电荷的CPAM/APAM复合物比带有阴电荷的复合物具有更强的絮聚能力,但是氢氧化镁铝与高比例的CPAM/APAM复合物具有很有限的协同助留作用。更多还原

【Abstract】 Magnesium aluminum hydroxide (MAH), a mixed metal hydroxide, is the most common hydrotalcite–like compound. In experiment, positively charged magnesium aluminum hydroxide was synthesized by co-precipitation of magnesium chloride and aluminum chloride with dilute alkaline solution. It was characterized by TEM, particle analyzer and zeta potential tester. Then, the retention and flocculation effects of the colloidal magnesium aluminum hydroxide as a single coagulant and cationic microparticulate component with cationic polyacrylamide (CPAM), anionic polyacrylamide(APAM) or cationic/anionic polyacrylamide complexes on fibers and fillers were investigated by means of Dynamic Drainage Jar(DDJ) and photometric dispersion analyzer (PDA2000), respectively. The retention mechanisms and flocculation characters of magnesium aluminum hydroxide based systems were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).The results indicate that the magnesium aluminum hydroxide (MAH) particles are complete crystals with hexagonal structure. The size of largest particle is 200nm. The average particle size is 100nm. The zeta potential of MAH colloid is increased gradually with the increase of peptization time. Consequently, its retention effects on stocks and flocculation effects on fillers are improved significantly with peptization time. In addition, appropriate shearing force may improve the dispersibility of MAH and in turn to enhance the retention of fiber and the flocculation of filler. However, MAH itself causes a weak flocculation of kaolin clay and shows a little retention effect on paper stocks. The kaolin clay is flocculated by bridging large kaolin clay particles with small loosely connected MAH particles while the talc powders are flocculated by the charge neutralization with MAH.MAH shows good synergistic retention effects with APAM on both stock retention and filler flocculation. Higher amount of MAH needs more APAM to achieve the best synergistic retention/flocculation effect. The flocculation of both stocks and fillers induced by MAH/APAM shows certain shear resistance. Higher stirring speed after MAH is immediately added, often results in higher final stock retention.CPAM/MAH system displays good retention effects on paper stocks. The addition sequence of CPAM followed by MAH commonly shows higher retention effects on paper stocks, and displays higher retention efficiency under neutral/alkaline pH. For the flocculation of kaolin clay, both addition sequences of MAH followed by CPAM and CPAM followed by MAH show significant synergistic flocculation effects. However, the addition sequence of MAH followed by CPAM may achieve its biggest flocculation effects on kaolin clay at lower addition levels of MAH. The flocculation mechanisms of kaolin clay caused by the different addition sequences of MAH and CPAM are different. When CPAM is first added to the clay suspensions, the clay particles flocculate to form dense flocs with the addition of MAH. When MAH is added to clay suspensions followed by CPAM, the clay particles are loosely connected together.In the system of the MAH with APAM/CPAM complexes, increasing the mass ratio of APAM/CPAM will enhance the first pass retention of wheat straw pulp. The APAM/CPAM complexes with cationic charges induce stronger flocculation than that with anionic charges. However, the MAH only shows very limited synergistic retention effect with APAM/CPAM complexes of higher CPAM/APAM mass ratios.更多还原