【作者】 曹文仲；

【导师】 钟宏；

【作者基本信息】 中南大学 ， 化学工艺， 2009， 博士

【摘要】 采用水溶液聚合法、反相乳液聚合法合成了淀粉接枝聚丙烯酰胺二元共聚物及淀粉-丙烯酰胺-丙烯酸(钠)三元共聚物,将其应用于拜耳法氧化铝赤泥工业化分离试验,取得了良好的处理效果。采用水溶液聚合法合成了淀粉接枝丙烯酰胺聚合物,研究了聚合反应动力学和聚合反应机理。以过硫酸铵为引发剂,淀粉与丙烯酰胺在水溶液中进行接枝共聚反应,研究了反应温度、原料比例、淀粉种类、糊化方式对接枝反应的单体转化率、接枝率、接枝效率以及产品特性粘度的影响。结果表明,在反应温度50℃、丙烯酰胺与淀粉的质量比2:1的条件下,70℃下糊化30 min,产品接枝率71%,接枝效率84%,单体转化率97%,支链聚合物的相对分子质量700万。在接枝反应初期、低引发剂浓度下,建立了聚合反应的动力学方程:表明淀粉与丙烯酰胺单体的接枝聚合反应过程符合自由基加聚反应机理,接枝共聚反应的链终止既有双基终止,又有初始自由基终止。采用反相乳液聚合法,合成了淀粉接枝聚丙烯酰胺的反相乳液产品,研究了反相乳液聚合工艺条件与聚合反应动力学。考察了乳化剂种类,乳化剂组成、乳化剂用量以及乳液形成方式对单体转化率、接枝率、乳胶粒径和产品特性粘度的影响。结果表明,以脂肪酸(盐)为乳化剂,乳液具有良好的稳定性和低温溶解性;将表面活性剂进行复配得到的混合乳化剂的乳化效果优于单一乳化剂。以油酸与油酸钠复配物为乳化剂时,合成了单体转化率99%,接枝率82.5%,特性粘度1300 ml/g的淀粉接枝丙烯酰胺反相乳液产品。考察了过硫酸铵、过硫酸铵-尿素和过氧化苯甲酰-亚硫酸钠三种引发剂体系对单体转化率、产品特性粘度的影响。结果表明,在接枝反应初期、低引发剂浓度下淀粉接枝丙烯酰胺反相乳液聚合反应动力学关联式为:符合反相乳液聚合反应规律。采用反相乳液聚合法,在淀粉接枝丙烯酰胺二元共聚体系中,加入离子型单体丙烯酸(钠),合成了具有不同电荷分布、电荷密度的淀粉-丙烯酰胺-丙烯酸(钠)三元共聚物。在过硫酸铵-尿素的引发下,考察了pH、单体比例对接枝反应转化率、接枝率的影响。结果表明,在pH值为6-7条件下,可得到负电荷在支链上均匀分布的接枝聚合物产品。考察了氨羧络合剂、EDTA2Na及其复配物E-N对过硫酸铵-尿素引发体系的催化作用。结果表明,三种催化剂均能有效降低过硫酸铵-尿素的引发温度,提高单体转化率和产品的特性粘度。在过硫酸铵-尿素-(E-N)催化引发下,丙烯酰胺与丙烯酸钠质量比为7:3,乙烯基单体与淀粉质量比为2:1,30℃反应6h时,合成了单体转化率99%,接枝率80.5%,产品特性粘度1650 ml/g的淀粉-丙烯酰胺-丙烯酸(钠)三元共聚反相乳液产品。用红外光谱、偏光显微镜、扫描电镜分析等手段表征了淀粉接枝二元和三元共聚物的化学结构、形态结构和反相乳液聚合物的乳胶粒粒度。结果表明,合成的淀粉接枝共聚物符合预期结构,未糊化的淀粉接枝后,聚合物保持团粒结构,表面接枝上了乙烯基均聚物;糊化的淀粉接枝后,形成了均匀的淀粉接枝共聚物。在比较淀粉接枝共聚物产品和已有的合成高分子絮凝剂产品的基础上,将产品应用于拜耳法氧化铝溶出赤泥的工业分离过程。考察了絮凝剂种类与用量对沉降速度、浮游物含量及底流固含等沉降分离指标的影响。结果表明,在进料量为820 m~3/h,絮凝剂用量为300 mg/Kg时,沉降速度高于16cm/min,浮游物含量低于0.15g/L,底流固含高于470 g/L,满足赤泥分离生产要求。更多还原

【Abstract】 A binary starch graft polyacrylamide copolymer and a ternary starch-acrylamide-acrylate acid (sodium acrylate) copolymer were synthesized by aqueous solution polymerization and inverse emulsion polymerization. The two starch graft copolymers were employed in the red-mud separation of alumina industrial processing, and both of them showed the excellent separation ability.One starch graft acrylamide copolymer was synthesized by graft copolymerization of starch and acrylamide in solution, and the polymerization kinetics and its mechanism was discussed. The influence of temperature, mass ratio of raw materials, types of starch and gelatinization on monomer conversion rate, grafting ratio, graft efficiency and intrinsic viscosity of products, when copolymerization was conducted in solution, with starch and acrylamide as raw materials and ammonium persulfate as initiator. The results showed that the grafting ratio is 71%, the graft efficiency is 84%, the monomer conversion rate is 97%, and the molecular weight of polyacrylamide grafted on starch is 7 million, when the reaction temperature was 50℃, the mass ratio of acrylamide to starch was 2:1, the gelatinization temperature was 70℃, and the gelatinization time was 30 min. The correlation equation of initial reaction stage was derived at low initiator concentration, shown as follows:Therefore, it can be concluded that the graft polymerization of starch and acrylamide is a free radical polymerization. The free radical termination undergoes between initial free radicals, as well as free radicals initiated by initial free radicals.Starch graft acrylamide copolymer was also synthesized by inverse emulsion polymerization, and the polymerization process conditions and the polymerization kinetics were studied. The types, composition and amounts of emulsifiers and emulsification methods affected the monomer conversion rate, grafting ratio, latex particle size and the intrinsic viscosity of the product. It showed that the emulsion is of good stability and solubility at low temperature with fatty acid (salt) as emulsifier, and the mixing emulsifier of surfactants reveals better emulsification property than a single emulsifier. So we synthesized the starch graft acrylamide by inverse emulsion polymerization using the mixture of oleic acid and sodium oleate as emulsifier, with the monomer conversion rate 99%, the graft ratio 82.5%, and the intrinsic viscosity 1300 ml/g. The effect of three kinds of initiators, including ammonium persulfate, ammonium persulfate-urea and benzoyl peroxide-sodium sulfite, on the monomer conversion rate and the intrinsic viscosity was investigated. The results show that the correlation equation of the inverse emulsion polymerization of starch graft acrylamide was derived at low initiator concentration for the initial reaction stage, shown as follows:It is according with the reaction regularity of inverse emulsion polymerization.The ternary starch-acrylamide-acrylate acid (sodium acrylate) copolymer with different electricity distributing and electricity consistency was synthesized by adding acrylate acid or sodium acrylate into the emulsion of binary starch graft polyacrylamide copolymer. With the polymerization initiated by ammonium persulfate-urea, the effect of pH and monomer mass ratio on monomer conversion rate and grafting ratio was studied. A novel ternary starch graft copolymer was prepared at around pH 6-7. The catalysis of complexon, EDTA2Na and their mixture (E-N) in the initiation reaction was studied. The results showed that the three catalysts can reduce the initiation reacting temperature, and can improve the monomer conversion rate and the intrinsic viscosity. At last, the ternary starch-acrylamide-acrylate acid (sodium acrylate) copolymer was synthesized by inverse emulsion polymerization using the mixture of ammonium persulfate-urea-(E-N) as catalyst and initiator. When the mass ratio of acrylamide to sodium acrylate was 7:3, the mass ratio of vinyl monomer and starch was 2:1, the reaction temperature was 30℃and the reaction time was 6 h, the monomer conversion rate reaches 99%, the graft ratio is 80.5%, and the intrinsic viscosity is 1650 ml/g.The chemical structure, morphology and the latex particle size of binary and ternary starch graft copolymers were characterized by FT-IR, polarizing microscope and SEM. The chemical structure of the products was proved by FT-IR. After the graft reaction of ungelatinized starch, the morphology of the copolymers kept the aggregate structure of starch, and vinyl copolymer is grafted on its surface; while the gelatinized starch forms homogeneous polymer which is totally different with ungelatinized products.The starch graft copolymers and commercial synthetic polymeric flocculants were applied in the red-mud separation of alumina production. The effects of the types and amounts of flocculants on settling velocity, the amount of supernatants and underflow were investigated. The results showed that the amount of the feed and the flocculant of 820 m~3/h and 300 mg/Kg, respectively, resulted in settling rate higher than 16 cm/min, the amount of supernatants and underflow of 0.15 g/L and 470 g/L, which totally fulfilled the separation of red-mud requirements.更多还原