【作者】 方莉；

【导师】 谭天伟；

【作者基本信息】 北京化工大学 ， 生物化工， 2006， 博士

【摘要】 本论文研究了聚天门冬氨酸树脂合成工艺的各个步骤,对交联、水解、干燥及后处理过程的工艺条件进行了研究和优化,对聚天门冬氨酸树脂的性能与结构进行了测试和表征,并对聚天门冬氨酸树脂的生物降解性、稳定性及保水性能和固沙效果进行了分析评价。开发了聚天门冬氨酸树脂合成的二段交联工艺,在有溶剂和分散剂存在的条件下,以聚琥珀酰亚胺(PSI)为原料,经过交联、水解后可以得到具有很好连续性及一定密度梯度、多级多孔网络结构的聚天门冬氨酸树脂,这种树脂具有较合理的基团配比及分布,在吸水性能、凝胶强度和产品收率等方面均优于现有工艺所获得的产品。采用一定分子量的PSI生产聚天门冬氨酸树脂的优化交联工艺条件为：己二胺和丁二胺为交联剂用量0.07～0.076g.g～1PSI,水为分散剂8-10m1·g1PSI,交联温度40℃,反应时间1h,溶剂用量28～32m1·g1PSI,搅拌转速为750rpm；所得到的树脂吸水率最高达1250g··g-1,在0.9%的NaCl溶液中吸水率达到147g·g1,凝胶强度可以达到15.02s。在水解过程中,反应体系的pH值、分散剂用量、水解温度及水解度的大小,均对聚天门冬氨酸树脂产品的吸水性能和凝胶强度有重要影响。优化的水解条件是,采用碱液滴加的方式进行水解,以等体积比的水/乙醇为分散剂,分散剂的用量与反应液等体积。在较大的搅拌转速及40℃条件下,慢速滴加27wt%的碱液,终点pH值为12。在研究过程中,建立了红外分析监控交联聚琥珀酰亚胺水解终点和水解度的方法。研究了鼓风干燥、真空干燥、喷雾干燥、冷冻干燥及微波干燥等不同的干燥方式。发现高温干燥、喷雾干燥及微波干燥均可造成聚天门冬氨酸树脂侧链和主链的严重破坏,影响产品吸水性能和凝胶强度。冷冻干燥会导致断链,但具有很好的成孔作用,并能提高结晶度。真空干燥具有很好的成孔性,并可避免热降解,所得产品性能优良。优化的干燥方式及干燥条件为：40℃高、真空度条件下快速脱水干燥。对凝胶进行后处理可改善凝胶的性能。陈化处理可促使聚天门冬氨酸树脂发生物理交联,强化聚天门冬氨酸树脂网络的骨架结构、增强网络连续性、提高结晶度和凝胶强度。但过度陈化会导致聚天门冬氨酸树脂的吸水能力降低。低温冷冻处理利于结晶,但同时导致聚天门冬氨酸树脂断链。冻融循环会导致聚天门冬氨酸树脂发生物理交联,有利于提高结晶度和凝胶强度。生物降解实验表明,-段交联反应制备的聚天门冬氨酸树脂BOD生物降解度为25.996,而其BOD/COD值为0.561,说明一段交联聚天门冬氨酸树脂易于生物降解；二段交联聚天门冬氨酸树脂BOD生物降解度为13.296,BOD/COD值为0.315,说明二段交联聚天门冬氨酸树脂既具有可生物降解性又具有较好的生物稳定性。聚天门冬氨酸树脂的吸水性能受原料、合成工艺、产品形态、结构及吸水环境等因素的综合影响。采用新开发的二段交联工艺所得到的聚天门冬氨酸树脂产品综合性能较好,具有良好的抗离子性能和pH值缓冲性能。研究过程中还发现,聚天门冬氨酸树脂的吸水动力学行为比较复杂,交联度较低,结构疏松,并具有较小的规整度和结晶度的一段交联树脂,易发生溶胀比大于平衡溶胀比的“超越现象”。二段交联树脂或交联度较大、结构紧密的一段交联树脂在20℃条件下的吸水动力学行为符合Fick定律,凝胶的吸水速度主要表现为扩散控制。高温条件下吸水发生热缩现象,说明是一种热缩性凝胶。对聚天门冬氨酸树脂进行了初步应用实验。保水性能实验表明,二段交联制备的聚天门冬氨酸树脂与土壤混合后,可有效提高保水性,保水时间可达到22天,优于一段交联聚天门冬氨酸树脂的保水性能。固沙实验表明,聚天门冬氨酸树脂有很好的固沙能力,二段交联的聚天门冬氨酸树脂固沙能力大于一段交联产品。对交联过程及水解过程的研究还发现,PSI与胺类交联剂的交联反应,及交联聚琥珀酰亚胺水解反应均属于亲核取代反应。紫外光照射可以导致聚天门冬氨酸和聚天门冬氨酸树脂发生自由基交联。更多还原

【Abstract】 This paper was to study and develop a new process of preparing PASP resin with excellent water-absorbency and gel strength from PSI with the existence of the cross-linking agent, including the cross-linking reaction, hydrolyzing process, drying technology and post-treatment process. In addition, the property and structure, stability, biodegradability and application of PASP resin were also investigated.At the cross linking stage, two-step cross linking method was employed. With feed of PSI, a kind of nice PASP resin obtained by the cross linking process and the following hydrolysis steps. This PASP resin has excellent continuity and a difference or gradient in cross-link density between an inner part and an outer part of each resin particle, and also has a proper proportion and distributing of functional groups. Its water absorbency and strength is superior to that of one step crosslinked product. With a feed of certain molecular weight, the optimum conditions as follows:The concentration of cross linking agent is0.07～0.076g·g-1PSI, the concentration of dispersant agent is8-10ml/g PSI, cross linking temperature is40℃, cross linking time islh, amount of solvent is28-32ml/g PSI, the stirring rotate speed is750rpm.At the hydrolysis stage, the pH of reaction system、the concentration of the dispersant agent, the temperature and degree of hydrolysis were all have effects on the structure and properties of PASP resin. the optimum conditions are:Temperature40℃, terminal pH=12, concentration of NaOH solution27%, and the income of NaOH solution is dropping mode. A method of estimating the hydrolysis end point and controlling degree of hydrolysis has been established.The drying stresses developed during drying can result in cavitation, shrinkage, warp, collapse, or even cracking to the gel body. The experiment results show that drying at the temperature above100℃, spray drying and microwave drying can induce the damage of PASP resin’s cross-linked bonds or side chain portions and backbone basic skeleton badly, and destroy the continuity of PASP resin network. A relatively fast dehydrating rate at lower temperature was in favor of the solid product with loose, uniform and nondestructive porous network structure to be obtained. This kind of product has excellent water-absorbency and gel strength. A vacuum drying at40℃under great vacuum is the most suitable drying condition.Post-treatment of a cross-linked PSI and polyaspartic acid resin can improve the network structure of resin, increase its water-absorbency and gel strength. The ageing treatment can result in physical crosslinking to PASP resin, strengthen the frameworks of network structure, and increase the continuity, crystallinity and gel strength of PASP resin, but an unduly time of the ageing treatment can decrease the water absorbency of PASP resin. Freezing treatment is in favor of increasing crystallinity of PASP resin, but can also induce the damage of PASP resin’s cross-linked bonds or side chain portions, freeze-thaw recycle can strengthen physical crosslinking in PASP resin.The biodegradability of PASP resin was evaluated, and the results show that the activated sludge of one step crosslinked PASP resin could degrade25.9%from BOD, the ratio of BOD/COD was0.561. it illustrated that one step crosslinked PASP resin is easy to be biodegraded. The activated sludge of two step crosslinked PASP resin could degrade13.2%from BOD, the ratio of BOD/COD was0.315, it illustrated that two step crosslinked PASP resin is biodegradable polymer material with some microbial stability.The properties of PASP resin was influence by raw material, preparation technology, shape and structure of PASP resin and environment factor. PASP resin, which was prepared by a novel two step cross-linking method, has excellent comprehensive property, ion-resistance property and pH buffering property. It has been observed that water-absorbency kinetic behavior of PASP resin is very complex, one step crossslinked PASP resin with a loose network structure, and a lower cross-linking degree and crystallinity, displays generally over-shooting. Two step crossslinked PASP resin or one step crossslinked PASP resin with a compact network structure, and a greater cross-linking degree and crystallinity, its water-absorbency kinetic behavior is in conformity with Fick’s law of diffusion. The water-absorbency rate is subject to the diffusion. The fact that PASP gel can shrink at a higher temperature implies that PASP gel is a thermal shrinkable gel.The application of PASP resin has been studied by some preliminary experiments. Water holding experiment shows that the water retention of the soil will increase by blended with PASP resin, and water holding time can reach22days, the water retention of two step cross-linked PASP resin is greater than that of one step cross-linked PASP resin. The fixing sand experiment shows that PASP resin has an excellent fixing sand capacity, and the fixing sand capacity of two step cross-linked PASP resin is greater than that of one step cross-linked PASP resin.The study on the cross-linking reaction and the hydrolysis process shows that the cross-linking reaction between PSI and diamine and the hydrolysis reaction of crosslinked PSI all belong to nucleophilic substitution reaction. In addition, UV treatment can cause free radical cross-linking reaction of PASP and PASP resin.更多还原