【作者】 朱肖楠；

【导师】 郑强； 宋义虎；

【作者基本信息】 浙江大学 ， 高分子材料， 2012， 博士

【摘要】 聚氯乙烯(PVC)综合性能优越,作为五大通用塑料之一广泛应用于建材、轻工、农业、电线电缆外皮等领域。然而,由于PVC在加工中存在易降解、难塑化等缺点,配方中需加入热稳定剂及其它加工助剂。随着人们环保和健康意识地不断增强,传统的铅盐、镉盐稳定剂因高毒性而受到多方限制,无毒高效的钙/锌及稀土/锌复合稳定剂逐渐成为研究和应用的热点。在使用中,传统钙／锌或稀土/锌热稳定剂无法兼顾PVC制品的透明性和促进塑化的性能,前期着色较重且自身易迁移并降低制品的维卡软化点,大大限制了其在硬制品、透明制品及对外观要求严格的制品中的应用。将具有稳定作用的官能团引入到与PVC相容性好的高分子上,被认为是解决该问题的方法之一丙烯酸酯型加工助剂ACR401分子量高,与PVC相容性良好,可促进PVC塑化。本论文采用表面刻蚀水解法,在不改变ACR颗粒形态与尺寸情况下将粒子表面羧酸化,采用离子配位法将金属元素修饰在ACR401粒子表面,制备ACR离聚物,以期得到兼具稳定性、促进塑化、保持制品透明性和力学性、低迁移率、安全环保的新型多功能PVC加工助剂。迄今,离聚物型加工助剂的相关研究与应用报道鲜有涉及。本文采用刚果红法、比色法、哈克转矩流变仪等测试手段系统研究了离聚物中金属基团种类与含量、羧酸含量、增塑剂种类等因素对离聚物结构及PVC性能的影响,探讨离聚物对PVC的稳定及促进塑化机理。研究发现镧型离聚物/硬脂酸锌(ZnSt2)复合稳定剂的热稳定效率与硬脂酸镧(LaSt3)/ZnSt2复合稳定剂相当。由于离聚物与PVC相容性良好,与LaSt3相比,使用离聚物可更好地保持PVC制品的透明性,透明度接近于以有机锡或液态钡锌为稳定剂的PVC透明制品。另外,镧型离聚物/ZnSt2复合稳定剂可比LaSt3/ZnSt2复合稳定剂更为有效地抑制PVC制品在加工中的前期着色。与小分子型稳定剂相比,离聚物加工助剂可赋予PVC更高的拉伸强度和模量。镧型离聚物成功地克服了金属皂类稳定剂透明性、前期着色性差,影响制品力学性能等缺点。ACR本身可降低PVC塑化时间,镧型离聚物促进PVC塑化能力明显强于ACR,塑化效率提高40%左右。与小分子稳定剂不同,镧型离聚物的热稳定效率并非随镧含量增加而逐渐增加,而是存在一个最佳羧酸镧基团含量。离聚物中镧基团超过该值后,热稳定效率反而降低。经动态力学热分析(DMTA)、差示扫描量热仪(DSC)、刚果红实验及傅立叶变换红外光谱(FT-IR)测试发现,羧酸镧官能团易在离聚物基体中团聚,形成cluster。团聚体在加工温度下保持稳定,阻碍官能团与PVC热分解产物氯化氢(HCl)及ZnSt2发生相互作用,影响稳定效率。与LaSt3相似,镧型离聚物与ZnSt2可形成复合物,发生协同效应。但是离聚物与ZnSt2形成复合物的速率较慢,可更好地抑制PVC的前期着色。羧酸镧与PVC分子间相互作用较强,可提高熔体强度,故离聚物具有比ACR更强的促进PVC塑化效率。增加离聚物中羧酸含量,可有效抑制cluster生成,提高离聚物对PVC的热稳定及塑化效率；另一方面,羧酸含量提高,镧离子可通过配位键与羧酸基结合,且羧酸基之间形成氢键,在PVC加工温度下金属离子从团聚体中解离速率更慢,从而降低羧酸镧基团与PVC、HCl及ZnSt2的作用速度。因此,提高离聚物中羧酸含量将降低离聚物对PVC的热稳定及塑化效率。这对竞争关系导致存在一个最佳羧酸含量,使离聚物具有最佳功能特性。邻苯二甲酸二异辛酯(DOP)能增塑离聚物中低极性基体部分,可更加有效地提高低镧型离聚物的促进塑化及热稳定效率。丙三醇可破坏离聚物中金属团聚体结构或使团聚体在更低的温度下发生解离,可更加有效地提高高镧型离聚物的促进塑化及热稳定效率。在相同羧酸含量的情况下,钙型离聚物更易形成cluster。故在羧酸钙基团含量较低(小于0.8mmol/g)时,钙型离聚物促进PVC塑化及热稳定效率均不如镧型离聚物显著。锌型离聚物较难形成cluster,促进PVC塑化的能力优于镧型、钙型离聚物,塑化效率比ACR401提高近一倍。然而,锌型离聚物易引起PVC锌烧,热稳定效率最差。环氧大豆油与离聚物/ZnSt2体系联用,可延缓PVC锌烧,提高PVC热稳定性。环氧大豆油还可有效促进PVC塑化,与离聚物/ZnSt2联用后,锌型离聚物促进PVC塑化的能力在三种离聚物中变为最差,镧型离聚物最好。全面衡量稳定性及促进PVC塑化能力,镧型离聚物的综合性能最佳。在加工过程中(180℃,65rpm,6min),含环氧大豆油/钙、锌型离聚物的PVC的粘度、塑化时间均低于含等量ACR/环氧大豆油的PVC混合物。这为开发更加有效、节能的加工助剂体系提供了新思路。更多还原

【Abstract】 Due to the excellent comprehensive performance, poly(vinyl chloride)(PVC) is one of the five most commonly used plastics and widely used in building materials, light industry, agriculture field and so on. However, it is prone to degrade and hard to fuse during processing. Hence, the thermal stabilizers and processing aids are necessities especially for the rigid PVC products. In the last decades, in respect of environmental protection and health, the traditional stabilizers, such as lead salts and cadmium salts are forbidden. Non-toxic calcium/zinc or rare earth/zinc composite stabilizers attract more and more attention. Nevertheless, metal soaps with short fatty or naphthenic chains are easy to volatilize during PVC processing and reduce heat deformation temperature of PVC products, though they could maintain the transparency of the products due to their good compatibility with PVC. On the other hand, the soaps stabilizers with long alkyl chains may undergo fogging easily owing to their limited compatibility with PVC, which limits their usage in transparent products. Acrylate processing aids (ACR) having a good compatibility with PVC are usually used to promote fusion of PVC in almost all rigid formula and many flexible ones. In this study, a ACR-based ionomer was synthesized with purpose to combine the fusion promotion function of ACR with a good compatibility to PVC and the stabilization function of rare earth compounds.Up to now, few relevant work about ionomer used as stabilizer for PVC is reported and the mechanism is nearly ignored. In this paper, the influence of ion content, acid content, the type of plasticizer and ion type of ionomer on the thermal stabilization, fusion behavior, transparency and mechanical properties of PVC was investigated by congo red test, color comparison, hake torque rheometer and so on. Furthermore, we try to explore the mechanism of stabilizing and promoting fusion of ACR-based ionomer.The results revealed lanthanide-containing ionomer behaves as a good HCl scavenger and shows synergistic effect with ZnSt2for stabilizing rigid PVC. It could improve static stability time and promote fusion of PVC with improvement of minimum and fusion torques. The transparency of the compounds stabilized by this kind of ionomer compares favourably with those stabilized by organotin and liquid Ca/Zn stabilizers. The ionomer has a comparable stabilizing efficiency to the commonly used lanthanide stearate for PVC. Moreover, the ionomer stabilized compounds show better initial discoloration, transparency and tensile strength than those stabilized by LaSt3.Being different from small molecular stabilizer, there is a critical content in ionomer. Increasing stabilizing functional groups further will lead a decrease in stabilizing efficiency of ionomer for PVC which is attributed to formation of cluster because of the serious aggregation of stabilizing functional groups. The aggregation is stable under processing temperature which restricts the reaction between stabilizing functional groups in it and hydrochloride (HCl) or zinc stearate (ZnSt2). The reaction rate between stabilizing functional groups in ionomer and ZnSt2is much slower than that between LaSt3and ZnSt2which endows PVC a better initial discoloration.Acid contents in ionomer strongly influence the structure and functionality of ionomer. The size of aggregation decreases with the acid content increasing, owing to restricting the formation of cluster. This is a positive factor of stabilizing and promoting fusion for PVC. On the other hand, increasing acid content in ionomer will increase dissociation temperature and slower the rate of dissociation which considerably lowers the stabilization and promoting fusion function of the ionomers. It is suggested that there is an optimal acid contents of the ionomer to reach a best functionality.Diisooctyl phthalate (DOP) could only plasticize the matrix of ionomer. So it could improve stabilizing and promoting fusion efficiency of the ionomer containing lower amount of stabilizing functional groups more significantly. Glycerol could improve the stabilization of PVC remarkably, but it will postpone the fusion of PVC. It could plasticize the ionic aggregation region in ionomer, destroy part of the ionic aggregation or lower the dissociation temperature of ionic aggregation. Hence, it could improve stabilizing and promoting fusion efficiency of the ionomer containing higher amount of stabilizing functional groups more significantly.It is more easily to form cluster for calcium-containing ionomer. So its stabilizing and promoting efficiency for PVC is lower than that of lanthanide-containing ionomer with stabilizing functional groups no more than0.8mmol/g. While it is more difficult to form cluster for zinc-containing ionomer, so its promoting fusion efficiency for PVC is better than calcium and lanthanide-containing ionomer. However, zinc ionomer will lead zinc burning which makes its stabilizing efficiency is the worst in these three kinds of ionomer.Epoxy soybean oil could improve the stabilization and promote fusion of PVC. When it is used with ionomer/ZnSt2together, it could make promoting fusion efficiency of zinc-containing ionomer become to be the worst of the three and that of lanthanide-containing ionomer become to be the best one. Epoxy soybean oil/ZnSt2/calcium or zinc-containing ionomer could make PVC fuse faster with a lower viscosity (180℃,65r/min,6min) compared with PVC compound containing the same epoxy soybean oil/zinc stearate/ACR content. Based on these results, it may provide a new method to develop a higher efficient and less energy cost processing aid formula.更多还原