桐油源酰亚胺热稳定剂中引入环氧基对PVC热降解后期色变度的影响

Thermal stabilizers are necessary to be in the formulation to prevent the undesirable degradation of PVC during process. Though the metal-free organic imides are efficient PVC thermal stabilizers, they will cause a high discoloration degree during the later stage of PVC degradation. Tung oil derivatives of methyl eleostearate and eleostearic acid contain conjugated double bond and carboxyl in their structure. This project is plan to prepare new glycidyl esters based on imide (GEI) with alicyclic structure in its molecules by tung oil derivatives. The adducts of maleic anhydride and the tung oil derivative will be prepared by the Diels-Alder addition, and subsequently converted to the corresponding GEI via successively reacting with 4-aminobenzoic acid(or p-methoxyaniline) and epichlorohydrin by ring opening reaction, imidization, esterification reaction and ring-closing reaction. The GEI will be applied to the PVC formulation to prevent the undesirable degradation during process. The thermal stability and mechanical properties of PVC samples will be determined using Congo red test, electric conductivity method, element analysis, Fourier transform infrared spectroscopy (FTIR), and the like. Many different kinds of mechanism, including free radical and mixed ion-radical have been proposed. According to the integration of the performance analysis and PVC degradation mechanism, this project is plan to discuss the relationship between the structures of GEI and properties of thermostability and mechanical properties, focus on the effect of the introduction of epoxy group into imide on the color variation during the later stage of PVC degradation, study the collaborative stability mechanism between epoxy group and imide in detail in this work. This project will promote the higher-value utilization of the forestry resource tung oil.

热稳定剂是聚氯乙烯（PVC）加工时必备助剂之一，可延缓PVC热降解的进度。无金属酰亚胺类PVC有机热稳定剂具有较优的热稳定效率，但其稳定的PVC在降解后期变色程度较高。为此，本项目利用桐甲酯及桐酸的共轭双键、羧基等天然分子结构，先后与马来酸酐、对氨基苯甲酸（或对氨基苯甲醚）、环氧氯丙烷经Diels-Alder加成反应、开环、亚胺化、酯化、闭环等反应构筑新型的含脂肪环结构的桐油源缩水甘油酯（环氧酰亚胺），并将其应用于PVC体系中。利用刚果红法、电导率法、元素分析法、红外光谱法等分析测试手段，结合PVC热降解机理如自由基机理、分子-离子机理等，探究环氧酰亚胺的分子结构与PVC材料热稳定性及力学性能间的构效关系，重点研究酰亚胺中环氧基团的引入对PVC热降解后期色变度的影响，分析环氧酰亚胺分子结构中酰亚胺与环氧基官能团间的协同稳定机理。本项目有利于推动绿色林特资源桐油的高附加值利用。

本项目的范畴属于热稳定剂研究领域。热稳定剂是聚氯乙烯（PVC）加工时必备助剂之一，可延缓PVC热降解的进度。无金属酰亚胺类PVC有机热稳定剂具有较优的热稳定效率，但其稳定的PVC在降解后期变色程度较高。本项目利用我国主要林产品桐油为原料，利用桐油中共轭三烯键易于发生加成反应的特点，将桐油经酯交换反应得到桐酸甲酯，再与顺丁烯二酸酐加成，合成了桐马酸酐（TMA）。以TMA为原料，构筑了新型的桐油源酰亚胺基缩水甘油酯（GEABTMI），重点研究酰亚胺中环氧基团的引入对PVC热降解后期色变度的影响。另外，本研究还以TMA、蓖麻油酸、2-甲基咪唑及其衍生物等为主要原料，经过氨解反应、环氧化反应、复分解反应等化学改性手段，制备出一系列含氮、磷官能团的热稳定剂如含富氮和羟基结构的桐油基缩水甘油酯（GEHTMA）、桐油源酰胺基钙锌复合热稳定剂、含富氮基团的多元醇辅助热稳定剂及其钙锌复合热稳定剂、蓖麻油基磷酸酯钙锌PVC热稳定剂及沸石咪唑框架结构化合物ZIF-8。将上述热稳定剂应用于PVC体系中，利用刚果红法、热老化烘箱法、热失重法等分析测试手段，结合PVC热降解机理，重点研究了桐油基热稳定剂的分子结构与PVC材料热稳定性及力学性能间的构效关系。研究结果表明，桐油基酰亚胺热稳定剂中环氧基官能团的引入有利于解决PVC树脂降解后期变色程度高的问题。GEHTMA中的三嗪环、环氧基、羟基、酯基等结构可改善其与PVC间的相容性、改善PVC的初期着色性和长期热稳定性。自制的桐油源二元酰胺基钙锌复合热稳定剂添加至PVC后，PVC材料静态热稳定时间Ts可延长至70min以上，且80min后才发生“锌烧”。含富氮基团的桐油源多元醇及其锌盐与硬脂酸钙复配使用，可使PVC体系的静态热稳定时间延长至89.28min。本研究可为创新生物基热稳定剂的开发提供理论指导，为林产资源桐油的高附加值利用开辟新的途径。研究过程中共发表SCI论文7篇，申请专利3项，其中已授权专利1项; 协助培养博士研究生1名，中青年骨干1名。