基于β-环糊精为骨架的星型大分子抗氧剂的制备及其对天然橡胶的抗氧化性能与机理研究

How to restrain effectively the migration of the antioxidants and play adequately their anti-oxidant role, is one of the key problem to be resolved in the development and application of natural rubber and its products. In our work, firstly, via designing molecular structure, β-cyclodextrin (β-CD) as framework material was changed to the β-CD intermediate with seven primary C6-hydroxy group(OH) by chemical modification. Secondly, using the difference of reaction activity between primary isocyanate group (NCO) and second NCO on isophorone diisocyanate (IPDI) used as bridging agent, and controlling the molar ratio, the primary NCO and the second NCO were reacted with the second OH on 4-hydroxymethyl-2,6-di-tert-butylphenol and seven primary C6-OH on the β-CD intermediate, respectively, and the star-shaped β-CD polymeric antioxidant with seven phenolic hydroxyl groups and special conical cavum was prepared. The structure of the star-shaped β-CD polymeric antioxidant was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance, gel permeation chromatography, mass spectrometry, etc. The absorbability and release behavior of the β-CD polymeric antioxidant to phosphate antioxidant were researched systematically, and especially the antioxidant capability of β-CD polymeric antioxidant to natural rubber and the mechanism were researched detailedly. Through the project research, the theoretical basis and technial support should be provided for the molecular design, industrialization development and the practical application in natural rubber of the novel excellent polymeric antioxidants with multi-phenolic hydroxyl groups.

如何有效抑制抗氧剂的迁移并充分发挥其抗氧化作用，是当前天然橡胶及其制品发展和应用所亟需解决的关键问题之一。本项目通过分子结构设计，首先对β-环糊精（β-CD）进行化学修饰，得到含7个C6位伯羟基的β-CD中间体；其次采用异佛尔酮二异氰酸酯（IPDI）为架桥剂，利用其伯异氰酸酯基（NCO）和仲NCO的反应活性差异，控制摩尔配比，使伯NCO和仲NCO分别与4-羟甲基-2,6-二叔丁基酚上的仲羟基和β-CD中间体上的7个C6位伯羟基反应，制备含7个酚羟基并具有特殊锥形空腔结构的星型β-CD大分子抗氧剂。采用红外光谱、核磁共振、凝胶渗透色谱、质谱等对星型β-CD大分子抗氧剂进行表征，系统研究该抗氧剂对亚磷酸酯的包合与释放行为，并重点研究其对天然橡胶的抗氧化性能及作用机理。通过本项目研究，可为新型含多酚羟基的大分子高效抗氧剂的分子设计、产业化发展以及对其在天然橡胶中的实际应用提供理论依据和技术支撑。

天然橡胶在加工、贮存及使用过程中，易受到热、氧、臭氧等的作用而发生老化现象，使其性能逐渐恶化而失去使用价值。为了抑制或延缓上述变化的进程，通常需加入抗氧剂。然而传统小分子抗氧剂由于分子量较低，存在着热稳定性较差和不耐溶剂抽提等缺点。因此，制备具有耐迁移性的大分子抗氧剂已备受关注。.本项目的主要研究内容、重要结果和数据如下：.（1）通过分子设计，采用伯羟基保护-仲羟基酯化-伯羟基脱保护的技术对β-环糊精（β-CD）进行化学修饰，制备了含7个活性伯羟基和14个乙酰基的β-CD衍生物β-CD-Ⅲ。采用傅立叶变换红外光谱（FT-IR）、核磁共振氢谱（1H-NMR）和基质辅助激光解析电离飞行时间质谱（MALDI-TOF-MS）对其结构进行了表征和确认。.（2）先将3,5-二叔丁基-4-羟基肉桂酸（DBHCA）与氯化亚砜反应制成酰氯，再将其接枝到β-CD-Ⅲ上制得七臂星型大分子抗氧剂β-CD-(DBHCA)7；采用FT-IR、1H-NMR和MALDI-TOF-MS对β-CD-(DBHCA)7进行结构表征，利用热重分析（TGA）研究其热稳定性，并研究了β-CD-(DBHCA)7对NR的抗热氧老化作用以及在天然橡胶中的耐抽提性能。与DBHCA相比，β-CD-(DBHCA)7具有更好的热稳定性以及对NR具有更持久的抗热氧老化性能。虽然在老化初期，添加了β-CD-(DBHCA)7的硫化胶的性能保持率略低于分别添加了DBHCA和Irganox 1010的，但在老化后期，其性能保持率却呈现反超趋势。此外，β-CD-(DBHCA)7在天然橡胶中的耐抽提性能优良。.（3）以异佛尔酮二异氰酸酯（IPDI）为桥接剂，通过两步法将2,6-二叔丁基-4-羟甲基苯酚（DBHMP）接枝到β-CD-Ⅲ上制备了分子量为4000的星型大分子抗氧剂β-CD-DBHMP，采用FT-IR、1H-NMR、MALDI-TOF-MS和凝胶色谱对其进行结构表征，借助TGA研究其热稳定性，并研究了β-CD-DBHMP对天然橡胶的抗热氧老化作用以及耐抽提性能。结果表明，酚羟基和氨基甲酸酯基可以起到协同抗氧作用，β-CD-DBHMP具有良好的热稳定性、抗热氧老化性能和优异的耐抽提性能。