Development of Biodegradable Plastics from Cellulose Acetate

二醋酸纤维素(CDA)是一种可生物降解的聚合物。然而，与广泛使用的塑料相比，CDA存在热塑性不足的问题。本研究致力于开发有效塑化CDA的新方法，为此，对CDA内部塑化的接枝方法进行了探索，但尚未得到充分的研究。在这些方法中，应保持或发展CDA的可生物降解性，并提高接枝效率和反应速度。具体地，研究了环酯和/或羟基酸的接枝反应。在前一种情况下，以2-乙基己酸亚锡(SnEHT2)为催化剂，进行了ε-己内酯的开环接枝共聚反应，以满足上述要求。通过使用双螺杆挤出机进行反应处理，可以有效地实现这种接枝，这种反应可以在低液比(酯化剂/CDA重量比)低至0.4的情况下进行。结果得到了摩尔取代度范围较大的产物，并对其热性能和力学性能进行了系统的研究。在摩尔分数小于1和/或8的范围内，接枝的CDA(g-CDA)没有明确的结晶结构，但在摩尔分数大于8的范围内，接枝的聚己内酯支链相互凝聚，导致其结晶。通过热压成型g-CDA制备的片材的拉伸性能以及片材的不透明和/或混浊的外观可以支持这些现象。当CLN与包括丙交酯在内的其他环酯接枝共聚时，没有发现这种接枝支链结晶现象。通过CLN与乳酸的接枝共聚，系统地进行了CDA的增塑。

Cellulose diacetate (CDA) was recently proved to be a biodegradable polymer. CDA is, however, suffered from an insufficiency of thermoplasticity when compared with wide-use plastics. This study has been carried out to develop novel methods plasticizing effectively the CDA.For this purpose, grafting methods for the internal-plasticization of CDA, which has not been studied sufficiently, have been tried to develop. In the methods, the biodegradability of CDA should be maintained or developed, and the grafting efficiency and the reaction rate should be enhanced. Concretely, the grafting of cyclic esters and/or hydroxy acids have been studied. In the former case, the ring-opening graft copolymerization of ε -caprolactone (CLN) into CDA was conducted to satisfy the above requirements by using Tin( II )2-ethylhexanoate (SnEht2) as the catalyst. This grafting was found to be effectively achievable by reactive-processing using twin-screw extruder, which enables reactions with a low liquid-ratio (esterifying agent / CDA weight ratio) as low as 0.4. As the result, products with the wide range of molar substitutions (MS) were obtained, and their thermal and mechanical properties were systematically studied. In the ranges with MS less than 1 and/or up to 8. the grafted CDAs (g-CDA) don't have well-defined crystallized structures, but in the ranges with the higher MS more than 8, the grafted branch chains of polycaprolactone condense each other to cause their crystallization. The tensile properties of the sheets prepared by hot-press molding of the g-CDA, as well as the appearances of non-transparencies and/or turbidities of the sheets can support these phenomena. Non occurrence of this grafted branch chain crystallization was found when CLN was graft co-polymerized with other cyclic esters including lactide. The plasticization of CDA was also systematically conducted by graft co-polymerization of CLN and lactic acid.