Development of Biodegradable Plastics from Cellulose Acetate

二醋酸纤维素（CDA）是一种可生物降解的高分子材料。然而，与广泛使用的塑料相比，CDA的热塑性不足。本研究旨在开发有效增塑CDA的新方法，并尝试开发研究尚不充分的CDA内增塑接枝方法。在这些方法中，应保持或发展CDA的可生物降解性，并应提高接枝效率和反应速率。具体地，已经研究了环酯和/或羟基酸的接枝。在前一种情况下，通过使用2-乙基己酸锡（II）（SnEht 2）作为催化剂进行ε-己内酯（CLN）到CDA的开环接枝共聚以满足上述要求。发现这种接枝可以通过使用双螺杆挤出机的反应性加工有效地实现，这使得反应具有低至0.4的低液体比（增稠剂/CDA重量比）。结果表明，合成的产物具有较宽的取代度范围，并对其热性能和力学性能进行了系统的研究。在MS小于1和/或至多8的范围内。接枝的CDA（g-CDA）不具有明确的结晶结构，但在MS大于8的较高范围内，聚己内酯的接枝分支链相互缩合，导致它们结晶。通过g-CDA的热压模塑制备的片材的拉伸性能以及片材的非结晶性和/或浊度的外观可以支持这些现象。当CLN与包括丙交酯在内的其它环酯接枝共聚时，没有发现这种接枝分支链结晶的发生。通过CLN与乳酸的接枝共聚，系统地研究了CDA的增塑作用。

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.