Chemical depolymerization of polylactic acid (PLA) was demonstrated in supercritical carbon dioxide medium. No catalyst, organic solvent or water was employed in the reaction. The primary feedstocks used in ring opening polymerization of PLA, lactide isomers, were produced with high yield. More specifically, lactides were produced as the sole nongaseous products with a 93 % yield based on the initial polymer mass at 200 °C and 310 bar in 120 min. The influences of the reaction temperature, time, and pressure on PLA depolymerization products were investigated. While the lactide yield and distribution were highly influenced by the reaction temperature and time, further improvement was attained with an increase in the pressure. The results demonstrate that supercritical CO2 can be applied as a promising reaction medium for PLA degradation, providing a high-yield production of its feedstock. The process can enable green depolymerization of polylactic acid and promote its circular economy with a closed loop production.

中文翻译：

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通过聚乳酸在超临界二氧化碳中解聚高产率生产丙交酯异构体


在超临界二氧化碳介质中证明了聚乳酸 （PLA） 的化学解聚。反应中未使用催化剂、有机溶剂或水。PLA 开环聚合中使用的主要原料丙交酯异构体的产量很高。更具体地说，丙交酯是作为唯一的非气态产品生产的，根据 200 °C 和 310 bar 下 120 分钟内的初始聚合物质量，产量为 93%。研究了反应温度、时间和压力对 PLA 解聚产物的影响。虽然反应温度和时间对丙交酯产率和分布有很大影响，但随着压力的增加，情况得到了进一步的改善。结果表明，超临界 CO2 可以作为 PLA 降解的有前途的反应介质，提供其原料的高产率生产。该工艺可实现聚乳酸的绿色解聚，并通过闭环生产促进其循环经济。