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2020-07-01View Original

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聚乳酸合成工艺：一步法https://image.juhecat.com/wp-content/uploads/2020/06/WechatIMG646.png?x-oss-process=image%2Fformat,webp简介：一步法也就是直接缩聚法，指的是在脱水剂的存在下，乳酸分子相互之间的羟基和羧基发生直接缩合脱水反应产生聚乳酸的一种合成加工工艺。优点：单体转化率较高，加工工艺简易也无需经过中间体的纯化，因此生产成本较低。缺点：游离乳酸、水、低聚物和丙交酯相互之间存在平衡。反应产生的水等副产品在黏性熔融物中较难去除，反应难以向正方向进行。一步法较难得到高分子量的聚合物，得到的聚合物分子量一般较低，仅为数万，且一般含带颜色。聚乳酸合成工艺：二步法https://image.juhecat.com/wp-content/uploads/2020/06/WechatIMG647.png?x-oss-process=image%2Fformat,webp简介：二步法先将乳酸单体缩聚脱水并由两分子乳酸环化得到丙交酯，再将丙交酯开环聚合得到聚乳酸。因为在开环聚合反应时不产生副产品水，能够精准把控聚合反应的分子量到达10万以上，并且能够在丙交酯的制备纯化上，去除乳酸原料内的杂质及小量的消旋乳酸，进一步提升化学纯度及光学纯度。优点：二步法制得的聚乳酸机械强度高，分子量可以达到上百万，比较适用于规模性工业化生产。缺点：相比于一步法而言两步法生产加工工艺流程较长、生产成本较高。

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