L-聚乳酸固相缩聚的工艺研究

Study on Technology of Poly (L-lactic acid) via Solid-state Polymerization

以L-乳酸单体为原料,采用复合催化剂通过直接熔融法合成低聚左旋聚乳酸(PLLA),然后分段控温进行固相缩聚(SSP)。对固相缩聚的工艺条件进行了详细的研究。采用粘度法和凝胶渗透色谱法(GPC)对固相缩聚产物PLLA的特性粘数([η])和分子量进行了表征。用差示扫描量热(DSC)研究了固相缩聚产物的熔融行为和结晶度。结果表明:绝对压力80Pa下,先在105℃下结晶2.5h,再升温至145℃反应35h,得到聚乳酸的重均分子量为42.6万,达到固相缩聚反应前的36倍;熔点达189.6℃,结晶度为69.25%,高分子量聚乳酸的成功制备为其工业化生产的新方法提供了方向。

Starting from L-lactic acid, poly（L-lactic acid） with low polymerization degree was first synthesized through direct melt polycondensation with composite catalyst. Then PLLA with higher molecular weight was obtained by solid-state polymerization with different temperature controlling. The conditions of solid-state polymerization were especially studied. Viscosity measurements and gel permeation chromatography（GPC） were used to measure intrinsic viscosity and molecular weight of resulting PLLA polymers, respectively. The differential scanning calorimetry （DSC） was used to characterize the melt properties and crystallinity of PLLA. The results showed that under absolute pressure 80 Pa with subsection temperature controlling（first at 105℃ for 2. 5h, then at 145℃ for 35h, the molecular weight（Mw） of PLLA is 426,000, which is 36 times higher than that of PLLA first prepared by melt polycondensation. The Tm and crystallinity （Xc） are 189.6℃and 69.25%, respectively. Preparation of high molecular weight polylactie acid provides direction for its industrial production of the new method.