低真空条件下D,L-丙交酯的合成研究

为了提高D,L-丙交酯的收率,研究了D,L-乳酸为单体,低真空条件下使乳酸单体先缩聚后解聚制备D,L-丙交酯的工艺条件。考察了制备过程中脱水温度、脱水率、催化剂量、聚合温度和解聚温度对丙交酯产率的影响。结果表明,以ZnO为催化剂,用量为1.2%,在全程低真空条件下,乳酸分别在120~160℃脱水和220~250℃解聚,以无水乙醇和乙酸乙酯作为溶剂改进了粗产品的提纯方法,可得到产率达40.2%的丙交酯。毛细管熔点法测定了产物的熔点,并用红外光谱、差示扫描量热法、X-射线衍射分析对产物进行了分析表征。所得产物为高纯的环状丙交酯。

Study on synthesis of D,L-lactide at low vacuum condition

With D,L-lactic acid as monomer,D,L-lactide has been synthesized by polymerization and depolymerization in low vacuum level condition.The effects of dehydration temperature,ratio of dehydration,catalyst dosage,polymerization and depolymerization temperature on the yield of D,L-lactide were studied.It is showed that the optimal conditions were as follows:amount of catalyst zinc oxide(ZnO) was 1.2%;dehydration temperature was 120~160 ℃,depolymerization temperature was 220~250 ℃,the purification method from coarse product was improved by using absolute ethyl alcohol and ethyl acetate as solvents.Under this optimal conditions,the yield of D,L-lactide reached 40.2%.Melting point of product was measured by capillary tube method and the ring lactide with high purity was identified by IR,DSC and XRD.