醇洗法纯化乙交酯的工艺及对开环聚合反应的影响

摘要

对本体解聚制备的乙交酯粗品进行醇洗纯化，研究了醇洗次数、溶剂用量、醇洗时间对乙交酯中游离酸、水含量及收率的影响；考察了醇洗后乙交酯中总氢质子含量对聚合反应的影响。筛选了不同醇类溶剂，优选异丙醇为合适的溶剂进行乙交酯粗品纯化，辅以抽滤、真空干燥等手段最终得到纯化的乙交酯。研究结果表明，醇洗次数3次，溶剂用量即V(醇)/M(乙交酯)=2mL/g，洗涤时间30min，乙交酯中的游离酸、水含量分别降低到1.7×10−5mol/g、468mg/L，总氢质子含量为43×10-6mol/g，通过双螺杆挤出机进行开环聚合，得到聚乙醇酸（PGA）特性黏度高达0.81dL/g；收率可达82%，比重结晶法纯化收率高。通过差示扫描量热法（DSC）测定醇洗后乙交酯纯度，得均值99.93%，满足聚合纯度的要求。%Crude glycolide which obtained via melting depolymerization was purified by alcohol washing. The effects of times of washing,amount of solvent,washing time on contents of free acid and H2O in glycolide and yield of glycolide were investigated. The effect of total hydrogen content on ring opening polymerization was also discussed. Isopropanol was chosen as the proper solvent for crude glycolide purification by comparing different alcohol solvents first,and purified glycolide was obtained by filtration and vacuum drying. The optimized purifying conditions were as follows:washing 3 times by alcohol,V(Alcohol)/M(Glycolide)=2mL/g and washing time for 30min in each time. The contents of free acid and H2O in glycolide were reduced to 17×10−6mol/g,and 468mg/L respectively,and total hydrogen content was 1.7×10−5mol/g. Through ring opening polymerization in twin screw extruder, glycolide was converted to PGA with high intrinsic viscosity of 0.81dL/g. After purification of glycolidevia alcohol washing,the yield was 82%,higher than that of the recrystallization process. Differential scanning calorimetry (DSC) was used to determine glycolide purity with average value of 99.93%,meeting the needs of ring opening polymerization.