聚羟乙基脂肪酸甲酯分层现象浅析

摘要

The thoroughly mixed sample of methyl ester of poly-ethoxyl fatty acid（abbreviated as MEE） was filtered by suction and centrifuged at high speed to separated into 2 layers,giving a clear supernatant upper layer and a turbid or solidified lower layer.The 2 layers were separated and collected for analytical study.Magnesium as a residual element from the catalyst was determined by FAAS.Polyethylene glycol（PEG） in both layers as a by-product in the synthesis of MEE was determined by the method of GB/T 5560-2003.Definite amount of lower layer was taken and its content of the by-product diester was determined by 1H NMR after hydrolysis and separation.It was found that residual amount of Mg2＋ in the lower layer was 0.421 mg·g-1;amount of PEG found in the lower layer was 3.68%;and mole percentages of the by-product diester（PEG removed preliminarily） and MEE with high EO addition number were found to be 16% and 84% respectively.It was proposed that the difference in composition and content of the 2 layers was the cause of the layer separation phenomenon.%将需分析的聚羟乙基脂肪酸甲酯（MEE）样品充分混匀,并经真空抽滤后,滤液经高速离心分成两层,上层为澄清液,下层呈浑浊或固化。收集上、下两层分别用于分析,用火焰原子吸收光谱法测定了下层中由催化剂所残留的镁量。用国标GB/T 5560-2003方法测定了上、下两层中作为合成中的副产物存在的聚乙二醇（PEG）。另取一定量的下层样品经水解处理并分离后,用核磁共振氢谱法测定其中副产物二酯的含量。结果表明：MEE下层样品中镁的残留量达0.421mg.g-1,下层样品中聚乙二醇质量分数为3.68%;下层中二酯（测定时预先除去样品中的PEG）及具有较高的环氧乙烷加合数的MEE的物质的量分数依次为16%和84%。据此认为上、下两层中组分及含量的不同是导致产生分层现象的原因。