沉淀聚合制备低分子量聚丙烯酸及残液循环利用

以偶氮二异丁腈(AIBN)为自由基引发剂,石油醚为溶剂,异丙醇为链转移剂,通过沉淀聚合制备了低相对分子质量(简称分子量,下同)的聚丙烯酸。考察了引发剂用量、链转移剂用量、单体质量浓度对聚合收率的影响,确定最佳聚合条件为:AIBN用量为单体质量的10%,链转移剂用量为单体质量的100%,单体质量浓度100g/L,反应温度80℃,反应时间4 h。反应结束后产品在底部沉淀析出,溶剂可循环利用,在最佳聚合条件下,残液循环利用5次,单体的累计转化率达到92.6%。凝胶渗透色谱(GPC)分析表明,通过残液循环制备的产品重均分子量(Mw)变化不大,保持在1 000～1 300,多分散性(PDI)为1.92～3.38。

Precipitation Polymerization of Low Molecular Weight Acrylic Acid and Recycling of Polymerization Residue

The low molecular weight acrylic acid was synthesized by precipitation polymerization in petroleum ether utilizing azo-bis-isobutyronitrile(AIBN) as the free radical initiator and isopropanol as the chain transfer agent.The influences of monomer mass concentration and initiator and chain transfer agent amount on the yield of polyacrylic acid were investigated.The results show that the optimal polymerization conditions were as follows:the mass percent of initiator(AIBN) was 10% relative to monomer,the chain transfer agent was 100% relative to monomer,the monomer mass concentration was 100 g/L,and the reaction was carried out at 80 ℃ for 4 h.The product was precipitated in the bottom and the solvent can be removed and recycled.An accumulative monomer conversion of 92.6% was achieved after the residue was recycled for 5 times under the optimized polymerization conditions.The results of the gel permeation chromatography(GPC) show that the weight-average molecular weight(Mw) of polyacrylic acid exhibited little change,being kept within the range of 1 000～1 300,and that a polydispersity index(PDI) of 1.92～3.38 was obtained.