正交实验优化低分子质量聚丙烯酸钠合成工艺

Synthesis process optimization of low molecular weight polyacrylic acid sodium by orthogonal experiment

采用水溶液聚合法,以丙烯酸为单体,过硫酸铵-亚硫酸氢钠为氧化还原引发体系,亚硫酸氢钠为链转移剂制得分子质量为3000～4000的聚丙烯酸钠。采用粘度法测得产物的黏均分子质量,对丙烯酸单体和聚丙烯酸钠聚合物的FTIR图谱进行了分析,通过正交实验研究了各因素对聚丙烯酸钠分子质量的影响趋势和程度。结果表明:影响最显著的因素为单体浓度,其次为反应温度,再次为引发剂用量,反应时间的影响最小。确定了最佳合成工艺条件:反应温度为45℃,反应时间为4h;丙烯酸单体质量分数为25%,引发剂过硫酸铵用量为单体质量的6%,链转移剂亚硫酸氢钠用量为单体质量的3%。FTIR谱图中不含碳碳双键,且有羧酸盐的特征峰出现,验证了聚合物的合成。该工艺节省能源,且制备方法简单,易于工业化生产。

The polyacrylic acid sodium with low molecular weight 3 000-4 000 was synthesized by aqueous solution polymerization using acrylic acid as monomer,（NH4） 2S2O8-NaHSO3 as redox initiation system and NaHSO3 as chain-transfer agent.The viscosity-average molecular weights were measured by viscosity method.The IR spectra of acrylic monomers and polyacrylic acid sodium polymer were analyzed.The influence trend and degree of each reaction factor on the molecular weight of polyacrylic acid sodium were investigated by orthogonal test.The results showed that the most significant factor was monomer concentration,the second was reaction temperature and the third was initiator dosage.The effect of reaction time was the least.The optimum reaction conditions were as followed：reaction temperature 45 ℃,reaction time 4 h,concentration of acrylic acid monomer 25 %,the initiator ammonium persulfate dosage 6% and the chain-transfer agent dosage 3% based on the monomer weight.The double bond of carbon did not appeared and the characteristic peak of carboxylate appeared in the IR,therefore the synthesized polymers were confirmed.The process saved energy and the preparation method was simple and easy to industrial production.