PTSA用量对聚羧酸减水剂大单体酯化反应的影响

摘要

The macromonomer,methoxy polyethylene glycol methacrylate ester(MPEGMA),used for polycarboxylate superplasticizer was prepared by esterification of methacrylic acid(MAA) and methoxy polyethylene glycol (MPEG1000),using p-toluene sulfonic acid(PTSA) as catalyst and phenothiazine(PTZ) as inhibitor,under the condition that water formed in the reaction was removed by nitrogen,and the product was a kind of intermediate used to synthesize polycarboxylate superplasticizer.The effect of the amount of PTSA on the esterification reaction time and esterification ratio was investigated by using single factor experiment.The influence of PTSA dosage on the esterification rate constant was analyzed and a judgment result was obtained that the esterification reaction belongs to a secondorder reaction based on the analysis of linear regression.The impact of the reaction temperature on the esterification rate constant was also considered and obtained different rate constants at different temperatures.In addition,the decomposition rate of macromonomer in neutral and acidic solution at room temperature was investigated.The result showed that increasing the amount of catalyst would shorten the reaction time and elevated the esterification ratio as well as the reaction rate constant.In the appropriate temperature range,higher reaction temperature led greater reaction rate constant.In neutral solution,the macromonomer was suitable for a short-term storage,which was favorable to the synthesis of polycarboxylate superplasticizer in future.%以聚乙二醇单甲醚(MPEG1000)和甲基丙烯酸(MAA)为原料,对甲苯磺酸(PTSA)为催化剂,吩噻嗪(PTZ)为阻聚剂,在通氮气赶水的条件下通过酯化反应制备聚乙二醇单甲醚甲基丙烯酸酯(MPEGMA)大单体,产物作为合成聚羧酸系减水剂的中间体.采用单因素试验考察了PTSA用量对酯化时间和酯化率的影响,分析了PTSA用量和反应温度对速率常数的影响规律,并对大单体于室温下在酸性溶液和中性溶液中各自的分解速率进行了测试.结果表明:酯化反应为二级反应,随着催化剂用量的增加,酯化反应时间缩短,酯化率提高,速率常数变大；在合适的温度范围内,温度越高,速率常数越大；在中性溶液条件下对大单体进行短期储存切实可行.