减压条件下聚羧酸系减水剂活性大单体MPEGMA的制备

研究了减压条件下甲基丙烯酸(MA)和单甲氧基聚乙二醇(MPEG)直接酯化合成甲基丙烯酸聚乙二醇单甲醚酯(MPEGMA)的过程,考察了真空度、反应温度、阻聚剂用量、催化剂用量以及反应时间等条件对酯化率的影响,并通过红外光谱分析表征了酯化产物的结构.结果表明,在优化的反应条件(阻聚剂氮氧自由基哌啶酮用量为甲基丙烯酸质量的0.2%,催化剂对甲苯磺酸用量为反应物总质量的6%,82.4 kPa,80℃,5 h)下,MPEG和甲基丙烯酸物质的量比为1:1时的酯化率可达到66.5%,酯化产物双键结构的红外特征峰明显,所得到的MPEGMA为单体通过共聚合成的聚羧酸减水剂具有良好的分散性和保塑性,掺入该减水剂0.3%质量分率的水泥净浆流动度可达到290 mm.

Preparation of Active Macromer MPEGMA for Polycarboxylate Based Superplasticizer under Vacuum Conditions

Methoxy (polyethyleneglycol) methacrylate (MPEGMA) was synthezied with the esterification of methacrylic acid(MA)and methoxy polyethylene glycol(MPEG)under vacuum.The influence of vacuum degree,reaction temperature,reaction time and the amount of inhibitor and catalysis on the esterification were investigated.Double-bond stretching vibration band in esterification product was characterized by Fourier transform infrared spectroscope(FT-IR).The results showed that the optimum reaction condition was as following:molar ratio of MA to MPEG 0.2%,mass ratio of catalyst(p-toluenesulfonic acid)to the total reactants 6%and reaction time 5 h.Under this condition.the esterification fraction could reach 66.5%and the double-bond stretching vibration band of the product was significant.Moreover,the polycarboxylate based superplasticizer prepared with the synthesized MPEGMA under this condition would show good plasticizing and fluidity.The fluidity of cement paste could reach 290 mm with the 0.39/% mass content of this polycarboxylate based superplasticizer.