马来酸类聚羧酸减水剂的合成与性能研究

 研究合成了聚乙二醇单甲醚（MPEG）的马来酸单酯(MAMPEG)，并将之与丙烯酸(AA)、甲基丙烯酸羟乙酯(HEMA)、乙烯基磺酸钠(SVS)等单体通过自由基水溶液共聚合得到了一系列聚羧酸减水剂，研究了单体加料方式、MPEG相对分子质量、单体组成、引发剂用量等对所得减水剂水泥净浆流动度的影响。结果表明，采用先加MALMPEG、后连续滴加其他单体的加料方式比MALMPEG和其他单体一起滴加的加料方式所得减水剂的性能更好，两者的水泥净浆流动度分别为310 mm和240 mm；随着MPEG相对分子质量增大，所得减水剂水泥净浆流动度先增大后减小，以MPEG-1000为最佳；随着单体组成中酸根离子单体与酯类单体比例的增加，所得减水剂的水泥净浆流动度先增大后减小，当(AA+SVS)/(MALMPEG-1000+HEMA)=1.39(摩尔比)时，所得减水剂的水泥净浆流动度最大；随着引发剂用量增加，所得减水剂水泥净浆流动度先增大后减小，适宜的引发剂用量为单体摩尔总量的1.5%～2.5%。

Synthesis and Properties of Polycarboxylic Water-Reducing Agents Based on the Monoester of Maleic Acid with Monomethoxyl Polyethylene Glycol

The synthesis and properties of polycarboxylic water reducing agents based on the monoester (MALMPEG) of maleic acid with monomethoxyl polyethylene glycol (MPEG) were investigated. Firstly, MALMPEG was synthesized by the esterification of maleic anhydride and MPEG with or without toluenesulfonic acid catalyst. The result showed that pure MALMPEG could be obtained almost quantitatively without the catalyst. Then, the synthesis and properties of polycarboxylic water reducing agents by the copolymerization of the obtained MALMPEG macromonomer with acrylic acid (AA), hydroxyethyl methacrylate (HEMA) and sodium vinylsulfonate (SVS) were investigated by the monomer addition method, chain length of MPEG, composition of co-monomers and amount of initiator (potassium persulphate, KPS). In monomer addition method A, MALMPEG and other monomers were added dropwise together during the polymerization. In monomer addition method B, MALMPEG was added entirely into the reaction flask while the other monomers were added dropwise during the polymerization. The water reducer obtained by method B showed higher fluidity of cement paste than that obtained by method A(310 mm vs 240 mm). The chain length of MPEG, ratio of acid/ionic monomers to ester monomers, namely (AA+SVS)/(MALMPEG+HEMA)(mole ratio) and amount of initiator showed significant effects on the fluidity of cement paste mixed ith the obtained water reducer. The optimal conditions were given in the following: Mn of MPEG was 1000, (AA+SVS)/(MALMPEG+HEMA)=1.39, amount of initiator was between 1.5%～2.5% of total monomers.