低能耗高保坍型聚羧酸系减水剂的合成及性能

Synthesis and properties of low-energy consumption and high slump retaining type of polycarboxylate superplasticizer

合成工艺的低能耗是减水剂绿色制备的一个重要发展方向,研制高保坍型聚羧酸系减水剂解决现代混凝土施工中面临的坍落度损失控制难题具有重要实践意义。采用复合氧化-还原体系,在20℃条件下,以异戊烯醇聚氧乙烯醚、丙烯酸丁酯、丙烯酸羟乙酯和丙烯酸为共聚单体,一步法合成了高保坍型聚羧酸系减水剂。通过单因素试验和正交试验研究了丙烯酸丁酯、丙烯酸羟乙酯、链转移剂、还原剂、氧化剂用量对聚合物分散性和保坍性的影响规律,得到了最佳合成工艺为:丙烯酸丁酯与丙烯酸羟乙酯等摩尔取代丙烯酸的用量为30%,链转移剂用量为0.25%,还原剂用量为0.22%,氧化剂用量为0.30%(占聚醚大单体质量),反应时间为4 h。与国外同类产品相比,按最佳合成工艺参数制备的保坍剂具有显著的小坍度保持能力和较低的掺量敏感性,特别适用于小坍落度高保坍要求的混凝土施工。

The synthesis process with low-energy consumption is an important developing direction for green synthesis of the water reducing agent. Developing a high slump retaining type of polycarboxylate superplasticizer has an important practical significance in solving the problems of the slump loss control in the modern concrete construction. A compound redox system was used to synthesize the high slump retaining type of polycarboxylate superplasticizer with one step method at 20 ^ , by using the isopentenol polyoxyethylene ether, butyl acrylate, hydroxyethyl acrylate and acrylic acid as a comonomer. The effects of the butyl acrylate, hydroxyethyl acrylate, chain transfer agent, reducdant and oxidant on the dispersing ability and slump retaining ability of the superplasticizer were studied by a single factor and orthogonal tests. The optimum synthetic process parameters are as follows： the equimolar substitution amount of acrylic acid replaced by the butyl acrylate and hydroxyethyl acrylate is 30% , the usage of the chain transfer agent, reductant and oxidant is 0. 25%, 0. 22%, 0. 33% respectively （with the mass ratio of the isopentenol polyoxyethylene ether） , and the reaction time is 4 hours. Compared with foreign similar products, the test results show that the developed superplasticizer has a small slump retention ability and lower dosage sensitivity, which is especially suitable for the low-slump concrete needing high slump retaining ability.