基于竞聚率设计制备组成均匀的聚羧酸减水剂

Preparation of polycarboxylate superplasticizer with uniform composition based on reactivity ratio

摘要:

基于试验得到的聚羧酸减水剂（PCE）共聚单体的竞聚率数据，采用控制转化率和补加活泼单体相结合的方法，结合理论计算和聚合单体摩尔分数实际测定结果，确定了活泼单体丙烯酸（AA）补加时间及补加量，使其在共聚过程中始终与大单体异丁烯基聚乙二醇醚（MAPEG）组成保持基本不变，以保证聚合反应不同时间段所生成的共聚物组成和结构与设计值一致。为系统研究控制工艺的准确性和可靠性，将其与传统投料工艺反应过程中所得产物的组成对比，考察了控制共聚物组成对分散性能的影响。结果表明，基于竞聚率的控制工艺制备PCE过程中，由于分段补加消耗较快的AA，抑制AA和MAPEG在共聚物瞬时组成的变化幅度，共聚物的平均酸醚比〔n(AA)/n(MAPEG)〕分别为2.79、3.77、4.82，基本接近设计酸醚比（A/E）的3.0、4.0、5.0；其制备的PCE平均主链长度及主链上羧基含量、大单体含量较高，使PCE覆盖面积和吸附层厚度增大，从而提升了净浆初始流动度和流动保持性能。

Abstract:

Based on the reactivity ratio of comonomers obtained from the experiment, the supplemental time and amount of acrylic acid (AA) were determined by controlling the conversion ratio and adding active monomer according to theoretical calculation and experimental determination, so that the monomer composition of AA and methyl allyl polyethylene glycol (MAPEG) remained unchanged in the copolymerization system, so as to ensure the consistency of the copolymer composition generated successively. In order to systematically study the accuracy and reliability of the controlled feeding process (CFP), the composition difference of the copolymers obtained in CFP and traditional feeding processes (TFP) was compared. The effect of controlling copolymer composition on dispersion performance was investigated. The results show that the average acid/ether ratio [n(AA)/n(MAPEG)] of polycarboxylate superplasticizer (PCE) copolymers prepared by CFP based on the reactivity are 2.79, 3.77, 4.82, respectively, which are basically consistent with the designed goal (3.0, 4.0, 5.0). PCE prepared by CFP have higher average main chain length, carboxyl molar fraction and macromonomer molar fraction, which increases the coverage area and adsorption layer thickness of PCE, thus improving the initial fluidity and fluidity retaining ability when used in cement paste.