Synthesis of polycarboxylic superplasticizer by Co2+, Ni2+ and Zn2+ catalysted NaHSO3-H2O2 initiation system

Polycarboxylate superplasticizer (PCA) as a new type of high performance water reducing agent, has many excellent properties, but still faces the problems of poor water slurry dispersion, early strengthening flowability, water reducing rate and fluidity of cement paste. In order to further improve the comprehensive performance of Polycarboxylate superplasticizer, optimize the synthesis process and reduce production cost, it is of great theoretical and practical significance to develop a new cost-effective composite initiator system of Polycarboxylate superplasticizer. In this paper, Co2+, Ni2+ and Zn2+ catalysted NaHSO3-H2O2 initiation system were designed as redox initiators to synthesis Polycarboxylate superplasticizer, leading to PCA (Co2+), PCA (Ni2+) and PCA (Zn2+), respectively. The complexes were characterised by FTIR, GPC, zeta potential, XRD, TG, SEM and HPLC methods. When the folded solid content was 0.15%, compared with PCA0, the functional group type of PCA was unchanged and the molecular weight of PCA was slightly reduced. The transition metal ions coordinated with the carboxyl group (-COO-) of acrylic acid, which shifted the carbon-carbon double bond conjugated electron cloud in the monomer to the carbonyl carbon, enhanced the double bond activity, and promoted the polymerization reaction. When the double bond retention rate of the raw material isopentenol polyoxyethylene ether (TPEG) was 94.34%, the conversion rate of the large monomer could increase to 93.82%, which was 16.48% higher than that of PCA0 (77.34%), and the dispersion and retention ability of the cement slurry were improved. PCA (Co2+), PCA (Ni2+) and PCA (Zn2+) are more conducive to the early hydration of cement slurry than PCA0. Compared with PCA0, the water reduction rates of PCA in modified synthesis all increased by at least 3%. Compared with PCA0, the fluidity of the modified PCA cement paste was improved by 51mm.

聚羧酸系减水剂（Polycarboxylate Superplasticizer，PCA）作为一类新型高性能减水剂，虽具备诸多优异性能，但仍面临水泥浆体分散性不佳、早期强度与流动度调控、减水率优化等相关问题。为进一步提升聚羧酸系减水剂的综合性能、优化合成工艺并降低生产成本，开发新型高性价比的聚羧酸系减水剂复合引发体系，具备重要的理论与实际研究意义。本文设计了以Co²+、Ni²+、Zn²+为催化剂的NaHSO₃-H₂O₂氧化还原引发体系，用于合成聚羧酸系减水剂，分别得到PCA(Co²+)、PCA(Ni²+)与PCA(Zn²+)。采用傅里叶变换红外光谱（FTIR）、凝胶渗透色谱（GPC）、Zeta电位、X射线衍射（XRD）、热重分析（TG）、扫描电子显微镜（SEM）与高效液相色谱（HPLC）等手段对产物进行了表征。当体系固含量为0.15%时，相较于PCA0，改性PCA的官能团类型未发生改变，但其分子量略有降低。过渡金属离子可与丙烯酸的羧基（-COO-）发生配位作用，使单体中碳碳双键的共轭电子云向羰基碳偏移，增强了双键活性，进而促进聚合反应的进行。当原料异戊烯醇聚氧乙烯醚（TPEG）的双键保留率为94.34%时，大单体的转化率可提升至93.82%，较PCA0的77.34%高出16.48%，同时水泥浆体的分散性与保坍性能均得到改善。PCA(Co²+)、PCA(Ni²+)与PCA(Zn²+)均较PCA0更有利于水泥浆体的早期水化。相较于PCA0，改性合成的聚羧酸系减水剂的减水率均提升至少3%。相较于PCA0，改性后聚羧酸系减水剂配制的水泥浆体流动度提升了51mm。