Thickener is a kind of relatively complex polymer, and various factors in the preparation process may have a significant impact on the properties of polymerization products. For example, the type of monomer and the pH value of the mixture.
The main monomer of synthetic thickener usually contains water-soluble groups such as carboxylate and sulfonate. Among them, the most used monomers are acrylic acid, sulfonic acid monomers, amide monomers, acrylic acid lipid monomers, etc. Different monomers play different roles in thickener products. For acrylic monomers and amide non monomers, acrylic monomers have strong water absorption but poor electrolyte resistance, while amide monomers have good electrolyte resistance but poor water absorption. There are two synthetic methods of thickener, namely homopolymerization and reverse copolymerization Yes. Homopolymerization reaction, if the monomer concentration is high, the reaction will be more intense, easy to generate polymerization and gel formation, reaction speed is faster, resulting in chain transfer reaction also increased, the corresponding branching and self crosslinking reaction also increased, so that the thickening performance of the polymerization products will be reduced. In addition, it has been found that the thickener synthesized with a single monomer has lower electrolyte resistance and thickening performance than the thickener prepared by copolymerization of several types of monomers. Therefore, people turn their research direction to the copolymerization of binary and ternary monomers to prepare thickener 36. The hydrophilic groups on the macromolecular chains of different monomers are also different, and the interaction between different hydrophilic groups will also have a great impact on the properties of polymers 9. Therefore, when preparing thickeners, the selection of monomers must depend on the specific situation, especially when selecting composite monomers, we must explore the appropriate polymerization proportion, so as to prepare thickeners whose thickening ability and electrolyte resistance can meet the needs.
In the synthesis process of thickener, the first step is to neutralize the water-soluble monomer with alkali to form salt. The H value of the mixture will directly affect the reaction rate during polymerization, and the performance of the polymerization product will also be affected. Acidic conditions are favorable for initiating reaction and conversion rate is high. However, the low pH value will reduce the concentration of ions in the resin, and the electrostatic repulsion and osmotic pressure will also decrease, and easily generate explosive polymerization and gel. The high pH value is not conducive to the initiation reaction, and the conversion rate will also be reduced. The excessive ion concentration in the resin will increase the soluble part of the resin, resulting in the enhanced repulsion of the three-dimensional structure after the water absorption and expansion of the product, and the thickening ability will be reduced. Therefore, a large number of experiments must be carried out to determine the appropriate pH value in order to prepare thickener with satisfactory performance.
