Emulsion polymerization

Emulsion polymerization means that the monomer is uniformly dispersed in water under mechanical stirring to form an emulsion, and then an initiator is added to initiate monomer polymerization.

Emulsion polymerization can adapt to higher reaction speed, and the obtained polymer has higher molecular weight, easy production control and easy removal of residual monomer. Based on these advantages, the research of this preparation method develops rapidly. Acrylic thickeners have excellent thickening and suspension properties, and they are used together with almost all nonionic, anionic, amphoteric surfactants and various cationic polymers, so they are favored by researchers.

Inverse emulsion polymerization

Inverse emulsion polymerization refers to the polymerization of water-in-oil emulsion formed by water-insoluble organic solvent and water-soluble monomer in water under the action of emulsifier.

The method has the advantages of high speed and mild conditions, and can obtain a relatively pure product with high molecular weight. Its products are superior to emulsion polymerization products in both thickening effect and electrolyte resistance.

The thickener type prepared by inverse emulsion polymerization is similar to that prepared by emulsion polymerization, and polyacrylic acid thickener is the main thickener. Compared with emulsion polymerization, inverse emulsion polymerization is more suitable for preparing electrolyte-resistant thickener. On the basis of inverse emulsion polymerization, new technologies, such as preparing printing thickener by radiation polymerization, are introduced, so that the polymerization rate can be controlled artificially to avoid too fast reaction.

Precipitation polymerization

There is little research on the preparation of thickener by precipitation method, which is usually the process of adding precipitant into the mixture of organic solvent (benzene, toluene or alkane, etc.) and acrylic monomer to prepare precursor precipitate, and then drying or calcining the precursor.

Compared with inverse emulsion polymerization, precipitation polymerization products have poor thickening performance and are sensitive to electrolyte. If some comonomers (such as octadecyl methacrylate) are introduced into the polymer, its electrolyte resistance can be improved.