Dispersion polymerization of N-vinylformamide and acrylonitrile in aqueous solution, amidinization, and flocculation performance

Polyamidine, which is an excellent flocculant, was prepared by a two-step process: the copolymerization of N-vinyl formamide (NVF) and acrylonitrile (AN) and the amidinization of the copolymer. The existing methods of copolymerization have many drawbacks such as high molecular weight loss during amidinization, environmental pollution, and high cost. We propose the use of pure water as the reaction medium for the dispersion polymerization of NVF and AN to overcome these shortcomings. The products of dispersion polymerization have great fluidity. Aqueous dispersions also help to reduce the amidinization time and molecular weight loss during amidinization, which effectively improves the charge density of polyamidine. The effects of polymerization temperature and monomer concentration on particle size and intrinsic viscosity were studied. The copolymer was processed to produce polyamidine under acidic conditions, and the influence of the reaction conditions on charge density was investigated. Compared with those of solution polymerization, the copolymer products of dispersion polymerization exhibit higher amidinization rate, charge density, and flocculation performance.