Polyvinyl pyrrolidone (PVP), referred to as PVP, is a non-ionic polymer compound. It is the most distinctive among N-vinyl amide polymers, and the deepest and most extensively studied variety of fine chemicals. Has developed into non-ionic, cationic, anionic three categories, industrial grade, pharmaceutical grade, food grade 3 specifications, relative molecular mass from thousands to more than one million homopolymer, copolymer and cross-linked polymer series products And it is widely used for its excellent and unique performance.
PVP is obtained from monomer vinylpyrrolidone (NVP) as a raw material through bulk polymerization, solution polymerization and other methods. In the preparation process of bulk polymerization, due to the high viscosity of the reaction system, the polymer is not easy to diffuse, and the polymerization reaction heat is not easy to remove, resulting in local overheating and other problems. Therefore, the resulting product has a low molecular weight, high residual monomer content, and is mostly Yellow, not much practical value. Industry generally uses solution polymerization to synthesize PVP.
There are two main routes for PVP production polymerization. The first is the solution polymerization of N-2-pyrrolidone (NVP) in an organic solvent, followed by steam stripping. The second route is the aqueous solution polymerization of NVP monomer and water-soluble cationic, anionic or nonionic monomer. The NVP monomer is directly heated to above 140°C, or the initiator is added to the NVP solution to heat, or the NVP solution (the solvent can be water, ethanol, benzene, etc.) is added to the initiator through radical solution polymerization, or directly used The PVP homopolymer can be obtained by irradiating NVP monomer or its solution with light. The polymerization method is different, and the structure and performance of the obtained polymer are different. The composition and structure of the polymer obtained by free radical solution polymerization are relatively uniform. The performance is also relatively stable. It is the most commonly used method for NVP homopolymerization. PVP homopolymers with different molecular weights and different water solubility can be obtained by adjusting the reaction conditions such as monomer concentration, polymerization temperature, and amount of initiator.
Process 1: NVP is configured as a solution with a mass fraction of 50%. A small amount of hydrogen peroxide is used as a catalyst. Under the action of azobisisobutyronitrile, the polymerization is initiated at 50°C, so that almost all NVP is converted into PVP. Ammonia water is added to the polymer to decompose the remaining azobisisobutyronitrile, the monomer polymerization conversion rate is nearly 100%, and the solid content is 50%.
Process 2: Add 0.4 g of dispersant P (NVP-co-VAc) and 80 g of dispersing medium ethyl acetate to a 250 mL four-necked flask. After stirring and dissolving in a 70°C constant temperature water bath, add 20 g of monomer NVP and 0.15 g to initiate The reagent AIBN was reacted for 6 h under a nitrogen atmosphere, cooled and filtered. The insoluble material was placed in a vacuum drying oven and vacuum dried for 24 h to obtain white PVP solid powder.
Most of the polymerization of PVP uses AIBN as the initiator. There is no literature on the use of water-soluble azo initiators to initiate the synthesis of PVP, but some people are doing this work. Since both NVP monomers and PVP are soluble in water, water-soluble azo initiators can be used to initiate polymerization to form linear PVP polymers. Moreover, AIBN contains a cyano group that is harmful to humans, while water-soluble azo compounds Most initiators do not contain cyano groups, and PVP is mostly used in direct contact with the human body, so water-soluble azo initiators have advantages over AIBN.